Sunday, May 8, 2011

DAY1SVR: Day 1 Convective Outlook

ACUS01 KWNS 090026
SWODY1
SPC AC 090024

DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0724 PM CDT SUN MAY 08 2011

VALID 090100Z - 091200Z

...THERE IS A SLGT RISK OF SVR TSTMS ACROSS PARTS OF THE NRN PLAINS
AND MID-MO VALLEY...

...THERE IS A SLGT RISK OF SVR TSTMS ACROSS PARTS OF THE SRN
PLAINS...

...NRN PLAINS/MID-MO VALLEY...
THE LATEST WATER VAPOR IMAGERY SHOWS AN UPPER-LEVEL RIDGE OVER THE
MID TO UPPER MS VALLEY WITH SOUTHWEST FLOW IN PLACE FROM THE CNTRL
HIGH PLAINS NEWD INTO THE NRN PLAINS. A NARROW AXIS OF STRONG TO
EXTREME INSTABILITY EXISTS FROM ERN NEB NNWWD INTO CNTRL SD WHERE
SCATTERED THUNDERSTORM INITIATION IS EXPECTED OVER THE NEXT FEW
HOURS. MESOANALYSIS CURRENTLY ESTIMATES MLCAPE VALUES TO BE IN THE
3000 TO 5000 J/KG RANGE AND THIS SHOULD HELP STORMS TO RAPIDLY
BECOME SEVERE AS STORM COVERAGE INCREASES THIS EVENING. THE
INSTABILITY COMBINED WITH VERY STEEP MID-LEVEL LAPSE RATES OF 8.0 TO
9.0 C/KM ALONG WITH SUBSTANTIAL DIRECTIONAL SHEAR SHOULD RESULT IN
SUPERCELL DEVELOPMENT WITH A THREAT FOR LARGE HAIL. THE MORE
DOMINANT SUPERCELLS MAY HAVE AN ISOLATED TORNADO THREAT AND MAY
PRODUCE ISOLATED VERY LARGE HAIL OF GREATER THAN 2 INCHES IN
DIAMETER. THE GREATEST SEVERE THREAT SHOULD EXIST THIS EVENING AS
THE STORMS DEVELOP ALONG THE AXIS OF STRONGEST INSTABILITY BUT THE
SEVERE THREAT SHOULD CONTINUE THROUGH MUCH OF THE OVERNIGHT PERIOD
AS A LOW-LEVEL JET STRENGTHENS ACROSS THE REGION.

...SRN PLAINS...
SCATTERED STRONG TO SEVERE THUNDERSTORMS ARE ONGOING ALONG AN AXIS
OF STRONG INSTABILITY FROM CNTRL OK SSWWD INTO NORTH TX. THE STORMS
ARE BEING SUPPORTED BY LARGE-SCALE ASCENT ASSOCIATED WITH A
SHORTWAVE TROUGH EVIDENT ON WATER VAPOR IMAGERY...CURRENTLY MOVING
EWD TROUGH WEST TX. THIS CONVECTION SHOULD BE SUSTAINED FOR A FEW
MORE HOURS AS THE STORMS MOVE EWD INTO INCREASING INSTABILITY.
MLCAPE VALUES OF 2500 TO 3500 J/KG AND VERY STEEP MID-LEVEL LAPSE
RATES ALONG WITH 30 TO 40 KT OF DEEP LAYER SHEAR SHOULD RESULT IN A
THREAT FOR ISOLATED LARGE HAIL. A WIND DAMAGE THREAT MAY ALSO
ACCOMPANY THE MORE INTENSE CELLS DUE TO THE RELATIVELY LARGE
TEMP-DEWPOINT SPREADS.

...SRN APPALACHIAN MTNS/CAROLINAS...
ISOLATED THUNDERSTORMS ARE CURRENTLY ONGOING IN ERN TN AND WRN SC
LOCATED ALONG THE NERN EDGE OF MODERATE INSTABILITY. THIS CONVECTION
IS LOCATED IN NORTHWEST FLOW ALOFT WITH ABOUT 40 KT OF DEEP LAYER
SHEAR ESTIMATED BY MESOSCALE ANALYSIS. THIS SHOULD BE ENOUGH FOR A
MARGINAL WIND DAMAGE THREAT BUT THE THREAT SHOULD DIMINISH QUICKLY
AS SFC TEMPS BEGIN TO COOL OFF LATER THIS EVENING.

..BROYLES.. 05/09/2011

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