Severe Thunderstorm Warning 96, NWS Huntsville, AL

AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE HUNTSVILLE AL
655 PM CST SAT DEC 21 2013

.MESOSCALE UPDATE...
00Z RAOBS SUGGEST A GRADIENT IN SFC-BASED INSTABILITY FROM N-S BASED
ON A NASHVILLE SOUNDING WHICH HAS LITTLE CAPE, WHILE BMX AND JAN SHOW
MORE SUBSTANTIAL CAPE IN THE 400-800 J/KG RANGE. SRH IS BASED LARGELY
IN THE LOWEST 1KM WITH VALUES NEARING 600 M2/S2 AT NASHVILLE AND
350-400 M2/S2 AT BIRMINGHAM. AMPLE LOW LEVEL FLOW IS ADVECTING DEW
POINTS INTO THE M60S OVER NRN AL NOW WITH TEMPS STILL IN THE L-M70S
(RECORD HIGH TEMP AT KMSL). PRIND ARE THAT THE SQLN WILL REACH THE AL
STATE LINE IN OUR CWA BY 03-04Z. CONVERGENCE LINES/SHRA ARE
DEVELOPING AHEAD OF THE SQLN WHICH HAS US SOMEWHAT CONCERNED FOR DISCRETE
SUPERCELL DEVELOPMENT BEFORE THE LINE OVERTAKES THIS. THE CAPE VALUES
WOULD SUGGEST THIS TO BE MORE LIKELY JUST S-SW OF OUR CWA, BUT GIVEN
ADVECTION FIELDS, I CANNOT RULE THIS OUT IN OUR AREA AS WELL. BASED
UPON THE MD ISSUED BY SPC, WE SHOULD SEE A WATCH ISSUED FOR OUR AREA
SOON. WE COULD SEE A WEAKENING TREND AS THE MAX SFC PRESSURE FALLS
ARE LIFTING WELL NORTH INTO IN/KY. IN THIS CASE, SOME
MOMENTUM/CONVERGENCE MAY WEAKEN SOMEWHAT AND WIND FIELDS BECOME MORE
PARALLEL TO THE LINE. IN THIS CASE, HEAVY RAIN MAY BECOME MORE OF A
PROBLEM.

KULA

&&

.AVIATION...
/ISSUED 522 PM CST SAT DEC 21 2013/
FOR 00Z TAFS... WINDY CONDITIONS WILL PREVAIL TONIGHT IN ADVANCE OF
SQUALL LINE. SPORADIC SHRA WILL OCCUR AHEAD OF THE SOLID LINE OF
SHOWERS AND THUNDERSTORMS, ALONG WITH VARIABLE MVFR CIGS AT TIMES.
THE SQUALL LINE MAY PRODUCE STRONG WINDS OF AT LEAST 40KT, BUT IT
COULD BE HIGHER ALONG WITH BRIEF HEAVY RAINFALL LOWERING VSBYS TO 1SM
OR LESS. BEHIND THE LINE, STRATIFORM RAINFALL AND MVFR CIGS WILL
OCCUR THRU MOST OF SUNDAY MORNING BEFORE SOME DRIER AIR WORKS IN
DURING THE AFTERNOON HOURS.

AK

&&

.HUN WATCHES/WARNINGS/ADVISORIES...
AL...WIND ADVISORY UNTIL 3 AM CST SUNDAY FOR ALZ001>010-016.

TN...WIND ADVISORY UNTIL 3 AM CST SUNDAY FOR TNZ076-096-097.

&&

FOR MORE INFORMATION PLEASE VISIT OUR WEBSITE
AT WEATHER.GOV/HUNTSVILLE.

HAZARDOUS WEATHER OUTLOOK...UPDATED
NATIONAL WEATHER SERVICE HUNTSVILLE AL
315 PM CST SAT DEC 21 2013

ALZ001>010-016-TNZ076-096-097-221100-
LAUDERDALE-COLBERT-FRANKLIN AL-LAWRENCE-LIMESTONE-MADISON-MORGAN-
MARSHALL-JACKSON-DEKALB-CULLMAN-MOORE-LINCOLN-FRANKLIN TN-
315 PM CST SAT DEC 21 2013

THIS HAZARDOUS WEATHER OUTLOOK IS FOR NORTH ALABAMA AND PORTIONS
OF SOUTHERN MIDDLE TENNESSEE.

.DAY ONE...TONIGHT...

SOUTHERLY WINDS WILL INCREASE 20 TO 30 MPH WITH GUSTS UP TO 40 MPH.
RIDGETOPS AND HIGHER ELEVATIONS ABOVE 1500 FEET WILL EXPERIENCE
STRONGER WIND GUSTS. A WIND ADVISORY IS IN EFFECT THROUGH 3 AM CST
SUNDAY.

LATER THIS EVENING AND OVERNIGHT...A LINE OF STRONG TO SEVERE
SHOWERS AND THUNDERSTORMS WILL MOVE ACROSS THE AREA. THE LINE WILL
BEGIN TO IMPACT NORTHWEST ALABAMA BETWEEN 8 AND 10 PM. POCKETS OF
DAMAGING WINDS OF 45 TO 65 MPH WILL BE THE PRIMARY THREAT.
HOWEVER...SHORT-LIVED TORNADOES ARE POSSIBLE...ESPECIALLY WITH ANY
DISCRETE STORMS THAT DEVELOP JUST ALONG AND AHEAD OF THE MAIN SQUALL
LINE. THE GREATEST RISK FOR SEVERE WEATHER WILL BE ALONG AND WEST OF
A FAYETTEVILLE TO HUNTSVILLE TO CULLMAN LINE. THE SQUALL LINE IS
EXPECTED TO GRADUALLY WEAKEN AS IT MOVES EAST OVERNIGHT...BUT THE
THREAT FOR SEVERE WEATHER WILL PERSIST UNTIL THE SHOWERS AND
THUNDERSTORMS EXIT THE AREA...SOMETIME BETWEEN 4 AND 8 AM CST SUNDAY.

IN ADDITION...ONE TO TWO INCHES OF RAINFALL COULD CREATE MINOR
LOWLAND AND URBAN FLOODING.

.DAYS TWO THROUGH SEVEN...SUNDAY THROUGH FRIDAY...

THE PROBABILITY OF WIDESPREAD HAZARDOUS WEATHER IS LOW.

THE EXITING LINE OF SHOWERS AND ISOLATED STORMS COULD POSE A
LINGERING THREAT FOR STRONGER WINDS THROUGH MID MORNING...MAINLY
ACROSS NORTHEAST ALABAMA.

.SPOTTER CALL TO ACTION STATEMENT...

ACTIVATION OF STORM SPOTTERS AND EMERGENCY MANAGEMENT PERSONNEL
IS LIKELY TONIGHT THROUGH EARLY SUNDAY MORNING.

CCC/DJN