SPC AC 212000
DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0300 PM CDT WED MAY 21 2008
VALID 212000Z - 221200Z
...THERE IS A SLGT RISK OF SVR TSTMS ACROSS PARTS OF THE HIGH
PLAINS...
...THERE IS A SLGT RISK OF SVR TSTMS ACROSS PARTS OF THE ERN GULF
COAST STATES...
...THERE IS A SLGT RISK OF SVR TSTMS ACROSS PARTS OF THE CNTRL
PLAINS...
...HIGH PLAINS/CNTRL PLAINS...
LATEST WATER VAPOR IMAGERY SHOWS A DEEPENING UPPER-LEVEL TROUGH OVER
THE INTERMOUNTAIN WEST WITH A SHARP UPPER-LEVEL RIDGE OVER THE
PLAINS STATES. A DRY SLOT IS LOCATED ACROSS THE FOUR CORNERS REGION
AND A BAND OF MID-LEVEL MOISTURE ASSOCIATED WITH INCREASING
LARGE-SCALE ASCENT IS MOVING THROUGH THE ROCKIES ATTM. AS HEIGHTS
FALL ACROSS THE HIGH PLAINS THIS AFTERNOON...THUNDERSTORM INITIATION
SHOULD OCCUR ALONG THE WRN EDGE OF AN AXIS OF INSTABILITY EXTENDING
NWD FROM THE TX PANHANDLE ACROSS FAR ERN CO INTO ERN AND NRN WY.
SEVERAL THUNDERSTORM CLUSTERS SHOULD ORGANIZE AND MOVE NEWD INTO THE
LOW-LEVEL JET TONIGHT.
CONCERNING THE SEVERE POTENTIAL...RUC DATA SHOWS THE STRONGEST
VERTICAL SHEAR ACROSS WY AND NE CO WITH 0-6 KM SHEAR VALUES IN THE
40 TO 55 KT RANGE. AS INSTABILITY CONTINUES TO INCREASE...THE SHEAR
SHOULD SUPPORT ISOLATED SUPERCELL DEVELOPMENT. STEEP MID-LEVEL LAPSE
RATES SHOULD FAVOR A THREAT FOR LARGE HAIL. ALTHOUGH LARGE HAIL WILL
BE THE GREATEST THREAT...THE RELATIVELY DRY BOUNDARY LAYER WITH
TEMPS IN THE 70S F AND SFC DEWPOINTS IN THE 40S F MAY LOCALLY
ENHANCE DOWNDRAFTS FOR A DAMAGING WIND THREAT.
FURTHER EAST ACROSS THE CNTRL PLAINS...MODEL FORECASTS CONTINUE TO
DEVELOP A BAND OF THUNDERSTORMS IN CNTRL KS SPREADING THE CONVECTION
NEWD ACROSS NE KS INTO SE NEB LATE TONIGHT. THIS STORM CLUSTER WILL
BE ASSOCIATED WITH THE LOW-LEVEL JET AND SHOULD BE ELEVATED IN
NATURE. AS A RESULT...THE MAIN THREAT WOULD BE LARGE HAIL WITH SOME
OF THE MORE INTENSE CELLS LATE TONIGHT.
...ERN GULF COAST STATES/LOWER MS VALLEY...
SCATTERED THUNDERSTORMS ARE ONGOING AHEAD OF A COLD FRONT ALONG AN
AXIS OF LOW-LEVEL MOISTURE. SFC DEWPOINTS ACROSS SRN GA ARE NEAR 70
F AND RUC DATA SUGGESTS MODERATE INSTABILITY EXISTS ACROSS THE
SLIGHT RISK AREA WITH MLCAPE VALUES IN THE 2000 TO 2500 J/KG RANGE.
IN ADDITION...WATER VAPOR IMAGERY SUGGESTS A SHORTWAVE TROUGH IS
APPROACHING THE AREA WHICH ALONG WITH THE INSTABILITY SHOULD ALLOW
STORM COVERAGE TO INCREASE THROUGH EARLY THIS EVENING. THE LATEST
WSR-88D VWPS ACROSS SRN GA AND THE FL PANHANDLE SHOW ABOUT 40 TO 50
KT OF VERTICAL SHEAR AND THIS SHOULD BE SUFFICIENT FOR SUPERCELLS.
WIND DAMAGE WILL BE POSSIBLE DUE TO THE UNIDIRECTIONAL LOW-LEVEL
FLOW AND LARGE HAIL MAY ALSO OCCUR WITH THE MORE INTENSE CELLS DUE
TO THE SHEAR...INSTABILITY AND STEEP MID-LEVEL LAPSE RATES.
..BROYLES/KIS.. 05/21/2008
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NOTE: THE NEXT DAY 1 OUTLOOK IS SCHEDULED BY 0100Z
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