Area Forecast Discussion
Issued by NWS New Orleans/Baton Rouge, LA

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395
FXUS64 KLIX 241426
AFDLIX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE NEW ORLEANS LA
826 AM CST WED DEC 24 2014

.SOUNDING DISCUSSION...
AFTER THE FRONTAL PASSAGE...NORTHWEST WINDS WERE PRESENT FROM SURF
TO 4KFT THEN WEST TO SOUTHWEST ABV. PRECIP WATER VALUES DECREASED
TO 0.75 WITH MOST OF THE DRY AIR ABV 700MB. STRONG SOUTHWEST WINDS
OF 130 KNOTS WERE NOTED AROUND 250MB OR 34000 FEET AHEAD OF THE
MAIN TROUGH.

&&

.PREV DISCUSSION... /ISSUED 411 AM CST WED DEC 24 2014/

SHORT TERM...

SURFACE RIDGING AND ATTENDANT DRY AND COLD AIR ADVECTION WILL
CONTINUE ACROSS THE FORECAST AREA THROUGH THE DAY. AT THE SAME
TIME...A DEEP UPPER LEVEL TROUGH AXIS WILL ALSO MOVE THROUGH THE
LOWER MISSISSIPPI VALLEY AND GULF SOUTH. STRONG GRADIENT FLOW
ASSOCIATED WITH THIS MID AND UPPER LEVEL TROUGH WILL CONTINUE
THROUGH THE DAY RESULTING IN CONTINUED NORTHWEST WINDS OF 15 TO 20
MPH FOR MUCH OF THE DAY. WITH 1000-500MB THICKNESSES PLUNGING TO
AROUND 5340 METERS AND 925 MB TEMPERATURES DROPPING TO NEAR 0
DEGREES CELSIUS...DAYTIME HIGHS WILL STRUGGLE TO CLIMB INTO THE
MIDDLE 50S THIS AFTERNOON.

THE GRADIENT FLOW WILL RAPIDLY DIMINISH TONIGHT AS SURFACE RIDGING
BECOMES CENTERED DIRECTLY OVER THE FORECAST AREA. WITH CLEAR
SKIES AND DRY CONDITIONS ALREADY IN PLACE...TEMPERATURES WILL
EASILY PLUNGE INTO THE LOWER TO MIDDLE 30S OVER MOST OF THE
FORECAST AREA LATE TONIGHT. A LIGHT FREEZE WILL BE POSSIBLE FOR
AREAS NORTH OF THE INTERSTATE 12 CORRIDOR.

TOMORROW WILL BE A DAY OF TRANSITION AS THE SURFACE HIGH SHIFTS TO
THE EAST...AND A A MID TO UPPER LEVEL RIDGE AXIS BUILDS OVER THE
AREA. STRONG SUBSIDENCE WILL CONTINUE THROUGHOUT THE ATMOSPHERIC
COLUMN...SO CLEAR SKIES ARE EXPECTED. ALTHOUGH THE HEART OF THE
UPPER LEVEL COLD POOL WILL HAVE MOVED EAST OF THE REGION
TOMORROW...TEMPERATURES SHOULD STILL RUN ABOUT 5 DEGREES BELOW
AVERAGE DUE TO THE COLD MORNING START AND CONTINUED WEAK OFFSHORE
FLOW. WINDS WILL FINALLY BEGIN TO VEER TO A MORE ONSHORE COMPONENT
THURSDAY EVENING...AS THE HIGH PUSHES FURTHER TO THE EAST. AT THE
SAME TIME...AN UPPER LEVEL VORT LOBE WILL SLIDE UP FROM THE
SOUTHWEST GULF OF MEXICO AND PASS THROUGH THE AREA. THIS UPPER
LEVEL FEATURE WILL INCREASE THE OVERALL GRADIENT FLOW ACROSS THE
REGION...AND ALLOW WARMER AND MORE MOIST AIR RESIDING IN THE
CENTRAL GULF TO PUSH BACK INTO THE FORECAST AREA. EXPECT TO SEE
CLOUDS INCREASE THROUGH THE NIGHT...AND A FEW SHOWERS DEVELOP OVER
COASTAL AREAS OF LOUISIANA BY DAYBREAK.

LOW LEVEL WIND SPEED CONVERGENCE ALONG THE COAST WILL PRODUCE A
REGION OF HIGHER OMEGA OVER THE FORECAST AREA ON FRIDAY. AS A
RESULT...EXPECT TO SEE SCATTERED SHOWERS OVERSPREAD MOST OF THE
AREA. AT THIS TIME...HAVE NOT INCLUDED A MENTION OF THUNDER DUE TO
THE PRESENCE OF A STRONG MID-LEVEL CAP. ANY MOISTURE AND LIFT
WILL BE FOUND BENEATH THIS CAP...AND EXPECT TO SEE ONLY MARINE
LAYER TYPE SHOWERS THROUGH THE DAY. TEMPERATURES WILL BE
SIGNIFICANTLY WARMER AS MOISTURE STREAMS BACK INTO THE AREA...WITH
READINGS CLIMBING BACK INTO THE 60S ACROSS BY FRIDAY AFTERNOON.

LONG TERM...

BY SATURDAY...BOTH MODELS INDICATE THAT CONDITIONS WILL BEGIN TO
TURN MORE UNSTABLE ALOFT...BUT A STABLE LAYER WILL REMAIN IN PLACE
IN THE LOW LEVELS. THE ONLY AREA WILL SURFACE BASED INSTABILITY IS
EXPECTED IS OVER THE OFFSHORE WATERS. HAVE KEPT IN LIKELY SHOWERS
FOR SATURDAY AND SATURDAY NIGHT...BUT ALSO ADDED IN A CHANCE FOR
SOME ELEVATED THUNDERSTORMS DURING PERIOD. TEMPERATURES WILL
CONTINUE TO WARM...AND READINGS WILL CLIMB TO AROUND 70 DEGREES BY
SATURDAY AFTERNOON. GIVEN THE HIGH DEWPOINTS AND WARM OVERNIGHT
TEMPERATURES IN THE UPPER 50S AND LOWER 60S...CONDITIONS LOOK
FAVORABLE FOR ANOTHER ROUND OF FOG TO POSSIBLY BOTH FRIDAY AND
SATURDAY NIGHTS. BOUNDARY LAYER FLOW LOOKS TO BE A BIT STRONGER
FRIDAY NIGHT...BUT THE FLOW FALLS OFF TO AROUND 10 KNOTS SATURDAY
NIGHT. AS A RESULT...SOME MORE WIDESPREAD ADVECTION FOG WILL BE
POSSIBLE SATURDAY NIGHT INTO EARLY SUNDAY MORNING.

CONDITIONS WILL TURN MORE FAVORABLE FOR SURFACE BASED CONVECTION
TO DEVELOP LATE SUNDAY MORNING AND SUNDAY AFTERNOON AS A SHORT
WAVE TROUGH EJECTING OUT OF TEXAS DRIVES A WEAK SURFACE LOW
THROUGH THE FORECAST AREA. OVERALL INSTABILITY AND SHEAR VALUES
LOOK TO BE FAIRLY WEAK...SO THE THREAT FOR ANY STRONGER CONVECTION
LOOKS MARGINAL AT BEST ON SUNDAY. THE LOW WILL QUICKLY PULL TO THE
EAST OF THE AREA SUNDAY NIGHT...AND EXPECT TO SEE SOME DRIER AIR
AND INCREASING SUBSIDENCE ADVECT INTO THE AREA. THERE WILL BE SOME
LINGERING CLOUDS AND SHOWERS SUNDAY NIGHT...BUT AS SUBSIDENCE
INCREASES INTO MONDAY MORNING SKIES SHOULD BEGIN TO CLEAR A BIT
AND THREAT OF RAINFALL WILL DIMINISH RAPIDLY. THE FRONTAL BOUNDARY
SHOULD STALL SOMEWHERE JUST OFFSHORE FOR MONDAY AND TUESDAY...AND
EXPECT SEE A THREAT OF ISOLATED SHOWERS LINGER ALONG THE COAST AND
OFFSHORE BOTH DAYS. HOWEVER...DRIER AIR WILL DOMINATE AWAY FROM
THE COAST. PARTLY CLOUDY SKIES AND DRY WEATHER IS CURRENTLY
EXPECTED FOR MONDAY AND TUESDAY FOR AREAS ALONG AND NORTH OF THE
INTERSTATE 10 CORRIDOR. TEMPERATURES WILL ALSO DROP BACK TO MORE
NORMAL LEVELS FOR LATE DECEMBER WITH HIGHS IN THE UPPER 50S AND
LOWER 60S AND LOWS IN THE 40S.


AVIATION...

DRIER AIR IN THE WAKE OF THE COLD FRONT IS CLEARING OUT THE LOWER
CLOUDS OVER THE AIRPORTS WEST OF I-55...AND THIS CLEARING TREND WILL
CONTINUE EAST THIS MORNING WITH THE REMAINING TAF AIRPORTS IMPROVING
TO VFR BY 14-16Z. NORTHWEST WINDS WILL BE A BIT GUSTY AT TIMES
THROUGH THIS MORNING ACROSS THE INLAND AIRPORTS AND THROUGH MUCH OF
THE DAY AT THE COASTAL AND SOUTH SHORE OF LAKE PONTCHARTRAIN
AIRPORTS. 22/TD

MARINE...

SMALL CRAFT ADVISORY CONDITIONS WILL PERSIST THROUGH THE MORNING
HOURS ACROSS ALL OF THE MARINE ZONES AS A STRONG PRESSURE GRADIENT
ASSOCIATED WITH A HIGH BUILDING INTO THE AREA CONTINUES. STRONG
NORTHWEST FLOW OF 20 TO 25 KNOTS WITH GUSTS OVER 30 KNOTS CAN BE
EXPECTED. CONDITIONS WILL BEGIN TO EASE THIS AFTERNOON OVER THE
SOUNDS AND TIDAL LAKES...BUT SMALL CRAFT CONDITIONS WILL CONTINUE
FOR THE OPEN GULF WATERS THROUGH THIS EVENING. THE SURFACE HIGH
WILL FINALLY BECOME CENTERED OVER THE AREA LATE TONIGHT AND
TOMORROW...ALLOWING WINDS TO DIMINISH BACK BELOW 15 KNOTS. THE
OFFSHORE FLOW WILL SWITCH TO AN ONSHORE COMPONENT TOMORROW NIGHT
AND THIS FLOW WILL CONTINUE THROUGH THE WEEKEND AS A HIGH PRESSURE
SYSTEM REMAINS CENTERED OVER THE EASTERN SEABOARD. THE GRADIENT
FLOW WILL INCREASE INTO EXERCISE CAUTION RANGE IN THE GULF WATERS
FRIDAY NIGHT AND SATURDAY AS AN UPPER LEVEL LOW SLIDES THROUGH. IN
ADDITION...SOME SEA FOG MAY IMPACT THE MARINE ZONES BOTH FRIDAY
AND SATURDAY NIGHTS.

DECISION SUPPORT...

DSS CODE...BLUE
DEPLOYED...NONE.
ACTIVATION...NONE.
ACTIVITIES...SLURRY SUPPORT
             SMALL CRAFT ADVISORY

DECISION SUPPORT SERVICES (DSS) CODE LEGEND
GREEN  = NO WEATHER IMPACTS THAT REQUIRE ACTION
BLUE   = LONG FUSED WATCH/WARNING/ADVISORY IN EFFECT OR HIGH
         VISIBILITY EVENT
YELLOW = HEIGHTENED IMPACTS WITH SHORT FUSED
         WATCH/WARNING/ADVISORY ISSUANCES; RADAR SUPPORT
ORANGE = HIGH IMPACTS - SLIGHT TO MODERATE RISK SEVERE; NEARBY
         TROPICAL EVENTS; HAZMAT OR OTHER LARGE EPISODES
RED    = FULL ENGAGEMENT FOR MODERATE TO HIGH RISK SVR
         AND/OR DIRECT TROPICAL THREATS; EVENTS OF NATIONAL
         SIGNIFICANCE.

&&

.PRELIMINARY POINT TEMPS/POPS...
MCB  54  31  57  40 /   0   0   0  20
BTR  55  34  58  43 /   0   0   0  20
ASD  56  32  56  42 /   0   0   0  20
MSY  56  40  55  47 /   0   0   0  20
GPT  57  35  56  44 /   0   0   0  10
PQL  58  32  56  40 /  10   0   0  20

&&

.LIX WATCHES/WARNINGS/ADVISORIES...
LA...NONE.
GM...SMALL CRAFT ADVISORY UNTIL MIDNIGHT THURSDAY FOR THE FOLLOWING
     ZONES: COASTAL WATERS FROM BOOTHVILLE LA TO THE SOUTHWEST
     PASS OF THE MISSISSIPPI RIVER OUT 20 NM...COASTAL WATERS
     FROM PASCAGOULA MS TO STAKE ISLAND LA FROM 20 TO 60
     NM...COASTAL WATERS FROM PASCAGOULA MS TO STAKE ISLAND LA
     OUT 20 NM...COASTAL WATERS FROM PORT FOURCHON TO LOWER
     ATCHAFALAYA RIVER FROM 20 TO 60 NM...COASTAL WATERS FROM
     PORT FOURCHON TO LOWER ATCHAFALAYA RIVER OUT 20
     NM...COASTAL WATERS FROM STAKE ISLAND LA TO THE SOUTHWEST
     PASS OF THE MISSISSIPPI RIVER FROM 20 TO 60 NM...COASTAL
     WATERS FROM THE SOUTHWEST PASS OF THE MISSISSIPPI RIVER TO
     PORT FOURCHON FROM 20 TO 60 NM...AND COASTAL WATERS FROM
     THE SOUTHWEST PASS OF THE MISSISSIPPI RIVER TO PORT
     FOURCHON OUT 20 NM.

     SMALL CRAFT ADVISORY UNTIL 9 AM WEDNESDAY FOR THE FOLLOWING
     ZONES: BRETON SOUND...CHANDELEUR SOUND...LAKE BORGNE...LAKE
     PONTCHARTRAIN AND LAKE MAUREPAS...AND MISSISSIPPI SOUND.

MS...NONE.
GM...SMALL CRAFT ADVISORY UNTIL 9 AM WEDNESDAY FOR THE FOLLOWING
     ZONES: BRETON SOUND...CHANDELEUR SOUND...LAKE BORGNE...LAKE
     PONTCHARTRAIN AND LAKE MAUREPAS...AND MISSISSIPPI SOUND.

     SMALL CRAFT ADVISORY UNTIL MIDNIGHT THURSDAY FOR THE FOLLOWING
     ZONES: COASTAL WATERS FROM BOOTHVILLE LA TO THE SOUTHWEST
     PASS OF THE MISSISSIPPI RIVER OUT 20 NM...COASTAL WATERS
     FROM PASCAGOULA MS TO STAKE ISLAND LA FROM 20 TO 60
     NM...COASTAL WATERS FROM PASCAGOULA MS TO STAKE ISLAND LA
     OUT 20 NM...COASTAL WATERS FROM PORT FOURCHON TO LOWER
     ATCHAFALAYA RIVER FROM 20 TO 60 NM...COASTAL WATERS FROM
     PORT FOURCHON TO LOWER ATCHAFALAYA RIVER OUT 20
     NM...COASTAL WATERS FROM STAKE ISLAND LA TO THE SOUTHWEST
     PASS OF THE MISSISSIPPI RIVER FROM 20 TO 60 NM...COASTAL
     WATERS FROM THE SOUTHWEST PASS OF THE MISSISSIPPI RIVER TO
     PORT FOURCHON FROM 20 TO 60 NM...AND COASTAL WATERS FROM
     THE SOUTHWEST PASS OF THE MISSISSIPPI RIVER TO PORT
     FOURCHON OUT 20 NM.

&&

$$







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