SPC AC 010541
DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1241 AM CDT TUE MAY 01 2007
VALID 011200Z - 021200Z
...THERE IS A SLGT RISK OF SVR TSTMS ACROSS PARTS OF SRN PLAINS...
...THERE IS A SLGT RISK OF SVR TSTMS ACROSS PARTS OF THE NRN OH
VALLEY...
...SRN PLAINS...
A WELL-DEFINED UPPER-LEVEL LOW EVIDENT ON WATER VAPOR IMAGERY OVER
THE TX PANHANDLE WILL MOVE SLOWLY EWD ACROSS OK TODAY AND TONIGHT.
LARGE-SCALE ASCENT ASSOCIATED WITH THE UPPER-LEVEL LOW WILL SHIFT
EWD INTO CNTRL TX THIS AFTERNOON AND AWAY FROM THE AXIS OF STRONGEST
INSTABILITY. ALTHOUGH SOME THUNDERSTORM ACTIVITY SHOULD BE ONGOING
THIS MORNING ACROSS NORTH AND CNTRL TX...THUNDERSTORM COVERAGE
SHOULD INCREASE THIS AFTERNOON AS DESTABILIZATION TAKES PLACE ACROSS
THE REGION. MCS DEVELOPMENT APPEARS LIKELY ACROSS PARTS OF CNTRL AND
NORTH TX THIS EVENING WITH STORMS MOVING SLOWLY EWD DURING THE
OVERNIGHT PERIOD.
FORECAST SOUNDINGS ACROSS CNTRL AND NORTH TX LATE THIS AFTERNOON
SHOW VEERING WIND PROFILES WITH HEIGHT RESULTING IN 0-6 KM SHEAR
VALUES IN THE 35 TO 45 KT RANGE. THIS SHOULD BE SUFFICIENT FOR
SUPERCELLS ESPECIALLY NEAR LOCALLY MAXIMIZED INSTABILITY.
HOWEVER...A MIX OF ORGANIZED MULTICELLS AND BOWING LINE-SEGMENTS
WILL ALSO BE LIKELY DUE TO THE LARGE NUMBER OF STORMS. SUPERCELLS
WITH LARGE HAIL POTENTIAL SHOULD BE MOST NUMEROUS ALONG THE I-35
CORRIDOR IN CNTRL TX WHERE INSTABILITY AND SHEAR PARAMETERS ARE
FORECAST TO BE BETTER PHASED. BACKED SFC WINDS AND A WELL-DEFINED
LOW-LEVEL JET SHOULD RESULT IN FAVORABLE LOW-LEVEL SHEAR PROFILES
FOR A TORNADO THREAT. THE GREATEST TORNADO THREAT SHOULD EXIST WEST
OF THE LOW-LEVEL JET WITH SUPERCELLS IN CNTRL TX AND NORTH TX LATE
THIS AFTERNOON AND EARLY THIS EVENING.
FURTHER SOUTHWEST ACROSS SW TX...A DRY SLOT WILL LIKELY BE PRESENT
AND LARGE-SCALE ASCENT WILL BE RELATIVELY WEAK. THIS SHOULD KEEP
THUNDERSTORM COVERAGE ISOLATED. IF A FEW THUNDERSTORMS DO
DEVELOP...FORECAST SOUNDINGS SHOW MODERATE VERTICAL SHEAR PROFILES
AND STEEP MID-LEVEL LAPSE RATES WHICH SHOULD BE FAVORABLE FOR
SUPERCELLS WITH A POTENTIAL FOR LARGE HAIL AND ISOLATED WIND DAMAGE.
...NRN OH VALLEY...
LATEST WATER VAPOR IMAGERY SHOWS A SUBTLE SHORTWAVE TROUGH LOCATED
ACROSS SASKATCHEWAN CANADA AND THE NRN PLAINS. THIS FEATURE IS
FORECAST TO AMPLIFY AND MOVE QUICKLY ESEWD INTO THE OH VALLEY TODAY.
LARGE-SCALE ASCENT ASSOCIATED WITH THE SHORTWAVE TROUGH SHOULD
SUPPORT SCATTERED TO NUMEROUS THUNDERSTORM DEVELOPMENT ACROSS THE
NRN OH VALLEY THIS AFTERNOON AND EVENING. THUNDERSTORMS SHOULD BE
CONCENTRATED ALONG A FRONTAL BOUNDARY EXTENDING ESEWD FROM A SFC LOW
OVER SRN LOWER MI. ALTHOUGH MODEL FORECASTS ARE OVER FORECASTING SFC
DEWPOINTS...INSTABILITY SHOULD BE SUFFICIENT FOR MCS DEVELOPMENT
DURING THE EVENING.
FORECAST SOUNDINGS ACROSS NRN OH LATE THIS AFTERNOON AND EARLY THIS
EVENING SHOW MAINLY UNIDIRECTIONAL SHEAR PROFILES WITH 0-6 KM SHEAR
VALUES IN THE 40 TO 50 KT RANGE NEAR AND TO THE NORTH OF THE
BOUNDARY. ALTHOUGH A FEW SUPERCELLS WILL BE POSSIBLE...FORECAST
SHEAR PROFILES SUGGEST THE MAIN MODE OF CONVECTION WILL BE
MULTICELLULAR WITH LINEAR ORGANIZATION LIKELY. IN
ADDITION...FORECAST SOUNDINGS SHOW VERY STEEP LOW-LEVEL LAPSE RATES
WHICH COMBINED WITH THE UNIDIRECTIONAL WIND PROFILES SHOULD BE
FAVORABLE FOR AN ENHANCED WIND DAMAGE THREAT. LARGE HAIL WILL ALSO
BE POSSIBLE WITH THE STRONGER CELLS LATE THIS AFTERNOON.
...NRN AND CNTRL HIGH PLAINS...
AN UPSLOPE FLOW REGIME IS FORECAST TO REMAIN IN PLACE ACROSS THE
CNTRL HIGH PLAINS. A MOIST AXIS SHOULD BE IN PLACE FROM NE CO
EXTENDING NWWD ACROSS ERN WY INTO SRN MT. THE UPSLOPE FLOW COMBINED
WITH SFC HEATING AND TOPOGRAPHIC FORCING SHOULD SUPPORT ISOLATED TO
SCATTERED THUNDERSTORM DEVELOPMENT THIS AFTERNOON ACROSS THE REGION.
FORECAST SOUNDINGS LATE THIS AFTERNOON ACROSS ERN WY SHOW STEEP
LAPSE RATES AND INVERTED-V PROFILES WITH ENOUGH VERTICAL SHEAR FOR
MARGINALLY SEVERE MULTICELL STORMS.
..BROYLES/GRAMS.. 05/01/2007
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