SWODY1
SPC AC 201952
DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0252 PM CDT SAT JUN 20 2009
VALID 202000Z - 211200Z
...THERE IS A SLGT RISK OF SVR TSTMS ACROSS THE ERN MIDDLE ATLANTIC
REGION AND NERN NC...
...THERE IS A SLGT RISK OF SVR TSTMS ACROSS PORTIONS OF CNTRL/SRN
KS...
...MID-ATLANTIC REGION...
IN WAKE OF OFFSHORE ACTIVITY...BOUNDARY LAYER HAS RECOVERED OVER ERN
VA...ERN MD AND DE WHERE MODEST 3-HRLY PRESSURE FALLS OF 2 MB
EXISTED. SCTD TSTMS HAVE DEVELOPED INVOF A CDFNT CROSSING INTO THE
PIEDMONT AS OF 19Z WITHIN THE DESTABILIZING AIR MASS. EXPECT A
MID-LATE AFTN THREAT FOR STG-SVR STORMS UNTIL THE CDFNT SWEEPS OFF
THE CST BY 00Z. DOVER VWP EXHIBITS A FAIRLY STRONG VEERING WIND
PROFILE IN THE LOWEST 1KM...ON THE ORDER OF 200 M2/S2 AND BULK SHEAR
VALUES IN EXCESS OF 45 KTS. THUS...THERE WILL BE A THREAT FOR A
TORNADO OR TWO ALONG WITH DMGG WINDS.
FARTHER S...WDLY SCTD STG STORMS HAVE DEVELOPED ALONG THE TRAILING
PORTION OF THE CDFNT IN FAVORABLE SWLY UPSLOPE REGIME IN NWRN NC
NWWD INTO THE SERN KY COALFIELDS. REGION IS LOCATED ALONG SRN
PERIPHERY OF LARGE SCALE HEIGHT FALLS ATTENDANT TO THE UPR TROUGH
MOVING ACROSS THE MID-ATLANTIC AREA. STORMS WILL PROBABLY HAVE A
TOUGH TIME MAKING INTO THE LOWER PIEDMONT OF NC WHERE STG DOWNSLOPE
HAS DEVELOPED AND MOUNTAIN-INDUCED CIRRUS HAS TEMPERED HEATING /IE
COMPARATIVELY STRONGER CINH/. HOWEVER...RISK FOR A STORM OR TWO IS
NON-ZERO OVER NC AND THUS HAVE MAINTAINED SLGT RISK FOR MAINLY DMGG
WINDS.
...CNTRL PLNS...
STG STORMS HAVE EVOLVED ALONG SRN/ERN PERIPHERY OF DEEP TROPOSPHERIC
MOISTURE PLUME ACROSS SRN KS SWWD INTO THE TX PNHDL. ICT VWP
EXHIBITS MODEST LLVL TURNING IN THE LOWEST 1KM AND GIVEN LOW LCL
ENVIRONMENT...A TORNADO THREAT WILL EXIST...PARTICULARLY ALONG THE
E-W RETREATING WRMFNT IN SRN/CNTRL KS.
...GRT BASIN THROUGH NRN ROCKIES...
STRONGEST STORMS HAVE BEEN FAVORING THE FAIRLY INTENSE PV-ANOMALY
BEGINNING TO EJECT NEWD THROUGH SCNTRL NV AMIDST 500-750 J/KG
MLCAPE. OTHER ACTIVITY WAS DEVELOPING BENEATH COOLER
MID-TROPOSPHERIC TEMPERATURES OVER WRN/CNTRL NV. SWLY H5 FLOW AOA
55 KTS WILL YIELD MODESTLY SHEARED AND LARGELY UNIDIRECTIONAL DEEP
LAYER FLOW FROM ERN NV/WRN UT NWD INTO ERN ID THROUGH EVENING. THIS
WILL BE CONDUCIVE FOR BRIEF DISCRETE ROTATING CELLS EVOLVING INTO
SMALL SCALE LEWPS/BOWS GIVING ISOLD DMGG WINDS/HAIL.
..RACY.. 06/20/2009
.PREV DISCUSSION... /ISSUED 1121 AM CDT SAT JUN 20 2009/
...MID ATLANTIC REGION...
STRONG UPPER TROUGH/VORTICITY CENTER IS WELL-DEFINED ON WATER VAPOR
IMAGERY MOVING EWD ACROSS WRN PA. FORCING FOR LARGE SCALE ASCENT IN
ADVANCE OF THE SYSTEM IS GENERATING A COMMA-SHAPED REGION OF CLOUDS
AND CONVECTION ARCING FROM SRN NY ACROSS NJ AND INTO THE DELMARVA
REGION. RELATIVELY CLEAR SKIES OVER SOUTH CENTRAL/SERN VA AND
ADJACENT PARTS OF NC HAVE ALLOWED STRONG DIABATIC HEATING TO OCCUR
WITH SURFACE TEMPERATURES IN THE UPPER 80S-LOWER 90S. AMPLE
LOW-LEVEL MOISTURE PERSISTS OVER THE AREA WITH SURFACE DEW POINTS
GENERALLY IN THE LOWER 70S...CONTRIBUTING TO MLCAPE OF 1000-2000
J/KG /DESPITE WEAK MID-LEVEL LAPSE RATES/. FARTHER NORTH...IN THE
WAKE OF THE CONVECTIVE BAND...BREAKS IN CLOUD COVER ARE EVIDENT FROM
WRN VA INTO SOUTH CENTRAL PA AHEAD OF THE ADVANCING SURFACE COLD
FRONT. THIS SHOULD PERMIT LOCALIZED AREAS OF HEATING AND
DESTABILIZATION TO OCCUR.
NEW CONVECTION IS CURRENTLY DEVELOPING OVER PARTS OF ERN WV INTO
EXTREME SWRN VA ALONG THE LEADING EDGE OF THE MID/UPPER LEVEL DRY
INTRUSION NOTED IN WATER VAPOR IMAGERY. THIS ACTIVITY IS LOCATED
ALONG THE WRN EDGE OF THE INSTABILITY GRADIENT WITHIN A BAND OF
40-50 KT WNWLY MID LEVEL FLOW ALOFT...AND WILL BE MONITORED FOR
SIGNS OF INTENSIFICATION AS IT MOVES ESEWD THIS AFTERNOON INTO AN
INCREASINGLY UNSTABLE ENVIRONMENT. IF THE STORMS CAN PERSIST AND
MOVE EAST OF THE HIGHER TERRAIN...30-40 KT DEEP LAYER SHEAR WILL
PROMOTE ORGANIZED STORM STRUCTURES INCLUDING BOW ECHOES AND ISOLATED
SUPERCELLS...WITH ASSOCIATED THREAT FOR DAMAGING WIND GUSTS AND
LARGE HAIL. AN ISOLATED TORNADO OR TWO MAY ALSO BE POSSIBLE.
ADDITIONAL STRONG/SEVERE STORMS MAY ALSO DEVELOP CLOSER TO THE
VORTICITY MAX FROM THE DELMARVA INTO SERN PA/SRN NJ...ALTHOUGH THE
COVERAGE OF STORMS WILL BE DEPENDENT ON THE DEGREE OF
DESTABILIZATION.
...CENTRAL PLAINS...
SCATTERED STORMS WILL CONTINUE DEVELOPING WITHIN PLUME OF DEEP
SUBTROPICAL MOISTURE THAT WILL PERSIST ALONG WRN PERIPHERY OF UPPER
RIDGE. LOW-MID LEVEL FLOW WILL INCREASE DURING THE AFTERNOON IN
ASSOCIATION WITH SHORTWAVE TROUGH EJECTING NEWD THROUGH CNTRL HIGH
PLAINS. HODOGRAPH SIZE WILL INCREASE AND BECOME FAVORABLE FOR A
THREAT OF LOW LEVEL MESOCYCLONES AND POSSIBLY ISOLATED
TORNADOES...ESPECIALLY WHERE THE LOW LEVEL JET INTERSECTS THE
FRONTAL BOUNDARY ACROSS KS. A LIMITING FACTOR WILL BE EXPECTED
MARGINAL THERMODYNAMIC ENVIRONMENT CHARACTERIZED BY WEAK INSTABILITY
AND MARGINAL LAPSE RATES.
...GREAT BASIN THROUGH NRN ROCKIES...
VERTICAL SHEAR WILL INCREASE IN ASSOCIATION WITH SHORTWAVE TROUGH
EJECTING NEWD FROM THE GREAT BASIN INTO THE NRN ROCKIES. MOIST
PROFILES AND LARGE SCALE ASCENT AHEAD OF THIS FEATURE WILL LIKELY
PROMOTE THE DEVELOPMENT OF NUMEROUS STORMS DURING THE AFTERNOON.
ISOLATED STORMS COULD BECOME CAPABLE OF PRODUCING STRONG WIND GUSTS
AND MARGINALLY SEVERE HAIL.
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