DAY1SVR: Day 1 Convective Outlook

ACUS01 KWNS 031259
SWODY1
SPC AC 031257

DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0657 AM CST MON DEC 03 2012

VALID 031300Z - 041200Z

...NO SVR TSTM AREAS FORECAST...

...SYNOPSIS...
EARLY-MORNING WATER VAPOR LOOPS DEPICT A SHORTWAVE TROUGH
PROGRESSING EWD OVER THE CNTRL UNITED STATES...NOW EMERGING OVER THE
HIGH PLAINS. THIS FEATURE WILL CONTINUE TO TRACK EWD THROUGH THE
REMAINDER OF THE PERIOD...WHILE AN ACCOMPANYING SFC LOW MOVES
EWD/ENEWD FROM SERN MANITOBA TO JAMES BAY. A STRONG COLD FRONT
TRAILING SOUTH OF THE LOW WILL SURGE EWD ACROSS THE UPPER/MIDDLE MS
VALLEY TO THE GREAT LAKES REGION...WHILE THE SRN EXTENT OF THE SAME
FRONT SHIFTS SEWD/SWD ACROSS THE CNTRL/SRN PLAINS. BY EARLY TUE
MORNING...THE FRONT WILL EXTEND FROM THE WEST END OF LAKE ERIE TO
CNTRL AR TO SWRN TX. THE FRONT WILL SERVE AS THE FOCUS FOR
THUNDERSTORMS...A FEW POSSIBLY SEVERE...FROM THE GREAT LAKES TO AS
FAR SOUTH AS NERN TX LATE THIS AFTERNOON INTO TONIGHT. A SEPARATE
AREA OF ISOLATED NON-SEVERE STORMS MAY EVOLVE ACROSS SERN TX AND
SWRN LA INVOF A LOW-LEVEL CONFLUENCE AXIS AND RELATIVELY RICHER
MOISTURE.

...SRN WI AND SWRN LOWER MI SWWD TO ERN OK AND W-CNTRL AR THIS
AFTERNOON AND TONIGHT...
A LONG FETCH OF SLY FLOW IN ADVANCE OF THE COLD FRONT WILL CONTINUE
TO SUPPORT DEWPOINTS IN THE MIDDLE 50S TO THE LOWER 60S. WHILE THIS
LOW-LEVEL MOISTURE IS RELATIVELY MODEST...PRE-FRONTAL BUOYANCY WILL
BE LOCALLY BOOSTED BY /1/ MID-LEVEL ASCENT ACCOMPANYING THE
AFOREMENTIONED SHORTWAVE TROUGH.../2/ THE INFLUX OF AN EML ACROSS
THE SRN PLAINS AND THE OZARKS...AND /3/ DIURNAL HEATING. FORECAST
SOUNDINGS GENERALLY AGREE THAT THESE FACTORS WILL SUPPORT MLCAPE
VALUES OF 300-800 J/KG IN ADVANCE OF THE FRONT DURING PEAK HEATING.
VERTICAL MIXING PROCESSES MAY MODULATE THE EFFECTIVENESS OF
ADDITIONAL BOUNDARY-LAYER MOISTENING TODAY AS DRIER AIR ALOFT
OVERSPREADS PARTS OF THE AREA...THUS LIMITING THE POTENTIAL FOR
STRONGER INSTABILITY TO DEVELOP.

STORMS WILL LIKELY INITIATE INVOF THE FRONT BY LATE AFTERNOON...WITH
INITIAL DEVELOPMENT MOST LIKELY ACROSS ERN IA/CNTRL IL AND POINTS
NWD/NEWD...WITH ADDITIONAL ACTIVITY DEVELOPING ALONG THE SRN EXTENT
OF THE FRONT THROUGH THE EVENING. THE MARGINAL DEGREE OF
INSTABILITY...ONLY MODEST EFFECTIVE BULK SHEAR MAGNITUDES...AND
STRONGER FORCING FOR ASCENT BEING DISPLACED TO THE NORTH OF ANY
SUBSTANTIAL BOUNDARY-LAYER-ROOTED BUOYANCY ARE EXPECTED TO PREVENT A
MORE SUBSTANTIAL SVR EPISODE FROM EVOLVING.

REGARDLESS...STRONG SWLY FLOW OF 35-55 KT WITHIN THE 850-700-MB
LAYER WILL YIELD AN ISOLATED THREAT FOR SVR WIND
GUSTS...PARTICULARLY WITH ANY MORE ORGANIZED/BOWING CONVECTIVE
SEGMENTS. THE GREATEST THREAT FOR THE STRONGEST STORMS WILL EXIST
FROM NERN MO NEWD ACROSS CNTRL/NRN IL INTO SRN WI AND ADJACENT LAKE
MI...WHERE THE STRONGEST 850-700-MB FLOW WILL BE PRESENT. IN THESE
AREAS...FORECAST SOUNDINGS SUGGEST A HODOGRAPH CHARACTERIZED BY
FAIRLY STRONG LOW-LEVEL SHEAR AIDED BY A VERTICALLY VEERING WIND
PROFILE IN THE LOWEST 1.5 KM AGL. AND...WITH THE ANTICIPATED MODEST
LOW-LEVEL MOISTURE...AN ISOLATED TORNADO OR TWO CANNOT BE RULED OUT.

..COHEN/CORFIDI.. 12/03/2012

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