SPC AC 250728
DAY 3 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0228 AM CDT WED JUL 25 2007
VALID 271200Z - 281200Z
...THERE IS A SLGT RISK OF SVR TSTMS FRI AFTN/EVE FROM THE LWR MO
VALLEY INTO THE LWR OH VALLEY....
...SYNOPSIS...
MODELS INDICATE THAT THE REMNANTS OF THE WEAK CLOSED LOW WILL
CONTINUE EASTWARD TOWARD THE HUDSON/CHAMPLAIN VALLEYS AND NORTHERN
MID ATLANTIC COAST DURING THIS FORECAST PERIOD...AS A SIGNIFICANT
POLAR TROUGH SLOWLY ADVANCES ACROSS THE EASTERN CANADIAN PROVINCES.
WHILE STRONGER WESTERLIES WILL LIKELY REMAIN GENERALLY CONFINED TO
THE CANADIAN PROVINCES...MID-LEVEL FLOW IS PROGGED TO TAKE ON AN
INCREASING NORTHWESTERLY COMPONENT FROM THE NORTH CENTRAL U.S. INTO
THE SOUTHEASTERN STATES. AND...MODELS...PARTICULARLY THE LATEST
GFS/ECMWF...ARE SUGGESTIVE THAT ONE OR MORE IMPULSES...EMANATING
FROM THE INTERMOUNTAIN WEST...WILL MIGRATE AROUND THE WEAKENING
WESTERN U.S. RIDGE...INTO THIS REGIME...OVER PARTS OF THE GREAT
LAKES/MID MISSOURI VALLEY BY EARLY FRIDAY. SOUTHEASTWARD
PROGRESSION INTO THE LOWER OHIO VALLEY IS FORECAST BY LATE FRIDAY
NIGHT OR EARLY SATURDAY.
...LOWER MISSOURI VALLEY INTO THE LOWER OHIO VALLEY...
EAST SOUTHEASTWARD ADVECTION OF AN ELEVATED MIXED LAYER FROM THE
PLAINS...AHEAD OF A SURFACE FRONT ASSOCIATED WITH THE EASTERN
CANADIAN TROUGH...IS EXPECTED TO CONTRIBUTE TO DESTABILIZATION
FRIDAY. OVERSPREADING A PRE-FRONTAL TONGUE OF 70F+ SURFACE DEW
POINTS...THIS SEEMS LIKELY TO SUPPORT THE DEVELOPMENT OF MIXED LAYER
CAPE AT OR ABOVE 2000 J/KG BY PEAK AFTERNOON HEATING...PROVIDING A
FAVORABLE THERMODYNAMIC ENVIRONMENT FOR STRONG WIND GUSTS AND HAIL
IN ANY CONVECTIVE ACTIVITY. AND...MID/UPPER FORCING MAY WEAKEN
INHIBITION SUFFICIENTLY FOR INCREASING THUNDERSTORMS BY EARLY FRIDAY
AFTERNOON...FROM PARTS OF NORTHERN MISSOURI/SOUTHEAST IOWA INTO
CENTRAL ILLINOIS. ONE OR MORE ORGANIZING CONVECTIVE CLUSTERS MAY
EVOLVE AS ACTIVITY DEVELOPS SOUTHEASTWARD INTO/THROUGH THE LOWER
OHIO VALLEY LATE FRIDAY AFTERNOON AND EVENING. ALTHOUGH DEEP LAYER
SHEAR IS FORECAST TO BE FAIRLY WEAK...20-30 KT MEAN LOWER/MID
TROPOSPHERIC FLOW WILL PROMOTE MODERATE STORM MOTIONS...AND COULD
ENHANCE DAMAGING WIND POTENTIAL...BEFORE CONVECTION WEAKENS LATE
FRIDAY EVENING OR OVERNIGHT.
..KERR.. 07/25/2007
CLICK TO GET WUUS03 PTSDY3 PRODUCT
NOTE: THE NEXT DAY 3 OUTLOOK IS SCHEDULED BY 1100Z
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