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New Orleans Local Weather thread - dkmac - 02-10-2009 08:00 AM

Area forecast discussion
national weather service new orleans la
427 am cst tue feb 10 2009

.discussion...
Latest surface analysis showed a deep 981mb low over central
minnesota with south flow along the western and central
gulf coast...surface ridge remained over north florida. Upper air
analysis showed the main trough over the western conus cyclonic
curvatures over minnesota and the great basin. Balloon sounding
from monday evening showed an inversion around 725mb...pw value
around 0.9 inch...veering winds with height and very little cape
value. Isotach analysis at 250mb a 120 to 130 knots from southern
new mexico to mid mississippi valley and on the back side of the
main axis 110 to 120 knots along the west coast. Ergo...trough
lifting should take place with jet max ahead of axis. Short range
models are in agreement with bringing the surface front and trough
axis through the lower mississippi valley wednesday.
Meanwhile...atm will likely hold onto the inversion through
tonight. Wind speeds will increase as the short wave over the
great basin tracks east quickly becoming negatively tilted over
western arkansas. This dynamic system will create a low level jet
at 850mb of 40 to 60 knots from north louisiana to west tennessee
tonight and breezy to windy condition at the surface
today...especially around btr. More speed shear across southern
mississippi and southeast louisiana...00z gfs run showed srh
approaching 700 m/s at 06z over northwest zones. However...06z gfs
has backed down to 360 m/s tonight and decrease wednesday. The
strong cap may contain a good majority of the convection today and
tonight. Strong forcing along the frontal boundary should create a
focus for linear storms wednesday morning. Timing of this system and
lack of surface heating may create strong to severe storms just
west of the area tonight and storms east of the area wednesday
into wednesday night. Slight risk of severe storms is possible
wednesday morning with isolated wind damage...but higher risk around
the forecast area. Pacific system will not drive the associated
surface boundary too far south into the coastal waters wednesday
and thursday. The next short wave that tracks east across the mid
section conus will tap the old boundary north across the area
friday. Gfs clears the front while ecmwf meander a messy boundary
over the forecast area over the weekend. Will lean toward gfs for
now.

&&
.aviation...
/preliminary 12z tafs/
as southerly winds continue to bring low level moisture in the
form low ceilings back into the area this morning. Expect to see
bkn015 as prevailing at most sites with tempo groups around
bkn005-010 as cold front passes to the north of the region. Cigs
will begin to lift after sunrise with the help of daytime heating
and winds strengthen into the 10 to 15 knot range. Ceilings will
rise to around bkn050 by afternoon and drop quickly during the
late afternoon and evening to bkn015-020. Tonight looks to repeat
the same conditions we see this morning. Expect another windy day
today.

&&

.marine...
A tightening pressure gradient will continue to result in strong
southerly winds over the coastal waters as a series of short waves
quickly move through the middle and lower mississippi valley. A long
fetch over the gulf will provide higher seas to 7 feet over most of
the outer waters. These seas will find their way into the 15 to 20
mile area of the inner water zones as well before subsiding to
around 5 feet by 10 miles out. Winds look to maintain around 20
knots with frequent gusts into the lower 20 knot range. For these
reasons...will bring up small craft advisory for all gulf waters.
Winds will maintain a range of 15 to 20 knots over the lakes so will
hold on to exercise caution headlines there.

A cold front will move through the coastal waters on wednesday with
winds expected to continue in the 20 to 25 knot range over the gulf
waters. Advisories will likely continue for all gulf coastal waters
ahead of the cold front. Behind the front...a weak surface ridge
will build into the area...but will quickly move east as another
front is expected to move through the region on friday. Another high
will build in behind this second front and will remain in place
through the weekend.


New Orleans Local Weather thread - dkmac - 02-11-2009 08:11 AM

Hazardous Weather Outlook
HAZARDOUS WEATHER OUTLOOK
NATIONAL WEATHER SERVICE NEW ORLEANS LA
636 AM CST WED FEB 11 2009

GMZ530-550-555-570-575-LAZ034>040-046>050-056>070-MSZ068>071-077-
080>082-111700-
LAKE PONTCHARTRAIN AND LAKE MAUREPAS-
COASTAL WATERS FROM THE SOUTHWEST PASS OF THE MISSISSIPPI RIVER
TO LOWER ATCHAFALAYA RIVER LA OUT 20 NM-
COASTAL WATERS FROM PASCAGOULA MS TO THE SOUTHWEST PASS OF THE
MISSISSIPPI RIVER OUT 20 NM-
COASTAL WATERS FROM THE SOUTHWEST PASS OF THE MISSISSIPPI RIVER
TO LOWER ATCHAFALAYA RIVER LA FROM 20 TO 60 NM-
COASTAL WATERS FROM PASCAGOULA MS TO THE SOUTHWEST PASS OF THE
MISSISSIPPI RIVER FROM 20 TO 60 NM-POINTE COUPEE-WEST FELICIANA-
EAST FELICIANA-ST. HELENA-TANGIPAHOA-WASHINGTON-ST. TAMMANY-
IBERVILLE-WEST BATON ROUGE-EAST BATON ROUGE-ASCENSION-LIVINGSTON-
ASSUMPTION-ST. JAMES-ST. JOHN THE BAPTIST-UPPER LAFOURCHE-
ST. CHARLES-UPPER JEFFERSON-ORLEANS-UPPER PLAQUEMINES-
UPPER ST. BERNARD-UPPER TERREBONNE-LOWER TERREBONNE-
LOWER LAFOURCHE-LOWER JEFFERSON-LOWER PLAQUEMINES-
LOWER ST. BERNARD-WILKINSON-AMITE-PIKE-WALTHALL-PEARL RIVER-
HAN****-HARRISON-JACKSON-
636 AM CST WED FEB 11 2009

THIS HAZARDOUS WEATHER OUTLOOK IS FOR PORTIONS OF COASTAL WATERS
OF SOUTHEAST LOUISIANA AND SOUTH MISSISSIPPI...SOUTHEAST
LOUISIANA AND SOUTHERN MISSISSIPPI.

.DAY ONE...TODAY AND TONIGHT
A COLD FRONT IS EXPECTED TO MOVE EAST ACROSS SOUTHEAST LOUISIANA
AND SOUTHERN MISSISSIPPI TODAY. THUNDERSTORMS ARE EXPECTED TO
REDEVELOP JUST AHEAD AND ALONG THE FRONT. ONE OR TWO STORMS MAY
BECOME SEVERE WITH DAMAGING WINDS ACROSS THE MISSISSIPPI COAST
LATER THIS MORNING INTO THIS AFTERNOON.

IN ADDITION...A SMALL CRAFT ADVISORY IS IN EFFECT FOR TIDAL LAKES
AND COASTAL WATERS THROUGH THIS AFTERNOON.

.DAYS TWO THROUGH SEVEN...THURSDAY THROUGH TUESDAY

ANOTHER COLD FRONT AND AREA OF LOW PRESSURE IS EXPECTED TO IMPACT
THE REGION FRIDAY INTO FRIDAY NIGHT. AT THIS TIME...IT APPEARS
THAT ATMOSPHERIC CONDITIONS WILL BE FAVORABLE FOR STRONG THUNDERSTORM
DEVELOPMENT.

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE NEW ORLEANS LA
418 AM CST WED FEB 11 2009

.SHORT TERM...
LATEST SURFACE ANALYSIS SHOWED A 998MB LOW OVER EASTERN MISSOURI
WITH A COLD FRONT EXTENDING SOUTHWEST TO THE ARKLATEX REGION AND ANOTHER
999MB LOW OVER NORTH CENTRAL OKLAHOMA. UPPER AIR ANALYSIS SHOWED
THE ASSOCIATED TROUGH AXIS FROM SOUTHWEST KANSAS TO NORTH CENTRAL
TEXAS. REGIONAL RADAR SHOWED WEAKENING CONVECTION FROM NORTH
CENTRAL LOUISIANA TO SOUTHWEST LOUISIANA. BALLOON SOUNDING FROM
TUESDAY EVENING SHOWED THE INVERSION AT 700MB AND CAPE VALUE 70
J/KG. LIGHTNING DETECTION SYSTEM SHOWED A STRIKE TOTAL NEAR 800
IN 15 MINUTES AROUND MIDNIGHT ALONG THE LINE OF STORMS. AT
09Z...LDS SHOWED A STRIKE TOTAL NEAR 30 IN 15 MINUTES. ISOTACH
ANALYSIS SHOWED THE JET MAX OF 130 TO 140 KNOTS FROM EAST TEXAS TO
CENTRAL ARKANSAS. THE TROUGH AXIS IS EXPECTED TO ROTATE EAST AND
BECOME MORE NEGATIVELY TILTED. THE ASSOCIATED VORT MAX WILL REMAIN
WELL NORTH. LOSS OF HEATING AND CONVECTION ENTERING INTO A STRONG
CAP ENVIRONMENT HAVE CREATED A DAMPENING FEATURE FOR THUNDERSTORM
DEVELOPMENT WELL AHEAD OF THE FRONTAL BOUNDARY. CONVECTION ALONG THE
FRONTAL BOUNDARY THIS MORNING WILL MORE LIKELY OCCUR. MORNING
SURFACE HEATING MAY HELP BUST CAP AND A REDEVELOPMENT OF
CONVECTION IS EXPECTED. THE MAIN THREAT FROM THIS LINEAR CONVECTION IS GUSTY
WINDS...ONE OR TWO WITH DAMAGING WIND STORMS. AFTER THE
PASSAGE...UPPER LEVEL FLOW REMAINS WEST TO SOUTHWEST AND THE
SURFACE BOUNDARY WILL NOT DRIVE THAT FAR SOUTH. THE NEXT
SYSTEM...CURRENTLY OVER JUST WEST OF OREGON...IS EXPECTED TO TRACK
EAST ACROSS THE CENTRAL PLAINS AND MID MISSISSIPPI VALLEY. AS PREV
GFS RUNS ADVERTISED...THIS WAVE WILL TAP THE OLD BOUNDARY AND PULL
MOISTURE NORTH ACROSS THE FORECAST AREA LATE THURSDAY AND FRIDAY.
WITH THE RIGHT TIMING OF THIS SYSTEM AND GOOD SURFACE HEATING
FRIDAY...CONVECTION WILL BE SCATTERED TO NUMEROUS FRIDAY
AFTERNOON OVER THE FORECAST AREA. UPPER LEVEL FLOW REMAINS WESTERLY
THURSDAY THROUGH EARLY SUNDAY...MEANING SOME LINGERING MOISTURE
MAY NOT EQUATE TO A CLEAN PASSAGE OF THIS SYSTEM. WILL LINGERING
CLOUDS IN GRIDS FOR SAT. ECMWF STILL CALLING FOR A WET SAT WITH A
MEANDERING FRONTAL BOUNDARY. CONFIDENCE IS NOT HIGH FROM SAT
THROUGH TUES. ECMWF AND GFS BOTH SHOW ANOTHER SYSTEM AFFECTING THE
SOUTH HALF AREA SUNDAY FOLLOWED BY ANOTHER SYSTEM TUESDAY.

&&

.AVIATION...
/PRELIMINARY 12Z TAFS/
EXPECT STRONG SOUTHERLY WINDS TO PERSIST AT ALL TERMINALS UNTIL THE
COLD FRONT MOVES THROUGH THE AREA. BEST CHANCES OF SH/TS WILL BE
ASSOCIATED WITH THE COLD FRONT. EXPECT FRONT TO MOVE THROUGH BTR
~14Z...MCB ~15Z...MSY ~17Z...GPT ~19Z. WINDS WILL SHIFT TO THE WEST
THEN NORTHWEST AND WEAKEN SIGNIFICANTLY FOLLOWING THE FRONTAL
PASSAGE. VFR CONDITIONS ARE EXPECTED AFTER FROPA AS CEILINGS LIFT TO
OVC100 THEN CLEAR OVERNIGHT.

&&

.MARINE...
STRONG SOUTHERLY AND SOUTHEASTERLY WINDS WILL PERSIST OVER THE
COASTAL WATERS THIS MORNING AS A COLD FRONT MOVES TOWARD THE
AREA. A LONG FETCH OVER THE GULF WILL CONTINUE TO RESULT IN ELEVATED
SEAS...ESPECIALLY BEYOND 15 NM FROM THE SHORELINE. AS THE COLD FRONT
PASSES...WINDS WILL BEGIN TO LAY QUITE A BIT AND SEAS WILL RESPOND
FALLING BELOW SMALL CRAFT ADVISORY CRITERIA DURING THE AFTERNOON. A
SWELL TRAIN WILL CONTINUE TO PRODUCE 3 TO 4 FT SWELL THROUGH THE
EARLY EVENING. THESE SEAS SHOULD ALSO FALL AS WE MOVE INTO THURSDAY.

THE RIDGE BEHIND THE COLD FRONT WILL QUICKLY MOVE EAST ALLOWING
ANOTHER FRONT TO MOVE THROUGH THE REGION ON FRIDAY. ANOTHER HIGH
WILL BUILD IN BEHIND THIS SECOND FRONT AND REMAIN IN PLACE THROUGH
THE WEEKEND.


New Orleans Local Weather thread - ROLLTIDE - 02-12-2009 01:19 AM

FXUS64 KLIX 120509 AAA
AFDLIX

AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE NEW ORLEANS LA
1109 PM CST WED FEB 11 2009

.UPDATE...
...06Z TAF DISCUSSION...

VFR CONDITIONS WILL BE THE RULE THROUGH THE PERIOD. SCATTERED HIGH
CLOUDS WILL PERSIST THROUGH THE PERIOD...WITH THE POSSIBILITY OF
SOME MID-LEVEL CLOUDS FILTERING IN AFTER 00Z AS ISENTROPIC LIFT
OVER A WEAK FRONTAL BOUNDARY IN THE GULF OF MEXICO BEGINS TO
DEVELOP. THIS ISENTROPIC LIFT WILL PLAY A BIGGER ROLE IN THE
FORECAST BEYOND 24 HOURS. WINDS WILL SHIFT THROUGH THE
PERIOD...FROM A NORTHWESTERLY COMPONENT TONIGHT TO A MORE
NORTHEASTERLY AND THEN EASTERLY COMPONENT FOR TOMORROW.

&&

.PREV DISCUSSION... /ISSUED 343 PM CST WED FEB 11 2009


New Orleans Local Weather thread - dkmac - 02-12-2009 06:59 AM

Area forecast discussion
national weather service new orleans la
421 am cst thu feb 12 2009

.discussion...
Latest surface analysis showed a 1022mb high over louisiana and
arkansas. The old frontal boundary was from the carolinas to
apalachee bay to 27n directly south of mississippi river. Upper air
analysis showed the next wave over northern california and nevada.
Isotach analysis revealed the jet stream from the great basin east to the
mid atlantic states and a jet max of 120 knots just ahead of the
wave axis. This short wave is expected to track east across the
rockies...central plains and mid mississippi valley today through
friday night. With the surf high moving east and the somewhat approaching
wave...this pattern should allow the old boundary to drift north.
Model sounding shows a deeper moisture coming back and more
instability. Cape values may increase up to 1500 j/kg by friday
night. With the track of the wave and dynamics so far
north...convection may not be as uniformed or linear as wind
profile becomes more speed shear through friday and friday night.
Gfs isotachs at 250mb shows a couplet over the area friday with the
southern stream increasing old mexico and other jet residing from
the mid south to the mid atlantic states friday. Precipitable
water values are expected to increase above 1.5 inches friday
afternoon and friday night. Different features are suggesting
differing degree of convection. Either way...the forecast will be
more wet than dry for friday and friday night. Have eluded in past
discussions of the northern track of wave friday possibly not
providing a push needed for the surf boundary to clear the land
and sea forecast area early saturday. Ecmwf models were similar
from run to run with not clearing the front saturday...will go
between gfs and ecmwf and linger rain chances through saturday
night. Both do agree on some clearing the second system sunday
into sunday. In addition...both are in agreement with a system
affecting the forecast area tuesday into wednesday.

&&

.aviation...
/preliminary 12z tafs/
vfr conditions will prevail through 06z friday. After that
time...isentropic lift approaching from the west will begin to
saturate the mid and low levels of the airmass from the west. Expect
everyone to remain vfr through 12z friday...but probably not much
longer after that at kbtr. 35
&&

.marine...
The cold front has moved entirely south of the area and seas have
responded to the lighter winds. Seas have fallen to 3 feet at buoy
42007 and 5 feet at buoy 42040. High pressure centered over the
lower mississippi river valley will quickly move eastward as another
cold front approaches the area on friday. This front is expected to
stall over the coastal waters and linger in the area through the
weekend. The following system around sunday night or monday will be
the next time that headlines may be needed for the coastal waters. 35


New Orleans Local Weather thread - dkmac - 02-13-2009 06:10 AM

Area forecast discussion
national weather service new orleans la
410 am cst fri feb 13 2009

.short term...
Latest surface analysis showed a broad 1022mb high over georgia
and florida and the old frontal boundary extending from central
florida to the north central gulf...around 28n. Circulation around
the high will allow the flow to become southerly and allow the old
boundary to drift north today. In addition...a developing low was
located over the texas panhandle was producing a southeast flow
texas. Upper air analysis revealed a short wave over colorado and
the jet stream from southwest conus to central plains to the mid
atlantic states. Short range models are in agreement with a
weakening short wave over colorado ejecting east toward the great
lakes by saturday. This features will maintain a southwest flow in
the mid layers and increase atm instability tonight into saturday.
Model cape values slowly increase to today and really increase up
to 1100 to 1500 j/kg over the forecast area tonight into saturday.
In addition...pw values increases up to 1.6 to 1.8 inches by this
afternoon. Some warming in the mid layers for only today may limit
some convection...but less warming tonight into saturday. As a
result...more showers today and little more convection tonight and
saturday. To the associated surface low will push east and drag a
cold front into the region saturday. With the main surface high
remaining north through sunday and west to southwest flow
aloft...the frontal push will be slow and training of storms is
possible late tonight and saturday. Will mention heavy rainfall in
weather outlook for sat along the slow boundary...up to 2 inches.
Looking for the high up north to slowly build south and drive the
front through area. Some help will come from up above. A second
wave will track east across the rockies to the mid mississippi
valley...a little farther south than the first...will slowly yield
west to northwest flow aloft. This should push the moisture
southeast away from the forecast area late sunday. Ecmwf...ukmet
and gfs are in agreement with next system pushing across the
tuesday into wednesday.

&&

.aviation...
/preliminary 12z tafs/
vfr conditions will be short lived this morning. Clouds around 3k
feet have moved into about the southern half of the area...and are
already producing ceilings in the new orleans metro area...including
kmsy. 295k isentropic chart shows saturation as low in the column as
980 mb...near 1k feet...as early as 18z at most or all terminals.
Expect prevailing ceilings to fall into the ifr range by early
afternoon with vsbys in the mvfr to ifr range in rain. Isolated tsra
also possible. With frontal boundary to move into the area and
become stationary overnight...anticipate little if any improvement
through 12z saturday. 35

&&

.marine...
Easterly winds will become more southeasterly and then southerly as
the surface ridge continues to move eastward and a cold front
approaches from the west. This front is expected to stall over the
coastal waters and linger in the area through the weekend. Another
frontal system will move through the area sunday evening with a
stronger ridge building in behind it. As this high builds into the
coastal waters...headlines may be needed on monday...but do not
anticipate any much before then. 35


New Orleans Local Weather thread - dkmac - 02-14-2009 07:44 AM

Short Term Forecast
SHORT TERM FORECAST
NATIONAL WEATHER SERVICE NEW ORLEANS LA
557 AM CST SAT FEB 14 2009

GMZ530-LAZ035>040-046>050-056>058-MSZ069>071-077-141400-
LAKE PONTCHARTRAIN AND LAKE MAUREPAS-WEST FELICIANA-
EAST FELICIANA-ST. HELENA-TANGIPAHOA-WASHINGTON-ST. TAMMANY-
IBERVILLE-WEST BATON ROUGE-EAST BATON ROUGE-ASCENSION-LIVINGSTON-
ASSUMPTION-ST. JAMES-ST. JOHN THE BAPTIST-AMITE-PIKE-WALTHALL-
PEARL RIVER-
INCLUDING THE CITIES OF...ST. FRANCISVILLE...JACKSON...CLINTON...
GREENSBURG...MONTPELIER...HAMMOND...PONCHATOULA...BOGALUSA...
FRANKLINTON...SLIDELL...MANDEVILLE...COVINGTON...LACOMBE...
PLAQUEMINE...WHITE CASTLE...PORT ALLEN...ADDIS...BRUSLY...
BATON ROUGE...GONZALES...DONALDSONVILLE...DENHAM SPRINGS...
WALKER...PIERRE PART...LABADIEVILLE...PAINCOURTVILLE...LUTCHER...
GRAMERCY...LAPLACE...RESERVE...GLOSTER...LIBERTY...CROSBY...
MCCOMB...TYLERTOWN...PICAYUNE
557 AM CST SAT FEB 14 2009

.NOW...

SCATTERED TO NUMEROUS SHOWERS AND THUNDERSTORMS WILL CONTINUE
ACROSS SOUTHEAST LOUISIANA AND COASTAL MISSISSIPPI COUNTIES.
EXPECT RAINFALL RATES OF UP TO A HALF INCH PER HOUR AND LOCALLY
HEAVIER RAINFALL RATES OF UP TO TWO INCHES ASSOCIATED WITH STRONGER
STORMS...GUSTY WINDS WILL BE POSSIBLE. THIS WILL CAUSE PONDING OF WATER
ON ROADWAYS AND FILL UP DRAINAGE DITCHES.

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE NEW ORLEANS LA
339 AM CST SAT FEB 14 2009

.SHORT TERM...
ACTIVE WEATHER PATTERN IN STORE FOR REGION NEXT 36 HOURS AS QUASI
STATIONARY FRONTAL BOUNDARY ACTS AS FOCUS FOR CONVECTION AS
SEVERAL SPEED MAX IN SOUTHERN JET STREAM MOVES ACROSS THE REGION.
THE BOUNDARY IS EXPECTED TO SAG SOUTH SOME TODAY WITH MODEL
GUIDANCE SUGGESTING WEAK WAVE OR LOW TO DEVELOP ALONG THE BOUNDARY
THIS EVENING AS SHORT WAVE IN JET STREAM MOVES ACROSS REGION.
MODEL SOUNDINGS INDICATE THAT DEEP MOISTURE IN PLACE OVER REGION
TODAY WITH PRECIP WATER NEAR 1.7 INCHES. WITH DEEP MOISTURE AND
QUASI STATIONARY BOUNDARY LOCALIZED HEAVY RAINFALL IS CERTAINLY
POSSIBLE. IN ADDITION AS SURFACE WAVE LATER TODAY LOW LEVEL WIND
FIELD STRENGTHENS INCREASING VERTICAL WIND SHEAR PROFILES
SUGGESTING THREAT OF SEVERE THUNDERSTORMS. MID AND UPPER FLOW
EVENTUALLY BECOMES MORE W TO NW ON SUNDAY ALLOWING SURFACE TO
BUILD SOUTH OVER REGION AND PUSHING DEEPER MOISTURE EASTWARD.

.LONG TERM...
DRIER WEATHER IN STORE ON MON AND TUE WITH MOISTURE RETURNING MID
WEEK RETURN FLOW OFF THE GULF STARTS AS DISTURBANCE IN SOUTHERN JET
STREAM MOVES ACROSS AREA. MORE SIGNIFICANT TROUGH IN NORTHERN JET
STREAM DEEPENS MEAN TROUGH POSITION ON EAST COAST BY LATE WEEK
ALLOWING MUCH STRONG SURFACE HIGH TO PUSH INTO THE GULF BRINGING
COOLER TEMPS AND LOWER HUMIDITIES.

&&

.AVIATION...
IFR CONDITIONS...ALONG WITH OCCASIONAL LIFR CONDITIONS...SHOULD
PREVAIL. STRONG CONVECTIVE WIND GUSTS POSSIBLE NEAR STRONGER
THUNDERSTORMS.


&&

.MARINE...
LIGHT TO MODERATE S AND SW FLOW PREVAILS BEFORE HIGH PRESSURE
BUILDS INTO COASTAL WATERS LATER SUNDAY. SMALL CRAFT ADVISORY
CONDITIONS POSSIBLE SUNDAY NIGHT INTO MONDAY.


New Orleans Local Weather thread - dkmac - 02-15-2009 06:54 AM

Area forecast discussion
national weather service new orleans la
321 am cst sun feb 15 2009

.synopsis...
Last nights frontal system is to the south of the area this
morning with an inverted surface trof pretty much running north-
south along interstate 55. Numerous showers and isolated thunder
continue to be observed on radar with the back edge of the main
area of precipitation just reaching the atchafalaya river at 09z.
Temperatures generally in the 50s across the area.
&&

.short term...
Short term issue is precipitation chances during the day today.
First period pops look pretty good from previous forecast...but
some minor adjustments may be needed based on radar trends just
before press time. Most precipitation should cut off with the
passage of a northern stream shortwave to the north. Expect this
to happen around 18z...with most of the afternoon remaining dry.

High pressure will move from the dakotas this morning to the east
coast by tuesday. This will allow southerly flow to bring moisture
back to the area as early as monday night...but more noticeable
tuesday. Will need to have small pops for late monday
night...chance pops for tuesday as warm advection should allow
some precipitation to develop. Cold front moves through wednesday
afternoon to end all precipitation.

Temperatures will be slightly below normal through tuesday. For
today...kept most of previous forecast...except for trimming a few
degrees far north...where mccomb a little bit more into cooler
air. Temperatures well above normal on wednesday ahead of next
cold front. 35
&&

.long term...
High pressure will move from the rockies on wednesday...to the
gulf of mexico by friday...and should control the weather across
the area thursday through all of next weekend. Northwest flow will
allow cold fronts to pass through the area dry. Temperatures
expected to average about 5 to 7 degrees below normal for the
thursday through sunday time frame. 35
&&

.aviation...
A cold front remains stationary along the louisiana coastal waters.
Numerous elevated showers have overspread southeast louisiana. A few
elevated thunderstorms are located in the coastal marches south of
new orleans. Ifr ceilings will be the rule this morning across
southeast la and southwest mississippi where the showers are most
numerous. The showers should be moving into the mississippi coastal
area during the next couple of hours brining onset of ifr ceilings.
Rainfall will gradually taper off from west to east by late morning
into the afternoon as the low pressure area moves east along the
louisiana and mississippi coastal waters. Ceilings should gradually
improve to mvfr as cooler...drier air moves into the bi state area.
&&

.marine...
Satellite imagery and radar data indicate that the showers and
thunderstorms are warm topped early this morning. Winds will become
more northerly as the low moves east of the area today. High
pressure will build over the lower mississippi valley tonight and
monday. The high will move east on tuesday as a cold front
approaches louisiana from the west. The cold front will move through
the louisiana and mississippi coastal waters on thursday. Small
craft conditions could develop over the coastal waters tuesday night
and wednesday. At this time i do not plan to make any significant
changes to the forecast grids.
&&


New Orleans Local Weather thread - dkmac - 02-16-2009 06:44 AM

Area forecast discussion
national weather service new orleans la
331 am cst mon feb 16 2009

.synopsis...
Axis of surface high this morning pretty much north-south over the
mississippi river valley. Cold front from saturday well south over
the southern gulf of mexico. Shortwave ridging moving eastward
from the rockies into texas. Quite a bit of cirrus coming over the
ridge into southwest portions of the area. Early morning
temperatures range from the lower 40s north to mid 50s far south.
&&

.short term...
Have gone with the somewhat slower gfs solution...as nam solution
an outlier compared to most other forecast models this run. Southern
stream to remain active through the short term period. Next
shortwave to start inducing isentropic lift over the cooler low
level air after midnight tonight for our area. Isentropic charts
show that we shouldn`t reach saturation until just before sunrise
tuesday...and mainly over the west. Will hold previous pops...with
any measurable precipitation limited to a few hundredths at most.
Chances for rain continue through tuesday...mainly over western
portions of the area...as southerly low level flow kicks in.

Shortwave in southern stream passes to our north tuesday night
into wednesday...as the associated surface low moves from colorado
to near lake erie by wednesday night. This will eventually drag a
cold front through the area wednesday night. Convection expected
to develop in advance of the front...with lifted indices around -4
and capes around 800-1000. Enough helicity available for
supercells...although better values to our north. Assuming we get
enough sunshine to reach the lower and mid 70s...severe weather a
good possibility. Will continue mention in hwo.

Temperatures should be 1 to 2 categories cooler today than on
sunday. This would generally be about 5 degrees below normal for
mid february. While boundary layer temperatures would indicate 5
to 7 degrees of warming tomorrow...cloud cover likely to cancel
most or all of this out. Wednesday to be much warmer as southerly
flow strengthens ahead of frontal system...generally mid 70s. 35
&&

.long term...
After frontal passage wednesday night...clear sailing through the
extended period. Northwest flow keeps things mostly dry...but cool
through the weekend. A strong system moving through the great
lakes will pull another front through on saturday...but the gulf
is pretty much closed for business after wednesday night...so no
significant precipitation is expected. Temperatures generally 5 to
10 degrees above normal through the weekend...but signs of a
warmup in both gfs and ecmwf solutions for early next week. 35
&&

.aviation...
/12z taf issuance/
significant high and mid clouds will spread into region during the
next 6 to 12 hours. Visibilities unrestricted as gusty winds persist
mainly around kmsy to kgpt. Vfr ceiling and visibilities will
persist...although clouds will increase and lower after midnight...
As next weather system spreads into region. Looking past this 24
hour package...on tuesday may get brief mvfr visibility/ceilings in
convective precipitation. 47
&&

.marine...
Offshore flow is expected to increase to around 20 knots with seas
building up toward 7 feet...as high pressure continues to build
south over the north gulf. Small craft should exercise caution
headlines will remain in place for the lakes pontchartrain and
maurepas...along with the inner coastal waters through 6 am this
morning. Small craft advisory is in effect for outer coastal waters
through noon today. 47


New Orleans Local Weather thread - dkmac - 02-17-2009 07:46 AM

Area forecast discussion
national weather service new orleans la
338 am cst tue feb 17 2009

.short term...
Winds have generally shifted to an easterly direction and will
continue to veer to a more southeastward direction by this
afternoon. The southerly component will help bring moisture back
into the area as a cold front approaches the area from the west.
Expect at least a few showers to pop up today driven mainly by
diurnal heating. Will carry chance pops for the northwest portion
of the area and slight chance for the southeast portion.

Chance of rain will continue to increase tonight as the front
nears...but best chances will be wednesday with high end chance
or likely pops across the entire area. Additionally...spc has
outlooked the area in a slight risk zone for wednesday. Sounding
analysis reveals li values across the area in the -2 to -4 degree
range with cape generally in the 600 to 1000 j/kg range. Storm
relative helicity will also be conducive for rotating updrafts
with values of up to 450 m2/s2. These high values are mainly due
to speed shear owing to a 50+ knot jet forecast to develop at 500
mb. The right entrance region of said jet is forecast to move
through the area...so lift shouldn/t be a problem either. Looks
like the limiting factor will be whether there are enough breaks
in the clouds for sufficient diurnal heating to kick start
surface-based convection. In any case...the biggest threats will
be hail and damaging winds.

.long term...
The front should finally move through the area wednesday afternoon
with a quick end to rain chances behind it since the front is
expected to have a strong enough push to move entirely through
the gulf. A reinforcing front is forecast to move through the
region saturday...but with limited moisture due to a very short
period of return flow...will only carry slight chance pops at this
time. Behind saturday/s front...dry high pressure will take hold
for sunday but is forecast to move quickly eastward as another
frontal system takes shape over the plains states during the first
part of next week.

&&

.aviation...
/12z tafs/
vfr conditions are expected to prevail at each of the terminal sites
today and through the early evening. Ceilings are expected to
gradually lower during the period. Mvfr ceilings will be possible
this evening after 00z on the 18th at kbtr and kmcb. It appears
that the best chance for any showers will hold off until after the
taf forecast period.

&&

.marine...
High pressure is expected to shift east of the area today as low
pressure deepens over the central plains. This will cause winds to
become southeast to south and increase this afternoon through
tonight as this deep low moves northeast across mid mississippi
valley late tonight. Conditions are expected in sca criteria tonight
and possibly wednesday...with sca more likely near and behind the
cold frontal passage wednesday night and thursday morning and again
thursday night. Gfs bl winds are about 6 to 9 knots higher than
emcwf over the coastal wednesday night. We went between the
two...both show significant drops in thickness layers after fropa
through friday morning. Cold may have a bite across waters near 60
degree. Another cold front is expected to increase winds and seas
again saturday night.


New Orleans Local Weather thread - dkmac - 02-18-2009 06:33 AM

hazardous weather outlook
national weather service new orleans la
1058 pm cst tue feb 17 2009

there is a slight risk of severe weather across the area on
wednesday. Thunderstorms are expected to develop ahead of an
approaching cold front and move through the area during the
daytime hours. The greatest threat will be damaging winds. Other
lesser threats include hail...frequent cloud to ground lightning
and isolated tornadoes. The area of greatest concern will be north
of the interstate 10 and 12 corridor.

Coastal hazards...a small craft advisory is in effect through
thursday morning as winds increase ahead of an approaching cold
front and continue behind the boundary. Seas in excess of 8 feet
will be possible wednesday night.

.spotter information statement...

The activation of storm spotters...ham radio operators...and
emergency management personnel in support of severe weather
operations...may be needed tomorrow.

area forecast discussion
national weather service new orleans la
347 am cst wed feb 18 2009

.synopsis...
Surface low pressure is centered over north central missouri wish
a cold front extending southwestward through central texas. A warm
front extends from the low southeastward through northeastern
arkansas and into central mississippi and alabama. A secondary cold
front extends from the surface low westward and northwestward
through the plains states.

Most of the local area is experiencing cloudy skies with
temperatures in the mid and upper 60s. Lows for the night have
already been reached and temperatures have been rising for the
past few hours due to increasing southerly flow.

&&

.discussion...
Main concern this package will be the potential for severe weather
today. Models continue to forecast cape values of 500 to 800 j/kg
across the area with li values of -2 to -4 degrees and plenty of
lift owing to forcing from a cold front and a 500 mb jet streak.
Storm relative helicity values range from 400 to 500 m2/s2 mainly
due to speed shear associated with the 500 mb jet streak. With
unidirectional flow forecast by noon today...expect the main
threats to be large hail and damaging wind gusts. The latter will
depend on whether the convection remains surface-based through the
afternoon. It looks like the highest probability of severe
weather will be far displaced to the northeast...over central
alabama. However...a few severe thunderstorms may affect the local
forecast area...mainly north of the interstate 10 corridor. Spc
has outlooked the majority of the local are in a slight risk zone.
For more detailed information...please refer to products issued by
the storm prediction center.

The cold front is expected to move through the local area this
afternoon and into tonight. Behind the front...expect rapid
clearing and a significant cool down for thursday. The high will
become centered over the region thursday night with min temps
forecast well below normal. A light freeze looks likely across
areas north of interstate 10 and east of interstate 55. The last
time any part of the local area experienced freezing temperatures
was over a month ago...so freeze products may need to be
considered as friday morning nears.

The high is forecast to shift eastward friday afternoon as another
cold front approaches the area. There are some minor timing
differences between the major models concerning this front. The
gfs and nam depict the front approaching the northwestern zones by
noon saturday...which is about 6 hours faster than the ecmwf. In
addition to timing differences...the gfs is wetter than the other
two models. For the time being...will go with a compromise between
the models.

High pressure builds into the area again behind the front for what
appears to be a gorgeous sunday. Beyond sunday...there are
significant differences between the major models. The gfs shifts the
high eastward by monday yielding southeasterly or southerly winds
that will help bring deep moisture back into the area as a cold
front approaches the area. The result is a wet forecast for monday
and tuesday. Conversely...the ecmwf holds the high in place an
extra day which yields a much drier forecast for monday and
tuesday. With such significant differences in the far extended...
Will continue to carry a slight chance of showers and
thunderstorms for both days. This will prove to be underdone if
the gfs is correct and overdone if the ecmwf is correct...so
future forecasts will need to refine the details of this system as
the time approaches.

&&

.aviation...
/12z taf issuance/
mvfr ceilings should play out most of the day. A few shra may impact
the kmcb and kbtr terminals during the early morning...but better
lift arrives later today and should begin to see sh/ts develop from
10am through the evening. Strongest ts activity should hold off
until after 18z today. Main issues expected with any severe wx will
be hail and high wind speeds causing shear near and around terminals
if one is nearby.

&&

.marine...
South winds will continue around 20 to 25 knots over the coastal
waters today as the deep surface low moves northeast from the
central plains to the mid mississippi valley. Marginal small craft
advisories/sca/ today. May see stronger sca conditions with 25 to 30
knots northerly winds tonight. There will be a bit of reprieve
thursday afternoon...then sca conditions may redevelop again
thursday night due to another cold air mass intrusion. Winds will become
light friday into early saturday...then another cold front is
expected to increase winds and seas again saturday night.