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

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951
FXUS64 KLIX 190104
AFDLIX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE NEW ORLEANS LA
704 PM CST TUE NOV 18 2014

.SOUNDING DISCUSSION...

THE 00Z SOUNDING CONTINUED TO SHOW A VERY DRY AND VERY STABLE
AIRMASS OVER THE AREA THIS EVENING. PW VALUES ARE LITTLE CHANGED
FROM THE 12Z SOUNDING AT 0.19 INCHES AND STRONG NORTHERLY FLOW OF
20 TO 30 KNOTS CONTINUES FROM 850MB UP TO 700MB. THERE IS ALSO A
STRONG JET NOTED IN THE UPPER LEVELS ...WITH 200MB WINDS OF 155
KNOTS OBSERVED. 32

&&

.PREV DISCUSSION... /ISSUED 449 PM CST TUE NOV 18 2014/

SHORT TERM /TONIGHT THROUGH THURSDAY NIGHT/...

MAIN CONCERN IS FREEZING TEMPERATURES TONIGHT AND WHERE TO ISSUE
FREEZE WARNINGS. PATTERN TONIGHT WILL BE QUITE A BIT DIFFERENT FROM
LAST NIGHT. TONIGHT THE COLD AIR WILL BE DRIVEN BY RADIATIONAL
COOLING UNDER CLEAR SKIES AND LIGHT TO CALM WINDS...WHILE LAST NIGHT
WAS DRIVEN BY COLD AIR ADVECTION TEMPERED SOMEWHAT BY A VEIL OF
CIRRUS CLOUDS THAT DEVELOPED LAST NIGHT AND THIS MORNING.

THE UPPER LEVEL SHORTWAVE TROUGH...STRONG JETSTREAM...AND ASSOCIATED
CIRRUS CLOUDS HAVE MOVED OFF TO THE EAST AND THERE ARE NO NOTABLE
FEATURES THAT COULD PRODUCE UNEXPECTED CLOUD COVER TONIGHT. VERY LOW
DEWPOINT TEMPERATURES IN THE TEENS TO LOWER 20S ARE NOTED OVER THE
FORECAST AREA. GIVEN ALL THESE FACTORS...GOING ON THE LOW SIDE OF
MOS GUIDANCE WOULD BE PRUDENT. HOWEVER...THE FLY IN THE OINTMENT IS
THERE WILL BE WARMING TEMPERATURES JUST ABOVE THE
SURFACE...ESPECIALLY IN THE 925 TO 900 LAYER AS THE CENTER OF THE
SURFACE HIGH SHIFTS EAST OF THE FORECAST AREA. HAVE USED A BLEND OF
THE COLDER MOS GUIDANCE AND THE WARMER BLENDED/CONSENSUS AND BIAS
CORRECTED GUIDANCE. THIS MEANS THERE IS A DECENT CHANCE OF A HARD
FREEZE WITH LOWS IN THE MID 20S FOR SEVERAL HOURS OVER THE FAR NORTH
CENTRAL AND NORTHEAST PORTIONS OF THE FORECAST AREA...MAINLY FROM
NEAR MCCOMB TO BOGALUSA TO INTERIOR AND DRAINAGE BASIN AREAS OF THE
MISSISSIPPI GULF COASTAL COUNTIES...AND A HARD FREEZE WARNING HAS
BEEN ISSUED TONIGHT. AREAS TO THE SOUTH LIKE HOUMA...INLAND
LAFOURCHE PARISH...AND THE RIVER PARISHES WEST OF KENNER ARE LIKELY
TO SEE AT LEAST A BRIEF LIGHT FREEZE. AREAS IN BETWEEN...FROM NEAR
AND NORTH OF BATON ROUGE TO ALONG THE I-12 CORRIDOR ARE LIKELY TO
EXPERIENCE A LONG DURATION LIGHT TO MODERATE FREEZE. EVEN THOUGH
MANY AREAS THAT ARE IN THE FREEZE WARNING AREA HAVE EXPERIENCED
SEVERAL FREEZES ALREADY...WE FELT IT WAS PRUDENT TO ISSUE THE
WARNING. IT DOES APPEAR THE WARMER URBAN AREAS OF METRO NEW ORLEANS
WILL MOSTLY STAY ABOVE FREEZING AGAIN TONIGHT SO A FREEZE WARNING
WAS NOT ISSUED...HOWEVER A FEW WESTBANK LOCATIONS COULD BRIEFLY GET
DOWN TO 32 DEGREES.

THE UPPER LEVEL PATTERN WILL DE-AMPLIFY WITH THE EASTERN U.S. TROUGH
LIFTING NORTHEAST WEDNESDAY INTO THURSDAY. AFTER THE VERY COLD START
WEDNESDAY...TEMPERATURES WILL START TO MODERATE/WARM AS SOUTHERLY
WINDS AND HIGHER HEIGHTS ALOFT TAKE HOLD OF THE REGION. HIGHS WILL
RETURN TO THE MID TO UPPER 50S WEDNESDAY AND MID TO UPPER 60S
THURSDAY. LOWS ARE EXPECTED TO BE MID 30S TO MID 40S WEDNESDAY NIGHT
AND 40S TO LOWER 50S THURSDAY NIGHT. PATCHY FOG WILL BE POSSIBLE
LATE THURSDAY NIGHT.

LONG TERM /FRIDAY THROUGH TUESDAY NIGHT/...

THE POSSIBILITY OF A SEVERE WEATHER EVENT IS A MAJOR CONCERN FOR A
PORTION OF THE WEEKEND...MAINLY LATE SATURDAY AND SATURDAY NIGHT.

AN AMPLIFYING SHORTWAVE TROUGH WILL BE MOVING EAST ACROSS THE U.S.
AND MEXICAN BORDER AND NORTHERN MEXICO FRIDAY INTO SATURDAY WITH THE
NORTHERN PORTION OF THE SHORTWAVE REACHING TEXAS FRIDAY NIGHT AND
SATURDAY. THE LOW LEVEL HIGH PRESSURE RIDGE WILL REMAIN WEDGED OVER
THE AREA THROUGH FRIDAY NIGHT...SO IT SHOULD REMAIN DRY WITH A
CONTINUED WARMING TREND FRIDAY AND FRIDAY NIGHT.

THE POTENT SHORTWAVE TROUGH IS EXPECTED TO TAKE ON A NEGATIVE TILT
AND MOVE NORTHEAST FROM EAST TEXAS THE THE WESTERN GULF COAST ACROSS
THE LOWER MISSISSIPPI VALLEY LATE SATURDAY AND SATURDAY NIGHT. THE
ASSOCIATED SURFACE LOW IS EXPECTED TO REMAIN NEAR THE CENTER OF THE
UPPER LOW/TROUGH OVER THE SOUTHERN PLAINS TO MID MISSISSIPPI VALLEY.
THIS WILL ALLOW A WARM FRONT TO LIFT NORTH THROUGH THE FORECAST AREA
AND PLACE THE AREA IN THE WARM SECTOR WITH DEWPOINTS LIKELY REACHING
AT LEAST THE MID 60S. THIS SHOULD PRODUCE VERY FAVORABLE DEEP
MOISTURE...SHEAR AND ADEQUATE INSTABILITY TO SUPPORT WIDESPREAD
THUNDERSTORMS WITH ALL MODES OF SEVERE WEATHER POSSIBLE ALONG WITH
VERY HEAVY RAINFALL. WILL CONTINUE TO MONITOR AND FINE TUNE THE
STRENGTH AND TIMING OF THIS SYSTEM AND IT/S POTENTIAL SEVERE WEATHER
IMPACTS.

MARINE...

NORTH WINDS ARE EXPECTED TO DECREASE TONIGHT...HOWEVER WINDS AND
SEAS ARE EXPECTED TO REMAIN ABOVE SMALL CRAFT ADVISORY CRITERIA
FOR MUCH OF THE COASTAL WATERS THROUGH THIS EVENING...SO HAVE
EXTENDED THE HEADLINE UNTIL 10 PM. HIGH PRESSURE OVER EAST TEXAS
WILL SLIDE EAST OVER THE FORECAST AREA TONIGHT AND EAST OF THE
AREA ON WEDNESDAY. SURFACE WINDS WILL FINALLY COLLAPSE OVER NEAR
SHORE WATERS LATER TONIGHT BUT REMAIN MODERATE WELL OFFSHORE
TONIGHT AND WEDNESDAY. A PACIFIC SYSTEM WILL SWEEP ACROSS THE
LOWER MISSISSIPPI VALLEY AND NORTH CENTRAL GULF SATURDAY. STRONG
ONSHORE FLOW SHOULD DEVELOP AHEAD OF THE ASSOCIATED FRONTAL
BOUNDARY AS EARLY AS FRIDAY NIGHT AND CONTINUING THROUGH
SATURDAY. AS A RESULT...SMALL CRAFT ADVISORIES MAYBE BE NECESSARY
DURING THIS TIME.

AVIATION...

VFR CONDITIONS WILL PREVAIL THROUGH WEDNESDAY.

DECISION SUPPORT...
DSS CODE...BLUE.
DEPLOYED...NONE.
ACTIVATION...NONE.
ACTIVITIES...SLURRY SUPPORT...FREEZING TEMPERATURES TONIGHT

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  25  56  39  66 /   0   0   0  10
BTR  27  59  40  69 /   0   0   0  10
ASD  27  57  37  67 /   0   0   0  10
MSY  35  59  45  68 /   0   0   0  10
GPT  27  56  41  65 /   0   0   0  10
PQL  25  56  37  65 /   0   0   0  10

&&

.LIX WATCHES/WARNINGS/ADVISORIES...
LA...FREEZE WARNING FROM MIDNIGHT WEDNESDAY TO 8 AM WEDNESDAY FOR THE
     FOLLOWING ZONES: ASCENSION...ASSUMPTION...EAST BATON
     ROUGE...EAST FELICIANA...IBERVILLE...LIVINGSTON...NORTHERN
     TANGIPAHOA...POINTE COUPEE...SOUTHERN TANGIPAHOA...ST.
     CHARLES...ST. HELENA...ST. JAMES...ST. JOHN THE
     BAPTIST...ST. TAMMANY...UPPER LAFOURCHE...UPPER
     TERREBONNE...WEST BATON ROUGE...AND WEST FELICIANA.

     HARD FREEZE WARNING UNTIL 8 AM WEDNESDAY FOR THE FOLLOWING
     ZONES: AND WASHINGTON.

GM...SMALL CRAFT ADVISORY UNTIL 10 PM TUESDAY 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 PORT FOURCHON TO LOWER ATCHAFALAYA
     RIVER FROM 20 TO 60 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.

MS...FREEZE WARNING UNTIL 8 AM WEDNESDAY FOR THE FOLLOWING ZONES:
     AMITE...AND WILKINSON.

     HARD FREEZE WARNING UNTIL 8 AM WEDNESDAY FOR THE FOLLOWING
     ZONES: HANCOCK...HARRISON...JACKSON...PEARL
     RIVER...PIKE...AND WALTHALL.

GM...SMALL CRAFT ADVISORY UNTIL 10 PM TUESDAY 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 PORT FOURCHON TO LOWER ATCHAFALAYA
     RIVER FROM 20 TO 60 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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