Today's severe weather outlook

NWS STORM PREDICTION CENTER NORMAN OK
0750 AM CDT THU APR 16 2009

VALID 161300Z - 171200Z

...THERE IS A SLGT RISK OF SVR TSTMS ACROSS THE CENTRAL/SOUTHERN
HIGH PLAINS...

...SYNOPSIS...
CLOSED UPPER LOW NEARING THE FOUR CORNERS AREA WILL MOVE SLOWLY EAST
TODAY...AS A DRYLINE/LEE TROUGH WILL PERSIST OVER THE HIGH PLAINS IN
ADVANCE OF THIS FEATURE. THE DRYLINE WILL MIX EASTWARD ACROSS WEST
TX DURING THE DAY...AND THEN RETREAT WESTWARD DURING THE EVENING
BEFORE IT IS OVERTAKEN BY AN OCCLUDING/PACIFIC COLD FRONT.

...CENTRAL/SOUTHERN HIGH PLAINS...
EARLY MORNING SURFACE ANALYSIS/12Z OBSERVED RAOBS DEPICT A
WEST-NORTHWESTWARD RETURN OF MODEST BOUNDARY LAYER MOISTURE ACROSS
TX SINCE LAST EVENING...ALTHOUGH 60+ F SURFACE DEWPOINTS ARE
CONFINED TO THE TX HILL COUNTRY/SOUTH TX AS OF 13Z. INITIALLY...ON
THE EASTERN PERIPHERY OF A STRONG ELEVATED MIXED LAYER SAMPLED BY
12Z REGIONAL RAOBS SUCH AS AMA/MAF/DRT/DDC...THERE IS SOME POTENTIAL
FOR EARLY DAY TSTMS TO POSE A HAIL RISK ACROSS PORTIONS OF CENTRAL
TX/HILL COUNTRY OWING TO A LEAD MID LEVEL IMPULSE CROSSING FAR
NORTHERN MEXICO EARLY THIS MORNING. WITH IMPLIED LIFT/MID LEVEL
MOISTENING NOTED EARLY THIS MORNING ACROSS THE TX HILL COUNTRY...A
CONDITIONAL SURFACE BASED SEVERE THREAT COULD EVOLVE WITHIN THIS
CORRIDOR...ALTHOUGH THE STRENGTH OF THE CAP /PER 12Z DRT RAOB/
SHOULD LIMIT APPRECIABLE SURFACE BASED DEVELOPMENT.

OTHERWISE...A MORE ORGANIZED SEVERE THREAT SHOULD DEVELOP FARTHER
WEST ACROSS THE CENTRAL/SOUTHERN HIGH PLAINS IN VICINITY OF THE LEE
TROUGH/DRYLINE LATER THIS AFTERNOON/EVENING. DIABATIC HEATING
BENEATH STEEP MID LEVEL LAPSE RATES WILL CONTRIBUTE TO
DESTABILIZATION/WEAKENING CINH ACROSS THE HIGH PLAINS BY
AFTERNOON...WITH MAINLY 50S F DEWPOINTS SUPPORTING AN AXIS OF MLCAPE
FROM 1000-1500 J/KG OVER THE TRANSPECOS REGION OF WEST TX TO AROUND
500 J/KG ACROSS EAST CENTRAL/SOUTHEAST CO. WHILE THE STRONG CAP
SHOULD LIMIT SURFACE BASED TSTM DEVELOPMENT THROUGH AT LEAST EARLY
AFTERNOON...GRADUAL LARGE SCALE HEIGHT FALLS/ADVANCING EXIT REGION
OF UPPER JET AIDED BY LOW LEVEL UPSLOPE TRAJECTORIES/AMPLE
HEATING...SHOULD LEAD TO A BROAD NNW-SSE CORRIDOR OF SURFACE BASED
TSTM DEVELOPMENT AROUND MID/LATE AFTERNOON ACROSS THE HIGH
PLAINS...INITIALLY FROM EASTERN CO/FAR WESTERN KS TO TX
PANHANDLE/WEST TX.

WITH SUFFICIENT INSTABILITY AND 35-50 KT SOUTH-SOUTHWESTERLY MID
LEVEL FLOW...LOW LEVEL VEERING/40+ KT OF EFFECTIVE SHEAR WILL
SUPPORT SUPERCELLS. SEVERE HAIL WILL LIKELY BE THE PRIMARY
THREAT...WITH DAMAGING WINDS POSSIBLE AS WELL VIA DEEP MIXING
ESPECIALLY ACROSS WEST TX AND/OR EVENTUAL STORM MERGERS LATER THIS
EVENING. ALTHOUGH A TORNADO OR TWO WILL BE POSSIBLE...MODEST
BOUNDARY LAYER MOISTURE AND/OR INITIALLY LIMITED HODOGRAPH SIZE WILL
TEND TO CURB THE THREAT.

THUNDERSTORM COVERAGE IS EXPECTED TO INCREASE...AND STORMS WILL
LIKELY GROW UPSCALE INTO ONE OR MORE QUASI-ORGANIZED MCS/S...LATER
IN THE EVENING/OVERNIGHT AS THE OCCLUDING/PACIFIC FRONT AND LEADING
EDGE OF COOLER MID-LEVEL TEMPERATURES/ASCENT ACCOMPANYING THE UPPER
TROUGH OVERTAKE THE RETREATING DRYLINE. THREAT FOR ISOLATED LARGE
HAIL/DAMAGING WIND WILL LIKELY CONTINUE INTO THE OVERNIGHT...MAINLY
ACROSS WEST/NORTHWEST TX AND FAR WESTERN OK.

..GUYER/JEWELL.. 04/16/2009

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