National Weather Service Weather Forecast Office

Area Forecast Discussion

491
FXUS64 KHUN 220152 AAB
AFDHUN

AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE HUNTSVILLE AL
852 PM CDT TUE MAY 21 2013

.UPDATE...
TO UPDATE FOR APPROACHING LINE OF THUNDERSTORMS.

&&

.DISCUSSION...
A LINE OF THUNDERSTORMS IS APPROACHING (AND ACCELERATING SOMEWHAT)
THE AREA FROM THE WEST OVER N MS/W TN. MESOSCALE ANALYSIS (VIA
RAP/NAM) OF THE ENVIRONMENT AHEAD OF THIS FRONT INDICATES A DECREASE
IN SB INSTABILITY WHILE ELEVATED INSTABILITY REMAINS. HOWEVER, EVEN
THEN CURRENT BMX SOUNDING DOES INDICATE A STEEP LAPSE RATE BTWN
891-500 MB WHICH COULD MEAN SOME ELEVATED REDEVELOPMENT LATER
TONIGHT. WIND SHEAR IS WEAK AHEAD OF THE LINE, BUT HAVE NOTICED SOME
BRIEF PERIODS OF ROTATION THAT DID NOT LAST FOR MORE THAN A VOLUME
SCAN OR TWO FURTHER WEST A COUPLE OF HOURS AGO. MOST OF THE MORE
SEVERE AND MORE ORGANIZED PORTIONS OF THE LINE APPEAR TO BE
CONCENTRATED FURTHER SOUTH OVER CENTRAL MS. LIGHTNING HAS FALLEN OFF
WITH THE PORTION OF THE LINE CLOSER TO NW AL, WITH THE LINE BREAKING
UP. THUS, HAVE INCREASED POPS TO LIKELY MAINLY FOR NW AL WITH CHANCE
OF THUNDERSTORMS FURTHER EAST. THERE IS AN OUTFLOW BOUNDARY
PROPAGATING SOUTHEAST FROM THE LINE WHICH COULD RESULT IN ADDITIONAL
DEVELOPMENT AHEAD OF THE LINE WHICH IS ANOTHER REASON FOR HIGHER POPS
OVER NORTH CENTRAL AL INTO NE AL.

IN ADDITION, MADE SOME ADJUSTMENTS TO DEWPOINT AND SKY COVER GRIDS
BASED ON THE CURRENT TRENDS.

SL.77

&&

.AVIATION...
/ISSUED 636 PM CDT TUE MAY 21 2013/
FOR 00Z TAFS...

VFR CONDITIONS SHOULD PREVAIL ACROSS N AL/S MIDDLE TN AT LEAST FOR
THE NEXT 9-11 HOURS. A LINE OF STRONG THUNDERSTORMS IS APPROACHING NW
AL AND SHOULD ARRIVE BTWN 08-10Z AFFECTING KMSL BY 09Z. THUS, HAVE
INCLUDED THE ONSET OF TSRA FOR KMSL AT 09Z/KHSV AT 11Z, BUT HAVE ONLY
INCLUDED A FEW-SCT020 CLOUD GROUP AT THIS TIME DUE TO SOME
UNCERTAINTY ON ITS STRENGTH/CIGS AS IT ARRIVES. ADDITIONAL -TSRA AND
INCREASE IN WIND SPEEDS ARE THEN POSSIBLE AFTER 15Z AS ANOTHER LINE
OF -TSRA CROSSES N AL/S MIDDLE TN.

SL.77

&&

.HUN WATCHES/WARNINGS/ADVISORIES...
AL...NONE.
TN...NONE.
&&

$$

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