SWODY1
SPC AC 121956
DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0256 PM CDT SAT MAY 12 2007
VALID 122000Z - 131200Z
..THERE IS A SLGT RISK OF SVR TSTMS OVER PARTS OF THE NRN
INTER-MOUNTAIN REGION INTO HIGH PLAINS...
..NRN INTER-MOUNTAIN REGION INTO HIGH PLAINS...
MODIFICATION OF 12Z OBSERVED SOUNDINGS FOR CURRENT SURFACE
CONDITIONS INDICATES THAT AIR MASS IS DESTABILIZING THIS AFTERNOON
INVOF SURFACE LOW AND ATTENDANT FRONTAL BOUNDARY FROM CNTRL MT SEWD
INTO NERN WY WITH MLCAPES OF 1000-1500 J/KG. ADDITIONAL
DESTABILIZATION /THOUGH NOT AS STRONG/ IS OCCURRING SWWD ALONG
TRAILING PORTION OF FRONTAL ZONE THROUGH THE CNTRL ID PNHDL INTO
NERN ORE. WHILE PRIMARY MID-LEVEL TROUGH REMAINS NEAR THE PACIFIC
NW COAST EARLY THIS AFTERNOON...WATER VAPOR IMAGERY SUGGESTS
EMBEDDED WEAKER IMPULSES OVER ERN ORE AND ANOTHER FARTHER TO THE E
OVER NERN NV/NRN UT INTO SERN ID.
STEEPENING LOW-LEVEL LAPSE RATES/AIR MASS DESTABILIZATION COUPLED
WITH INCREASED FORCING FOR ASCENT ASSOCIATED WITH THESE SHORT WAVE
TROUGHS IS LIKELY CONTRIBUTING TO THE DEEPENING CONVECTIVE
DEVELOPMENT OCCURRING OVER CNTRL ID/SWRN MT SEWD INTO WRN WY. WITH
TIME...STORMS SHOULD BECOME INCREASINGLY NUMEROUS OVER THE ID PNHDL
AND WRN MT...ALONG THE WRN EDGE OF STRONGER INSTABILITY IN PLACE
OVER CNTRL/ERN MT. REGIONAL VWPS AND RUC OBJECTIVE FIELDS INDICATE
THAT DEEP LAYER VERTICAL SHEAR IS ALREADY SUPPORTIVE OF
ORGANIZED...SEVERE STORMS INCLUDING SUPERCELLS WITH 40-45 KT OF
EFFECTIVE BULK SHEAR. LARGE HAIL AND LOCALLY DAMAGING WINDS WILL BE
THE PRIMARY SEVERE THREAT WITH THE MOST INTENSE STORMS.
STORMS MAY TEND TO GROW UPSCALE INTO CLUSTERS OR AN MCS WITH THE
SEVERE THREAT CONTINUING INTO CNTRL MT TONIGHT.
ISOLATED SEVERE STORMS WITH A THREAT OF LOCALLY DAMAGING WINDS AND
SEVERE HAIL WILL BE POSSIBLE INVOF LEE TROUGH THIS AFTERNOON AND
EVENING FROM ERN WY INTO WRN SD AND THE NEB PNHDL. MARGINAL
VERTICAL SHEAR SHOULD LIMIT A MORE ORGANIZED SEVERE WEATHER THREAT.
..MN...
BANDS OF ELEVATED TSTMS /ORIENTED IN NW-SE FASHION/ HAVE PERSISTED
TODAY FROM ERN SD INTO SRN MN AND NRN IA...DRIVEN BY LOW-LEVEL WAA
TO THE NE OF SURFACE FRONTAL ZONE. LATEST MODEL GUIDANCE SUGGESTS
THAT LLJ MAY WEAKEN TEMPORARILY THIS AFTERNOON...PRIOR TO
REINTENSIFYING ACROSS SAME GENERAL AREA LATER TONIGHT. AS THIS
OCCURS...ELEVATED STORMS MAY INCREASE IN AREAL COVERAGE...MAINLY
AFTER 13/06Z. STEEP MID-LEVEL LAPSE RATES AND RESULTANT MUCAPES OF
1000-1500 J/KG WILL BE SUPPORTIVE OF SOME SEVERE HAIL WITH THE MORE
INTENSE STORMS.
..CNTRL APPALACHIANS AND CHESAPEAKE BAY AREA SWWD INTO TX...
LATEST MESOANALYSIS INDICATES THAT A WARM AND MOIST LOW-LEVEL AIR
MASS HAS DEVELOPED OVER A FAIRLY WIDESPREAD AREA THIS
AFTERNOON...CONTRIBUTING TO POCKETS OF MODERATE INSTABILITY WITH
MLCAPES OF 1000-2000 J/KG. ALSO CONTRIBUTING TO THIS INSTABILITY
WERE MODESTLY COOL MID-LEVEL TEMPERATURES /ESPECIALLY OVER THE CNTRL
GULF COAST/ WITH 500 MB TEMPERATURES OF -11 TO -14 C. VERTICAL
SHEAR REMAINS QUITE WEAK ACROSS THE AREA...HOWEVER THE MODERATE
INSTABILITY WILL SUPPORT A FEW ORGANIZED STORMS CAPABLE OF DAMAGING
WINDS AND SEVERE HAIL. THE DAMAGING WIND THREAT WILL BE GREATEST
WITH STORM CLUSTERS THAT CAN FORWARD-PROPAGATE ALONG
MERGING/ORGANIZING COLD POOLS.
.MEAD.. 05/12/2007
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