SWODY2
SPC AC 300539
DAY 2 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1239 AM CDT WED JUL 30 2008
VALID 311200Z - 011200Z
...THERE IS A SLGT RISK OF SVR TSTMS THU/THU NIGHT ACROSS PARTS OF
THE ERN DAKOTAS INTO THE UPPER MS VALLEY....
...THERE IS A SLGT RISK OF SVR TSTMS LATE THU AFTN/EVE ACROSS MUCH
OF THE CAROLINA INTO SE VIRGINIA....
...SYNOPSIS...
A CONSIDERABLE RANGE OF POSSIBLE SOLUTIONS CONTINUES TO EXIST AMONG
THE SREF MEMBERS...AND AMONG THE VARIOUS MODELS...CONCERNING THE
SHORT WAVE DEVELOPMENTS WITHIN A STRONGER BELT OF POLAR WESTERLIES
LIKELY TO REMAIN NEAR THE CANADIAN/U.S. BORDER AREA. AND...THIS IS
CONTRIBUTING TO UNCERTAINTY IN THE FORECAST... PARTICULARLY WITH
REGARD TO THE LOCATION AND TIMING OF ANY POSSIBLE APPRECIABLE SEVERE
THREATS...LEADING TO SEVERE PROBABILITIES MOSTLY LOW IN
MAGNITUDE/CONFIDENCE.
IN GENERAL...HOWEVER...GUIDANCE INDICATES THAT SUBTROPICAL RIDGING
WILL CONTINUE TO EXPAND NORTHWARD/EASTWARD OUT OF THE FOUR CORNERS
STATES THURSDAY. AS THIS OCCURS...FLOW ACROSS THE CENTRAL
INTERNATIONAL BORDER AREA WILL BECOME BROADLY ANTICYCLONIC...WHILE
BROAD CYCLONIC FLOW LINGERS ACROSS PARTS OF THE GREAT LAKES INTO THE
NORTHEAST...AND ACROSS THE PACIFIC NORTHWEST...WHERE A VIGOROUS
SHORT WAVE IMPULSE PROBABLY WILL BEGIN TO MIGRATE INLAND LATE
THURSDAY OR THURSDAY NIGHT.
...PARTS OF THE ERN DAKOTAS INTO THE UPPER MISSISSIPPI VALLEY...
PATTERN EVOLUTION WILL REMAIN SUPPORTIVE OF POTENTIAL FOR ORGANIZED
STORM CLUSTERS. DOWNSTREAM OF THE UPPER RIDGE AXIS...BROADLY
DIFLUENT MID/UPPER FLOW IS EXPECTED TO BECOME FOCUSED ACROSS THE
REGION...NEAR A ZONE OF STRONGER LOWER/MID TROPOSPHERIC WARM
ADVECTION...WHICH MAY PERSIST THROUGH MUCH OF THE FORECAST PERIOD.
MODELS CONTINUE TO SUGGEST MODERATE TO STRONG DESTABILIZATION WILL
OCCUR WITHIN THIS REGIME...WHERE PRONOUNCED VEERING WITH HEIGHT OF
MODEST FLOW FIELDS IS EXPECTED TO CONTRIBUTE TO STRONG DEEP LAYER
SHEAR. THERE ARE INDICATIONS THAT FORCING MAY BECOME ENHANCED BY A
WEAK MID-LEVEL IMPULSE...OR TWO...TOPPING THE CREST OF THE UPSTREAM
RIDGE...BUT IT IS NOT ENTIRELY CLEAR WHETHER INITIATION OF THE MAIN
CONVECTIVE DEVELOPMENT WILL OCCUR EARLY IN THE DAY...OR LATER...IN
THE LATE AFTERNOON/EVENING HOURS. IF/WHEN THIS OCCURS...A FEW
SUPERCELLS ARE POSSIBLE BEFORE POTENTIAL UPSCALE GROWTH INTO A
MESOSCALE CONVECTIVE SYSTEM ACCOMPANIED BY THE RISK FOR DOWNBURSTS
AND STRONG SURFACE COLD POOL DEVELOPMENT.
...OH VALLEY THROUGH THE ATLANTIC SEABOARD AND GULF COAST...
THUNDERSTORMS MAY BECOME FAIRLY NUMEROUS THURSDAY ACROSS NEW
ENGLAND...IN ASSOCIATION WITH FORCING ACCOMPANYING THE MAIN IMPULSE
WITHIN THE BROADER SCALE UPPER TROUGH...AND SOUTH OF A SHEAR AXIS
TRAILING FROM AN INITIAL SHORT WAVE IMPULSE OFF THE NORTHERN MID
ATLANTIC COAST...WEST SOUTHWESTWARD THROUGH THE OHIO/ TENNESSEE
VALLEYS INTO THE SOUTHERN PLAINS. CONFIDENCE IS LOW... BUT THE BEST
POTENTIAL FOR STORMS APPROACHING OR EXCEEDING SEVERE LIMITS SEEMS TO
EXIST ACROSS THE CAROLINAS INTO SOUTHEAST VIRGINIA...AS UPPER
FORCING AIDS CONVECTIVE DEVELOPMENT DURING THE LATE
AFTERNOON/EVENING HOURS. MODELS ARE SUGGESTIVE THAT STRONGEST
DAYTIME HEATING WILL OCCUR ACROSS THIS REGION... CONTRIBUTING TO A
FAVORABLE ENVIRONMENT FOR DOWNBURSTS AND SURFACE COLD POOLS
ACCOMPANIED BY POTENTIALLY DAMAGING WIND GUSTS.
..KERR.. 07/30/2008
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