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

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085
FXUS64 KLIX 150113
AFDLIX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE NEW ORLEANS LA
713 PM CST SUN DEC 14 2014

...SOUNDING DISCUSSION...

BULK OF THE MOISTURE THAT WE DO HAVE OVER THE AREA IS BELOW 8200
FEET THIS EVENING...WHICH IS QUITE SIMILAR TO LAST EVENING. NO
TEMPERATURE INVERSIONS WERE SAMPLES DURING THE FLIGHT.
TEMPERATURES COMPARED TO 24 HOURS AGO ARE HIGHER /WARMER/ ABOVE
12000 FEET. THE TEMPERATURE NET CHANGE IN THE LOW-LEVELS IS
ESSENTIALLY ZERO WITH SLIGHTLY COOLER AIR NEAR THE SURFACE AND
SLIGHTLY WARMER AIR BETWEEN 2000 AND 5000 FEET. WINDS WERE UNDER 20
KNOTS AND VARIABLE BELOW 22000 FEET AND THEN BECAME FROM THE WEST-
SOUTHWEST AND WEST ABOVE 22000 FEET. A PEAK WIND SPEED OF 69 KNOTS
WAS LOCATED AT 43200 FEET.

00Z BALLOON INFO: THIS EVENING/S FLIGHT WAS A SUCCESS LASTING
108 MINUTES. THE BALLOON REACHED A HEIGHT OF 21.3 MILES ABOVE THE
GROUND BEFORE BURSTING NEAR LATIMER MS 62 MILES DOWNRANGE FROM THE
OFFICE.

ANSORGE

&&

.PREV DISCUSSION... /ISSUED 337 PM CST SUN DEC 14 2014/

SHORT TERM...

A STRONG SHORT WAVE TROUGH WILL CONTINUE TO LIFT TO THE NORTHEAST
THROUGH THE OZARKS AND INTO THE MIDWEST TONIGHT INTO TOMORROW. A
TRAILING FRONT WILL APPROACH THE FORECAST AREA TONIGHT...AND PASS
THROUGH THE AREA DURING THE DAY TOMORROW.  THERE WILL BE ENOUGH OVERALL OMEGA
DUE TO THE COMBINATION OF DIVERGENT FLOW ALOFT AND FORCING ALONG
THE FRONTAL BOUNDARY TO BRING A CHANCE OF RAIN TO THE AREA. HOWEVER...LAPSE
RATES AND OVERALL INSTABILITY ARE NOT FAVORABLE FOR THUNDERSTORM
DEVELOPMENT...AND HAVE ONLY INCLUDED A SLIGHT CHANCE OF THUNDER IN
THE FORECAST FOR TOMORROW AND TOMORROW EVENING. HIGHS WILL WARM
SIGNIFICANTLY AHEAD OF THE FRONTAL BOUNDARY...WITH READINGS
CLIMBING INTO THE LOWER TO MIDDLE 70S TOMORROW AFTERNOON. THESE
READINGS ARE A GOOD 10 DEGREES ABOVE NORMAL.

INCREASING NEGATIVE VORTICITY ADVECTION WILL TAKE HOLD OF THE AREA
TOMORROW NIGHT AND CONTINUE INTO TUESDAY...WHICH WILL RESULT IN
CLEARING SKIES AND DRIER AIR ADVECTING INTO THE REGION. THERE WILL
BE SOME WEAK COLD AIR ADVECTION IN THE WAKE OF THE FRONT...BUT
OVERALL FLOW ALOFT WILL REMAIN ZONAL IN NATURE. AT
WORST...TEMPERATURES WILL DROP BACK TO MORE NORMAL LEVELS FOR MID-
DECEMBER.

LONG TERM...

A WEAK AND HIGHLY SHEARED SHORT WAVE TROUGH WILL SLIDE THROUGH THE
MID-SOUTH ON THE BACK OF THE ZONAL FLOW ALOFT WEDNESDAY NIGHT INTO
THURSDAY. AN ELONGATED REGION OF INCREASED UPPER LEVEL OMEGA AND A
WEAK STATIONARY FRONT WILL BE FOUND OVER NORTHERN LOUISIANA AND
CENTRAL MISSISSIPPI DURING THIS PERIOD. THE FORECAST AREA WILL SEE
INCREASING CLOUD COVER THROUGH THE NIGHT WEDNESDAY NIGHT WITH
MOSTLY CLOUDY CONDITIONS EXPECTED BY THURSDAY. MOISTURE POOLING
ALONG THE WEAK FRONTAL BOUNDARY AND WEAK ISENTROPIC FORCING OVER
THIS BOUNDARY COULD PRODUCE SOME ISOLATED TO SCATTERED SHOWERS TO
THE AREA ON THURSDAY. RAIN CHANCES WILL BE HIGHEST ACROSS
SOUTHWEST MISSISSIPPI AND THE BATON ROUGE AREA WHERE OVERALL
OMEGA AND THETA E IS HIGHER. TEMPERATURES WILL REMAIN NEAR
SEASONAL NORMS AS THE MID AND UPPER LEVEL FLOW REMAINS ZONAL.

A VERY STRONG TROUGH WILL KICK OUT OF THE FOUR CORNERS AND BEGIN
TO TAKE ON A NEGATIVE TILT OVER THE SOUTHERN PLAINS THURSDAY NIGHT
INTO FRIDAY. A STRONG SURFACE LOW AND ASSOCIATED COLD FRONT IS
ALSO EXPECTED TO FORM OVER EAST TEXAS FRIDAY AFTERNOON AND QUICKLY
RACE TO THE NORTHEAST TOWARD THE OHIO VALLEY BY SATURDAY MORNING.
AS THIS LOW DEEPENS...THE COLD FRONT WILL INTENSIFY AND ALSO RACE
EASTWARD ACROSS THE FORECAST AREA. HAVE KEPT IN HIGH END CHANCE
POPS FOR THE AREA ON FRIDAY...AND EXPECT TO SEE A MIX OF SHOWERS
AND THUNDERSTORMS IN ADVANCE OF THE FRONT. THE ATMOSPHERE WILL BE
HIGHLY SHEARED IN DIRECTIONAL AND SPEED DIFFERENTIAL TERMS...WITH
HELICITY VALUES IN EXCESS OF 400 M2/S2 EXPECTED ACROSS THE AREA.
HOWEVER...THERE WILL BE LITTLE INSTABILITY TO WORK WITH ACROSS THE
AREA. THE BEST INSTABILITY VALUES WILL BE ELEVATED...DUE TO A
COOLER MARINE LAYER AIRMASS REMAINING IN PLACE IN THE LOW LEVELS.
AS A RESULT...THE SEVERE THREAT LOOKS LIMITED FOR THE REGION AT
THIS TIME. IF THE MARINE LAYER CAN MIX OUT AND THE ATMOSPHERE
DESTABILIZE A BIT...THAN THE SEVERE POTENTIAL WILL INCREASE
DRAMATICALLY GIVEN THE HIGH SHEAR VALUES AND AMPLE UPPER LEVEL
FORCING ACROSS THE GULF SOUTH.

THE FRONT WILL CLEAR THE AREA BY SATURDAY MORNING AND SOME WEAK
UPPER LEVEL RIDGING WILL BEGIN TO BUILD OVER AREA. THERE WILL BE A
SURGE OF DRIER AND COLDER AIR ADVECTING INTO THE AREA...AND EXPECT
TO SEE TEMPERATURES FALL ABOUT 5 DEGREES BELOW NORMAL FOR BOTH
SATURDAY AND SUNDAY. WITH INCREASING SUBSIDENCE TAKING
HOLD...SKIES WILL ALSO BEGIN TO CLEAR SATURDAY MORNING AND SHOULD
BE PARTLY CLOUDY THROUGH THE WEEKEND.

AVIATION...

VFR CONDITIONS THROUGH TONIGHT BEFORE ONSHORE FLOW USHERS A MARINE
LAYER CLOUD DECK AROUND SCT-BKN020 MONDAY MORNING...TRENDING
BKN020-025 MONDAY AFTERNOON. -SHRA POSSIBLE GENERALLY BETWEEN
15Z-21Z FROM WEST-EAST WITH FRONTAL WIND SHIFT FROM S TO WNW BY THE
END OF TAF VALID PERIOD. 24/RR

MARINE...

SOUTH TO SOUTHWEST WINDS OF 10 TO 15 KNOTS AND SEAS GENERALLY
RANGING FROM 1 TO 3 FEET WILL BE FOUND OVER THE AREA TONIGHT INTO
TOMORROW. THE PASSAGE OF A FRONT WILL SWITCH WINDS TO THE NORTHWEST
AND THEN NORTH TOMORROW NIGHT INTO TUESDAY. THE WINDS CONTINUE TO
VEER ON WEDNESDAY WITH A EASTERLY FLOW EXPECTED BY WEDNESDAY
EVENING. A LOW PRESSURE SYSTEM WILL IMPACT THE COASTAL WATERS
THURSDAY AND FRIDAY...CAUSING WINDS TO INCREASE FROM 5 TO 10 KNOTS
WEDNESDAY NIGHT TO 15 TO 20 KNOTS THURSDAY NIGHT AND FRIDAY. SEAS
WILL ALSO INCREASE FROM 1 TO 2 FEET ON WEDNESDAY TO 3 TO 5 FEET BY
FRIDAY.

DECISION SUPPORT...

DSS CODE...GREEN.
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  50  72  48  63 /  50  50  10   0
BTR  51  75  50  65 /  50  50  10  10
ASD  48  73  53  69 /  30  40  20  10
MSY  53  75  55  67 /  30  30  20  10
GPT  48  70  52  68 /  20  30  20  10
PQL  41  72  49  70 /  10  30  20  10

&&

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

$$







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