DAY1SVR: Day 1 Convective Outlook

ACUS01 KWNS 020053
SWODY1
SPC AC 020051

DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0751 PM CDT TUE MAY 01 2007

VALID 020100Z - 021200Z

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

..THERE IS A SLGT RISK OF SVR TSTMS ACROSS PARTS OF SCNTRL AND SW
TX...

..NRN OH VALLEY...
LATEST WATER VAPOR IMAGERY SHOWS SEVERAL SHORTWAVE TROUGH FEATURES
OVER THE GREAT LAKES REGION. THE FIRST IS LOCATED NEAR LAKE SUPERIOR
WITH THE SECOND MORE SUBTLE TROUGH OVER SRN LOWER MI. THIS SECOND
FEATURE IS SUPPORTING NUMEROUS THUNDERSTORM DEVELOPMENT ACROSS NRN
OH AND WRN PA. THE THUNDERSTORM ACTIVITY IS ONGOING ALONG A COLD
FRONT EXTENDING WWD FROM A SFC LOW OVER SW PA. AN AXIS OF MODERATE
INSTABILITY IS LOCATED AHEAD OF THE BOUNDARY AND THIS SHOULD SUSTAIN
THE CONVECTION THROUGH THE REST OF THE EVENING WITH THE LINEAR MCS
MOVING SLOWLY SEWD INTO SE OH AND SW PA.

RUC ANALYSIS SHOWS A WELL-DEFINED 70 KT MID-LEVEL JET FROM NE WI
EXTENDING ESEWD ACROSS SRN LOWER MI INTO FAR WRN NY. THIS FEATURE IS
CREATING STRONG VERTICAL SHEAR PROFILES MAINLY FROM THE COLD FRONT
NWD WHICH SHOULD CONTINUE TO BE SUPPORTIVE OF ORGANIZED LINEAR
MULTICELLS AND A FEW SUPERCELLS. IN ADDITION...FORECAST SOUNDINGS
SHOW VERY STEEP LAPSE RATES BOTH AT THE LOWER-LEVELS AND AT
MID-LEVELS SUGGESTING THE THREAT FOR LARGE HAIL AND ISOLATED WIND
DAMAGE WILL CONTINUE THIS EVENING. THE SEVERE THREAT SHOULD
GRADUALLY BECOME MARGINAL BY LATE THIS EVENING.

..SCNTRL AND SW TX...
A CLOSED LOW CENTERED OVER OK IS EVIDENT ON WATER VAPOR IMAGERY AND
RUC ANALYSIS SHOWS A BAND OF STRONGER LOW TO MID-LEVEL FLOW FROM
CNTRL TX EXTENDING NEWD INTO THE ARKLATEX. LARGE-SCALE ASCENT ALONG
THIS BAND OF STRONGER FLOW IS LIKELY SUPPORTING THUNDERSTORM
DEVELOPMENT ALONG A BOUNDARY LOCATED FROM CNTRL TX EXTENDING EWD TO
THE SABINE RIVER. THE GREATEST INSTABILITY ALONG THIS CORRIDOR
EXISTS IN THE TX HILL COUNTRY WHERE OBJECTIVE ANALYSIS SHOWS MLCAPE
VALUES FROM 2000 TO 3000 J/KG. AS A RESULT...THE GREATEST SUPERCELL
THREAT WILL BE IN THE TX HILL COUNTRY THIS EVENING. LAPSE RATES ARE
VERY STEEP IN THE TX HILL COUNTRY AND THIS IS SUPPORTED BY THE DEL
RIO TX 00Z SOUNDING. IN ADDITION....SFC WINDS ARE BACKED WITH
SUBSTANTIAL VEERING IN THE LOW-LEVELS SHOWN ON FORECAST SOUNDINGS.
FOR THIS REASON...SUPERCELLS WITH A THREAT FOR LARGE HAIL AND
POSSIBLY A TORNADO OR TWO SHOULD CONTINUE FOR SEVERAL MORE HOURS.
THE SEVERE THREAT SHOULD DIMINISH AT SOME POINT LATE THIS EVENING AS
SFC TEMPS AND INSTABILITY DROP ACROSS THE REGION.

.BROYLES.. 05/02/2007

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