SWODY1
SPC AC 161603
DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1103 AM CDT TUE OCT 16 2007
VALID 161630Z - 171200Z
..THERE IS A SLGT RISK OF SVR TSTMS PARTS OF SOUTHERN HIGH
PLAINS...
..SYNOPSIS...
SURFACE/UPPER LOW WILL MOVE NNEWD ACROSS MN THIS AFTERNOON AND
WEAKEN AS A POWERFUL POLAR JET AND NEGATIVELY TILTED TROUGH RAPIDLY
DEVELOPS EWD ACROSS SWRN U.S. AT THE SURFACE OLD FRONTAL ZONE
ACROSS LOWER MS VLY/SRN PLAINS WILL REDEVELOP NWD ACROSS CENTRAL
PLAINS INTO LOWER MO VALLEY TONIGHT IN RESPONSE TO LEE CYCLOGENESIS
CENTRAL HIGH PLAINS. TROPICAL LIKE AIR MASS IN PLACE S TX WILL
ACCELERATE NWD THRU SRN INTO CENTRAL HI PLAINS THIS FORECAST PERIOD
AS 40-50KT SLY LOW LEVEL JET KICKS IN TONIGHT.
..ERN WI INTO NRN IND AND WRN OH...
CURRENT CLOUD COVER ACROSS THIS AREA EXPECTED TO THIN AS MID LEVEL
DRYING SPREADS NEWD TO E OF UPPER LOW OVER SRN MN. ALTHOUGH OVERALL
SYSTEM IS WEAKENING...SUFFICIENT LOW LEVEL MOISTURE TO SUPPORT
SURFACE BASED THUNDERSTORM DEVELOPMENT AS TEMPERATURES WARM TO NEAR
70F. WITH 30-40KT OF SHEAR AND POTENTIALLY MLCAPES TO 500 J/KG IN
AREAS OF GREATEST SURFACE HEATING...A FEW STRONG/SEVERE
THUNDERSTORMS ARE POSSIBLE BY MID AFTERNOON. ANY SEVERE THREAT
SHOULD QUICKLY END AFTER SUNSET GIVEN THE OVERALL MARGINAL SETUP AND
THE WEAKENING OF THE UPPER SYSTEM.
..SRN PLAINS...
COMBINATION OF INCREASING LARGE SCALE ASCENT/WAA AND MOISTURE INFLUX
BENEATH EML PLUME SWEEPING E FROM THE SRN PLATEAU SHOULD LEAD TO
TSTM DEVELOPMENT ALONG NW FRINGE OF MOIST AXIS...POSSIBLY AS EARLY
AS THIS EVENING INVOF THE TX/NM BORDER. THIS ACTIVITY SHOULD
INCREASE IN COVERAGE AND SPREAD NE ALONG DEVELOPING WARM FRONT INTO
OK TONIGHT/EARLY WEDNESDAY AS UPR SYSTEM CONTINUES RAPIDLY EWD.
GIVEN INCREASING DEGREE OF INSTABILITY /MUCAPE TO 1000 J PER KG/
WITH STRENGTHENING ASCENT AND DEEP SHEAR...SETUP MAY SUPPORT A FEW
SUSTAINED STORMS/POSSIBLE SUPERCELLS WITH HAIL. AND...GIVEN THE
TIME OF DAY AND CHARACTER OF FORCING...MOST OF THIS ACTIVITY LIKELY
WILL BE SLIGHTLY ELEVATED. A LIMITED POTENTIAL
WILL...HOWEVER...EXIST FOR A FEW SFC-OR NEAR SFC-BASED STORMS THAT
MAY POSE A BRIEF TORNADO THREAT GIVEN EXPECTED EFFECTIVE SRH VALUES
OF 250-350 M2/S2.
.HALES/KIS.. 10/16/2007
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