SWODY1
SPC AC 132001
DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0301 PM CDT FRI APR 13 2007
VALID 132000Z - 141200Z
..THERE IS A HIGH RISK OF SVR TSTMS ACROSS PARTS OF NORTH CENTRAL
AND NORTHEAST TEXAS THROUGH THIS EVENING...
..THERE IS A MDT RISK OF SVR TSTMS SURROUNDING THE HIGH RISK ACROSS
NRN/ERN TX...PARTS OF FAR SRN OK TO SWRN AR AND NRN/WRN LA...
..THERE IS A SLGT RISK OF SVR TSTMS SURROUNDING THE MODERATE RISK
ACROSS THE SRN PLAINS TO THE LOWER MS VALLEY...
..THREAT FOR ACTIVE SEVERE WEATHER WITH POTENTIAL FOR A FEW
SIGNIFICANT TORNADOES...VERY LARGE AND DESTRUCTIVE HAIL...AND
DAMAGING WINDS BECOMING MORE PROBABLE ACROSS NORTH CENTRAL TO
NORTHEAST TX INTO THIS EVENING...
STRONG MID LEVEL SHORT WAVE TROUGH LOCATED OVER ERN HALF OF NM IS
PROGGED TO MOVE ENEWD THIS FORECAST PERIOD ACROSS THE SRN PLAINS AND
SHOULD REACH THE OZARKS/LOWER MO VALLEY BY 12Z SATURDAY...WITH LONG
WAVE TROUGH EDGING EWD INTO THE SRN PLAINS. ASCENT AHEAD OF THESE
FEATURES AND ATOP MODIFYING AIR MASS WILL SUPPORT AN ACTIVE SEVERE
WEATHER EVENT ACROSS PARTS OF N TX TO NRN LA THROUGH TONIGHT...WITH
A RISK OF A FEW STRONG TO SIGNIFICANT TORNADOES... VERY LARGE HAIL
AND DAMAGING WINDS. THUS...A HIGH RISK HAS BEEN ADDED TO THE
CONVECTIVE OUTLOOK ACROSS PARTS OF NORTH CENTRAL TO NE TX.
AFTERNOON WATER VAPOR IMAGERY INDICATED A LEAD SHORT WAVE TROUGH
CENTERED OVER THE TX/OK PANHANDLES. ATTENDANT DEEP LAYER ASCENT
WITH THIS FEATURE IS AIDING STRONG/SEVERE TSTM DEVELOPMENT VICINITY
OF SURFACE LOW SWD ALONG WIND SHIFT/DRY LINE IN NW TX. ALTHOUGH
THIS LEAD WAVE IS PROGGED TO MOVE NEWD INTO KS...A SECOND ZONE OF
ASCENT NOW MOVING INTO TX AHEAD OF PRIMARY NM SHORT WAVE TROUGH WILL
SPREAD EWD ACROSS TX/OK TOWARD THE LOWER MS VALLEY MAINTAINING TSTM
DEVELOPMENT THROUGH THE FORECAST PERIOD ALONG/E OF DRY LINE. EARLY
AFTERNOON SURFACE ANALYSIS SHOWED A LOW/TRIPLE POINT OVER NW TX
/VICINITY STONEWALL COUNTY/ WITH A WARM FRONT EXTENDING SEWD TO
SOUTH OF FTW/DAL METRO AREA TO NORTH OF HOU. DRYLINE EXTENDED SSWWD
FROM SURFACE LOW TO THE TX BIG BEND REGION. SURFACE LOW SHOULD
TRACK ENEWD ALONG THIS WARM FRONT AND BE LOCATED ALONG/JUST EAST OF
THE ARKLATEX REGION BY 12Z SUNDAY.
BROAD 50 KT SLY LLJ LOCATED OVER THE ERN HALF OF TX INTO LA WILL
MAINTAIN INFLUX OF RICH GULF MOISTURE ACROSS THE WARM SECTOR...AS
WARM FRONT CONTINUES TO SHIFT N TOWARD THE RED RIVER VALLEY AND
EVENTUALLY INTO NRN LA/SRN AR AND SWRN MS LATER THIS EVENING. STEEP
LAPSE RATES ATOP THIS MOISTURE RETURN COMBINED WITH ADDITIONAL
SURFACE HEATING ALONG/E OF DRY LINE WILL SUPPORT MODERATE
INSTABILITY DEVELOPING/EXPANDING EWD INTO CENTRAL/NRN PARTS OF TX.
DEEP LAYER SHEAR WILL REMAIN SUPPORTIVE FOR ORGANIZED STORMS THIS
AFTERNOON INTO THE EVENING WITH POTENTIAL FOR LONG-LIVED TORNADIC
SUPERCELLS VICINITY OF SURFACE LOW AND WARM FRONT...WHERE 0-3 KM SRH
VALUES IN EXCESS OF 400 M2/S2 WILL FAVOR LOW LEVEL ROTATIONS WITHIN
MOISTENING AIR MASS. SEVERE THREAT IS EXPECTED TO SPREAD EWD
OVERNIGHT INTO THE LOWER MS VALLEY WITH POTENTIAL FOR MORE LINEAR
STRUCTURE AS SHEAR VECTORS BECOME ORIENTED MORE PARALLEL TO
PROGRESSIVE COLD FRONT.
NORTH OF THE WARM FRONT...SCATTERED STRONG TO SEVERE THUNDERSTORMS
ARE EXPECTED TO INCREASE THROUGH THE AFTERNOON/EVENING FROM SRN OK
EWD TO PARTS OF AR/NRN MS...AHEAD OF APPROACHING UPPER TROUGH.
ELEVATED SUPERCELLS ARE POSSIBLE OVER THIS REGION...ABOVE STABLE
BOUNDARY LAYER...WITH LARGE HAIL BEING THE MAIN THREAT.
.PETERS.. 04/13/2007
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