SWODY2
SPC AC 071720
DAY 2 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1220 PM CDT THU JUN 07 2007
VALID 081200Z - 091200Z
..THERE IS A SLGT RISK OF SVR TSTMS FROM NY/WRN NEW ENGLAND SWWD
THROUGH THE OH/TN/MID MS VALLEYS AND INTO CENTRAL/WRN TX...
..SYNOPSIS...
UPPER TROUGH OVER THE UPPER MS VALLEY/UPPER GREAT LAKES REGION AT
THE START OF THE PERIOD WILL MOVE ENEWD INTO ONTARIO/QUEBEC WITH SRN
EDGE OF TROUGH MOVING THROUGH UPPER OH VALLEY AND INTO NY/PA BY LATE
IN THE DAY. AS THIS TROUGH LIFTS ENEWD...WHILE THE MID LEVEL WINDS
WILL REMAIN MODERATELY STRONG ACROSS THE NERN QUARTER OF THE
COUNTRY...WIND FIELDS WILL WEAKEN CONSIDERABLY FROM THE LOWER OH
VALLEY SWWD INTO THE SRN PLAINS.
COLD FRONT ASSOCIATED WITH UPPER TROUGH IS FORECAST TO MOVE RAPIDLY
EWD THROUGH THE OH VALLEY DURING THE AFTERNOON...BUT DRIFT ONLY
SLOWLY SEWD ACROSS THE MID MS/TN VALLEYS AND SRN PLAINS AS UPPER
TROUGH AND STRONGER FLOW ALOFT LIFTS NEWD AWAY FROM THIS REGION.
..WRN NEW ENGLAND/NY SWWD ACROSS THE OH VALLEY...
WEAKENING THUNDERSTORMS ARE EXPECTED TO STRETCH FROM MI SWWD INTO
PORTIONS OF IN/IL AT THE START OF THE PERIOD. DIURNAL HEATING AND
ADVECTION OF 65-70 DEGREE DEWPOINTS FROM THE LOWER/MID MS VALLEY
NEWD INTO THE AREA SHOULD RESULT IN STRONG INSTABILITY BY
AFTERNOON...WITH MLCAPE VALUES IN THE 2000-3000 J/KG RANGE. THIS
SHOULD AID IN REMNANT STORM ACTIVITY INTENSIFYING BY EARLY AFTERNOON
ACROSS PARTS OF INDIANA...OH...AND KY. THE STORMS ARE LIKELY TO
ORGANIZE INTO A LINE ALONG THE FRONT AND THEN MOVE ENEWD AT 30-40 KT
IN RESPONSE TO DEEP UNIDIRECTIONAL WSWLY WIND FIELDS. ALTHOUGH THE
WIND FIELDS ARE FORECAST TO WEAKEN IN THE LOWER 3 KM ...40-50 KT MID
LEVEL WINDS AND THE POSSIBLE DEVELOPMENT OF A COLD POOL SHOULD BE
SUPPORTIVE OF NUMEROUS STRONG/SEVERE WIND GUSTS AS SYSTEM SPREADS
EWD ACROSS OH AND INTO PA/NY BY LATE AFTERNOON. THOUGH THE TOTAL
SEVERE PROBABILITY HAS BEEN INCREASED TO 45 PERCENT ACROSS NERN
OH...NWRN PA...AND WRN NY...DID NOT UPGRADE TO MODERATE RISK ATTM
DUE TO THE FORECAST OF WEAK LOW LEVEL WIND FIELDS. HOWEVER...AN
UPGRADE IS POSSIBLE ON THE DAY 1 OUTLOOKS... ONCE THE DEVELOPMENT OF
A FAST MOVING ORGANIZED LINE APPEARS CERTAIN.
THE LINE/STORMS SHOULD GRADUALLY WEAKEN DURING THE EVENING HOURS AS
THE ACTIVITY MOVES INTO WRN NEW ENGLAND AND ENCOUNTERS A MORE STABLE
ENVIRONMENT.
..TEXAS TRANSPECOS REGION...
COLD FRONT WILL SETTLE INTO AREA DURING THE AFTERNOON AND RESULT IN
RICH BOUNDARY LAYER MOISTURE/INSTABILITY TO SHIFT WWD INTO THE AREA
FROM THE EDWARDS PLATEAU DURING THE AFTERNOON HOURS. THE DEEPENING
ELY BOUNDARY LAYER WINDS...WITH WINDS VEERING TO SWLY WITH
HEIGHT...SHOULD RESULT IN FAVORABLE SHEAR FOR A FEW SUPERCELLS.
ALTHOUGH DYNAMICAL FORCING WILL BE WEAK...LOW LEVEL WARM ADVECTION
AND UPSLOPE FLOW SHOULD AID IN STORM INITIATION DURING THE LATE
AFTERNOON HOURS. THE LOW LEVEL SHEAR WILL BE WEAK AND MID LEVELS
WARM SO SEVERE WIND GUSTS AND MARGINALLY SEVERE HAIL SHOULD BE THE
MAIN THREATS.
..MID MS/TN VALLEYS WSWWD INTO CENTRAL TX...
MODERATE INSTABILITY AND WEAK CONVERGENCE ALONG AND AHEAD OF COLD
FRONT SHOULD RESULT IN SCATTERED THUNDERSTORMS TO OCCUR THROUGHOUT
THE DAY FRIDAY. SOME UNCERTAINTY EXISTS ON ORGANIZATION AND AMOUNT
OF SEVERE WEATHER COVERAGE DUE TO VERY WEAK LARGE SCALE ASCENT AND
WEAKENING WINDS FIELDS. HOWEVER...A VERY MOIST BOUNDARY LAYER
AIRMASS/MODERATE INSTABILITY COMBINED WITH DAYTIME HEATING SHOULD
RESULT IN MULTICELL CLUSTERS WITH ISOLATED DAMAGING WINDS AND
PERHAPS ISOLATED HAIL. THE MAIN SEVERE THREAT SHOULD COINCIDE WITH
THE DIURNAL INSTABILITY MAXIMUM...SO STORMS SHOULD DIMINISH RAPIDLY
DURING THE EVENING HOURS.
.IMY.. 06/07/2007
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