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

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167
FXUS64 KLIX 181302
AFDLIX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE NEW ORLEANS LA
802 AM CDT THU SEP 18 2014

...SOUNDING DISCUSSION...

DRIER AIR THAT FILTERED INTO THE AREA LAST EVENING HAS LINGERED
AS NOTED BY THE DRY AIR IN THE MID-LEVELS AND A PRECIPITABLE WATER
NEAR THE CLIMATOLOGICAL VALUE FOR SEPTEMBER. WHILE WINDS ABOVE
600MB ARE FROM THE WEST OR NORTHWEST...WINDS BENEATH THIS LEVELS ARE
MOSTLY OUT OF THE SOUTHEAST AND LIGHT. A PEAK WIND OF 68 KNOTS WAS
LOCATED 46220 FEET ABOVE THE GROUND. MLCAPE VALUES WERE CALCULATED
AT 1350 J/KG AND THE LIFTED INDEX WAS -5. WHILE WE ARE EXPECTING
THUNDERSTORMS AS NOTED BELOW IN SHORT TERM DISCUSSION...SEVERE
WEATHER IS NOT ANTICIPATED. STORMS MAY MOVE RATHER SLOWLY AS STORM
MOTIONS THIS MORNING WERE DETERMINED TO BE AROUND 1 KNOT.

12Z BALLOON INFO: NO ISSUES WITH THIS MORNING/S FLIGHT WITH THE
BALLOON BURSTING 19.7 MILES DOWNRANGE OVER THE EAST CENTRAL PART
OF LAKE BORGNE AT A HEIGHT OF 19.7 MILES ABOVE THE GROUND.

ANSORGE

&&

.PREV DISCUSSION... /ISSUED 341 AM CDT THU SEP 18 2014/

SHORT TERM...
FORECAST FOR TODAY WILL BE HIGHLY CONTINGENT ON UPPER LEVEL
IMPULSE ENERGY CURRENTLY OVER TEXAS THAT IS ANTICIPATED TO EXPAND
EASTWARD BY THIS AFTERNOON. NORTHWEST FLOW WAS PREVALENT ABOVE
20KFT WITH A VORTICITY SHEAR ZONE NOTED IN WIND DATA AND EMULATED
IN BROADER RADAR PRESENTATION ACROSS TEXAS. THE COMPLEX CURRENTLY
OVER THE AUSTIN AREA SHOULD CONTINUE TO MOVE SOUTHWARD ALONG MAX
THETA-E AXIS. GFS...NAM AND ECMWF ARE IN FAIRLY GOOD AGREEMENT IN
INDICATING A VORTICITY STRUCTURE AND STRONG OMEGA MOVING INTO THE
AREA BUT DO HAVE SOME VARIATIONS ON TIMING. THE GFS IS EARLIEST
WITH A 17Z-18Z ONSET IN THE FORECAST AREA...THE ECMWF ABOUT MID-
AFTERNOON PEAK ONSET AND NAM LATE AFTERNOON WITH MORE EMPHASIS ON
NOCTURNAL CONVECTION THAN THE OTHER TWO. HAVE OPTED TO GO CLOSER
TO GFS TIMING GIVEN CURRENT TRENDS. DESPITE ALL THIS...POPS WILL
STILL BE INDICATED ON THE LOWER SIDE...20-30 PERCENT FOR EASTERN
2/3 OF CWA...TRENDING TO 50 PERCENT ADJACENT TO WFO LCH AREA WHERE
THE GREATER FOCUS SHOULD REMAIN. THIS IS A DECENT BLEND WITH
NEIGHBORING OFFICES. DID INDICATE SOMEWHAT HIGHER THAN TYPICAL
POPS FOR THIS EVENING AS ACTIVITY MAY LINGER LONGER BEFORE MOVING
OFF THE COAST AFTER MIDNIGHT. THIS SITUATION SHOULD ALSO SERVE AS
A FRONTOGENETIC PROCESS THAT FLUSHES THE REGION OF DEEP MOISTURE
FOR FRIDAY...WHICH LOOKS NOW TO BE A DRY DAY OVER LAND AREAS.

LONG TERM...
SATURDAY AND SUNDAY WILL BE INDICATED TO BE DRIER THAN CLIMO WITH
ONLY 20 PERCENT INDICATED FOR THE AFTERNOON GULF BREEZE
CONSIDERATIONS. STRONGER COLD FRONT MOVES STEADILY THROUGH THE
AREA MONDAY WITH SOME ATTENDANT MOISTURE WORTHY OF 30 PERCENT POPS
PRE-FRONTAL. DRIER CONTINENTAL AIR THEN MOVES INTO THE AREA FOR
TUESDAY THROUGH AT LEAST WEDNESDAY BEFORE THE FRONT RETURNS SLOWLY
NORTHWARD NEXT THURSDAY. TEMPERATURES SHOULD ONLY BE AFFECTED TO
THE COOL SIDE BY A COUPLE OF DEGREES BUT GREATER INFLUENCES WILL
BE ON HUMIDITY LEVELS FOR NEXT WEEK. 24/RR

AVIATION...
SOME PATCHY FOG IS DEVELOPING EARLY THIS MORNING.  HAVE INCLUDED A
MENTION OF MVFR VISIBILITY RESTRICTIONS FROM AROUND 10Z THROUGH 13Z
AT MOST OF THE TERMINALS.  SOME INCREASED MIXING OF THE BOUNDARY
LAYER AT KMSY...KNEW...AND KGPT SHOULD KEEP REDUCED VISIBILITIES AT
BAY AT THESE TERMINALS.  KHUM WILL SEE THE LOWEST
VISIBILITIES...WITH A PERIOD OF IFR RESTIRCTIONS POSSIBLE EARLY THIS
MORNING.  ONCE THE LOW LEVEL INVERSION MIXES OUT AROUND 14Z...A
SCATTERED TO BROKEN CU FIELD RANGING FROM 2500 TO 3500 FEET WILL
BECOME ESTABLISHED.  AN UPPER LEVEL VORT LOBE WILL ALSO MOVE INTO
THE AREA.  THIS COULD SPARK OFF SOME AFTERNOON CONVECTION...AND HAVE
INCLUDED SOME PROB 30 GROUPS WITH TS WORDING TO REFLECT THIS RISK.
BRIEF PERIODS OF MVFR AND POSSIBLY IFR VISIBILITY RESTRICTIONS AND
GUSTY WINDS CAN BE EXPECTED WITH ANY CONVECTIVE ACTIVITY.  BY 02Z
TONIGHT...THE CONVECTION SHOULD DISSIPATE AND A RETURN TO VFR
CONDITIONS IS EXPECTED. 32

MARINE...
LIGHT EASTERLY FLOW OF 5 TO 10 KNOTS AND SEAS OF 1 TO 2 FEET WILL BE
FOUND OVER THE WATERS TODAY.  GRADIENT FLOW WILL INCREASE BEGINNING
TOMORROW WITH A PERIOD OF EXERCISE CAUTION CONDITIONS EXPECTED OVER
THE GULF COASTAL WATERS BEGINNING TOMORROW NIGHT AND PERSISTING
THROUGH SATURDAY.  THIS INCREASED EASTERLY FLOW WILL BE IN RESPONSE
TO A WEAK LOW PRESSURE SYSTEM MOVING OFF THE TEXAS COAST AND THEN
PUSHING EASTWARD ACROSS THE CENTRAL GULF TOWARD FLORIDA. WITH
STRONGER WINDS IN PLACE...SEAS WILL CORRESPONDINGLY RISE TO AROUND 3
TO 5 FEET ON FRIDAY AND THEN FURTHER INCREASE TO 4 TO 6 FEET FOR
SATURDAY.  SOME HIGHER THAN NORMAL TIDES WILL ALSO BE POSSIBLE BY
SATURDAY GIVEN THE PERSISTENT STRONG ONSHORE FLOW.  TIDES WILL BE
MOST ELEVATED ALONG EAST FACING SHORES. AS THE LOW PULLS EAST OF THE
AREA...THE GRADIENT WILL RELAX THROUGH THE DAY ON SUNDAY...WITH A
RETURN TO LIGHTER EASTERLY FLOW OF 5 TO 10 KNOTS FOR MONDAY. SEAS
WILL ALSO FALL BACK TO 2 TO 3 FEET BY MONDAY.  THESE CONDITIONS WILL
PERSIST THROUGH TUESDAY. 32

DECISION SUPPORT...
DSS CODE...GREEN.
DEPLOYED...NONE.
ACTIVATION...NONE.
ACTIVITIES...SLURRY SUPPORT AND SUPPORTING USCG SSW OF PASCAGOULA.

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  88  66  89  67 /  30  30   0  10
BTR  86  68  89  70 /  40  30  10  10
ASD  87  74  87  76 /  30  30  20  10
MSY  86  73  86  76 /  30  30  20  10
GPT  87  75  86  76 /  30  20  20  10
PQL  88  74  87  75 /  20  20  20  10

&&

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

$$







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