SWODY2
SPC AC 150558
DAY 2 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1258 AM CDT FRI MAY 15 2009
VALID 161200Z - 171200Z
...THERE IS A SLGT RISK OF SVR TSTMS ACROSS THE NORTH CENTRAL
APPALACHIANS/NORTHEAST STATES...
...THERE IS A SLGT RISK OF SVR TSTMS ACROSS THE SOUTHWEST TX BIG
BEND...
...SYNOPSIS...
LARGE SCALE PATTERN WILL AMPLIFY OVER THE LOWER 48 ON
SATURDAY...HIGHLIGHTED BY A PROGRESSIVE UPPER TROUGH OVER EASTERN
CANADA AND THE ADJACENT GREAT LAKES REGION...WITH A BUILDING UPPER
RIDGE OVER THE WESTERN STATES. ASSOCIATED WITH THE EASTERN LONGWAVE
TROUGH...THE PRIMARY FOCUS FOR DEEP CONVECTION POTENTIAL WILL BE
ALONG/AHEAD OF AN EASTWARD MOVING COLD FRONT ACROSS THE OHIO VALLEY
TO NORTHEAST STATES/APPALACHIANS...WITH THE SOUTHERNMOST PORTION OF
THE FRONT MOVING SOUTHWARD ACROSS TX/MID-SOUTH AND GULF COAST
REGION.
...NORTH CENTRAL APPALACHIANS/NORTHEAST STATES..
IT SEEMS LIKELY THAT SHOWERS/TSTMS WILL BE ONGOING EARLY SATURDAY
MORNING ALONG/AHEAD OF THE EAST ADVANCING COLD FRONT ACROSS THE OHIO
VALLEY. ALTHOUGH THE LIKELIHOOD OF CLOUD COVER/SCATTERED
PRECIPITATION COMPLICATES THE DETAILS...AN INCREASINGLY MOIST
AIRMASS WILL CONTINUE TO ADVECT INTO THE NORTHEAST STATES IN THE
WAKE OF A NORTHWARD RETREATING WARM FRONT. WITH 60S F SURFACE
DEWPOINTS IN MUCH OF THE PREFRONTAL WARM SECTOR...POCKETS OF
STRONGER HEATING/DIURNAL DESTABILIZATION AMIDST STEADY LARGE SCALE
HEIGHT FALLS/AMPLE LARGE SCALE ASCENT SUGGESTS AN UPSWING IN TSTMS
ALONG THE COLD FRONT OR PERHAPS A PREFRONTAL TROUGH DURING THE
AFTERNOON.
QUASI-DISCRETE MULTICELLS/FEW SUPERCELLS MAY BE POSSIBLE EARLY IN
CONVECTION EVOLUTION /MAINLY PA INTO SOUTHERN NY/...BUT OTHERWISE
THE NATURE OF THE FORCING AND LARGELY UNIDIRECTIONAL WIND PROFILES
SUGGEST A MULTICELLULAR/LINEAR CONVECTIVE MODE WITH SMALL SCALE BOWS
SHOULD DOMINATE ESPECIALLY NEAR THE COLD FRONT. AS SUCH...DAMAGING
WINDS WOULD LIKELY BE THE PRIMARY HAZARD OVERALL...WITH HAIL/PERHAPS
AN ISOLATED TORNADO POSSIBLE AS WELL.
...SOUTHWEST TX...
SHOWERS/TSTMS WILL BE COMMON ALONG THE STEADILY SOUTHWARD MOVING
COLD FRONT ACROSS TX. ALTHOUGH QUESTIONS EXIST REGARDING THE TIMING
OF THE FRONT/DEGREE OF DESTABILIZATION...THE RELATIVELY GREATEST
POTENTIAL FOR SEVERE TSTMS WOULD APPEAR TO BE ACROSS SOUTHWEST TX IN
THE BIG BEND/RIO GRANDE VICINITY...ALONG THE FRONT AND/OR IN ITS
WAKE VIA DEVELOPING EASTERLY UPSLOPE INTO THE HIGHER TERRAIN.
VEERING WIND PROFILES/STEEP MID LEVEL LAPSE RATES COULD SUPPORT SOME
SUPERCELLS WITH A PRIMARY RISK OF SEVERE HAIL.
...TN VALLEY/ARKLATEX/MID-SOUTH...
SCATTERED TSTMS WILL BE COMMON ALONG/AHEAD OF THE SOUTHEAST
ADVANCING COLD FRONT ACROSS THE TN VALLEY/MID-SOUTH/ARKLATEX.
PREFRONTAL POCKETS OF MODERATE POTENTIAL INSTABILITY...BUT RATHER
ANEMIC WIND PROFILES...SUGGESTS SOME PULSE-TYPE/EPISODIC WIND DAMAGE
WILL BE POSSIBLE ON AN ISOLATED BASIS.
..GUYER.. 05/15/2009
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