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

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FXUS64 KLIX 212143
AFDLIX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE NEW ORLEANS LA
443 PM CDT THU MAY 21 2015

.DISCUSSION...

FRONTAL BOUNDARY PUSHED INTO THE NORTH AND NORTHWEST PORTIONS OF
THE FORECAST AREA THIS AFTERNOON...AND AS EXPECTED SOME STRONG TO
SEVERE THUNDERSTORMS AND HEAVY RAINFALL HAVE DEVELOPED DUE TO
AMPLE MOISTURE AND INSTABILITY ALONG WITH SOME UPPER LEVEL
SUPPORT. THE FRONTAL BOUNDARY WILL CONTINUE TO PUSH SOUTH THROUGH
MOST OF THE FORECAST AREA THROUGH TONIGHT WITH HIGH PRESSURE WITH
DRIER AND SLIGHTLY COOLER AIR MOVING IN THE WAKE OF THE FRONTAL
PASSAGE. SHOWERS AND THUNDERSTORM COVERAGE TONIGHT WILL BE HIGHEST
FROM JUST BEHIND TO IN ADVANCE OF THE COLD FRONT.

UPPER LEVEL TROUGH OVER THE GREAT LAKES INTO THE MID
MISSISSIPPI AND OHIO VALLEYS WILL MOVE EAST TONIGHT AND FRIDAY
REACHING THE NORTHEAST U.S. AND MID ATLANTIC COAST FRIDAY
AFTERNOON. A MID/UPPER LOW/TROUGH WILL MOVE INTO THE DESERT
SOUTHWEST WITH A SHORTWAVE RIDGE BUILDING OVER THE LOWER
MISSISSIPPI VALLEY. THE FRONTAL BOUNDARY WILL LINGER ACROSS THE
AREA ON FRIDAY BEFORE BECOMING DIFFUSE ON SATURDAY. HIGH PRESSURE
WILL SETTLE OVER THE EASTERN SEABOARD AND SOUTHEAST FLOW
DEVELOPING OVER THE LOWER MISSISSIPPI VALLEY AND FORECAST AREA
SATURDAY AFTERNOON. EVEN WITH THE DRIER AIR MOVING IN...THERE WILL
REMAIN JUST ENOUGH LINGERING MOISTURE AND INSTABILITY FOR ISOLATED
TO SCATTERED SHOWERS AND THUNDERSTORMS ON FRIDAY.

THE UPPER LEVEL RIDGE ALONG WITH OVERALL DRIER AIR IN THE
ATMOSPHERIC COLUMN SHOULD HAMPER MOST CONVECTION ON
SATURDAY...EXCEPT FOR ISOLATED COVERAGE FOR WESTERN AND SOUTHERN
ZONES. RAIN CHANCES WILL GO UP AGAIN ON SUNDAY AS THE UPPER RIDGE
AXIS SHIFTS TO THE EAST OF THE REGION AND DISTURBANCES IN THE
SOUTHWEST FLOW ALOFT AHEAD OF A WESTERN CONUS SYSTEM BEGIN TO
IMPACT THE REGION. THIS PATTERN WILL CONTINUE THROUGH THE EARLY TO
MID PART OF NEXT WEEK WITH DAILY CHANCES FOR SCATTERED SHOWERS AND
THUNDERSTORMS. MORE NUMEROUS SHOWERS AND THUNDERSTORMS AND HEAVY
RAINFALL POTENTIAL MAY NEED TO BE ADDRESSED WITH LATER FORECASTS
DURING THE MONDAY THROUGH TUESDAY PERIODS IF THE 12 ECMWF QPF
BECOMES A MODEL CONSENSUS.

&&

.AVIATION...

MAIN ISSUE IN THE NEAR TERM PORTION OF THE TAFS IS SCATTERED TO
NUMEROUS TSRA...A FEW OF WHICH WILL BE STRONG TO SEVERE WITH
FREQUENT LIGHTNING...HAIL AND STRONG GUSTY WINDS. WILL CONTINUE TO
FINE TUNE MENTION IN THE TAFS BASED ON RADAR TRENDS...HOWEVER MOST
AIRPORTS SHOULD HAVE FEW IMPACTS FROM TSRA AFTER 00Z. ALTHOUGH
PATCHY LIGHT FOG COULD BRING SOME MVFR CATEGORY VSBYS LATE
TONIGHT...THE DRIER AIR ASSOCIATED WITH A WEAK COLD FRONT SHOULD
KEEP ANY SIGNIFICANT FOG FROM DEVELOPING.

&&

.MARINE...

WEAK WEST TO EAST ORIENTED COLD FRONT WILL PUSH SOUTH INTO THE
COASTAL WATERS LATE THIS EVENING AND OVERNIGHT. THERE WILL BE
SUFFICIENT COOLER AND DRIER AIR AND A PRESSURE GRADIENT TO BRING
THE WINDS UP TO NEAR 15 KNOTS OR 15 TO 20 KNOTS OVER THE TIDAL
LAKES...SOUNDS...AND MUCH OF THE COASTAL WATERS NORTHEAST OF
SOUTHWEST PASS TO OFF THE MISSISSIPPI COAST AFTER MIDNIGHT. WINDS
WILL LIKELY REMAIN ELEVATED ON FRIDAY...MAINLY IN THE
MORNING...WITH DIMINISHING WINDS IN THE AFTERNOON AND EVENING.
HIGH PRESSURE WILL QUICKLY SHIFT EAST AND MODERATE TO STRONG
ONSHORE FLOW WILL DEVELOP OVER THE WEEKEND AS A STRONGER PRESSURE
GRADIENT DEVELOPS BETWEEN HIGH PRESSURE TO THE EAST AND LOWER
PRESSURE OVER THE SOUTHERN PLAINS.

&&

.DECISION SUPPORT...

DECISION SUPPORT...
DSS CODE...YELLOW.
DEPLOYED...NONE.
ACTIVATION...NONE.
ACTIVITIES...STRONG TO SEVERE THUNDERSTORMS AND HEAVY RAINFALL
REMAINDER OF THIS AFTERNOON.

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 RISK SVR AND/OR DIRECT
         TROPICAL THREATS; EVENTS OF NATIONAL SIGNIFICANCE



&&

.PRELIMINARY POINT TEMPS/POPS...
MCB  62  81  65  87 /  20  30  10  20
BTR  65  84  69  87 /  30  40  20  30
ASD  67  82  69  86 /  40  30  20  20
MSY  70  83  73  86 /  40  40  20  20
GPT  68  82  68  86 /  40  20  10  10
PQL  65  83  64  86 /  40  20  10  10

&&

.LIX WATCHES/WARNINGS/ADVISORIES...
LA...NONE.
GM...NONE.
MS...NONE.
GM...NONE.
&&

$$

22/TD


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