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New Orleans Local Weather thread - dkmac - 11-27-2008 07:09 AM

000
fxus64 klix 271022
afdlix

area forecast discussion
national weather service new orleans la
422 am cst thu nov 27 2008

.short term...
Have continued to slow things down more tonight as model
solutions are finally beginning to show the slowness of the upper
trough and cold air sinking southward. An initial sfc low will
form along the front over se tx friday and move ne dragging the
cold front into the area by saturday morning. This is where the
fun starts.

Strong dynamic forcing will begin along the frontal boundary as
the upper trough begins to kick out of the gulf south. This will
cause a moderate divergent jet level flow inducing lift through
the column which will in turn cause a sfc low to begin forming by
sat evening. Now comes the problem. Model solutions for the upper
flow initialized very well and look good. The issue with this is
the solved sfc low position is not in line with the mid and upper
trough. The sfc low should develop over the coast or over se la
and slip ene toward coastal miss/ala. This is a slight move north
of where the models place the low but it will be important with
regards to rainfall and hazardous weather for sat afternoon and
sat night. Will go with isolated severe possible sat afternoon and
night for those areas in the warm sector of the front. This should
be mainly an area from houma to chalmette southward but will
suffice to set all of the south shore in an isolated risk. Heavy
rainfall would be the next possibility for this same area. Attm
will mention these two parameters in the hwo but leave out of the
zones for now.

Things begin to calm down and cool down by sat night and sunday as
the cold front moves quickly east.

.long term...
Return flow should start up once again by tue. Fog is hard to pick
up on even within the short term but i can`t find one variable
that tells me fog will not form wed night into thu morning of next
week. Wed night may be the first signifigant fog night so far
this season but to pin down one night so far out is never a good
idea so will only mention it here for now that we could see this
tue night or wed night.

&&

.marine...
South to southwest winds today will be increasing in strength friday
in advance of a slow moving cold front. The front will likely stall
before reaching the mouth of the mississippi river saturday as a
weak area of low pressure probably develops in the west gulf and
moves along the stalled frontal boundary...ultimately swinging the
front eastward sunday. Cold high pressure will then build into the
gulf to bring strong northwest winds late sunday and particularly
monday. Seas will be building sunday and monday...possibly reaching
10 to 12 feet late monday in the outer waters. Thunderstorms will be
on the increase friday and saturday across the coastal waters with a
risk of strong water spouts under the more intense storms before
flushing out of the area sunday. 24

&&

.aviation...
/12z taf issuance/
moisture is slowly returning to the area with mid-level vfr clouds
lowering to high end mvfr/low end vfr ceilings later this morning
and lingering through tonight before becoming prevailing mvfr friday
with increasing convection in the region. Patchy mvfr br possible at
some locations this morning and again friday morning. 24


New Orleans Local Weather thread - dkmac - 11-28-2008 06:23 AM

000
fxus64 klix 280953
afdlix

area forecast discussion
national weather service new orleans la
353 am cst fri nov 28 2008

.short term...
Gfs still determined to keep wrong placement of trough axis and
mass fields. These two items are obviously found over northern la.
This has already been accounted for in the ongoing package and
only minor changes need to be made. Sfc low should begin to
develop today over eastern tx and move ene through tonight
bringing the first round of sh/ts with it and forcing the cold
front to move into the area. This is when the best chances of rain
should come to most of the area. The best forcing comes in on
saturday right along the frontal axis which should be located over
se la. This is where we could see some areas of heavy rainfall and
strong weather through saturday evening. The new sfc low should
move ne into the ala/pensacola area around midnight sat night
dragging the cold front with it through the northern gulf.

The system begins to occlude as it moves into the ne while the
700mb thermal trough begins to rotate through the deep south. This
simply spells out cold and cloudy conditions. Believe we will see
some sun on sunday before the 700 trough comes through sunday
night into monday. Tue will still be cold but improving.

.long term...
Return flow to begin tue and wed of next week. A stalling front
will settle into the northern or central la area before moving
back north. This is a perfect scenario for a signifigant fog event
to occur around wed night...thu night or possibly both. And fog seems
to be the main hazard posed by this next system.

&&

marine...
Frontal boundary has become stationary well north of the coastal
waters...generally along the i-20 corridor from dallas texas through
jackson mississippi. This weak front is expected to eventually
settle south to near the coast by saturday morning then get forced
well into the gulf by sunday morning and much colder high pressure
moves out of the northern rockies into the middle of the country.
Winds and seas are expected to increase significantly sunday and
monday before the settling down going into tuesday. Unseasonably
warm moist air across the north gulf will be capable of supporting
thunderstorms later today through sunday morning as the front nears
and ultimately passes southward. Squallid conditions are possible
saturday and saturday night along with the potential for large
waterspouts prior to frontal passage in the gulf waters. 24

&&

.aviation...
/12z taf issuance/
airmass continues to destabilize and radar trends are showing
scattered showers developing in the vicinity of kmcb. A rather solid
line of convection extends from tyler texas to vicksburg mississippi
to near crystal springs...drifting very slowly north. This area
demarks a stationary frontal zone that will linger through much of
today before proceeding south as a stronger cold front saturday.
Convective coverage should increase at the area terminals throughout
the day and especially saturday. A large expanse of mvfr and ifr
ceilings across the western half of louisiana will spread east this
morning and may persist through much of the day mainly at kbtr and
kmcb...though kmsy and kgpt will have intermittert lowering of
ceilngs through entire taf valid time. 24


New Orleans Local Weather thread - dkmac - 11-29-2008 06:04 AM

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fxus64 klix 290941
afdlix

area forecast discussion
national weather service new orleans la
341 am cst sat nov 29 2008

.short term...
A slow moving cold front extends from southwest la into southwest
ms. Numerous showers and scattered thunderstorms are focused along
and just to the north of the front. An area of scattered light
showers is concentrated in the coastal waters mainly east of the
ms river. Light southerly flow will keep dewpoints high ahead of
the front as it moves into southeast la and coastal ms by this
evening.

.long term...
A strong upper level jet in the rockies will dive southward
causing the upper level flow to back with time and increase the
strength from the tx big bend into tn. These factors will
increase the upper level divergence over the mid gulf coast region
today and tonight which should provide strong upper level support
for showers and thunderstorms. However weak surface based
instability will limit the severe thunderstorm threat...even as
vertical wind shear increases today and tonight. With cold front moving
slowing through the area today...there will be a chance for
locally heavy rain. The heavy rain threat should end most areas by
midnight. The ground in most areas is pretty dry...the lone
exception is southwest mississippi where nearly 3 inches of rain
fell yesterday due to training of numerous showers and
thunderstorms across this area.

As the upper level trough deepens in the central plains
overnight...there will be plenty of cold air invading the gulf
coast states during sunday and monday with highs in the 50s and
lows falling into the 30s. The upper level low will weaken and
move northeast by mid week allowing more seasonal temperatures to
return.

&&

.aviation...
Rather chaotic weather expected through the next 24 hours as slow
moving frontal zone over south-central mississippi sags southward
this morning then accelerates as strong canadian cold dome advances
southward and catches up to frontolytic boundary. Ifr ceilings at
kmcb will be spreading southward with convective rain area through
18z and should move into the kbtr terminal area before 12z...then
kmsy and kgpt area after 15z. Improving ceiling and vsby conditions
expected after 00z tonight as shallow cold dome settles into the
region and lifting ceilings to mvfr or low end vfr in time. Low
level wind shear may become an issue late tonight and sunday with
strong north winds near surface encountering moderate southwest
winds about 1kft above surface behind front for several hours. 24

&&

.marine...
A long fetched southerly onshore flow has a 5 ft swell train
established into the coastal waters this morning. This will be
maintained and become mixed with a short period northerly wind wave
later this evening once the front moves offshore. Very shallow cold
air will allow for turbulent mixing to produce a period of gale
force gusts and high end sustained small craft advisory conditions
going into sunday afternoon. Will not hoist advisory this package
but will interject `small craft likely` type wording in body of
forecast. 24


New Orleans Local Weather thread - dkmac - 11-30-2008 08:16 AM

000
fxus64 klix 300952
afdlix

area forecast discussion
national weather service new orleans la
352 am cst sun nov 30 2008

.short term...
Decreasing cloudiness...breezy and cool weather will be the
prevailing today as strong subsidence and cool advection takes
hold. The cool weather is being ushered into the area by a large
strong upper low pressure system which extends from the mid ms
valley south to the gulf states. The low will move slowly east
through tuesday.

.long term...
As the large upper level low weakens and moves to the northeast by
wednesday...a westerly upper level flow will usher in warming
temperatures. At the surface...southerly winds will bring a return
of gulf moisture by mid week. Another weaker cold front and upper
level trough will move through la and ms wednesday night.

&&

.aviation...
Ceilings are steadily improving from west to east with ifr line
moving through kpib-kasd-khum...mvfr line roughly kjan-kbtr-klft and
cavok line approaching the mississippi river east of kmlu to just
west of klft. Higher cirrus clouds over texas may move into area
later today. Some light low level wind shear due to turbulent mixing
of colder air over warmer ground up to a few hundred feet this
morning should abate after 20z as upper trough axis swings through
the area. 24

&&

.marine...
Small craft advisory conditions will be spreading from west to east
as cold air advection gets underway over the warmer waters. Seas
should build to 7 feet in the outer waters by early this afternoon
after mixing out the southwesterly component swell train. Duck
hunters and interests in the coastal marshes should be aware of
tides falling below normal due to strong offshore flow and should
avoid shallow flats that could drain completely this morning before
high tide returns later this evening. 24


New Orleans Local Weather thread - dkmac - 12-01-2008 06:11 AM

000
fxus64 klix 011002
afdlix

area forecast discussion
national weather service new orleans la
402 am cst mon dec 1 2008

.short term...

A very strong and deep trough will dominate the area through
tomorrow. This deep troughing across the eastern half of the
nation will bring cool and dry conditions of the entire cwa.
Temperatures will be 15 to 20 degrees below normal today and
tomorrow. A few passing clouds are expected over northern and
eastern zones...as the main vort max associated with the deep
trough passes through mississippi into alabama. However...given
the strong negative vorticity advection taking place and lack of
any deep moisture...have removed mention of pops for the cwa for
today.

Going into wednesday and wednesday...the pattern will change
dramatically...as the deep trough pulls to the east of the
region...and a more zonal flow takes hold of the gulf south. Low
level ridging will shift east as well...allowing for southerly
flow to develop across the region on wednesday. The southerly flow
will be enhanced through the day...as a fast moving trough axis
pulls into the southern plains...increasing the gradient flow
across the region. This stronger and deeper southerly flow off the
gulf of mexico will allow for rapid moisture return...and
correspondingly warmer temperatures wednesday into wednesday
night. As the short wave races to the east...an area of low
pressure is expected to develop beneath the entrance region of jet
streak in the arklatex. A cold front trailing this surface low
will race through the cwa wednesday night into early thursday
morning. Have went with high end chance pops for wednesday
night...as strong low level forcing...combined with deep lift
aloft...and marginally unstable conditions will allow for the
formation of a line of showers and thunderstorms along the frontal
boundary.

.long term...

The frontal boundary will quickly pull through the coastal waters
thursday...with clearing skies expected thursday night. In the
wake of the front...a surge of strong cold and dry air advection
will also take hold...with 1000-500mb thicknesses plunging from
the low 560 range into the upper 540 range thursday night into
friday. Expect temperatures to be fairly steady or slowly falling
throughout the day on thursday...as this strong cold air advection
takes hold. Readings should be 15 to 20 degrees below normal on
friday as the main cold pool slides through. Strong subsidence in
the wake of the upper level tr0ugh will allow for clear skies
friday and saturday.

Going into sunday and monday...the pattern will once again turn
more zonal...as the trough over the eastern third of the nation
lifts to the northeast. Southerly flow will take hold once again
in the low to mid-levels of the atmosphere. However...the timing
of the next system sliding through the zonal is highly uncertain
at this time...with wide disagreement between the gfs and ecmwf
model runs. Due to the overall low confidence in the timing of
this system...have just went with a general slight chance pop for
monday. However...one certainty is that temperatures will moderate
substantially sunday into monday...as southerly flow in the low
levels takes hold. Expect temperatures to rise back to around
normal.

&&

.aviation...
Vfr conditions will prevail through tuesday. Some mainly mid and
high level clouds are expected today with bases aoa 5k feet.
Winds...which have backed to southwest and decreased to less than 10
knots early this morning...will go back to west then northwest and
increase to around 15 knots with gusts 20-25 knots by late morning
or afternoon. 22

&&

.marine...
Small craft advisory/sca/ has been extended through 8 pm for the
lakes...midnight for the inner coastal waters...and 3 am for the
outer coastal waters. West to northwest winds will be 15 to 25 knots
over the tidal lakes and 20 to 30 knots over the coastal waters
today and early tonight. There will likely be occasional gusts to
gale force over the coastal waters for several hours this morning
and again late in the afternoon and early in the evening. Seas will
be up to 11 feet over the far offshore waters through this evening.
Winds and seas are expected to fall below sca criteria late tonight.
The next cold front is expected to bring sca conditions again
thursday into friday. 22


New Orleans Local Weather thread - dkmac - 12-02-2008 06:33 AM

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fxus64 klix 020940
afdlix

area forecast discussion
national weather service new orleans la
340 am cst tue dec 2 2008

.short term...

Strong negative vorticity advection and resultant subsidence will
dominate the region today...as a deep upper level trough begins to
lift to the northeast. Temperatures will remain well below
normal...as a deep cold pool associated with this troughing will
remain over the gulf south. Daytime highs are expected to be 15 to
20 degrees below normal for today. Conditions will begin to
moderate tonight...as upper level ridging begins to build over the
area...and weak low level southerly flow develops on the western
edge of a high centered over the southeast. 1000-500mb thicknesses
will increase from the lower 540 range to the upper 540
range...which will in turn result in temperatures running about 10
degrees warmer for tonight.

Deeper southerly flow will develop across the cwa on
wednesday...which will in turn lead to increasing moisture...and
much warmer temperatures. Strong warm air advection from the
central gulf of mexico will allow thicknesses to rise into the low
560 range by wednesday afternoon...with more normal daytime highs
expected. Cloud cover will also increase through the day...as
low and mid-level moisture streams into the area. However...a lack
of deeper moisture will limit rainfall chances for wednesday.
Going into wednesday night...strong positive vorticity advection will
take hold...as another fast moving upper level trough begins to
deepen in the plains states. Deep upper level lift will be in
place by late wednesday...just as a cold front begins to plow into
the lower mississippi valley. In the low levels...marginally
unstable conditions are expected to develop...as a warm and moist
airmass remains in place. These conditions will be supportive of
some convection along and ahead of the frontal boundary late
wednesday night into thursday. Have included mention of isolated
thunder in the forecast to reflect this. However...model soundings
do not support the formation of severe thunderstorms. In
fact...most thunderstorm activity should remain elevated...as
lapse rates look best above 850mb. As the front sweeps through
on thursday...expect nearly steady temperatures...with a sharp drop
off toward sunset.

.long term...

The cold front will slowly pass through the cwa...as the best
upper level forcing pulls away from the region...and more westerly
flow aloft develops. This will hang the front up along the coast
into thursday night...and reflect this with chance pops continuing
for the coastal waters through thursday night. However...it
appears that a secondary impulse will swing down through the
northwest flow late thursday night...allowing the front to clear
the entire cwa by friday afternoon. Strong cold and dry air
advection will take hold after the front passes through...with
rapidly clearing skies and much cooler temperatures expected.
Thicknesses will drop around 100 meters from thursday into friday
across the region. As a result...temperatures will once again run
a good 15 degrees below normal friday into friday night.
However...with this progressive pattern in place...the cold snap
will be short-lived. The trough should lift out of the region on
saturday...allowing for a more zonal flow to set up. With this in
mind...a return to more normal temperatures is expected by sunday.
Conditions will remain dry through the weekend...as a very dry
airmass aloft stays parked over the region.

Going into monday and tuesday of next week...another fast moving
short wave trough will slip through the region. This system looks
weaker than the previous systems...and thus do not expect any
major temperature swings as a weak frontal boundary slides passes
through the cwa. Moisture will remain fairly limited...as no
strong return flow off the gulf is expected. However...there
should be enough upper level lift to spark off a few showers...and
have included this in the grids.

&&

.aviation...
Mostly clear skies...very good vsbys...and relatively light winds
will prevail the next 24-30 hours as surface high pressure moves
across the central gulf coast region. 22

&&

.marine...
Last small craft advisory headlines expired at 3 am. Have kept
/small craft exercise caution/ headline in effect for outer waters
until 8 am where there will continue to be some gusts in the 20 to
25 knot range for a few hours and seas up around 6 feet. The high
pressure area will build right over the coastal areas around
midday...so winds and seas will fall rather quickly this morning. As
the high moves east late today and tonight...winds will shift to
southerly and increase in response to a developing low pressure area
over the high plains. Waters will get choppy with seas building
again on wednesday in response to south winds 15 to 20 knots. The
next cold front is expected to move through coastal sections and the
coastal waters on thursday. Small craft advisory conditions are
expected to develop thursday night and persist into friday.
Relatively calm conditions are expected saturday as high pressure
settles over the water. 22


New Orleans Local Weather thread - ROLLTIDE - 12-02-2008 05:38 PM

FXUS64 KLIX 022123
AFDLIX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE NEW ORLEANS LA
323 PM CST TUE DEC 2 2008

.SYNOPSIS...
SURFACE HIGH PRESSURE IS CENTERED OVER THE NORTHEASTERN GULF OF
MEXICO WITH CLEAR SKIES ACROSS THE FORECAST AREA. A SURFACE LOW
WITH ACCOMPANYING COLD FRONT IS LOCATED NORTHER OF MINNESOTA.

&&

.SHORT TERM...
THE DEEP UPPER TROUGH CURRENTLY DOMINATING THE EASTERN HALF OF THE
CONUS WILL BROADEN AND LIFT OUT OF THE AREA OVERNIGHT TONIGHT. AS
THE CORE OF THE COLD AIRMASS MOVES AWAY FROM THE REGION...LOW
TEMPERATURES TONIGHT WILL NOT BE NEARLY AS COLD AS LAST NIGHT.
GENERALLY FORECASTING TEMPERATURES IN THE UPPER 30S TO AROUND 40
DEGREES NORTH OF THE LAKE AND MID TO UPPER 40S SOUTH OF THE LAKE.

RETURN FLOW WILL CONTINUE TO PUMP MOISTURE INTO THE AREA WEDNESDAY
AS THE NEXT FRONTAL SYSTEM TAKES SHAPE OVER THE PLAINS STATES.
MODELS ARE IN GOOD AGREEMENT THAT THE FRONT WILL BEGIN TO MOVE
THROUGH THE LOCAL AREA WEDNESDAY NIGHT AND THAT IT WILL SLOW NEAR
THE COAST AS FLOW BECOMES MORE WESTERLY ALOFT. FORECAST SOUNDINGS
DO NOT SUPPORT SEVERE WEATHER WITH THIS FRONTAL PASSAGE AND IT
APPEARS AS THOUGH MOST OF THE SURFACE BASED INSTABILITY WILL BE
LIMITED TO THE GULF WATERS. HOWEVER...WITH A BIT OF INSTABILITY
STILL FORECAST ABOVE 850 MB...WILL CONTINUE TO MENTION A SLIGHT
CHANCE OF THUNDER ALONG THE FRONTAL BOUNDARY AS IT MOVES THROUGH
THE REGION.

.LONG TERM...
NO REAL PROBLEMS IN THE EXTENDED PERIOD. AS HIGH PRESSURE BUILDS
IN BEHIND THE COLD FRONT...ANOTHER ROUND OF COLDER WEATHER CAN BE
EXPECTED. ON THE NORTH SHORE OF LAKE PONTCHARTRAIN...HIGHS AND
LOWS ARE FORECAST AROUND 10 TO 15 DEGREES BELOW NORMAL FRIDAY AND
CONTINUING INTO SATURDAY MORNING. SOUTH OF THE LAKE...THE
DIFFERENCES WILL BE MUCH MORE NOTICEABLE DURING THE AFTERNOON
HOURS WITH HIGHS ABOUT 10 DEGREES BELOW NORMAL ON FRIDAY. LOWS ARE
ONLY FORECAST AROUND 5 DEGREES BELOW NORMAL FOR FRIDAY AND
SATURDAY. THE AIRMASS WILL BEGIN TO MODERATE ON SATURDAY AS THE
SURFACE HIGH LIFTS OUT OF THE AREA.

THE MODELS HAVE HAD CONSISTENCY ISSUES...BOTH RUN TO RUN
AND BETWEEN THE INDIVIDUAL MODELS...CONCERNING THE NEXT FRONTAL
PASSAGE. AS OF THE 12Z MODEL RUNS...THE ACTUAL FRONTAL PASSAGE
APPEARS TO BE SOME TIME NEXT TUESDAY OR WEDNESDAY...WHICH IS JUST
OUTSIDE THE CURRENT FORECAST PERIOD. HOWEVER...THE LARGE
DIFFERENCES IN TIMING AND STRENGTH ALSO LEAD TO DIFFERENCES IN
THE FEW DAYS LEADING UP TO THE FRONTAL PASSAGE. CURRENTLY...THE
ECMWF CARRIES A SLOWER...BUT MORE POTENT SYSTEM WITH THE UPPER
TROUGH AND SURFACE FRONT NOT CLEARING THE AREA UNTIL LATE TUESDAY
NIGHT OR EARLY WEDNESDAY MORNING. THE GFS ON THE OTHER
HAND...CARRIES A FASTER AND WEAKER SYSTEM...AND PUSHES BOTH THE
UPPER TROUGH AND SURFACE COLD FRONT THROUGH THE REGION EARLY
TUESDAY EVENING.

GIVEN THE UNCERTAINTIES...HAVE MADE VERY FEW CHANGES TO THE
EXTENDED AS THERE IS VERY LITTLE CONFIDENCE IN ANY ONE SOLUTION.
THE CURRENT FORECAST SEEMS TO BE A FAIRLY GOOD BLEND WITH A
SLIGHT WARMING TREND SUNDAY AND MONDAY AND A SLIGHT CHANCE OF RAIN
BEGINNING MONDAY NIGHT AS THE FRONT SHOULD BE APPROACHING THE
AREA BY THAT TIME.

&&


New Orleans Local Weather thread - dkmac - 12-03-2008 05:53 AM

000
fxus64 klix 030957
afdlix

area forecast discussion
national weather service new orleans la
357 am cst wed dec 3 2008

.short term...

A progressive pattern across the conus will continue through the
end of the work week. A roller coaster ride of a week can be
expected due to this pattern. For the remainder of today into
tonight...deep southerly flow will develop across the
cwa...allowing for a rapid rise in temperatures and humidity
through the day. This strong southerly flow off the gulf is in
direct relation to a fast moving upper level trough currently
moving into the southern plains and texas. This fast moving system
will sweep through the gulf coast states tonight into
tomorrow...forcing a cold front through the region. Due to the
deep moisture in place...and ample forcing in the low levels...and
aloft due to a broad area of positive vorticity advection taking
hold...expect likely pops from late tonight through tomorrow
afternoon for the cwa. Model soundings indicate that elevated
lapse rates above 850mb will be conducive to some elevated
thunderstorms...and have a chance of convection in the forecast.
However...surface based convection looks to be limited...and do
not expect any severe thunderstorm activity with this frontal
passage. The front should push into the offshore waters late
tomorrow afternoon into tomorrow night. In the wake of the
front...strong dry and cold air advection will take place.
Temperatures should actually slowly fall through the afternoon
hours on thursday...with much colder temperatures expected
tomorrow night into friday.

.long term...

The progressive pattern will continue into the weekend...but may
begin to break down a bit going into next week. As of the 00z
runs...the gfs and ecmwf have divergent solutions on another
system affecting the region tuesday and wednesday of next week. The
gfs keeps the trough positively tilted...and forces the front
through very quickly. However...the ecmwf has a much deeper and
more negatively tilted solution. The overall speed of the system
is also slower...with the frontal passage delayed until wednesday.
Due to the uncertainty...have went with only low end chance pops
for tuesday and wednesday. Before this latter system... It appears
that a reinforcing...but dry frontal passage will take place on
saturday. This will secondary shot of cooler air will keep
temperatures below normal through the weekend.

&&

.aviation...
/12z tafs/
vfr conditions are expected through 06z tonight...then mvfr
conditions are likely at kmcb and kbtr after 06-09z thursday along
with the likelihood of shra and a chance of tsra as a low pressure
system and cold front approach. Kmsy-kgpt should remain vfr
through 12z thursday...then conditions will worsen through the day
thursday as shra/tsra and the cold front move through. Ifr weather
will be possible at all taf sites thursday. The increased pressure
gradient over the lower mississippi valley will lead to gusty
southerly winds across the area...particularly late this morning and
this afternoon. 22

&&

.marine...
Southerly winds will continue to increase today in advance of a cold
front forecast to push across the coastal waters during the day
thursday. Small craft should exercise caution headline is in effect
for the coastal waters west of southwest pass today. Scattered to
numerous showers and possible thunderstorms will move through the
marine area late tonight through thursday evening...but strong
thunderstorms are not expected. Strong offshore flow will develop in
the wake of the front thursday night and friday morning...but have
backed off from around 25 knots to near 20 knots based on all
available guidance and the movement of the upper trough. Winds will
diminish friday night and saturday as high pressure builds into the
gulf coast region. Winds will increase somewhat again saturday night
and sunday as high pressure is reinforced across the region. 22


New Orleans Local Weather thread - ROLLTIDE - 12-03-2008 06:19 PM

FXUS64 KLIX 032137
AFDLIX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE NEW ORLEANS LA
337 PM CST WED DEC 3 2008

.SYNOPSIS...
MUCH WARMER TODAY THAN YESTERDAY. SOUTHERLY WINDS HAVE HELPED
BRING WARM AND MOIST AIR BACK TO THE REGION. GENERALLY SEEING
TEMPERATURES IN THE LOW TO MID 70S ACROSS THE AREA. A TIGHTENING
PRESSURE GRADIENT HAS RESULTED IN STRONGER WINDS OF 10 TO 15 MPH
AND OCCASIONAL GUSTS IN THE 20 TO 25 MPH RANGE.

A SURFACE LOW IS LOCATED NORTH OF MICHIGAN WITH A COLD FRONT
EXTENDING SOUTHWESTWARD THROUGH ILLINOIS...MISSOURI...ARKANSAS
AND TEXAS.

&&

.DISCUSSION...
THE AFOREMENTIONED COLD FRONT WILL CONTINUE TO MOVE
SLOWLY EASTWARD AND SHOULD BEGIN TO AFFECT THE NORTHWESTERN
PORTION OF THE LOCAL AREA OVERNIGHT TONIGHT. THE BEST CHANCES OF
RAIN TONIGHT WILL GENERALLY BE NORTHWEST OF A LINE FROM TYLERTOWN
TO DONALDSONVILLE. WINDS HAVE BEEN INCREASING THROUGH THE
AFTERNOON HOURS AS THE PRESSURE GRADIENT TIGHTENS...AND ARE
FORECAST TO REMAIN AT OR SLIGHTLY ABOVE 10 MPH OVERNIGHT. THIS
SHOULD KEEP THE AIRMASS WELL MIXED...SO WILL BE FORECASTING LOW
TEMPERATURES 3 TO 5 DEGREES HIGHER THAN GUIDANCE.

BY THURSDAY MORNING...THE FRONT SHOULD BE DRAPED ACROSS THE REGION
WITH RAIN LIKELY. SEVERE THUNDERSTORMS ARE NOT EXPECTED AT THIS
TIME...HOWEVER...DECENT LAPSE RATES FORECAST ABOVE 850 MB SHOULD
SUPPORT THE DEVELOPMENT OF AT LEAST SOME ELEVATED THUNDERSTORMS.
THEREFORE HAVE CONTINUED TO CARRY A CHANCE OF TRW IN THE ZONES FOR
THURSDAY.

THE FRONT SHOULD CLEAR THE AREA AND MOVE INTO THE GULF BY LATE
AFTERNOON OR EARLY EVENING THURSDAY. AS A STRONG SURFACE HIGH
BUILDS INTO THE REGION BEHIND THE FRONT...A RETURN TO BELOW NORMAL
TEMPS CAN BE EXPECTED. FORECAST TEMPERATURES ARE GENERALLY IN THE
LOW 30 TO MID 30S NORTH OF THE LAKE AND LOW 40S SOUTH OF THE LAKE
FOR FRIDAY AND SATURDAY MORNINGS...WITH HIGHS GENERALLY FORECAST
IN THE 50S TO AROUND 60 FOR BOTH AFTERNOONS.

ON SUNDAY...A REINFORCING SHOT OF COOL AND DRY AIR WILL ARRIVE AS
A BROAD UPPER TROUGH MOVES ACROSS THE REGION. MOISTURE WILL BE
VERY LIMITED AND AM NOT FORECASTING ANY PRECIP AS THIS TROUGH
MOVES THROUGH. WILL CONTINUE TO SHOW A SLIGHT COOLING TREND FROM
SATURDAY TO SUNDAY.

BY MONDAY...THE MODELS BEGIN TO DIVERGE SIGNIFICANTLY. COMPARED TO
YESTERDAY/S MODEL RUNS...THE GFS AND ECMWF APPEAR TO HAVE TRADED
ROLES. THE 12Z GFS NOW DEPICTS A MORE AMPLIFIED UPPER TROUGH THAT
TAKES ON A SLIGHTLY NEGATIVE TILT OVER CENTRAL MISSISSIPPI AND
ALABAMA. THE SURFACE LOW ASSOCIATED WITH THIS SYSTEM IS ALSO MUCH
FARTHER SOUTH AND MUCH SLOWER THAN PREVIOUSLY FORECAST. THIS
SCENARIO IS VERY SIMILAR TO THE SOLUTION FROM THE 00Z ECMWF. ON
THE OTHER HAND...THE ECMWF NOW CARRIES A BROADER AND MUCH FASTER
MOVING UPPER TROUGH...BRINGING THE FRONT THROUGH THE AREA LATE
THURSDAY EVENING OR EARLY THURSDAY NIGHT...WHICH IS A SIMILAR
SOLUTION TO THE 00Z GFS.

ONCE AGAIN...WITH LITTLE CONFIDENCE IN EITHER SOLUTION...HAVE
MADE FEW CHANGES IN THE EXTENDED PERIOD. HOWEVER...DID BUMP UP THE
POPS SLIGHTLY ON TUESDAY AS BOTH SCENARIOS INDICATE A DECENT
CHANCE OF RAIN THAT AFTERNOON. THE TEMP FORECAST FOR THIS PERIOD
IS CLOSE TO HPC GUIDANCE AND IS AN ATTEMPT AT A CONSENSUS BETWEEN
THE TWO DIFFERENT SOLUTIONS.

&&


New Orleans Local Weather thread - dkmac - 12-04-2008 06:17 AM

000
fxus64 klix 041000
afdlix

area forecast discussion
national weather service new orleans la
400 am cst thu dec 4 2008

.synopsis...
Cold front over central louisiana will move across the atchafalaya
river in the next hour or two. Band of rain and thunderstorms
accompany front...along with some wind gusts around 30 knots.
Temperatures generally in the 60s ahead of the front.
&&

.short term...
Most of the forecast problem is in the first period of the forecast.
For verification purposes...basically trying to forecast location of
cold front at 12z. It should be east of btr at that point and just
about on top of mcb. Based on movement of precipitation...front
should be through most or all of our area by 18z. Will go with
likely pops ahead of front...with chance behind it for this
morning...then slight chance all areas for the afternoon...to
account for the few showers behind the front. Temperatures at 12z
may be the max for the daytime hours behind the front...depending on
whether clearing occurs behind the front. Nam rather bullish on
holding clouds in...but will trend toward gfs solution...which will
diminish clouds during the afternoon.

After the first period...going forecast looks good. In fact...mav
guidance in very good agreement with what we already had in
forecast...so little change needed at this time. Only fly in the
ointment could be a small chance of precipitation late friday or on
saturday as next shortwave moves by to the north. Current solutions
have precipitation remaining offshore...but this will need to be
monitored. 35
&&

.long term...
Both gfs and ecmwf solutions have issues with handling portions of
the forecast. Ecmwf has upper low moving through the southwest
sunday and monday...where gfs has a ridge. Gfs has issues with the
strength of upper vortex...being 4sd below normal heights to
pennsylvania by midweek. Hpc not really supporting details of either
solution with their early morning medium range discussion.

Considering this is my first midnight shift of this set...not
comfortable with the lack of model continuity. Will not make
significant changes to the extended forecast at this time. 35
&&

.aviation...
/12z tafs/
shra/possible tsra will continue to affect the kmcb and kbtr
terminals through about 12-13z...and the kmsy-kgpt terminals 12-18z
time frame. Will be amending the tafs before 1015z to provide better
timing of shra/tsra for kmsy and kgpt. Mvfr to ifr conditions will
develop with the precipitation and arrival of the cold front this
morning...then drier air should bring back vfr conditions late this
afternoon into this evening. The cold front will shift winds to
northerly and they will likely gust near or over 20 knots at kmsy
tonight. 22
&&

.marine...
Pressure gradient will continue to support south to southwest winds
15 to 20 knots and seas up to 6 feet in advance of cold front over
warmer waters...except lower over cool near shore waters. Small
craft should exercise caution today. Numerous showers and scattered
thunderstorms will move across the tidal lakes this morning...and
the coastal waters by mid morning into early afternoon. Behind the
cold front...northerly winds should increase to around 20 knots. A
small craft advisory will likely be required tonight into friday
morning. Winds will decrease friday afternoon into saturday...then
increase a bit saturday night into sunday as reinforcement of cool
high pressure moves into the marine area. 22