DAY1SVR: Day 1 Convective Outlook

ACUS01 KWNS 250600
SWODY1
SPC AC 250558

DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1258 AM CDT TUE SEP 25 2007

VALID 251200Z - 261200Z

..THERE IS A SLGT RISK OF SVR TSTMS ACROSS PARTS OF THE GREAT LAKES
AND NRN OH VALLEY...

..SRN GREAT LAKES/NRN OH VALLEY...
AN UPPER-LEVEL TROUGH OVER THE NRN PLAINS WILL MOVE EWD INTO THE
UPPER MIDWEST TODAY. AT THE SFC...A COLD FRONT WILL MOVE EWD INTO
THE WRN GREAT LAKES REGION AND MID MS VALLEY. SFC DEWPOINTS AHEAD OF
THE BOUNDARY WILL BE IN THE UPPER 60S AND LOWER 70S F WHICH SHOULD
RESULT IN MODERATE INSTABILITY ACROSS THE WARM SECTOR BY THIS
AFTERNOON. THUNDERSTORMS WILL LIKELY INITIATE ALONG THE BOUNDARY
AROUND MIDDAY WITH THE ACTIVITY BECOMING QUITE NUMEROUS BY LATE
AFTERNOON. SEVERAL LINEAR MCS/S APPEAR LIKELY TO DEVELOP ACROSS THE
REGION BY THIS EVENING. OTHER MORE SCATTERED CONVECTION SHOULD
DEVELOP ACROSS THE WARM SECTOR IN THE NRN OH VALLEY ASSOCIATED WITH
A PLUME OF MOISTURE EXTENDING NWD AROUND A HIGH PRESSURE SYSTEM
ALONG THE ERN SEABOARD.

CONCERNING THE STORM ENVIRONMENT...A 70 KT MID-LEVEL JET ON THE ERN
SIDE OF THE UPPER-LEVEL TROUGH WILL DRIFT EWD TOWARD THE REGION.
AHEAD OF THIS FEATURE...WINDS ALOFT WILL BE STRONG ENOUGH TO CREATE
MODERATE VERTICAL SHEAR ACROSS THE SLIGHT RISK AREA. THIS WILL BE
SUFFICIENT FOR ORGANIZED STORMS WHERE INSTABILITY BECOMES MAXIMIZED
THIS AFTERNOON. UNIDIRECTIONAL WIND PROFILES SHOWN ON FORECAST
SOUNDINGS SHOULD BE ADEQUATE FOR A WIND DAMAGE THREAT IN THE LATE
AFTERNOON WHEN LOW-LEVEL LAPSE RATES WILL BE STEEP. ALTHOUGH
SHORT-LINE SEGMENTS SHOULD BE QUITE COMMON TODAY...AN ISOLATED
SUPERCELL THREAT MAY ALSO DEVELOP ACROSS THE WRN PART OF THE SLIGHT
RISK AREA WHERE VERTICAL SHEAR PROFILES SHOULD BE A BIT STRONGER DUE
TO INFLUENCE FROM THE MID-LEVEL JET. ALSO...MID-LEVEL TEMPS ACROSS
THIS AREA SHOULD BE COOLER RESULTING IN STEEPER MID-LEVEL LAPSE
RATES WHICH MAY BE FAVORABLE FOR LARGE HAIL WITH THE STRONGER CELLS.

..OZARK PLATEAU...
A PLUME OF MOISTURE CURRENTLY EXTENDS NWD ACROSS THE LOWER AND MID
MS VALLEY EVIDENT ON WATER VAPOR IMAGERY. CURRENT RUC ANALYSIS
SUGGESTS A DISTURBANCE IS MOVING NWD ACROSS AR AND THIS FEATURE
SHOULD BE LOCATED IN ERN MO OR SRN IL BY MIDDAY. LIFT ASSOCIATED
WITH THIS FEATURE AND SFC HEATING SHOULD RESULT IN SCATTERED TO
NUMEROUS THUNDERSTORMS IN THE WARM SECTOR ACROSS THE OZARK PLATEAU
AND NEAR THE MS RIVER THIS AFTERNOON. NUMEROUS THUNDERSTORMS WILL
ALSO DEVELOP ALONG THE FRONTAL BOUNDARY AS MODERATE INSTABILITY AND
LOW-LEVEL CONVERGENCE INCREASES THIS AFTERNOON. ALTHOUGH VERTICAL
SHEAR PROFILES ARE GENERALLY FORECAST TO BE LESS THAN 30
KT...BOUNDARY LAYER FLOW AND STEEP LOW-LEVEL LAPSE RATES MAY BE
ENOUGH FOR A MARGINAL WIND DAMAGE THREAT THIS AFTERNOON.

.BROYLES/GRAMS.. 09/25/2007

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