SWODY1
SPC AC 261616
DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1116 AM CDT THU MAY 26 2011
VALID 261630Z - 271200Z
...THERE IS A SLGT RISK OF SVR TSTMS FROM THE LOWER GREAT LAKES AND
NW NEW ENGLAND TO CNTRL/ERN GULF COAST...
...LOWER GREAT LAKES/NEW ENGLAND...
A BELT OF STRONG /50-70 KT/ 500 MB FLOW WILL BE MAINTAINED ACROSS
THE REGION TODAY IN ADVANCE OF OPENING MIDLEVEL LOW TRANSLATING
ACROSS THE OH VALLEY. IN THE LOW LEVELS...PRIMARY SURFACE LOW AND
ATTENDANT COLD FRONT WILL REMAIN W OF REGION THROUGH THE DIURNAL
HEATING CYCLE. IT APPEARS THAT PRE-FRONTAL TROUGH/CONFLUENCE ZONE
OVER CNTRL PA/NY AND REMNANT OUTFLOW BOUNDARIES FROM LAST NIGHT/S
STORMS WILL SERVE AS THE FOCUS FOR TSTM DEVELOPMENT THIS AFTERNOON.
LATE MORNING SURFACE ANALYSIS SHOWS AN AXIS OF 65-70 F DEWPOINTS
EXTENDING FROM THE MID ATLANTIC PIEDMONT AND COASTAL PLAIN INTO
CNTRL NY. WHEN COUPLED WITH ABUNDANT SUNSHINE...AIR MASS IS
EXPECTED TO BECOME MODERATELY TO STRONGLY UNSTABLE WITH MLCAPE
VALUES OF 2000-3500 J/KG. WHEN COUPLED WITH 40-50 KT OF DEEP SWLY
SHEAR...SETUP WILL FAVOR THE DEVELOPMENT OF SUPERCELLS AND BOWING
STRUCTURES WITH A RISK FOR VERY LARGE HAIL...DAMAGING WINDS AND
TORNADOES. THE GREATEST TORNADO THREAT IS EXPECTED TO DEVELOP FROM
N-CNTRL/NERN PA INTO THE MID/UPPER HUDSON VALLEY WHERE LOCALLY
BACKED NEAR GROUND WINDS WILL SERVE TO ENHANCE LOW-LEVEL SHEAR.
...CNTRL/SRN APPALACHIANS TO CNTRL/ERN GULF COAST...
MULTIPLE CLUSTERS OF TSTMS ARE PRESENT THIS MORNING FROM MIDDLE/ERN
TN TO FAR SERN MS/SWRN AL. ACTIVITY APPEARS TO BE ASSOCIATED WITH A
CORRIDOR OF HEIGHT FALLS/FORCING FOR ASCENT ATTENDANT TO SHORT WAVE
TROUGH TRANSLATING EWD THROUGH THE TN AND MID MS VALLEYS. 12Z
REGIONAL SOUNDINGS INDICATE THAT AMBIENT WARM SECTOR AIR MASS ACROSS
MS/AL/GA IS MOIST AND ALREADY MODERATELY UNSTABLE WITH MLCAPE VALUES
OF 2000-2500 J/KG. CONTINUED HEATING OF BOUNDARY LAYER WILL SUPPORT
FURTHER DESTABILIZATION THIS AFTERNOON WITH MLCAPE RISING ABOVE 3000
J/KG WITH A CORRESPONDING INCREASE IN STORM COVERAGE AND INTENSITY.
MIDLEVEL HEIGHT GRADIENT IS FORECAST TO RELAX WITH TIME FROM S-N
ACROSS THE REGION...RESULTING IN A GRADUAL DECREASE IN VERTICAL
SHEAR THIS AFTERNOON. NONETHELESS...DEEP-LAYER WIND FIELD WILL
REMAIN SUFFICIENTLY STRONG /GIVEN THE INSTABILITY/ TO SUPPORT
ORGANIZED STORMS INCLUDING...SUPERCELLS AND LINE SEGMENTS...WITH THE
PRIMARY HAZARDS BEING LARGE HAIL AND DAMAGING WIND GUSTS.
...NRN/CNTRL HIGH PLAINS...
EXIT REGION OF STRONG UPPER-LEVEL JET STREAK WILL PROPAGATE INTO
REGION INTO THE REGION TODAY...ENHANCING DEEP-LAYER ASCENT BY
AFTERNOON ALONG INTENSIFYING LEE TROUGH. BOUNDARY LAYER DEWPOINTS
IN THE 40S WILL TEND TO LIMIT THE POTENTIAL FOR MORE ROBUST
DESTABILIZATION THIS AFTERNOON INTO EVENING. HOWEVER...THE PRESENCE
OF STEEP LOW TO MIDLEVEL LAPSE RATES AND VERTICALLY VEERING WIND
PROFILES WILL SUPPORT THE THREAT FOR A FEW ROTATING STORMS CAPABLE
OF MAINLY SOME HAIL AND LOCALLY STRONG WIND GUSTS.
..MEAD/GRAMS.. 05/26/2011
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