SWODY1
SPC AC 291959
DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0259 PM CDT SUN MAR 29 2009
VALID 292000Z - 301200Z
...THERE IS A SLGT RISK OF SVR TSTMS ACROSS PORTIONS OF THE MID
ATLANTIC STATES...
...MID ATLANTIC STATES...
AS OF 20Z...LATEST RADAR/SATELLITE TRENDS FEATURE A GRADUAL INCREASE
OF TSTMS ALONG THE MD/PA BORDER NORTHWEST OF WASHINGTON DC SINCE
EARLY AFTERNOON. A SPECIAL 18Z RAOB FROM WASHINGTON-DULLES PORTRAYS
CONSIDERABLE MIXING/DRYING SINCE THIS 12Z THIS MORNING. AS
ADDITIONAL MIXING OCCURS ACROSS THE PRE-COLD FRONTAL WARM SECTOR
THIS AFTERNOON ACROSS VA...THIS SUPPORTS THE IDEA OF THE PRIMARY
SEVERE POTENTIAL BEING CONFINED TO A RELATIVELY NARROW ZONE
ALONG/JUST NORTH OF A SECONDARY/GRADUALLY DEEPENING SURFACE LOW AND
STALLING WSW-ENE ORIENTED WARM FRONT FROM CENTRAL/EASTERN MD AND FAR
NORTHERN VA INTO SOUTHEAST PA AND NJ. AS SAMPLED BY THE
AFOREMENTIONED 18Z KIAD RAOB...STEEP MID LEVEL LAPSE RATES AND
SURFACE MODIFIED/NEAR WARM FRONT SBCAPE ESTIMATES OF 750-1000 J/KG
AMIDST FAVORABLE SHEAR WILL SUPPORT A RISK OF WELL ORGANIZED TSTMS
CAPABLE OF HAIL/WIND INTO EARLY EVENING. FARTHER SOUTH ACROSS
VA...CONSIDERABLE DRYING SHOULD KEEP ANY SEVERE THREAT RATHER
ISOLD/MARGINAL WITH SOUTH EXTENT IN THE WARM SECTOR.
..GUYER.. 03/29/2009
.PREV DISCUSSION... /ISSUED 1128 AM CDT SUN MAR 29 2009/
...MID ATLANTIC THIS AFTERNOON...
A DEEP CLOSED LOW OVER OH THIS MORNING WILL MOVE NEWD INVOF THE
LOWER GREAT LAKES THROUGH TONIGHT. A STRONG SHORTWAVE TROUGH
ROTATING AROUND THE SRN PERIPHERY OF THE LOW THIS MORNING WILL EJECT
NEWD TOWARD THE MID ATLANTIC BY LATE EVENING. THIS WILL CONTRIBUTE
TO SECONDARY SURFACE LOW DEVELOPMENT ENEWD ALONG A PRE-EXISTING
BAROCLINIC ZONE FROM NEAR THE TRIPLE POINT IN NRN VA AS OF LATE
MORNING TO SE NEW ENGLAND OVERNIGHT. THE SECONDARY LOW WILL BE
ACCOMPANIED BY A SMALL WARM SECTOR TODAY FROM VA ACROSS SE PA TO
NJ...WHERE SURFACE TEMPERATURES WILL WARM INTO THE 70S ACROSS VA AND
MID-UPPER 60S INTO DEL/NJ S OF THE RETREATING FRONT. RELATIVELY
COOL MID LEVEL TEMPERATURES/STEEP LAPSE RATES AND THE WARMING
SURFACE TEMPERATURES WILL ALLOW THE DEVELOPMENT OF MUCAPE OF
500-1000 J/KG.
A SMALL BAND OF THUNDERSTORMS SHOULD DEVELOP ALONG THE COLD FRONT
NEAR THE TRIPLE POINT THIS AFTERNOON /POTENTIALLY EVOLVING FROM THE
WEAK CONVECTION NOW OVER THE BLUE RIDGE/ AND STREAK ENEWD OVER THE
DELMARVA/NJ/SE PA. VERTICAL SHEAR WILL BE SUFFICIENT FOR LOW-TOPPED
SUPERCELLS AND SMALL BOWING SEGMENTS CAPABLE OF PRODUCING ISOLATED
LARGE HAIL AND DAMAGING WINDS THIS AFTERNOON THROUGH EARLY EVENING.
...CENTRAL/S FL THIS AFTERNOON...
A WEAKENING BAND OF CONVECTION PRECEDES THE COLD FRONT MOVING SEWD
ACROSS CENTRAL FL. SOME SURFACE HEATING HAS OCCURRED ACROSS SE FL
TO THE SE OF THE THICKER CLOUDS...AND NEW STORMS WILL LIKELY FORM
AHEAD OF THE BAND. A LINGERING BELT OF 30-40 KT WSWLY LOW-LEVEL
FLOW SE OF THE FRONT COULD SUPPORT GUSTY WINDS WITH THE STRONGER
EMBEDDED STORMS...BUT THE SEVERE STORM THREAT APPEARS TO BE QUITE
MARGINAL AND DIMINISHING WITH TIME.
...ROCKIES AREA...
A STRONG SHORTWAVE TROUGH AND FOCUSED BELT OF ASCENT WILL MOVE SEWD
FROM THE NRN GREAT BASIN TO THE CENTRAL ROCKIES THROUGH TONIGHT.
THE STRONG ASCENT AND SUFFICIENTLY STEEP LAPSE RATES WILL PROMOTE
THE DEVELOPMENT OF A FEW THUNDERSTORMS THIS AFTERNOON FROM ERN UT
ACROSS NW CO INTO WY.
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