SPC AC 031630
DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1130 AM CDT THU JUL 03 2008
VALID 031630Z - 041200Z
...THERE IS A SLGT RISK OF SVR TSTMS THIS AFTERNOON/EVENING FROM THE
UPPER OH VALLEY INTO NEW ENGLAND...
...THERE IS A SLGT RISK OF SVR TSTMS THIS AFTERNOON/EVENING FOR THE
INTERIOR PAC NW...
...UPPER OH VALLEY INTO NEW ENGLAND THIS AFTERNOON/EVENING...
A SURFACE COLD FRONT IS MOVING SEWD ACROSS THE SAINT LAWRENCE
VALLEY/LOWER GREAT LAKES INTO OH/PA/NY AND NRN NEW ENGLAND IN
ASSOCIATION WITH A MID LEVEL TROUGH PROGRESSING EWD OVER
ONTARIO/QUEBEC. REGIONAL 12Z SOUNDINGS AND SURFACE ANALYSES REVEAL
POOR LAPSE RATES IN THE PRE-FRONTAL WARM SECTOR...WHILE LOW-LEVEL
MOISTURE HAS BEEN LIMITED BY A PRIOR FRONTAL PASSAGE.
ADDITIONALLY...SATELLITE IMAGERY CONFIRMS A BAND OF CLOUDS PRECEDING
THE COLD FRONT ACROSS PA/NY/NRN NEW ENGLAND...SUCH THAT THE STRONGER
SURFACE HEATING/DESTABILIZATION WILL LIKELY OCCUR S OF THE FRONT AND
WITHIN THE ZONE OF RELATIVELY POOR LOW-LEVEL MOISTURE. THE NET
RESULT SHOULD BE WEAK INSTABILITY AT BEST WITHIN THE WARM SECTOR.
A BELT OF 40-50 KT MID LEVEL FLOW WILL ACCOMPANY THE FRONTAL PASSAGE
THIS AFTERNOON FROM PA/NY INTO NEW ENGLAND. THIS MODERATE MID LEVEL
FLOW WILL CONTRIBUTE TO SUFFICIENT VERTICAL SHEAR FOR
ORGANIZED/EMBEDDED LINE SEGMENTS AND THE ATTENDANT THREAT FOR
DAMAGING WINDS...DESPITE THE POOR INSTABILITY. THE WIND DAMAGE
THREAT WILL REACH A RELATIVE PEAK BY MID-LATE AFTERNOON...AND THEN
DIMINISH SLOWLY BY LATE EVENING.
...INTERIOR ORE/WA THROUGH EARLY TONIGHT...
A MID LEVEL LOW IS MOVING NNEWD AROUND THE NWRN PERIPHERY OF THE
MEAN RIDGE OVER THE ROCKIES...WHILE EMBEDDED SHORTWAVE TROUGHS PIVOT
NNEWD AROUND THE E/SE SIDE OF THE LOW TOWARD WRN ORE/WA. SCATTERED
THUNDERSTORMS HAVE PERSISTED OVERNIGHT AND INTO THIS MORNING OVER
THE CASCADES AND WITHIN THE PRIMARY MID LEVEL MOISTURE PLUME
PRECEDING THE MID LEVEL TROUGH. THE THREAT FOR WIDELY SCATTERED
SEVERE STORMS WILL INCREASE LATER THIS AFTERNOON/EVENING OVER AND
IMMEDIATELY E OF THE CASCADES IN ORE/WA AS SURFACE HEATING
DESTABILIZES THE LOW LEVELS AND REMOVES CONVECTIVE INHIBITION. THE
COMBINATION OF STEEP MID LEVEL LAPSE RATES...BOUNDARY LAYER
DEWPOINTS IN THE MID 50S...AND EFFECTIVE BULK SHEAR IN EXCESS OF 40
KT ALL SUPPORT THE POTENTIAL FOR A FEW SUPERCELLS OR SMALL BOWS
PROGRESSING NEWD OFF THE HIGH TERRAIN. LARGE HAIL AND DAMAGING
WINDS WILL BE THE PRIMARY SEVERE THREATS FROM ABOUT 21-03Z.
...CENTRAL HIGH PLAINS THIS AFTERNOON/EVENING...
A COOL/MOIST AIR MASS IS IN PLACE E OF THE FRONT RANGE IN THE WAKE
OF THE FRONTAL PASSAGE YESTERDAY. AREAS E OF THE FRONT RANGE WILL
LIKELY REMAIN CAPPED THROUGH THE DAY...WHILE CONVECTIVE INITIATION
WILL BE MORE PROBABLY NEAR THE HIGH TERRAIN. MODEST INSTABILITY AND
VERTICAL SHEAR IN THE POST-FRONTAL REGIME COULD SUPPORT MULTICELL
CLUSTERS OR MARGINAL SUPERCELL STRUCTURES...WITH THE POSSIBILITY OF
ISOLATED LARGE HAIL/DAMAGING WINDS LATE THIS AFTERNOON/EVENING.
...OK TO THE LOWER OH VALLEY...
A SURFACE COLD FRONT HAS DRIFTED SEWD TO JUST N OF I-44 IN
OK/MO...WHILE A REMNANT MCV AND ASSOCIATED DIFFUSE OUTFLOW BOUNDARY
ARE LOCATED OVER WRN KY/SE MO. STRONG SURFACE HEATING ALONG AND S
OF THESE BOUNDARIES WILL CONTRIBUTE TO MODERATE INSTABILITY AND ONLY
WEAK CONVECTIVE INHIBITION THIS AFTERNOON. A FEW CLUSTERS OF
PULSE-TYPE SEVERE STORMS WILL BE POSSIBLE THIS AFTERNOON...WITH
ISOLATED DAMAGING WINDS AND LARGE HAIL THE MAIN THREATS.
..THOMPSON/LEVIT.. 07/03/2008
CLICK TO GET WUUS01 PTSDY1 PRODUCT
NOTE: THE NEXT DAY 1 OUTLOOK IS SCHEDULED BY 2000Z
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