SWODY1
SPC AC 080457
DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1157 PM CDT THU AUG 07 2008
VALID 081200Z - 091200Z
...NO SVR TSTM AREAS FORECAST...
...NY/SRN NEW ENGLAND TODAY...
A COLD CORE MID LEVEL LOW WILL BE MAINTAINED OVER QUEBEC/ONTARIO AS
ONE SHORTWAVE TROUGH ROTATES EWD FROM PA/NY TO SRN NEW
ENGLAND...ACCOMPANIED BY A WEAK SURFACE LOW NEAR THE SE NEW ENGLAND
COAST. RESIDUAL BOUNDARY LAYER DEWPOINTS OF 56-62 F AND POCKETS OF
SURFACE HEATING WITHIN CLOUD BREAKS WILL SUPPORT SOME DIURNAL
DESTABILIZATION. GIVEN RELATIVELY COOL MID LEVEL TEMPERATURES
AROUND -15 C AT 500 MB...INSTABILITY MAY BECOME SUFFICIENT FOR A FEW
STORMS WITH MARGINALLY SEVERE HAIL AND GUSTY OUTFLOW WINDS.
HOWEVER...THE OVERALL SEVERE STORM THREAT WILL BE LIMITED AS A
RESULT OF WEAK VERTICAL SHEAR...ONLY MODEST SURFACE HEATING...AND
THE RICHEST LOW-LEVEL MOISTURE CONFINED TO NEAR OR JUST OFF THE SE
NEW ENGLAND COAST.
...NRN ROCKIES TODAY INTO EARLY TONIGHT...
THE LARGE SCALE REGIME WILL CHANGE LITTLE FROM THE PREVIOUS TWO DAYS
AS A MID LEVEL RIDGE PERSISTS OVER INTERMOUNTAIN WEST...AND A MID
LEVEL TROUGH MOVES SLOWLY EWD TO THE PAC NW COAST. A SERIES OF
EMBEDDED MID LEVEL SPEED MAXIMA WILL ALSO CONTINUE TO MOVE NWD/NNEWD
FROM CA AND THE GREAT BASIN TO THE NRN ROCKIES...WITH THE MOST
PRONOUNCED WAVE NOW APPROACHING NRN CA. LOW-MID LEVEL MOISTURE HAS
INCREASED GRADUALLY DURING THE PAST COUPLE OF DAYS AND LOW-MID LEVEL
LAPSE RATES REMAIN STEEP. THERE IS SOME CONCERN THAT INSTABILITY
COULD BE LIMITED A LITTLE BY RESIDUAL CLOUDS/CONVECTION THAT COULD
PERSIST OVERNIGHT FROM ORE INTO ID...THOUGH SOME CLOUD BREAKS AND
SURFACE HEATING ARE STILL LIKELY BY AFTERNOON FROM THE ID PANHANDLE
INTO WRN MT. MODEST VERTICAL SHEAR AND INSTABILITY COULD SUPPORT
STORMS WITH ISOLATED LARGE HAIL AND STRONG OUTFLOW WINDS DURING THE
AFTERNOON...BEGINNING IN NE ORE/ERN WA AND SPREADING NEWD ACROSS THE
ID PANHANDLE INTO WRN MT DURING THE EVENING.
...SRN STATES THIS AFTERNOON...
A SURFACE COLD FRONT...AUGMENTED BY OUTFLOW FROM WIDESPREAD
CONVECTION THURSDAY AFTERNOON/EVENING...WILL CONTINUE TO MOVE
SWD/SEWD TO NEAR THE SE ATLANTIC AND NE GULF COASTS BY THIS
AFTERNOON. THE WRN EXTENT OF THIS BOUNDARY WILL DRIFT SWWD FROM ERN
TOWARD CENTRAL TX. COMPARED TO THURSDAY...IT APPEARS THAT BOTH
INSTABILITY AND VERTICAL SHEAR WILL BE WEAKER NEAR THE BOUNDARY.
ISOLATED WET MICROBURSTS MAY OCCUR ACROSS N FL AND/OR E TX WITH
AFTERNOON STORMS INVOF THE BOUNDARY...BUT THE OVERALL SEVERE STORM
THREAT IS TOO MARGINAL TO WARRANT MORE THAN LOW DAMAGING WIND
PROBABILITIES.
...CENTRAL HIGH PLAINS THIS AFTERNOON INTO EARLY TONIGHT...
A WEAK MID LEVEL TROUGH NOW OVER ERN UT/WRN CO...EMANATING FROM THE
MONSOONAL MOISTURE PLUME OVER THE GREAT BASIN...WILL CREST THE MID
LEVEL RIDGE AND DRIFT EWD TO THE CENTRAL HIGH PLAINS BY EARLY
SATURDAY. DIURNAL CONVECTION APPEARS LIKELY WITH THIS SYSTEM
TODAY...ESPECIALLY OVER THE HIGHER TERRAIN OF NE UT AND CO. STORMS
SHOULD SPREAD GRADUALLY EWD OVER THE HIGH PLAINS DURING THE
AFTERNOON/EVENING...AND COULD BE MAINTAINED OVERNIGHT BY A
DEVELOPING 30 KT LLJ AND MOISTURE FEED ALONG THE COOL SIDE OF A
STALLED FRONT. HOWEVER...RATHER ANEMIC MID LEVEL LAPSE RATES/MOIST
PROFILES AND WEAK VERTICAL SHEAR SUGGEST THAT ANY HAIL/WIND THREAT
WILL BE QUITE LIMITED.
..THOMPSON/JEWELL.. 08/08/2008
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