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New Orleans Local Weather thread - dkmac - 03-10-2009 07:17 AM

Area forecast discussion
national weather service new orleans la
438 am cdt tue mar 10 2009

.short term...no significant changes in the short term. It still
looks like a weak cold front will enter the cwa wed aftn. Ahead of
this front temps will be well abv normal then things will start to
cool off some as the front approaches the coast.

Today and tonight will be relatively quiet...pretty much a carbon
copy of yesterday. Fog/low stratus has developed over most of the
area but dense fog had not developed yet mainly thanks to the winds
which has allowed for more stratus to develop. That said i will
continue to keep an eye on the fog as some observations are hinting
at the stratus dropping to the deck which would may require me to
issue a short duration dense fog adv. Fog/stratus will start to burn
off after sunrise and once the sun starts to break through temps
will begin to climb quickly. Ll temps have warmed slightly with h925
temps approaching 18 across the cwa. This would lead to highs around
79-82. Add another degree or two for a superadiabatic skin layer and
highs will more than likely range from 81-83 with the exception of
locations along the coast where highs will likely stay in the upper
70s. Skies will clear out again this evn and if winds can die down
then fog will probably develop once again but if winds tend to stay
up then we will see mostly stratus.

Tomorrow will be the last day with highs in the upper 70s to lower
80s for at least a week. The front will approach the cwa from the nw
and should begin to enter our nwrn zones by aftn. Ahead of the front
temps will be able to warm up nicely with highs in the upper 70s to
lower 80s over much of the area. As the front slowly moves south
clouds will increase along with the possibility of some shra but
overall i am not expecting too much activity with the front wed...or
thu for that matter. With sw flow aloft there will just not be any
real push to this front and it will stall across the nrn gulf with
most of the precip remaining off to our nw at first.

.long term...the medium range mdls are in decent agreement through
the first half of the weekend but by sun morning the ecmwf and gfs
really begin to diverge with their handling of the piece of energy
dropping out of the pac nw and merging with the low that moves out
of the desert sw. Overall i don`t necessarily like the closed low over
the lower ms valley by wed next week that the ecmwf is advertising
but i am more in favor of a slower moving trough through the cntrl
conus which the ecmwf does depict before developing its closed low.
The gfes and ukmet do agree more with the ecmwf and with that i will
stick closer to the ecmwf for sun through tue.

Fri rain chances will begin to increase as both the gfs and ecmwf
show better forcing moving overhead as the upper low over the desert
sw starts to open up and push into the plains. Isentropic lift will
also increase across the cwa as cyclogenesis begins to occur in the
wrn gulf. With pw`s approaching 1.5" and the increase in lift sct
shra should begin to develop fri with activity increasing across our
nwrn 3rd fri evn and into sat. I will keep tsra out until sat when
we finally move back into a modified warm sector.

Late sat through tue...the trough will continue to slowly move
through the cntrl conus while our developing sfc low causes the
stalled bndry to begin to retreat back to the north. The sfc low
will move to the ne through the lower/mid ms valley but on the back
side there will be little push to the bndry with sw flow still
aloft. This will lead to the bndry remaining draped across swrn
la/cntrl ms. This baroclinic zone will be the focus for further shra
and isltd tsra sun through mon as multiple weak impulses move over
the region.

I have made some significant deviations from the gui with this
package. The main changes were to pops from fri through mon. With
real good agreement b/t the gfs and ecmwf through sat i have gone
abv the mex pops by 10-20%...especially in the nw where i have
included likely pops. Since i stuck closer to the ecmwf i raised
pops about 10% abv the mex for sun and mon to get shra wording in
the zones/grids. As for temps the only real changes were to highs
today and tomorrow where i continued the trend of going a few
degrees abv the mav in many locations. Elsewhere temps should be
pretty close to the mex. /cab/

&&

.aviation...
Again this morning...the story is boundary layer moisture and winds.
Enough low level moisture around to produce a stratus deck only a
few hundred feet off the surface. This has been a repeat from
saturday and sunday mornings. The difference yesterday morning is
that winds went calm yesterday morning...and have been around 5
knots the other three mornings. Unless winds drop off in the next
hour or two...this will remain a stratus event with ifr to lifr
ceilings and mvfr to ifr visibilities. In either case...boundary
moisture should mix out around 15z...give or take an hour. Once
fog/stratus has cleared out... Redevelopment of sct030 deck is
expected. Looks like another persistance forecast after sunset...and
current plans are to forecast stratus for early wednesday morning
vice dense fog. /35/

&&

.marine...
Surface high pressure extending into the gulf of mexico will keep
serly flow through wednesday along with 1 to 4 foot seas. A cold
front will approach the northern gulf coast wednesday evening before
stalling. May end up in a situation where wind direction in the
coastal zones is determined by location of the front. Areas north of
the boundary will be n/ne while areas to the south will have e/se
winds. Forecast confidence after saturday rather low...but wind
forecast generally based on gfs solution for now. /35/


New Orleans Local Weather thread - dkmac - 03-11-2009 06:37 AM

Area forecast discussion
national weather service new orleans la
450 am cdt wed mar 11 2009

.short term...the biggest issue in the short term is progression of
the front. Initially not expecting a great deal of weather with the
front but by thu night/fri things will begin to change.

First thing this morning is to get rid of the clouds and fog out
there. This should once again happen a few hrs after sunrise. Patchy
to areas of dense fog are still possible this morning but like last
night it has had a tough time. After the fog/low clouds burn
off/lift the area will begin to warm up nicely. A weak front is
slowly working its way twrds the cwa and should begin to move into
our nw this aftn. Ahead of the front temps will get into the upper
70s to lower 80s even if there are clouds out there. The front will
continue to work south through the cwa twrds the coast tonight and
should finally stall out over the nrn gulf by early thu mrng. As for
rain with the bulk of the support remaining nw of the area we are
not expecting anything more than isltd to sct shra late this aftn
and through tomorrow and mainly w of the i 55 corridor. Clouds will
be on the increase this aftn with brk to ovc skies thu. Highs thu
will be a good bit cooler than the last 4-5 days but they will still
be close to normal.

.long term...well the mdls were beginning to come into better
agreement for this weekend but now there are some rather large
differences...mainly with the handling of the front. The
ecmwf/gfes/can are in decent agreement bringing a sfc low into cntrl
ms and briefly putting the cwa in the warm sector while the gfs
keeps the sfc low further to the se thus causing the bndry to bisect
the cwa and a 20 degree range in temps across the cwa. With the
majority of the mdls backing the ecmwf we will lean more twrds it
from sat mrng through most of the extended.

Fri and through the weekend...rain will finally begin to become more
sct to widespread in nature on fri as isentropic lift really starts
to crank up. This is evident in the 290 and 295k levels across the
nwrn half/3rd of the cwa. This will finally get more rain to develop
and this will be the beginning of off and on convection through mon.
As a sfc low develops in the wrn gulf and works to the ne through
cntrl ms sat and into the ohio valley by sun night it will allow our
stalled bndry to retreat to the north. After to low lifts out it
will then leave a baroclinic zone across the lower ms valley and srn
la in its wake. This will be the focus for shra and tsra this
weekend. It will also lead to temps climbing some. Decent waa in the
ll sat will cause h925 temps jump back up to 14-15c leading to highs
ranging from the mid 60s nw to near 70 se. As for rain...it should
be a wet over most of the cwa with widespread shra and isltd tsra
fri night/sat and possibly continuing into mon. That said there will
be a break in the activity it is just too difficult to pinpoint when
that break will be but i do expect a couple episodes of rain to
occur during that 48-60 hr time frame. Sw flow aloft will send
numerous impulses across the cwa and with each convection will
increase. Pws will hover right around 1.25-1.5" and with weak
divergence aloft moderate rain will likely occur with a good
possibility of getting up to 2" of rain across some areas from fri
through mon.

By mon and into tue things should begin to quiet down and there are
indications that we could see a cool down some time around the mid
to late portions of next week. If the ecmwf is right then we could
see lows flirt with upper 30s once again. That said the is a great
deal on uncertainty in the fcst past mon. /cab/

&&

.aviation...
/preliminary 12z package discussion/
pressure gradient still fairly weak this morning...and still on the
cusp of whether we see fog or stratus this morning. A few sites have
seen ifr ceilings temporarily...but kpql has decoupled completely
with 1/2sm vsbys already. By the time tafs go to press...expect ifr
to lifr conditions at most terminals with br/fg more prevalent than
stratus. Low conditions will mix out at most terminals around
15z...give or take an hour. Vfr conditions for the remainder of the
day and this evening. Cold front will drift into the area this
evening and become stationary. Expect mvfr ceilings to be associated
with the area around the front after 06z thursday. /35/

&&

.marine...
The surface ridge thats been dominating the coastal wind pattern
will be broken down today as a cold front approaches the area.
Results will be winds shifting to a more east to southeasterly
direction. The second effect will be a general decrease in wind
speeds to closer to 10 kts. Seas will remain in the 1 to 4 foot
range. The cold front will stall along the coastal waters thursday
and gradually lift northward into the weekend. A surface low will
develop and track across the state...dragging a weak front with it
just brushing the coastals. A stronger cold front is expected to
sweep through the area early to mid next week. Expect no flags
before early next week. /35/


New Orleans Local Weather thread - ROLLTIDE - 03-11-2009 04:58 PM

NATIONAL WEATHER SERVICE NEW ORLEANS LA
329 PM CDT WED MAR 11 2009

.SHORT TERM...
SURFACE COLD FRONT EXTENDS FROM MCCOMB TO JUST NORTHWEST OF BATON
ROUGE LATE THIS AFTERNOON. COOL AIR IS VERY SHALLOW BEHIND THE
COLD FRONT. THE COLD FRONT SHOULD CONTINUE TO MOVE SOUTH OVER
NIGHT BEFORE STALLING ACROSS EXTREME SOUTHEAST LOUISIANA AND
COASTAL MISSISSIPPI. THE FRONT SEEMS TO BE LOOSING SOME OF ITS
UPPER LEVEL SUPPORT AS THE FIRST SHORT WAVE IN THE TENNESSEE
VALLEY LIFTS OUT. WE DON`T PLAN TO MAKE ANY SIGNIFICANT CHANGES
TO THE FORECAST GRIDS DURING THE OVER NIGHT PERIOD.

.LONG TERM...
WE WILL CONTINUE TO FOLLOW THE GFS AS THE MODEL OF CHOICE WHICH
WILL KEEP US IN GOOD AGREEMENT WITH ADJACENT FORECAST OFFICES.
A SERIES OF UPPER LEVEL DISTURBANCES WILL BE MOVING THROUGH
A WELL ESTABLISHED SOUTHWEST FLOW PATTERN. THIS PATTERN WILL NOT
CHANGE UNTIL EARLY NEXT WEEK WHEN THE MAIN UPPER LEVEL TROUGH
SHIFTS EAST AND ALLOWS A NORTHWEST FLOW TO DOMINATE THE AREA. THE
NEXT MAJOR UPPER LEVEL DISTURBANCE WILL MOVE FROM THE SOUTHWEST
U.S. ACROSS TEXAS ON THURSDAY AND THROUGH LOUISIANA ON FRIDAY
WHICH WILL BRING THE STALLED COASTAL FRONT INLAND. A COLD FRONT
WILL MOVE THROUGH THE AREA FRIDAY NIGHT AND THEN BECOME STATIONARY
ACROSS THE MISSISSIPPI DELTA AND COASTAL COASTAL MISSISSIPPI.
ANOTHER UPPER LEVEL DISTURBANCE WILL APPROACH LOUISIANA SATURDAY
AND SUNDAY WHILE THE SURFACE ND COLD FRONT MOVES SLOWLY EAST OF
THE AREA ON MONDAY. HIGH PRESSURE WILL BUILD OVER THE MID GULF
STATES TUESDAY THROUGH THURSDAY.


&&

.AVIATION...
COLD FRONT HAS BEEN SLOWLY BUT STEADILY PROGRESSING SOUTHWARD ACROSS
THE STATE NOW THROUGH MCB AND NOT FOR FROM BTR. THERE IS ONLY A
FEW SHOWERS DEVELOPING BEHIND THE BOUNDARY...SO LEFT OUT SHOWERS FROM
MSY AND GPT. THE COLD FRONT WILL STALL ACROSS THE AREA LENDING TO
GENERALLY EAST TO NE WINDS THROUGH THE EVENING HOURS. A SHORT
PERIOD AFTER THE FRONT PASSES...CIGS WILL DROP TO AROUND 1KFT.
CLOUD DECK WILL GRADUALLY LOWER THROUGH THE NIGHT TO IFR/LIFR NEAR
SUNRISE. VIS MAY OCCASIONALLY DECREASE TO AROUND 4SM BUT NOT
EXPECTING FOG. ALTHOUGH A STRAY SHOWER IS POSSIBLE THURS
MORN...MOST ACTIVITY SHOULD BE DELAYED UNTIL AFTERNOON OR EVENING.


New Orleans Local Weather thread - dkmac - 03-12-2009 06:14 AM

Area forecast discussion
national weather service new orleans la
434 am cdt thu mar 12 2009

.short term...the front is still slowly moving south and is
approaching the coast but it has really lost a lot of its steam and
will likely come to a halt this morning. Sw flow remains over the
area with the first of numerous impulses moving into the lower ms
valley this morning

today and tonight i am not to impressed with the possibility of
rain. We will actually be under ll anticyclonic flow with the best
ll convergence well to our north. In addition the first upper level
disturbance(which will be well off to our north as well) will be
departing to the ne with subsidence over most of the cwa. These two
features alone don`t bode to well for rain...combine that with pw`s
starting off today below 1" and i could i really see most of the
area remaining dry today and probably through much of the night. The
ern half of the cwa will at best only see isltd shra late this aftn
and tonight but just to the n and nw of btr where the environment
will be a little better sct shra will be possible late this aftn and
overnight.

Tomorrow should hold better for rain across most of the region.
Isentropic lift will be on the increase especially across the nw
where numerous shra should begin to develop during the late morning
hrs. Coverage will increase to the east with at least sct shra
across the entire cwa by aftn. Isltd tsra will also begin to develop
tomorrow aftn as better instability tries to work in from the west.
By tomorrow aftn pw`s will have climbed...approaching 1.5". Combine
that with increasing divergence aloft and this will lead to shra and
tsra being slightly more efficient rain producers. Rain coverage
will continue to increase through the night.

.long term...again there are some differences in the extended b/t
the medium range mdls. The gfs continues to be the outlier keeping
us on the cooler side of the front through mon and then breaks down
the wrn conus ridge quickly next week. The ecmwf does keep things a
little warmer and then builds a stout ridge over the wrn conus with
nwly to nrly flow from tue through the end of the work week driving
a decent cold front into the area late wed. I have again decided to
side with the ecmwf which continues to have support from the gfes
and canadian.

This weekend things will be quiet wet. The bndry will remain draped
across the area as swly flow continues to send impulses across the
region. This will cause multiple rounds of shra and isltd tsra. Pw`s
will remain b/t 1.25 and 1.5" and h85 theta e air of 326-327k
continuing to pump into the region. At the same time we will move
under a more favorable position in relation to the upper jet and
these features should lead to moderate and maybe heavy rain at
times. This is welcome as we could use the rain. Total rainfall
accumulations could approach 4" across the n/nw with most of the
region seeing at least 2" from fri through mon mrng.

By mon things will begin to wind down as the nrn and srn streams
begin to phase together with our trough pushing east through the
cntrl conus. Look for the trough axis to move through mon night with
all rain coming to an end mon aftn/evn. We will dry out after this
and cool off slightly...mainly morning lows thanks to the drier air
and clear skies. Around the end of the fcst the ecmwf is continuing
to indicate a potent dry cold front moving through the region late
wed. Ahead of this front ll temps surge up indicating highs could
jump into the mid 80s but once the front passes ll temps cool
drastically...we shall see.

As for deviations to gui i have again made numerous changes. First
off was to lower pops over most of the area today and tonight by
10-20%. Outside of those two periods i either went with or abv the
mav/mex pops from fri through mon with categorical pops in some
locations from fri aftn through sun mrng. As for temps...i didn`t
make any significant changes early in the fcst but in the extended
grids i did have to make some changes since i used the ecmwf as my
mdl of choice. Sun and mon i raised both lows and highs and then
began to go lower than the mex beginning tue...especially for lows
wed mrng. Outside of wed mrng i stuck closer to the mex since this
is day 6/7. Now if the ecmwf shows this cool down one more night
then we will need to start showing cooler temps for thu. /cab/

&&

aviation...
/preliminary 12z taf package/
leading edge of drier air near a kgpt-knbg-kptn ln. North of this
boundary...vfr conditions predominate...including kbtr...kmcb...kmsy
and knew. Certainly some potential for mvfr ceilings around sunrise
at these sites...but for the most part...ceilings should remain at
or above 3k feet. At kgpt...currently lifr ceilings...but anticipate
as drier air moves in...vfr conditions will as well. Current
indications are that vfr conditions should be the rule until friday
evening...when precipitation becomes a little more prevalent. /35/

&&

.marine...
A cold front is tracking southward through louisiana...currently
approaching the coast. It is not expected to move much past the near
shore area before stalling...although it appears that the boundary
may extend farther into the gulf along western portions of the
forecast area. With the front stalled...winds should be primarily
eastward at around 10 knots with seas in the 1 to 4 foot range. The
subtropical jet will become active with several impulses moving
across southern la. Most rainfall will be inland with some bleedover
into the coastals. A surface low will develop friday and again on
monday...enhancing the shower activity. A stronger front looks to
finally push through monday night. Currently...no flags appear
necessary through the forecast period. /35/


New Orleans Local Weather thread - dkmac - 03-13-2009 06:33 AM

Area forecast discussion
national weather service new orleans la
458 am cdt fri mar 13 2009

.short term...favorable pattern in place for a couple of bouts of
showers and isolated thunderstorms with the first likely today.
Overall things remain similar for the weekend. Sw flow aloft will
send numerous impulses across the region and our bndry will meander
across the region for the next 3-4 days.

Today and through the weekend the cwa will see rain off and on. The
old front is still draped over the region stretching with another
impulses already moving through sern tx/swrn la. This has developed
a decent area of shra and even a few isltd lightning strikes moving
across the sabine river/teledo bend area and into cntrl/nrn la. Most
of this first batch of rain will stay off to our north but as a sfc
low begins to develop in the wrn gulf and isentropic lift increases
over the area sct to numerous shra will begin to develop over wrn
portions of the cwa. The sfc low will then track to the ne moving
into cntrl ms by early tomorrow mrng. This will help drive our
bndry to the north a little putting our area in the warm sector.
Instability will increase a little. At the same time mid level flow
will increase to around 50kts and we will move under the rrq of a
100kt upper jet. This will at least help develop isltd if not sct
tsra. A few of these storms could become strong with gusty winds and
heavy rain but with the lack of instability or overwhelming forcing
tsra will have a hard time reaching svr limits.

Our closed low in the desert sw will open up and begin to move into
the cntrl plains with our sfc low moving into the tn/oh valleys
leaving the bndry draped over the cwa still. This will be the focus
for further rain to develop as sw flow continues to send weak
disturbances over the region. Timing these separate impulses at this
time is difficult and with each one we will see shra and isltd tsra.
We remain under a favorable region in relation to the upper jet and
with pws ranging b/t 1.25-1.5" moderate rain will fall at times with
total rainfall from fri through sun ranging from 2-4" over most of
the area.

.long term...drier conditions will return in the extended. The gfs
and ecmwf again have some disagreement but there differences aren`t
the normal timing/pattern issues. They actually have a similar
pattern set up for the area. They both have the region under nw flow
with sfc ridging over the region. It is the sensible weather where
they differ. The gfs even though we will be in nw flow with high
pressure dominating the sern conus(ridge axis extending in the
ncntrl/nwrn gulf) it tries to develop precip off and on from tue
through fri. The is dry with nw flow and a stronger sfc high. I
again like the ecmwf which has support from the gfes so i will
tailor my fcst twrds the ecmwf.

Mon the last bit of rain will occur that day. As the upper trough
continues to push east through the plains/mid/upper ms valley the
front will finally begin to push to the se. By mon aftn/evn the
front should be in the gulf with drier air infiltrating from the nw.
The trough axis will move through the lower ms vally and into the
sern conus overnight. Once this passes through all the rain will be
over and probably before that as the moisture ahead of the trough
will already be shunted to our east. So with that it looks like the
rain should for the most part come to an end mon aftn.

Tue through fri...will be drier and cooler mainly from a mrng low
standpoint. Ll temps will really not cool much but the nw flow
driving a sfc high into the sern conus will bring us much drier air.
Skies will also generally be mostly clear and this could cause lows
to fall into the upper 40s to mid 50s for about 3 mrngs in a row.
H925 temps will generally be around 16c. This should translate into
highs in the lower to mid 70s since for tue through thu. By fri the
ecmwf tries to drive a weak cold front into the cwa which may help
cool things some for the weekend.

As for deviations to gui...mav and even mex gui pops for today
through mon were generally in good shape so any adjustments i made
were minimal. By mon night and through the remainder of the fcst i
lower the mex pops over numerous locations. I completely removed
rain chance from tue and wed and went about 10% below mex pops for
mon night as the ecmwf kept the entire cwa dry mon night. As for
temps the biggest deviations were mrng lows sat and sun. I raised
temps about 2-5 degrees and even more in some places over the 0z mav
gui. In the extended the main changes were to lows tue/wed/thu.
Again since i stuck closer to the ecmwf mrng lows were a good 2-4
degrees cooler than what the mex advertised and probably could be
another few degrees cooler. That is about...it enjoy the much needed
rain. /cab/

&&

.aviation...
A frontal boundary is currently stalled along the northern gulf of
mexico. Abundant subtropical moisture will continue to stream
northeastward across the state behind this front. The majority of
rainfall will remain north of the area today. A stray shower or two
will be possible mainly over the btr to mcb terminals. Mvfr cigs
will prevail for most of the day over the nw portion of the area
while morning ifr ceilings should be found closer to the coast at
msy and gpt. These ceilings will improve into the upper mvfr range
by late morning through the afternoon with breaks. Showers and an
isolated ts will reach msy and gpt by late tonight or saturday.

&&

.marine...
A cold front remains stalled along the northern gulf coast from lake
pontchartrain through the rigolets to over the miss sound barrier islands.
Winds north of the boundary have been north the northeast and
southeast south of the front causing seas to continue relatively
steady at 2 feet. This pattern is expected to persist through
this weekend and into early next week. A series of upper level
impulses will move through mostly inland areas over the weekend but
will still have some showers track through the coastal waters. A
stronger cold front will push through the northern gulf monday
night...bringing 15kt northeast winds to the area.


New Orleans Local Weather thread - dkmac - 03-14-2009 06:06 AM

Area forecast discussion
national weather service new orleans la
419 am cdt sat mar 14 2009

.short term...
Frontogenetic boundary gaining some integrity over the forecast
area this morning as a 1013mb low pressure center traverses the
boundary nne 30 knots into southern mississippi near mccomb at
09z. Temperatures were in the mid 50s west of the boundary and
upper 60s to around 70 east of the front. Some enhanced convective
elements in the shape of small-scale comma heads have appeared
from time to time in elevated instability a few hundred feet off
the surface and above. An unstable warm sector has developed as
msas shows surface computed li`s in the -1 to -4 range from the
mississippi shore...across lake pontchartrain to morgan city
southward...with hardest axis indicated from manchac to lower
terrebonne parish. This front makes some progress eastward this
morning before elongating and stalling once again south of the
mississippi and louisiana coast later tonight.
Meanwhile...persistent southwesterly flow aloft with embedded
disturbances...the next one currently over north-central
mexico...will overrun the frontal zone to produce what should be
widespread stratiform and elevated showers tonight and sunday for
much of the forecast area. Upper level short-wave over desert
southwest should then move across forecast area monday and bring
an end to the rain by late monday or early monday night.

Thunderstorms have been rare tonight with only a strike or two
from the more organized cells. Local chap program shows sub-severe
potentials on wind gusts...mainly around 30 knots/35 mph...only
spout vortex potential...no hail indications through 12z. This
sounds reasonable and will be basis for hazardous weather
outlook in the short term.

.long term...
Short-wave amplifies a bit in southern branch while moving
overhead monday night. Ridging develops aloft briefly tuesday
before pattern becomes a northwest flow regime by late next week
as large amplitude trough develops across the eastern states. This
pattern should persist into next weekend. The transition from
westerly to northwesterly thursday may bring a brief threat of
rain but moisture may be somewhat limited. Temperatures should
remain above normal each day tuesday through friday. 24/rr


&&

.aviation...
A slowly moving cold front will move into the northern gulf today
before stalling once again by tonight. Weak disturbances will
continue to move along the fronts axis enhancing the shower activity
and producing isolated ts at times. Behind the front...ifr ceilings
will be found over most locations with some lifr ceilings as well.
Frontal lift will keep elevated sh/ts for most of the day. This will
lend to moderate shear profiles at around 1k`. Large area of light
to moderate showers will remain mostly behind the front. Low level
moisture with warmer temps ahead of the front will keep mvfr cigs in
place for msy and gpt until fropa. 17

&&

.marine...
A cold front will slowly move into the coastal waters today before
stalling tonight. Winds south of the boundary remain southeast 10 to
15 knots causing seas to continue relatively steady at 2 feet. As
the front stalls winds will shift from southerly over the outer
waters to northerly over the inner waters. A series of upper level
impulses will move over the front causing scattered to widespread
showers across the coastal waters. A stronger cold front will push
through the northern gulf monday evening...bringing northeast winds
to all coastal waters. No flags expected through the period. 17


New Orleans Local Weather thread - dkmac - 03-17-2009 05:17 AM

Area forecast discussion
national weather service new orleans la
347 am cdt tue mar 17 2009

.short term...
All showers are now well south of the region with the cold front
half way across the gulf of mexico. Previous lix sounding shows
complete saturation up to around 7k feet. While mid level drying
is likely already occurring with mid level dry air advection...low
level clouds are expected to persist into the mid morning and
should be clear for the afternoon. Surface high pressure will keep
northeasterly flow through today. Temperatures will moderate
reaching into the mid to upper 70s across the area. Guidance
suggests a few locations could see fog wed morning...mainly along
and north of the i-12 corridor but opted not to include any in the
zones after analyzing model soundings. Looks like saturation will
only occur right at the surface vs this morning where a more
substantial layer is satrd and still not seeing any sites with
fog. Overnight lows will drop about 5 degrees or so as dewpoints
gradually fall today and tonight.

.long term...
Upper level trough will quickly eject and continue out into the
atlantic. Only slight upper level ridging will take place as the
next broad trough tracks along the northern conus. Highs will be in
the upper 70s again on wed and thurs before the next cold front
approaches thurs night. This boundary looks to be little more than a
wind shift and slight cool down. Moisture never really gets a chance
to return with a generally ne to easterly flow regime in place.
So...this front is expected to be primarily dry. May decide to
introduce slgt chnc pops a later time if conditions merit.
Otherwise...not much to talk about for the longterm. Upper level
ridge will build into the area over the weekend. Temperatures will
be slightly above normal and rain chances are below any mention.

Meffer
&&

.aviation...
/12z taf issuance/
variable mvfr ceilings across the area due to very shallow moisture
trapped below surface based frontal inversion. Air mass very dry
above inversion and once daytime heating begins...should mix the
column for cloud and fog dissipation...mainly after 14z or 15z. Vfr
conditions expected thereafter with a light northeast wind through
taf forecast period. 24/rr

&&

.marine...
Winds running light to moderate and seas are relatively flat this
morning. This should continue to be the case for much of today and
wednesday. A stronger surface surge takes place late thursday with
stronger northeast winds and building seas for friday. Concerns
developing for coastal flood threat this weekend along east facing
shores as strong high pressure area parks over southeast conus and
maintains a persistent easterly flow from florida straits and east
gulf. Will introduce this threat into hazardous weather outlook as
tides above normal but may warrant and advisory or watch at some
point heading into the weekend and early next week. 24/rr


New Orleans Local Weather thread - dkmac - 03-18-2009 07:23 AM

Area forecast discussion
national weather service new orleans la
356 am cdt wed mar 18 2009

.short term...
Fairly benign weather expected in the near term. Patchy light fog
has developed mainly along the coastal parishes. Other areas across
the cwa are likely experiencing similar conditions but in a more
spotty fashion. Surface high pressure continues to extend across the
area lending to relatively weak sfc flow. Highs are expected to be a
couple degrees warmer today which will push temps to near or
slightly above 80 along and north of the i-12 corridor and upper 70s
to the south. Gfs/nam bufr soundings show low level saturation near
sunrise on thurs. The combination of light to calm winds and good
radiational cooling from clear skies will likely result in a repeat
in patchy fog conditions tomorrow morning. Near normal lows for
tonight.

.long term...
Little to no change is expected on thursday with similar temps but
possibly a few more clouds moving through. Upper level trough
tracking along the u.s./canadian border will dig across the great
lakes and into the northeast sending a cold front through the
region. Models are in fairly good agreement with this boundary
reaching the cwa by fri 06z an into the gulf by sunrise. Gfs is only
slightly faster than the nam and ecmwf. The actual timing makes
little difference other than when the wind shift takes place b/c
theres not expected to be any precip along the front due to a lack
of moisture to work with. Temperatures will get bumped down 5 to 7
degrees with high pressure somewhat building in on friday. Same goes
for over night lows sat and sun morning with the sfc ridge
positioned to the northeast resulting in areas from mcb to gpt
seeing the coolest temperatures. Temps will then begin to gradually
moderate during the latter part of the weekend and into early next
week as the upper level ridge builds in. The surface ridge along the
appalachian mountains will sag serd into the western atlantic
setting up a for an extended period of increasing se winds. Above
normal tides are expected to occur late this weekend through early
next week.

Models indicate a deeper upper level trough digging through the
desert southwest early next week. As a closed low develops and
pivots northeast towards the high plains...a slow moving cold front
will move towards the region. Attm...this boundary doesn/t look to
reach the area until late next week which is getting towards the end
of the forecast period. So...will hold off on increasing pops. If
models end up being correct...could become an extended period of
rainfall with good moist subtropical flow and a slow moving front.

Meffer
&&

.aviation...
/12z taf issuance/
some tempo ifr vsbys in shallow fog around daybreak. Otherwise vfr
conditions cavu after 14z through 19/12z. 24/rr

&&

.marine...
Weak ridge axis along the gulf coast to maintain relatively light
winds and low seas today and thursday prior to a surge of high
pressure from canada thursday evening. This high should settle
across the southeast states in time to maintain a long duration east
to southeast swell train and enhanced tides primarily along our east
facing shores from late saturday through next wednesday. Coastal
flood watches may need to be considered this weekend into next week.


New Orleans Local Weather thread - dkmac - 03-19-2009 06:10 AM

Area forecast discussion
national weather service new orleans la
425 am cdt thu mar 19 2009

.update...
Sending out update for dense fog advisory issuance. Latest obs
indicate that vis continue to drop and become more extensive in
cove age.

&&

.prev discussion... /issued 410 am cdt thu mar 19 2009/

short term...
Biggest issue early this morning is areal fog. Areas north and west
of a houma to hammond line have very patchy light fog. South and
east of that line is more continuous in coverage as well as more
dense. Not going with dense fog advisory quite yet...but will
continue to closely monitor. In the interim...short term advisories
will be issued regularly to cover the reduced vis. Based on the
sounding from yesterday evening...the atmosphere dries out quickly
with height. So...the depth of the fog is likely very shallow and
should burn off quickly this morning. Mostly sunny to partly cloudy
for today. Temperatures will warm into the upper 70s to lower 80s
again with locations possibly a degree or two warmer than
yesterday. An inverted sfc trough in the gulf is the focusing
mechanism for a few showers that have been popping up in the outer
coastal waters. Models have picked up on this feature so decided
to add slgt chnc pops in the coastals for today.

An upper level trough is currently moving across the great lakes
towards the atlantic coast. An associated cold front is sliding
southward across the central u.s. And now about half way through
arkansas. Movement hasn/t been too fast which is explained by
mediocre pressure rises behind the boundary of no more than 1
millibar per hour. The front may speed up slightly later this
afternoon as the upper trough digs a little more southward. Fropa
still looks to be sometime between sunset and midnight. This weak
cold front will not bring any significant changes to the current
weather. Temperatures will drop about 7 degrees or so which will
bring the are more in line to climatological norms. Dewpoints will
drop slightly and winds will be out of the north to northeast for a
couple days.

Long term...
The weekend is setting up to be quite tranquil. The only issue will
be possibly a few showers along western portions of the cwa. The
above mentioned upper trough is progged to quickly shift east and
out into the atlantic ocean. Surface ridge behind this trough will
settle in to the eastern seaboard and move little for the next
several days. Meanwhile...an upper level ridge will build into the
southeastern conus. Persistent southeast flow will gradually bring
increased moisture to se la as well as the potential for above
normal tides along the coast. Showers could develop along and west
of a baton rouge to houma line sunday afternoon. Not completely sold
on the idea but with a few models hinting at the possibility...went
ahead and added them in.

The next weather maker to affect the cwa will be an upper trough
expected to track across the rockies by the middle of next week. A
frontal boundary associated with this feature will slowly move into
the region during this time. With ample moisture in place...wont
need a whole lot of lift to fire off a few shwrs/tsrms. Instability
looks to be enough for the mention of thunder but not expecting any
severe. Models indicate that the boundary will stall and lift north
as a warm front. So...kept slgt chnc showers through the end of the
forecast period.

Meffer

aviation...
Fog will be the main forecast problem through mid morning. Kgpt has
dropped to 1/4 mile vsby and is likely to vary from 1/2 to 1/4 mile
through 12-13z. Kmsy should remain mostly mvfr for vsbys...but could
drop to ifr for an hour or two before 13z. Slightly drier air around
kbtr and kmcb have kept them vfr thus far...but they should drop to
mvfr by 12z. All taf sites should be vfr after 14-15z with
few-sct050 and sct-bkn250 decks expected by late afternoon and early
evening. Looking ahead to thursday night...fog should not be a
problem due to passage of cold front overnight. 22/td

marine...
A cold front followed by building high pressure will surge south
into the coastal waters tonight. High pressure should become
generally anchored over the carolinas into the central gulf coast
and maintain moderate and long duration e to se wind flow this
weekend. Wind velocities may increase and become more se to s early
next week as strong low pressure moves across central and southern
plains into great lakes with tightening of pressure gradient. Small
craft advisories for wind and seas may be needed later in the
weekend and early next week. Above normal tides are expected to
develop with prolonged onshore flow by sunday into early next week.
22/td


New Orleans Local Weather thread - dkmac - 03-20-2009 04:35 AM

Area forecast discussion
national weather service new orleans la
416 am cdt fri mar 20 2009

.short term...
Cold front is currently slowly moving through the cwa and south
of the new orleans metro area. Locations still waiting for the
boundary will experience a brief 3 to 5 degree warm up as the
front passes simply as a result of mixing. No significant weather is
expected through the weekend. Temperatures will cool about 5
degrees from yesterday with highs generally in the mid 70s along
with few if any clouds to speak of. About the same drop in temp
for highs will occur on the overnight lows...mid 40s to the north
to almost 60 along the coast. Models have been indicating low end
pops sunday afternoon but not buying into it. Gfs and nam bufr
soundings show a fairly pronounced cap at around 800mb which will
likely suppress any shower development.

Upper level ridge will continue building over the area through
sunday while sfc high moves little from the carolina coast. This
setup will bring ashore gulf moisture as southeast winds gradually
increase. Rising dewpoints will keep lows from dropping as much sat
and sun nights. Cloud cover will gradually increase to close to
mostly cloudy by saturday evening.

.long term...
A pacific northwest trough will progressively move across the
western half of the nation early next week. An associated sfc trough
will develop on the east side of the rockie mountains resulting in
sharpening the sfc pressure gradient over the area. This will
solidify saturation of the atmo column. So...as the cap weakens on
monday as evaporative cooling begins to take place from moisture
increase...shower potential will be on the rise. Kept pops on the
low end for tuesday and progressively increase from this point on.
Cold air advection will create a more unstable atmosphere by
tuesday so decided to at thunder into the mix. Models have become
slightly more progressive in speed of the sfc trough/cold front
during the week. From wed on...model discrepancy comes into play.
The gfs has a deeper and faster moving upper trough which brings in
the heavier rainfall by wed afternoon and sweeps it to the coast.
The ecmwf is slightly slower in initial speed as well as overall
progression. The nam is the slowest of all. So...went mainly with
ecmwf as a compromise with some input from gfs. Attm...shwrs/tsrms
stand the chance to continue through the end of next week depending
on if the front stalls per gfs or just slowly moves through as
ecmwf. Extensive cloudcover will keep lows above normal and highs
near normal through the week.

Meffer
&&

.aviation...
Cold front has moved south of the taf airports. Clear skies and
drier air will maintain vfr conditions today...saturday...and likely
sunday as well. Northeast winds will be highest at/near kmsy this
morning with sustained values 10 to 15 knots with occasional gusts
15 to 20 knots. Klix vad wind profile shows ene/ne winds around 25
knots at 1000-2000 feet at 0900z. 22/td

&&

.marine...
A cold front moving through coastal sections early this morning has
increased north to northeast winds to 15 to 20 knots over the near
shore waters east of the ms river. Will carry a /small exercise
caution/ statement for the eastern waters through 10 am this
morning. High pressure should become generally anchored over the
carolinas into the central gulf coast with a tightening pressure
gradient maintaining moderate to strong east and then southeast wind
flow beginning this weekend and continuing into early next week.
Given the long duration of this moderate to strong onshore
flow...tides are expected to increase to above normal levels along
the coast and in the tidal lakes by the last half of the weekend and
continuing into next week. Tides of 1 to perhaps 2 feet above normal
are possible.

Winds and seas are expected to meet small craft should exercise
caution criteria saturday and may reach small craft advisory
conditions at times sunday. Small craft advisories are very likely
for strong onshore winds and seas 7 feet and higher monday into
tuesday. 22/td