SPC AC 280738
DAY 3 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0238 AM CDT FRI SEP 28 2007
VALID 301200Z - 011200Z
...NO SVR TSTM AREAS FORECAST...
...SYNOPSIS...
DOWNSTREAM OF A STRONG INCREASINGLY ZONAL JET ACROSS THE NORTHERN
PACIFIC...MODELS INDICATE THAT A SERIES OF AMPLIFIED TROUGHS WILL
REMAIN PROGRESSIVE WITHIN THE BELT OF POLAR WESTERLIES CURVING
ACROSS THE GREAT BASIN THROUGH THE NORTH ATLANTIC SEABOARD. WHILE
ONE SHORT WAVE IMPULSE PROGRESSING EAST OF THE NORTH ATLANTIC
COAST...AND ANOTHER DIGGING INTO THE PACIFIC COAST STATES...ARE
SIMILARLY HANDLED BY MOST MODEL GUIDANCE...THE SPREAD OF POSSIBLE
SOLUTIONS REMAINS LARGE CONCERNING THE SYSTEM EXPECTED TO PROGRESS
THROUGH THE NORTH CENTRAL STATES. AND...THE RATE AT WHICH THIS
LATTER SYSTEM LIFTS ACROSS THE UPPER MISSISSIPPI VALLEY/UPPER GREAT
LAKES REGION...WITH A FAIRLY STRONG EASTWARD SURGING COLD
FRONT...WILL HAVE A SIGNIFICANT IMPACT ON THE CONVECTIVE POTENTIAL
SUNDAY/SUNDAY NIGHT.
...UPPER MISSISSIPPI VALLEY...
IF THE SLOWER MODEL SOLUTIONS PAN OUT...A NARROW PRE-FRONTAL TONGUE
OF MOISTURE COULD BECOME THE FOCUS FOR AT LEAST WEAK DESTABILIZATION
SUNDAY AFTERNOON...FROM PARTS OF EASTERN IOWA/MINNESOTA INTO
WESTERN WISCONSIN/NORTHWEST ILLINOIS. STRONGER COOLING ALOFT WILL
PROBABLY LAG THE SURFACE COLD FRONT...AND SURFACE HEATING COULD BE
RESTRICTED BY EARLY DAY CLOUD COVER. BUT...STRONG FORCING FOR
UPWARD VERTICAL MOTION AND STRONG WIND FIELDS/VERTICAL SHEAR
ASSOCIATED WITH THE UPPER SYSTEM AND COLD FRONT SUPPORT AT LEAST
SOME POTENTIAL FOR VIGOROUS CONVECTIVE DEVELOPMENT. SEVERE THREAT
APPEARS BELOW CATEGORICAL /15%/ SEVERE PROBABILITIES AT THE PRESENT
TIME DUE TO MODEL UNCERTAINTIES.
REGARDLESS OF MODEL SOLUTION...ANY SEVERE POTENTIAL IS EXPECTED TO
DIMINISH AS SURFACE FRONT PROGRESSES EAST OF THE UPPER MISSISSIPPI
VALLEY INTO THE GREAT LAKES/LOWER OHIO VALLEY REGION...OVERTAKING
DRIER LOW-LEVEL AIR MASS EMANATING FROM THE LARGE SOUTHEASTERN
STATES SURFACE RIDGE.
...SOUTH CENTRAL PLAINS...
SEASONABLY STRONG HEATING OF MOIST AIR MASS ALONG/SOUTH OF STALLING
SURFACE FRONT IS EXPECTED TO CONTRIBUTE TO WEAK TO MODERATE
INSTABILITY SUNDAY AFTERNOON. DESTABILIZATION WILL GENERALLY ONLY
BE LIMITED BY A RELATIVELY WARM MID-LEVEL ENVIRONMENT BENEATH A
SUBTROPICAL RIDGE. BUT...THERMODYNAMIC PROFILES WITH WEAK LOW/MID
LEVEL FLOW REGIME COULD BECOME SUPPORTIVE OF AN ISOLATED SEVERE
STORMS OR TWO WITH STRONG GUSTY WINDS...POSSIBLY SOME MARGINALLY
SEVERE HAIL.
..KERR.. 09/28/2007
CLICK TO GET WUUS03 PTSDY3 PRODUCT
NOTE: THE NEXT DAY 3 OUTLOOK IS SCHEDULED BY 1100Z
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