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

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703
FXUS64 KLIX 231048
AFDLIX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE NEW ORLEANS LA
448 AM CST MON FEB 23 2015

.SHORT TERM...HIGHLY UNCERTAIN FCST IN THE MAKING. OVERALL THE LAST
FEW DAYS THINGS HAVE UNDER PERFORMED WITH RESPECT TO SPEED OF COLD
AIR AND PRECIP AND AM CONCERNED THIS COULD STILL BE THE CASE.
HOWEVER...IF THERE IS ANY SLIGHT NUDGE TWRDS OUR SETUP PERFORMING TO
ITS POTENTIAL OR EVEN SLIGHTLY OVER PERFORMING...THEN THERE COULD BE
SOME ISSUES IN SWRN MS AND INTO ADJACENT LA PARISHES.

OVER THE NEXT 36 HRS THE FCST IS MESSY. CONFIDENCE IS QUITE LOW AS
ONLY A MINOR SHIFT IN ONE DIRECTION OR THE OTHER...WILL...HAVE
SIGNIFICANT IMPACTS WITH WHAT OCCURS. FRONT HAS PUSHED THROUGH TO
THE COAST WITH BVE FINALLY SHOWING A NW WIND. TEMPS HAVE COOLED AND
CONTINUE TO DO SO SLOWLY APPROACHING FCST LOWS. FIRST QUESTION THEN
BECOMES HOW COLD WILL THE NW GET BEFORE SUNRISE AND THEN HOW MUCH IF
ANY WARM UP WILL THE AREA AS A WHOLE SEE. WEAK CAA WILL OCCUR BELOW
H875 AND ALMOST TO THE SFC ALL DAY. COMBINE THAT WITH BROAD WEAK
LIFT IN THE MID LVLS ALL DAY AS WELL AND THE AREA WILL LIKELY SEE A
COLD CLOUDY DAY WITH SHRA INCREASING DURING THE AFTN AND HEADING
INTO THE EVNG. ANY RAIN THAT FALLS COULD HELP DROP TEMPS ANOTHER
DEGREE OR TWO INITIALLY THROUGH EVAPORATIVE COOLING
PROCESSES...ESPECIALLY IF IT IS MODERATE TO HEAVY RAIN. WITH THAT
LIKE PREV DISCUSSION MENTIONED MORNING LOWS COULD VERY WELL BE
TODAYS HIGHS FOR MANY LOCATIONS. THIS WOULD THEN LEAVE PORTIONS OF
SWRN MS AND JUST ACROSS THE LA BORDER WITH AN INTERESTING STARTING
OFF POINT WITH RESPECT TO TEMPS.

HEADING INTO TONIGHT MDLS ARENT ANY CLEARER ABOUT THINGS. IN FACT
THERE IS SIGNIFICANT DIFFERENCE WITH RESPECT TO POPS. LATEST GFS
REALLY DRIES THINGS OUT BEFORE 6Z WHERE THE ECMWF IS QUITE A BIT
WETTER. THE ECMWF APPEARS TO HAVE FAR BETTER SUPPORT FROM THE NAM
AND CAN SO WILL TREND MORE TWRDS IT. WITH THAT IT APPEARS WE WILL
STILL HAVE BROAD SUPPORT ALOFT ALONG WITH SOME ISENTROPIC LIFT TO
WORK WITH AND THIS SHOULD GET NUM TO SCT SHRA TO DEVELOP DURING THE
EVNG...SLOWLY TAPERING OFF FROM NORTH TO SOUTH (OR POSSIBLY MORE NW
TO SE) OVERNIGHT. OVER MOST OF THE AREA THE IMPACTS WILL BE NILL AS
IT WILL JUST BE A COLD RAIN BUT ALONG AND NORTHWEST OF A LINE FROM
NEAR NEW ROADS TO NEAR MCCOMB THERE IS THE RISK OF FREEZING RAIN.
ONE POSITIVE FROM A FCST STANDPOINT...IT APPEARS CLEAR CUT THAT IN
THAT AREA IT WILL EITHER BE RAIN OR FREEZING RAIN AS LL TEMPS WILL
BE FAR TOO WARM AND THE WARM LAYER WILL BE FAR TOO THICK FOR SLEET
AND SNOW TO REACH THE SFC SO THE KEY ISSUE IS GOING TO BE GROUND
TEMP. LOCATIONS IN NRN POINTE COUPEE AND WILKINSON HAVE THE BEST
CHANCE OF SEEING FREEZING RAIN AND COULD VERY WELL NEED A WINTER
WEATHER ADVISORY FOR LIGHT ACCUMULATIONS BUT CLOSER TWRDS MCCOMB IT
IS VERY TRICKY. THERE IS A GOOD CHANCE THAT MCB COULD STAY AT 33
MOST OF THE NIGHT AND IT WOULD JUST BE A COLD RAIN BUT IT ONLY TAKES
A DROP OF A DEGREE TO BEGIN TO CREATE SOME PROBLEMS. THE OTHER
CONCERN FOR TONIGHT IS QPF. AGAIN IF THE GFS TURNS OUT TO BE RIGHT
THEN THERE SHOULD BE NO OR VERY LITTLE IMPACTS BUT IF THE ECMWF/S
QPF FIELD IS CORRECT THEN THERE IS THE OUTSIDE CHANCE OF A TENTH TO
TWO TENTHS OF AN INCH ACCUMULATION OF FREEZING RAIN. THE WINDOW FOR
FREEZING RAIN APPEARS TO BE FROM NEAR 3Z THROUGH 14Z TUE. WILL STILL
HOLD ONTO RAIN OR FREEZING RAIN FOR THE PREVIOUSLY MENTIONED AREA
BUT WITH FCST CONFIDENCE ON THE LOW END HAVE OPTED OUT OF ANY WINTER
WEATHER PRODUCTS FOR NOW AND ALLOW THE DAY CREW TO TAKE ANOTHER LOOK
AT THINGS...ESPECIALLY HOW TEMPS RESPOND TODAY.

TUE THINGS SHOULD BE ON THE QUIET SIDE BUT LIGHT SHRA WILL BE
POSSIBLE ACROSS THE SRN HALF OF THE CWA DURING THE DAY. THAT SAID
TUE WILL BE ANOTHER COLD AND DREARY DAY. THIS WILL CHANGE AS WE HEAD
INTO TUE NIGHT. /CAB/

.LONG TERM...OVERALL THE MEDIUM RANGE MDLS ARE IN DECENT AGREEMENT
WITH FCST THROUGH THE WORK WEEK AND THEN THE ECMWF SPEEDS THINGS UP
A TAD HEADING INTO THE WEEKEND. TUE NIGHT AND WED ARE THE MAIN
IMPACT DAYS IN THIS PORTION OF THE FCST BUT AT LEAST IT WONT BE A
WINTER WEATHER ISSUE.

TUE NIGHT AND WED LOOK TO BE WET. A GULF LOW IS EXPECTED TO DEVELOP
OVERNIGHT TUE AND DEEPEN THROUGH THE DAY WED. THIS WILL HELP WITH
ISENTROPIC LIFT AND GREATLY INCREASE THE RAIN CHANCES AFTER 6Z WED.
BULK OF THE RAIN WILL LIKELY OCCUR DURING THE DAY WED AND START TO
SLOWLY TAPER OFF WED EVNG AS BOTH OUR GULF LOW DEPARTS TO THE EAST
AND A STRONG S/W MOVE THROUGH THE LOWER MS VALLEY OVERNIGHT.
WIDESPREAD 1 TO 2 INCHES OF RAIN COULD OCCUR WITH THIS SYSTEM.

THU AND FRI A BROAD L/W TROUGH COVERING MOST OF THE CONUS WILL SEND
A RE-ENFORCING COLD AIRMASS SOUTH WHICH SHOULD HELP DRY THINGS OUT
FOR THE REMAINDER OF THE WORK WEEK. AS WE MOVE INTO THE WEEKEND SRLY
FLOW IN THE LL AND SWRLY FLOW ALOFT WILL LEAD TO MOISTURE INCREASING
AND THE REINTRODUCTION OF RAIN AND POSSIBLY EVEN TSRA TO START OFF
NEXT WEEK. /CAB/

&&

.AVIATION.../ISSUED WITH THE 06Z TAF PACKAGE/

A COLD FRONT HAS VERY SLOWLY PUSHED SOUTH ACROSS THE AREA THROUGH
THE EVENING HOURS AND WAS NOW SOUTH OF EACH OF THE TAF SITES. MAINLY
IFR CEILINGS WERE BEING OBSERVED BEHIND THE FRONT...AND IFR TO
MVFR CEILINGS WILL PREVAIL AT THE TERMINALS THROUGHOUT THE TAF
FORECAST PERIOD. SOME LIGHT FOG MAY BE OBSERVED AT KMSY AND KHUM
FOR THE NEXT HOUR OR SO UNTIL SOME DRIER AIR BEHIND THE FRONT MAKES
IT FARTHER SOUTH. AREAS OF LIGHT RAIN WILL BE POSSIBLE
OVERNIGHT AND MONDAY MORNING...ESPECIALLY ACROSS NORTHERN AND
WESTERN SECTIONS. A BETTER CHANCE FOR RAIN WILL BE IN THE OFFING
FOR LATER MONDAY. 11

&&

.MARINE...COLD FRONT HAS PUSHED INTO THE COASTAL WATER OVERNIGHT AND
COLD AIR ADVECTION LEADING TO MOD TO STRONG OFFSHORE WINDS WILL
CONTINUE TO PROVIDE A CONFUSED SEA THROUGH THIS MORNING. SMALL CRAFT
ADVISORY CONDITIONS ARE EXPECTED CONTINUE FOR THE BETTER PART OF
TODAY BEFORE SETTLING TO LOWER LEVELS OVERNIGHT TONIGHT. OFFSHORE
WINDS WILL CONTINUE THROUGH TUE BEFORE QUICKLY BECOMING INFLUENCED
BY A DEVELOPING GULF LOW OVER THE NWRN/N-CNTRL GULF TUE NIGHT AND
WED. THIS WILL PROVIDE HAZARDOUS WINDS AND SEAS WED AND THROUGH WED
NIGHT. /CAB/


&&

.DECISION SUPPORT...
DSS CODE...BLUE.
DEPLOYED...NONE.
ACTIVATION...NONE.
ACTIVITIES...SLURRY SUPPORT
             WINTER WEATHER POTENTIAL FOR MON NIGHT
             SMALL CRAFT ADVISORY THROUGH MON EVENING

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  44  31  46  40 /  60  70  30  50
BTR  46  33  47  39 /  60  60  40  50
ASD  51  36  49  44 /  60  60  50  50
MSY  52  40  48  46 /  50  60  50  50
GPT  52  37  49  46 /  50  60  40  50
PQL  53  36  49  44 /  50  60  40  50

&&

.LIX WATCHES/WARNINGS/ADVISORIES...
LA...NONE.
GM...SMALL CRAFT ADVISORY UNTIL MIDNIGHT TUESDAY FOR THE FOLLOWING
     ZONES: BRETON SOUND...CHANDELEUR SOUND...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...COASTAL WATERS FROM THE SOUTHWEST PASS OF THE
     MISSISSIPPI RIVER TO PORT FOURCHON OUT 20 NM...LAKE
     BORGNE...LAKE PONTCHARTRAIN AND LAKE MAUREPAS...AND
     MISSISSIPPI SOUND.

MS...NONE.
GM...SMALL CRAFT ADVISORY UNTIL MIDNIGHT TUESDAY FOR THE FOLLOWING
     ZONES: BRETON SOUND...CHANDELEUR SOUND...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...COASTAL WATERS FROM THE SOUTHWEST PASS OF THE
     MISSISSIPPI RIVER TO PORT FOURCHON OUT 20 NM...LAKE
     BORGNE...LAKE PONTCHARTRAIN AND LAKE MAUREPAS...AND
     MISSISSIPPI SOUND.

&&

$$

CAB




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