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000
FXUS64 KHUN 171737 AAC
AFDHUN

AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE HUNTSVILLE AL
1237 PM CDT FRI MAY 17 2013

.UPDATE...
FOR 18Z TAFS

&&

.DISCUSSION...
/ISSUED 1041 AM CDT FRI MAY 17 2013/
A SLOW MOVING WEAK MID-LEVEL SHORTWAVE TROUGH IS ENHANCING MOISTURE
TRANSPORT AND LIFT ACROSS THE TN VALLEY. THIS IS RESULTING IN
NUMEROUS SHOWERS AND ISOLATED THUNDERSTORMS DEVELOPING AND MOVING
EAST ACROSS THE NORTH MS INTO NW AL. SFC AND 850 MB ANALYSIS
INDICATES A NARROW AXIS OF LOW-LEVEL MOISTURE STRETCHING FROM THE LA
COASTLINE NORTHWARD INTO THE MID MS RIVER VALLEY. MOST OF THE
ACTIVITY IS ORIGINATING WITH PARCELS LIFTING OVER THE MID-LEVELS OF
THE VERTICAL COLUMN (090-120 KFT) AT THIS POINT. SATURATION AND
DIMINISHING DEWPOINT DEPRESSIONS AT THE LOW LEVELS HAVE COMBINED TO
PRECIP MAKING IT TO THE GROUND. BASED ON RADAR/SAT TRENDS, HAVE
INCREASED POPS FOR THIS MORNING INTO THE EARLY AFTERNOON WITH
ISOLATED THUNDERSTORMS THIS MORNING.

VIS SATELLITE IS INDICATING POCKETS OF CLEARING WITH THINNER CLOUDS
JUST TO THE WEST/SW OF CONVECTION SPARKED BY THE SHORTWAVE OVER
SOUTH CENTRAL MS AND THE MS RIVER. THIS COULD BE INDICATIVE OF A DRY
SLOT WHICH COULD DESTABILIZE THE TN VALLEY BRIEFLY AND RESULT IN SOME
DAYTIME HEATING (ENOUGH TO WARM TEMPERATURES INTO THE UPPER 70S TO
LOW 80S). IF THIS OCCURS, A NARROW WINDOW OF OPPORTUNITY FOR STRONGER
STORMS WILL BE POSSIBLE MAINLY OVER NW AL (AROUND THE SOUTHERN
PERIPHERY OF THE SHORTWAVE TROUGH/DEFORMATION ZONE) WHERE GREATER
WIND SHEAR (30-35 KTS) AND LIFT WILL EXIST. THUS, WILL KEEP ONGOING
TEMP FORECAST FOR NOW, BUT FURTHER ADJUSTMENTS MAY BE NEEDED IF THE
BREAKS IN THE CLOUDS DO NOT MATERIALIZE AND INSTABILITY REMAINS
ELEVATED.

DAYTIME HIGHS STILL LOOK ON TRACK WITH COOLER HIGHS OVER NW AL AND
WARMER HIGHS OVER THE REST OF THE AREA. NOW, THIS TEMP FORECAST IS
BASED ON THE ASSUMPTION THAT THE CLOUD COVER BREAKS DO INDEED
MATERIALIZE. DID MAKE SOME SLIGHT ADJUSTMENTS TO THE DEWPOINT AND QPF
FORECAST BASED ON THE CURRENT TRENDS. OTHERWISE, THE REST OF THE
FORECAST LOOKS FINE.

SL.77

&&

.AVIATION...
FOR 18Z TAFS...

VFR CONDITIONS ARE EXPECTED TO CONTINUE TO PREVAIL THROUGH THE NEXT
9-10 HOURS AS MID LEVEL BASED (080-120 CIGS) SHRA CONTINUE. TSRA ARE
DEVELOPING FURTHER SW OVER CENTRAL MS AND THESE TSRA ALONG WITH MORE
DEVELOPMENT IS POSSIBLE AFTER 19Z. HAVE INCLUDED TEMPO GROUPS IN
BOTH TERMINALS FOR THE POSSIBILITY OF TSRA BTWN 19-01Z THAT REDUCE
CIG TO MVFR. ADDITIONAL TSRA MAY OCCUR AFTER 01Z, BUT IS DIFFICULT
TO TIME AT THIS POINT. A DROP IN CIG TO MVFR IS THEN LIKELY AFTER 04Z
AS SFC MOISTURE INCREASES.

SL.77

&&

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

$$

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