SWODY1
SPC AC 180536
DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1236 AM CDT MON AUG 18 2008
VALID 181200Z - 191200Z
...THERE IS A SLGT RISK OF SVR TSTMS ACROSS PARTS OF NY AND NEW
ENGLAND...
...THERE IS A SLGT RISK OF SVR TSTMS ACROSS PARTS OF SRN AND CNTRL
FL...
...NEW YORK/NEW ENGLAND....
AN UPPER-LEVEL TROUGH IS FORECAST TO MOVE EWD ACROSS SERN CANADA
TODAY AS A WELL-DEVELOPED 40 TO 55 KT MID-LEVEL JET DRIFTS EWD
ACROSS SRN QUEBEC. AT THE SFC...A COLD FRONT WILL APPROACH THE
REGION FROM THE NORTHWEST WITH AN AXIS OF INSTABILITY LOCATED AHEAD
OF THE FRONT FROM WRN NY EXTENDING NEWD INTO MAINE. SCATTERED
THUNDERSTORMS SHOULD DEVELOP ALONG AND AHEAD OF THE BOUNDARY
INCREASING IN COVERAGE IN THE AFTERNOON AND MOVING SEWD ACROSS THE
REGION.
CONCERNING THE SHEAR ENVIRONMENT...VERTICAL SHEAR PROFILES WILL
GRADUALLY INCREASE THIS AFTERNOON ACROSS THE NERN U.S. AS THE
UPPER-LEVEL TROUGH AND ASSOCIATED MID-LEVEL JET APPROACHES. FORECAST
SOUNDINGS AT 21Z MONDAY SHOW 30 TO 40 KT OF 0-6 KM SHEAR WHICH
SHOULD BE ENOUGH FOR ISOLATED SUPERCELLS WHERE INSTABILITY BECOMES
MAXIMIZED. ALTHOUGH LARGE HAIL WILL BE POSSIBLE WITH
SUPERCELLS...RELATIVELY STRONG LOW-LEVEL FLOW AND UNIDIRECTIONAL
WINDS SHOULD FAVOR LINE SEGMENTS CAPABLE OF PRODUCING WIND DAMAGE.
THE THREAT MAY PERSIST SEWD INTO SRN NEW ENGLAND ALTHOUGH THE THREAT
SHOULD BECOME INCREASINGLY MARGINAL BY EARLY EVENING.
...SRN FLORIDA...
TROPICAL STORM FAY IS FORECAST BY THE NATIONAL HURRICANE CENTER TO
MOVE NWD TOWARD THE FLORIDA KEYS TODAY AND TO BECOME A HURRICANE
TONIGHT. AS A RESULT...RAINBANDS ASSOCIATED WITH FAY WILL SPREAD NWD
ACROSS SRN AND CNTRL FL WITH THE BRUNT OF CONVECTION FORECAST TO
MOVE OVER TONIGHT. FORECAST SOUNDINGS ACROSS SRN FL GRADUALLY
INCREASE LOW-LEVEL SHEAR PROFILES THIS AFTERNOON INTO THE EVENING AS
FAY APPROACHES. AS A RESULT...CONDITIONS WILL BECOME INCREASINGLY
FAVORABLE FOR ROTATING STORMS AND TORNADOES EMBEDDED IN THE
RAINBANDS OF FAY.
...WEST TX...
AN UPPER-LEVEL LOW OVER CNTRL CO IS FORECAST MOVE SEWD INTO THE TX
PANHANDLE TODAY. AHEAD OF THE UPPER-LEVEL LOW...AN MCS SHOULD BE
ONGOING IN WEST TX AT THE BEGINNING OF THE PERIOD WITH OTHER STORMS
LOCATED NEAR THE CORE OF THE UPPER-LEVEL LOW. AS SFC TEMPS WARM LATE
THIS MORNING INTO THIS AFTERNOON...SCATTERED THUNDERSTORMS SHOULD
DEVELOP AND MOVE SSEWD ACROSS THE REGION. MODEL FORECAST SOUNDINGS
AT 21Z MONDAY SHOW ABOUT 30 KT OF 0-6 KM SHEAR SUGGESTING AN
ISOLATED SUPERCELL THREAT WITH MARGINALLY SEVERE HAIL WILL BE
POSSIBLE. HOWEVER...MULTICELLS WILL LIKELY BE THE DOMINANT STORM
MODE CONSIDERING INSTABILITY AND LAPSE RATES ARE NOT FORECAST TO BE
THAT STRONG.
...WRN ORE/WRN WA...
A HIGHLY MERIDIONAL UPPER-LEVEL TROUGH WILL APPROACH THE WEST COAST
TODAY AS HEIGHTS CONTINUE TO FALL ACROSS THE REGION. STRONG
LARGE-SCALE ASCENT AND SFC HEATING SHOULD RESULT IN SCATTERED
THUNDERSTORM DEVELOPMENT THIS AFTERNOON ALONG AN AXIS OF INSTABILITY
EXTENDING NWD ACROSS WRN ORE AND WRN WA. FORECAST SOUNDINGS ACROSS
THE REGION AT 21Z SUGGEST ABOUT 40 KT OF VERTICAL SHEAR WILL EXIST
WHICH COMBINED WITH STEEP MID-LEVEL LAPSE RATES MAY SUPPORT ROTATING
STORMS WITH AN ISOLATED HAIL THREAT. LOW-LEVEL LAPSE RATES ARE ALSO
FORECAST TO BE QUITE STEEP SUGGESTING A MARGINAL WIND DAMAGE THREAT
WILL ALSO BE POSSIBLE.
..BROYLES.. 08/18/2008
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