SPC AC 021724
DAY 2 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1224 PM CDT TUE JUN 02 2009
VALID 031200Z - 041200Z
...THERE IS A SLGT RISK OF SVR TSTMS FROM SRN PARTS OF THE OH VALLEY
INTO THE MID ATLANTIC REGION...
...SYNOPSIS...
A BROAD UPPER TROUGH /ANCHORED BY VORTEX OVER NRN QUEBEC/ WILL
PERSIST OVER CNTRL/ERN CANADA INTO THE GREAT LAKES AND NEW ENGLAND.
SEVERAL VORTICITY MAXIMA WILL ROTATE THROUGH THIS TROUGH. FARTHER
SOUTH...A VORTICITY MAXIMUM CURRENTLY OVER WRN KS EMBEDDED WITHIN
WEAKER FLOW REGIME WILL SLOWLY DRIFT EWD TOWARD THE LOWER MS VALLEY.
IN THE WEST...A CUTOFF UPPER LOW WILL REMAIN JUST OFF THE CA COAST
WITH SEVERAL IMPULSES ROTATING AROUND THIS FEATURE ACROSS CA/NV INTO
THE PACIFIC NW.
AT THE SURFACE...WEAK LOW PRESSURE INITIALLY OVER THE UPPER OH
VALLEY WILL DEVELOP ENEWD ALONG FRONTAL ZONE THROUGH THE DELMARVA
WHILE TRAILING PORTION OF BOUNDARY SLOWLY SAGS SWD FROM THE OH INTO
TN VALLEY. THIS FRONTAL SEGMENT WILL LINK WITH A SECONDARY LOW
PRESSURE AREA DEVELOPING SEWD INTO THE LOWER MS VALLEY. THE WRN
EXTENSION OF THIS FRONT WILL SHIFT SWD THROUGH TX.
...SRN PORTION OF THE OH VALLEY THROUGH MID ATLANTIC...
A FRONTAL BOUNDARY...PARTIALLY REINFORCED BY AREAS OF ONGOING POST
FRONTAL CONVECTION...SHOULD EXTEND FROM THE MID ATLANTIC WSWWD
THROUGH SRN MO OR NRN AR EARLY WEDNESDAY. AMPLE DIABATIC WARMING OF
THE BOUNDARY LAYER AND MID 60S DEWPOINTS WILL CONTRIBUTE TO MODERATE
INSTABILITY...BUT MODEST 6-6.5 C/KM MID LEVEL LAPSE RATES SHOULD
LIMIT MLCAPE TO 1500-2000 J/KG. STORMS ARE EXPECTED TO INCREASE IN
COVERAGE AND INTENSITY ALONG FRONT AND OVER THE HIGHER TERRAIN AS
THE ATMOSPHERE DESTABILIZES. ACTIVITY DEVELOPING IN VICINITY OF THE
FRONT WILL BE ON SRN FRINGE OF THE STRONGER WINDS ALOFT WITH WLY
25-30 KT DEEP LAYER FLOW...BUT WITH BULK SHEAR GENERALLY AOB 30 KT.
STORMS ARE EXPECTED TO REMAIN MULTICELLULAR WITH LINE SEGMENTS AND
SMALL CLUSTERS CAPABLE OF PRODUCING ISOLATED STRONG TO DAMAGING WIND
GUSTS AND HAIL THROUGH EARLY EVENING AS ACTIVITY DEVELOPS SEWD.
...ERN TX THROUGH LOWER MS AND TN VALLEYS...
WITH AMPLE LOW-LEVEL MOISTURE IN PLACE...ATMOSPHERE WILL LIKELY ONCE
AGAIN BECOME MODERATELY UNSTABLE /1500-2500 J/KG MLCAPE/ IN ADVANCE
OF SEWD MOVING FRONT. STORMS ARE EXPECTED TO REDEVELOP ALONG AND
SOUTH OF THE FRONT DURING THE AFTERNOON. THE WARM SECTOR WILL HAVE
BEEN SHUNTED SOUTH OF THE STRONGER FLOW ALOFT WITH WEAK VERTICAL
SHEAR SUPPORTIVE OF PULSE AND MULTICELL STORMS. SOME OF THE STORMS
COULD BECOME CAPABLE OF PRODUCING ISOLATED STRONG WIND GUSTS AND
HAIL THROUGH EARLY EVENING.
..CNTRL/SRN HIGH PLAINS...
ISOLATED...DIURNAL STORMS WILL BE POSSIBLE ALONG HIGHER TERRAIN
WITHIN POST-FRONTAL UPSLOPE REGIME. PRESENCE OF STEEP LAPSE RATES
AND 30-35 KT OF DEEP LAYER SHEAR WILL FOSTER AN ENVIRONMENT
MARGINALLY FAVORABLE FOR SUSTAINED/ROTATING UPDRAFTS CAPABLE OF SOME
HAIL.
...PACIFIC NW AND SIERRAS...
PRESENCE OF DEEP MOISTURE AND A SERIES OF VORTICITY MAXIMA LIFTING
NWD ALONG ERN PERIPHERY OF UPPER LOW WILL PROMOTE AREAS OF WIDELY
SCATTERED THUNDERSTORMS IN THIS REGION. INSTABILITY WILL REMAIN
MARGINAL...BUT LOW-MID LEVEL LAPSE RATES MAY BECOME SUFFICIENT FOR A
THREAT OF ISOLATED GUSTY WINDS AND MARGINALLY SEVERE HAIL AS THE
BOUNDARY LAYER DESTABILIZES.
..DIAL.. 06/02/2009
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NOTE: THE NEXT DAY 2 OUTLOOK IS SCHEDULED BY 0600Z
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