SWODY1
SPC AC 221906
DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0206 PM CDT MON MAR 22 2010
VALID 222000Z - 231200Z
...THERE IS A SLGT RISK OF SVR TSTMS LATE THIS AFTERNOON ACROSS
PARTS OF NRN VA...CNTRL/WRN MD...S CNTRL PA AND THE ERN WV PNHDL....
...20Z UPDATE...MID ATLANTIC STATES...
DRY LINE TYPE STRUCTURE HAS BECOME THE FOCUS FOR ONGOING
STRONG/SEVERE STORM DEVELOPMENT ACROSS NORTH CENTRAL THROUGH
SOUTHEAST VIRGINIA...IN THE PRESENCE OF MODERATE TO STRONG
SHEAR...BUT GENERALLY WEAK MIXED LAYER CAPE LESS THAN 500 J/KG.
HOWEVER...THIS BOUNDARY IS SLOWLY BEING OVERTAKEN BY LOW-LEVEL
COOLING/DRYING WRAPPING INTO DEEPENING WEST VIRGINIA LOW
CENTER...WHILE COOL MARINE LAYER ADVECTING OFF THE ATLANTIC HOLDS
FIRM ACROSS EXTREME EASTERN VIRGINIA AND THE DELMARVA. AS A
RESULT...THE RISK FOR STRONG/SEVERE STORMS BEYOND THE NEXT HOUR OR
TWO SEEMS LIKELY TO BECOME CONFINED TO PORTIONS OF NORTH CENTRAL
VIRGINIA/CENTRAL MARYLAND WESTWARD INTO THE ALLEGHENY FRONT.
..KERR.. 03/22/2010
.PREV DISCUSSION... /ISSUED 1108 AM CDT MON MAR 22 2010/
COLD VORTEX/UPR LOW CONTINUES ITS ENEWD TREK SERN STATES FROM A
POSITION THIS MORNING NWRN GA/TN BORDER TO SERN VA 12Z TUE. STRONG
COLD FRONT EXTENDS FROM SURFACE LOW OVER NRN WV SSEWD TO OFF THE SRN
NC COAST. SURFACE LOW WILL MOVE NEWD INTO CENTRAL PA BY THIS EVENING
AS COLD FRONT PUSHES OFFSHORE OF THE NC/SERN VA COAST BY 21Z.
...MID ATLANTIC STATES NWD TO SRN PA...
AIR MASS IN ADVANCE OF THE COLD FRONT IS MARGINALLY UNSTABLE ACROSS
SERN VA/NERN NC WITH MLCAPES GENERALLY LESS THAN 1000 J/KG. HOWEVER
WITH PRIMARILY UNIDIRECTIONAL SHEAR OF 40-50KT ALONG WITH RELATIVELY
STEEP MID LEVEL LAPSE RATES...7C/KM...THERE IS POTENTIAL OF
STRONG/ISOLATED SEVERE THUNDERSTORMS THRU LATER THIS AFTERNOON.
WITH THE MARGINAL INSTABILITY AND UNIDIRECTIONAL SHEAR...PRIMARY
THREAT WITH THE STRONGEST STORMS WILL BE ISOLATED LARGE HAIL AND
GUSTY/BRIEF DAMAGING WINDS.
PRONOUNCED DRY SLOT SPREADING NNEWD AHEAD OF COLD VORTEX ACROSS
APPALACHIANS LEADING TO SOME HEATING OF THE STILL MOIST AIR MASS
AHEAD OF COLD FRONT AND NE OF WV SURFACE LOW INTO SRN PA.
WITH THE LAPSE RATES OF 7C/KM OR GREATER AND THE LOW LEVEL VEERING
SHEAR PROFILES ON THE NERN QUAD OF THE SURFACE LOW...THERE IS THE
POTENTIAL OF SURFACE BASED STORMS DEVELOPING ALONG/JUST AHEAD OF
COLD FRONT VICINITY PA/MD BORDER SEWD ACROSS THE DELMARVA DURING THE
AFTERNOON.
INSTABILITY WILL BE MARGINAL WITH MLCAPES GENERALLY LESS THAN 1000
J/KG...HOWEVER GIVEN THE COLD AIR ALOFT AND 7C/KM LAPSE
RATES...HAIL WILL BE LIKELY ASSOCIATED WITH THE STRONGEST UPDRAFTS
UNTIL THIS EVENING. WITH THE BACKED BOUNDARY LAYER FLOW TO THE N/NE
OF SURFACE LOW THE POSSIBILITY DOES EXIST FOR ROTATING
STORMS...INCREASING LARGE HAIL POTENTIAL AND ALSO THE RISK OF A
BRIEF TORNADO.
THREAT OF ANY SEVERE SHOULD QUICKLY DIMINISH WITH CESSATION OF
DAYTIME HEATING.
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