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

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313
FXUS64 KLIX 211027
AFDLIX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE NEW ORLEANS LA
427 AM CST SAT FEB 21 2015

.SHORT TERM...
QUITE DIFFERENT CONDITIONS ARE IN PLACE OVER THE AREA THIS MORNING
FROM 24 HOURS AGO. TEMPERATURES HAVE RISEN SIGNIFICANTLY AND ARE A
WHOPPING 30 DEGREES WARMER WITH MOST LOCATIONS NEAR THE 60 DEGREE
MARK. MOISTURE LEVELS HAVE COME UP JUST AS MUCH WITH DEWPOINTS IN
THE 50S COMPARED TO TEENS. THE LOCAL 00Z SOUNDING FROM YSTRDY SHOWS
THAT THE ATMOSPHERE WAS GENERALLY COMPLETELY SATURATED FROM A LITTLE
ABOVE THE SFC TO 700MB. THERE WAS A POCKET OF DRIER AIR FROM THERE
UPWARDS TO 400MB. THIS WILL BE A LIMITER TO QPF THROUGH THE FIRST
HALF OF THE MORNING AS SHOWERS MOVE THROUGH. RADAR DOES SHOW A FEW
BANDS OF HIGHER RETURNS...BUT OTHERWISE THIS ACTIVITY WILL BE JUST
ENOUGH TO GET YOUR HAIR WET. THE DRY LAYER WILL DISSIPATE FOR THE
MOST PART BY AFTERNOON AS THIS TOP DOWN METHOD CONTINUES AND GULF
MOISTURE MOVES IN.

A LEESIDE TROUGH OF LOW PRESSURE THAT DEVELOPED OVER THE TEXAS
PANHANDLE HAS BEGUN MOVING EAST IN RESPONSE TO AN UPPER LEVEL TROUGH
DIGGING OUT OF CANADA AND INTO THE CENTRAL PLAINS. THIS LOW WILL
TRACK ACROSS OKLAHOMA AND ARKANSAS THIS MORNING AND TOWARDS THE OHIO
RIVER VALLEY THIS AFTERNOON. GULF MOISTURE BEING DRAWN INTO THIS LOW
WILL ENHANCE SHOWER DEVELOPMENT OVER THE CWA BUT IN A LIMITING
FACTOR AS MENTIONED EARLIER. MESO MODELS ACTUALLY PAINT A HIGHER
COVERAGE PICTURE THAN THE MEDIUM RANGE MODELS DO. SO FORECAST IS A
BLEND OF THE TWO.

AN ELONGATED TROUGH OF LOW PRESSURE WILL REMAIN IN PLACE ACROSS
TEXAS AND LOUISIANA TODAY. THIS WILL BE THE FOCUS FOR HIGHER RAIN
CHANCES OVERNIGHT AS THIS BOUNDARY MOVES SOUTH TOWARDS THE CWA. LATE
IN THIS PERIOD...THE BOUNDARY WILL BE GETTING REINFORCEMENT FROM A
COLD AIR MASS MARCHING SOUTH ACROSS THE CENTRAL PLAINS. THE RESULT
SHOULD BE WIDESPREAD SHOWERS NORTH OF INTERSTATE 12. SOME
INSTABILITY WILL DEVELOP TONIGHT AS WELL WHICH WILL INCREASE THE
LIKELIHOOD OF THUNDERSTORMS DEVELOPING. THE COLD FRONT WILL CONTINUE
SOUTH ON SUNDAY...REACHING THE COAST BY LATE IN THE AFTERNOON. THERE
WILL BE QUITE A LARGE GRADIENT IN TEMPS ACROSS THE AREA AS THE COLD
AIR MOVES IN. TIMING WILL BE CRITICAL ON OBSERVED MAX TEMPS.

.LONG TERM...
CHANCE POPS WILL CONTINUE ON MONDAY AS THE AREA REMAINS UNDER AN
UPPER LEVEL SHEAR AXIS BETWEEN TROUGH TO THE NORTH AND RIDGE TO THE
SOUTH AND A WEAK VORTICITY MAXIMUM MOVES THROUGH. MEANWHILE...COLD
AIR ADVECTION WILL BRING TEMPS DOWN CONSIDERABLY. HIGHS WILL
STRUGGLE TO REACH LOWER 40S TO 50 DEGREES ACROSS THE CWA. AS WITH
PREVIOUS FORECASTS...THERE STILL APPEARS TO BE A WINDOW OF
OPPORTUNITY FOR FREEZING RAIN ALONG THE MISSISSIPPI/LOUISIANA BORDER
IN THE CWA MONDAY NIGHT. THE GFS MODEL SOUNDINGS HAVE BEEN SHOWING
SUB FREEZING TEMPS JUST ABOVE THE SFC AND TEMPS RIGHT AT FREEZING IN
MCB. FURTHER SOUTH AROUND BTR LOOKS TO BE A COUPLE DEGREES WARMER AT
THE SFC AND ABOVE. THE ECMWF DID COME DOWN A FEW DEGREES FOR MIN
TEMPS AT MCB. THIS INCREASED CONFIDENCE ENOUGH TO GO AHEAD AND PUT
ZR- IN A SMALL PORTION OF THE CWA FROM POINTE COUPEE PARISH TO
WILKINSON COUNTY DURING THE OVERNIGHT PERIOD FROM AROUND MIDNIGHT TO
JUST AFTER SUNRISE.

MODELS DO LOOK BETTER IN TERMS OF AGREEMENT FOR MIDDLE OF NEXT WEEK
WITH PLACEMENT/MOVEMENT OF UPPER LEVEL AND SFC FEATURES THAN THEY
DID 24 HRS AGO. A WEAK UPPER LEVEL LOW WILL RACE ACROSS TEXAS
TUESDAY NIGHT AND SWING OVER THE GULF COAST WEDNESDAY. THIS WILL
PROMOTE THE DEVELOPMENT OF A SURFACE LOW IN THE NORTH CENTRAL GULF
OF MEXICO NEAR THE CWA/S COAST BY 12Z WED. THIS WILL BE THE FOCUS
FOR HIGHER RAIN CHANCES WED FOR AREAS EAST OF BATON ROUGE. ONCE THIS
SYSTEM KICKS OUT WED NIGHT...LOOKS LIKE THE AREA WILL FINALLY SEE A
DAY OR MAYBE EVEN 2 OF DRYNESS. SHOWERS TO RETURN THOUGH POSSIBLY
GOING INTO THE WEEKEND.

MEFFER
&&

.AVIATION...
WINDS ARE THE MAIN CONCERN THROUGH THE DAYLIGHT HOURS TODAY.
UNUSUALLY STRONG SOUTHEAST WINDS CONTINUE FOR THIS TIME OF NIGHT
WITH SUSTAINED SPEEDS OF AROUND 20 MPH WITH GUSTS TO 25 KNOTS AT
NEW. THESE WINDS MAY CYCLE DOWN AND UP EARLY THIS MORNING BEFORE
STAYING FAIRLY STRONG WITH CONSISTENT GUSTS BY MID MORNING THROUGH
MOST OF THE AFTERNOON TODAY. VFR CONDITIONS HAVE PREVAILED AND
LIKELY TO CONTINUE TO PREVAIL UNTIL MORE NUMEROUS AND HEAVIER SHRA
DEVELOP AND DEWPOINT TEMPERATURES INCREASE...WHICH WILL BE TOWARDS
THE LATER AFTERNOON AND EVENING HOURS. MVFR TO IFR CIGS WILL BE
MOVING IN FROM THE NORTH OVERNIGHT WITH THE APPROACH OF A COLD FRONT
AND ASSOCIATED SHOWERS AND STORMS.

MEFFER
&&

.MARINE...
ANOTHER STRONG COLD FRONT WILL MOVE OVER THE COASTAL WATERS SUNDAY
NIGHT INTO MONDAY MORNING. STRONG ONSHORE FLOW AHEAD OF THE FRONT
WILL GIVE WAY TO STRONG NORTH WINDS BEHIND THE FRONT. STRONG
SOUTHERLY WINDS TODAY WILL GUST TO 40 KNOTS AT TIMES. MORE FREQUENT
GUSTS WILL BE FOUND ON PLATFORMS. SMALL CRAFT ADVISORIES WILL REMAIN
HOISTED THROUGH MUCH OF TODAY FOR SHALLOW WATER AREAS AND THROUGH
TONIGHT FOR OPEN GULF WATERS. A SFC LOW WILL DEVELOP OVER THE
WESTERN GULF AND MOVE ENE THROUGH THE OUTER COASTAL WATERS WED. RAIN
AND COLD TEMPERATURES WILL REMAIN THROUGH MID WEEK.

&&

.DECISION SUPPORT...
DSS CODE...BLUE.
DEPLOYED...NONE.
ACTIVATION...NONE.
ACTIVITIES...SLURRY SUPPORT.

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  70  56  61  38 /  40  80  50  40
BTR  74  59  65  41 /  40  80  50  40
ASD  72  58  70  44 /  30  60  50  40
MSY  74  61  71  47 /  30  40  50  40
GPT  69  58  70  45 /  30  60  50  40
PQL  70  57  70  44 /  30  60  50  30

&&

.LIX WATCHES/WARNINGS/ADVISORIES...
LA...NONE.
GM...SMALL CRAFT ADVISORY UNTIL 3 AM SUNDAY 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...AND
     COASTAL WATERS FROM THE SOUTHWEST PASS OF THE MISSISSIPPI
     RIVER TO PORT FOURCHON OUT 20 NM.

     SMALL CRAFT ADVISORY UNTIL 2 PM SATURDAY FOR THE FOLLOWING
     ZONES: AND LAKE PONTCHARTRAIN AND LAKE MAUREPAS.

     SMALL CRAFT ADVISORY UNTIL 6 PM SATURDAY FOR THE FOLLOWING
     ZONES: LAKE BORGNE...AND MISSISSIPPI SOUND.

MS...NONE.
GM...SMALL CRAFT ADVISORY UNTIL 2 PM SATURDAY FOR THE FOLLOWING
     ZONES: AND LAKE PONTCHARTRAIN AND LAKE MAUREPAS.

     SMALL CRAFT ADVISORY UNTIL 6 PM SATURDAY FOR THE FOLLOWING
     ZONES: LAKE BORGNE...AND MISSISSIPPI SOUND.

     SMALL CRAFT ADVISORY UNTIL 3 AM SUNDAY 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...AND
     COASTAL WATERS FROM THE SOUTHWEST PASS OF THE MISSISSIPPI
     RIVER TO PORT FOURCHON OUT 20 NM.

&&

$$







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