SWODY1
SPC AC 071620
DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1120 AM CDT SAT MAY 07 2011
VALID 071630Z - 081200Z
...THERE IS A SLGT RISK OF SVR TSTMS ACROSS EASTERN ILLINOIS AND
MUCH OF CENTRAL/SOUTHEAST INDIANA...
...IL/IND...
AS ALLUDED TO IN 13Z OTLK DISCUSSION AN UPGRADE TO SLGT RISK APPEARS
LIKE A REASONABLE APPROACH TO THE FCST THIS AFTERNOON AND EVENING
ACROSS ERN IL AND MUCH OF CNTRL IND. THERE IS VERY GOOD CONSENSUS
AMONGST STORM SCALE GUIDANCE THAT AT LEAST ISOLD TSTM DEVELOPMENT
WILL OCCUR NEAR WEAK SFC LOW/WAVE TRACKING EAST ACROSS THESE AREAS
LATER TODAY. SHORT WAVE TROUGH EVIDENT IN SATELLITE IMAGERY AND
MODEL DIAGNOSES ACROSS IA ATTM IS EXPECTED TO ENHANCE LARGE SCALE
ASCENT OVER THE AREA COINCIDENT WITH BOUNDARY LAYER HEATING AND
MODEST DESTABILIZATION /SBCAPE TO 1000 J PER KG/. GIVEN HEATING AND
PERSISTENT LOW LEVEL CONVERGENCE NEAR SFC LOW/WAVE...GENERALLY WEAK
CAPPING SHOULD BE OVERCOME WITH THE POTENTIAL FOR TSTM INITIATION
OCCURRING AROUND 21 UTC.
WNWLY FLOW ALOFT AND 50-60KT JET STREAK TRAVERSING THE
REGION...COUPLED WITH WEAKER LOW LEVEL SWLY FLOW...WILL CONTRIBUTE
TO EFFECTIVE SHEAR VALUES SUPPORTIVE OF SUPERCELLS. LOCALLY BACKED
LOW LEVEL WINDS NEAR SFC LOW/WAVE MAY ENHANCE HODOGRAPH CURVATURE
AND LOW LEVEL SRH. LATEST INDICATIONS SUGGEST THAT ISOLATED TO
WIDELY SCATTERED STORMS MAY INITIATE AND PERSIST FOR A FEW HOURS IN
THIS ENVIRONMENT AND RESULT IN A FEW LARGE HAIL EVENTS AND PERHAPS
EVEN A TORNADO OR TWO.
...NORTHEAST...
A FEW MARGINALLY SEVERE HAILSTORMS APPEAR POSSIBLE FROM NERN PA AND
NRN NJ ACROSS SERN NY AND SRN NEW ENGLAND THROUGH THE AFTERNOON.
HEIGHT FALLS AND STEEPENING DEEP-LAYER LAPSE RATES ASSOCIATED WITH
UPPER TROUGH CROSSING THE NORTHEAST TODAY HAVE ALREADY SUPPORTED THE
DEVELOPMENT OF SHOWERS AND LOW-TOPPED TSTMS ACROSS NRN PA/WRN NY.
MINUS 25C TO -28C COLD POOL AT 500MB AND LOW FREEZING
LEVELS...COUPLED WITH DIURNAL HEATING...WILL CONTRIBUTE TO MLCAPE
VALUES PERHAPS CLIMBING TO 500 J/KG. BACKGROUND ASCENT WITH THE
UPPER TROUGH AND GENERALLY WEAK EFFECTIVE SHEAR SUGGEST POORLY
ORGANIZED/SHORT-LIVED STORMS WITH A LOW PROBABILITY OF HAILSTONES
REACHING 1 INCH IN DIAMETER.
..CARBIN/COHEN.. 05/07/2011
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