SPC AC 240547
DAY 2 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1247 AM CDT WED JUN 24 2009
VALID 251200Z - 261200Z
...THERE IS A SLGT RISK OF SVR TSTMS THU FROM PARTS OF THE MID
MS/OHIO VALLEYS THRU THE LWR GREAT LAKES...
...SYNOPSIS...
IN A BROAD SENSE...LATEST MODEL RUNS ARE FAIRLY SIMILAR WITH REGARD
TO THE UPPER FLOW EVOLUTION THROUGH THIS FORECAST PERIOD. WITHIN
THE PRIMARY BELT OF WESTERLIES NEAR THE CANADIAN/U.S. BORDER...A
COUPLE OF SIGNIFICANT TROUGHS AND EMBEDDED SMALLER SCALE IMPULSES
LIKELY WILL REMAIN PROGRESSIVE. IT APPEARS THAT ONE WILL DIG ACROSS
THE GREAT LAKES/OHIO VALLEY REGION INTO THE NORTHEASTERN
U.S...FINALLY CONTRIBUTING TO THE NORTHEASTWARD ACCELERATION OF
REMNANT CLOSED LOW AWAY FROM THE ATLANTIC SEABOARD...THOUGH A
TRAILING SHEAR AXIS TO ANOTHER CIRCULATION NEAR THE FLORIDA GULF
COAST MAY LINGER. MEANWHILE...AN UPSTREAM TROUGH IS PROGGED TO
SHIFT EAST OF THE CANADIAN ROCKIES INTO THE CANADIAN PRAIRIES. AND
GUIDANCE CONTINUES TO SUGGEST THAT THIS FEATURE WILL CONTRIBUTE TO
NORTHEASTWARD/INLAND ACCELERATION OF THE CLOSED LOW/TROUGH NOW WEST
OF THE SOUTHERN CALIFORNIA COAST. SUBSTANTIAL DISCREPANCIES REMAIN
AMONG MODELS CONCERNING THE MANNER AND SPEED AT WHICH THIS
OCCURS...WHILE CONSIDERABLE SPREAD PERSISTS AMONG NCEP SREF/MREF
MEMBERS CONCERNING THIS FEATURE AND OTHER SHORT WAVE DEVELOPMENTS
WITHIN THE EVOLVING PATTERN...WHICH WILL BE OF IMPACT TO THE
CONVECTIVE OUTLOOK.
...MID MS/OHIO VALLEYS THROUGH THE LOWER GREAT LAKES/NORTHEAST...
DESPITE THE UNCERTAINTIES...A REMNANT PLUME OF MODESTLY STEEP
MID-LEVEL LAPSE RATES ADVECTING EASTWARD ALONG THE SOUTHERN FRINGE
OF THE STRONGER WESTERLIES SEEMS LIKELY TO CONTRIBUTE TO MODERATE TO
STRONG POTENTIAL INSTABILITY THURSDAY...AHEAD OF THE DIGGING UPPER
TROUGH APPROACHING THE REGION. WITH HEATING OF A MOIST BOUNDARY
LAYER CHARACTERIZED BY SURFACE DEW POINTS IN THE UPPER 60S/LOWER
70S...GUIDANCE SUGGESTS THAT MIXED LAYER CAPE WILL REACH 1500-3000
J/KG. GIVEN RELATIVELY WEAK INHIBITION...THIS
DESTABILIZATION...COUPLED WITH FAVORABLE MID/UPPER FORCING...IS
EXPECTED TO SUPPORT WIDESPREAD CONVECTIVE DEVELOPMENT. ALTHOUGH
FLOW FIELDS...PARTICULARLY IN LOWER/MID LEVELS...SHOULD REMAIN
FAIRLY WEAK...THERMODYNAMIC PROFILES WILL BE FAVORABLE FOR
DOWNBURSTS AND THE EVOLUTION OF CONVECTIVELY GENERATED COLD POOLS IN
LOOSELY ORGANIZED EASTWARD/SOUTHEASTWARD ADVANCING CONVECTIVE
BANDS/CLUSTERS. THESE MAY BE ACCOMPANIED BY POTENTIALLY DAMAGING
WIND GUSTS THROUGH THE AFTERNOON AND EARLY EVENING HOURS...BEFORE
BOUNDARY LAYER INSTABILITY WANES LATE THURSDAY EVENING.
...GREAT BASIN...
UNCERTAINTIES REMAIN TOO LARGE TO CONFIDENTLY DELINEATE SLIGHT RISK
PROBABILITIES. BUT...STRENGTHENING SOUTHWESTERLY MID/UPPER FLOW /UP
TO 40-50 KT AT 500 MB/ APPEARS A POSSIBILITY THURSDAY ACROSS PARTS
OF CENTRAL/EASTERN NEVADA...PERHAPS INTO WESTERN UTAH. ASSOCIATED
MOMENTUM AND INCREASING DEEP LAYER SHEAR... COUPLED WITH LARGE-SCALE
FORCING DOWNSTREAM OF APPROACHING IMPULSE...COULD CONTRIBUTE TO
ORGANIZED CONVECTIVE DEVELOPMENT AS DESTABILIZATION OCCURS WITH
DAYTIME HEATING. SOME HAIL COULD ACCOMPANY STRONG STORMS...BUT
STRONG WIND GUSTS ARE EXPECTED TO BE THE PRIMARY THREAT...AIDED BY
LARGE LINGERING SUB-CLOUD TEMPERATURE/DEW POINTS SPREADS.
..KERR.. 06/24/2009
CLICK TO GET WUUS02 PTSDY2 PRODUCT
NOTE: THE NEXT DAY 2 OUTLOOK IS SCHEDULED BY 1730Z
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