SPC AC 221947
DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0247 PM CDT SAT JUL 22 2006
VALID 222000Z - 231200Z
...THERE IS A SLGT RISK OF SVR TSTMS FROM SRN NEW ENGLAND SWD ALONG
THE ATLANTIC COAST AND WWD ALONG THE GULF COAST...
...THERE IS A SLGT RISK OF SVR TSTMS OVER PARTS OF THE UPPER
MIDWEST...
...SRN NEW ENGLAND INTO THE CAROLINAS...
AFTERNOON WATER VAPOR IMAGERY SHOWS VIGOROUS SHORT WAVE TROUGH
LIFTING NEWD THROUGH THE LOWER GREAT LAKES WITH AN ACCOMPANYING BELT
OF 35-45 KT SWLY MID-LEVEL FLOW FROM THE CNTRL APPALACHIANS INTO NEW
ENGLAND. ATTENDANT SURFACE LOW OVER THE LOWER HUDSON VALLEY IS
FORECAST TO CONTINUE NEWD THROUGH THE REMAINDER OF THE AFTERNOON AND
TONIGHT WITH TRAILING COLD FRONT PUSHING TOWARD THE MIDDLE ATLANTIC
COAST.
THUS FAR...STRONGEST TSTM DEVELOPMENT HAS OCCURRED ALONG LEE TROUGH
FROM VICINITY OF SURFACE LOW OVER SERN NY SWWD INTO CNTRL/ERN MD
WHERE BREAKS IN THE CLOUDS HAVE ALLOWED FOR STRONGER DAYTIME
HEATING. THIS ISOLATION COUPLED WITH DEWPOINTS OF 70-75 F ARE
CONTRIBUTING TO MLCAPES OF 500-1500 J/KG. CURRENTLY...REGIONAL VWPS
INDICATE THAT STRONGEST LOW AND DEEP-LAYER SHEAR /150-250 M2/S2 0-1
KM SRH AND 35-45 KTS OF 0-6 KM SHEAR/ EXISTS FROM NRN/CNTRL NJ NWD
INTO THE SRN NEW ENGLAND AND THE MIDDLE HUDSON VALLEY...WHERE
STRONGEST ISALLOBARIC RESPONSE IS OCCURRING E OF SURFACE LOW.
HOWEVER...18Z ALBANY AND UPTON NY SOUNDINGS INDICATE THAT
CONSIDERABLE CLOUDS AND PRECIPITATION HAVE LIMITED DESTABILIZATION
WITHIN THIS REGION OF STRONGER SHEAR.
EXPECT GREATEST SEVERE THREAT TO EXIST FROM SERN NY/NJ SSWWD INTO
CHESAPEAKE BAY THIS AFTERNOON AND EVENING...WHERE BEST COMBINATION
OF INSTABILITY AND STRONGER VERTICAL SHEAR WILL BE CO-LOCATED.
HERE...POTENTIAL WILL EXIST FOR SMALL-SCALE BOWING STRUCTURES AND
PERHAPS A SUPERCELL OR TWO CAPABLE OF MAINLY DAMAGING WINDS.
GREATEST THREAT OF A TORNADO WILL LIKELY EXIST OVER SERN NY INTO
SWRN NEW ENGLAND...SHOULD SUFFICIENT DESTABILIZATION OCCUR TO
SUSTAIN DEEP CONVECTION.
FARTHER S INTO THE CAROLINAS...VERTICAL SHEAR DECREASES WITH SWD
EXTENT...THOUGH AIR MASS REMAINS HOT AND MOIST FROM VICINITY OF LEE
TROUGH WWD TOWARD COLD FRONT. CONTINUED HEATING/DESTABILIZATION
SHOULD SUPPORT AN INCREASE IN TSTM COVERAGE ALONG THESE BOUNDARIES
LATE THIS AFTERNOON INTO THE EVENING WITH A THREAT OF LOCALLY
DAMAGING WINDS WITH THE MOST INTENSE STORMS.
...GA WWD INTO THE LOWER MS VALLEY...
WIDESPREAD TSTMS HAVE DEVELOPED THIS AFTERNOON ALONG AND AHEAD OF
SURFACE COLD FRONT AND PRE-FRONTAL TROUGH FROM GA WWD INTO LA.
TEMPERATURES IN THE 90S COUPLED WITH DEWPOINTS IN THE UPPER 60 TO
LOWER/MID 70S ARE CONTRIBUTING TO A MODERATELY UNSTABLE PRE-FRONTAL
AIR MASS WITH MLCAPES OF 1500-2500 J/KG. VERTICAL SHEAR REMAINS
WEAK...THOUGH NE-SW ORIENTED TSTM BANDS FROM CNTRL AL INTO CNTRL LA
WILL HAVE THE POTENTIAL TO ORGANIZE COLD POOLS AS THEY MOVE/DEVELOP
SEWD. DAMAGING WINDS WILL BE THE MAIN SEVERE WEATHER THREAT.
...UPPER MIDWEST...
TSTMS ARE BECOMING MORE NUMEROUS THIS AFTERNOON FROM WI INTO LOWER
MI SWD INTO NERN IA AND NRN IL...IN ASSOCIATION WITH A SHORT WAVE
TROUGH TRANSLATING SEWD THROUGH THE REGION. THOUGH BOUNDARY LAYER
DEWPOINTS ARE NOT PARTICULARLY HIGH /MID 50S TO LOWER 60S/...THE
PRESENCE OF STEEP LOW-LEVEL LAPSE RATES AND MODESTLY COOL MID-LEVEL
TEMPERATURES /I.E. -14 TO -16 C AT 500 MB/ ARE CONTRIBUTING TO
MLCAPES OF 500-1000 J/KG. REGIONAL VWPS AND PROFILERS INDICATE THAT
THE STRONGEST VERTICAL SHEAR EXISTS TO THE W OVER WRN MN/IA IN
ASSOCIATION WITH MID AND HIGH-LEVEL JET STREAKS DIGGING SWD.
THEREFORE...EXPECT THAT STORMS WILL REMAIN MULTICELLULAR AND CAPABLE
OF GUSTY WINDS AND SOME MARGINALLY SEVERE HAIL THROUGH THE EVENING
HOURS.
...WRN STATES...
WATER VAPOR IMAGERY SHOWS TWO WELL-DEFINED IMPULSES ROTATING AROUND
UPPER HIGH...ONE MOVING SWD THROUGH CNTRL CO...AND THE OTHER
SHIFTING WWD THROUGH THE LOWER CO VALLEY. THESE FEATURES COUPLED
WITH STRONG DIABATIC HEATING ALONG THE HIGHER TERRAIN WILL SUPPORT
AN INCREASE IN TSTM ACTIVITY THIS AFTERNOON INTO TONIGHT. THE MOST
INTENSE STORMS WILL BE CAPABLE OF SEVERE MICROBURSTS OWING TO THE
STRONG EVAPORATIONAL COOLING POTENTIAL IN THE SUB-CLOUD LAYER.
..MEAD.. 07/22/2006
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