DAY2SVR: Nws Storm Prediction Center Norman Ok

ACUS02 KWNS 211731
SWODY2
SPC AC 211729

DAY 2 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1229 PM CDT MON MAY 21 2012

VALID 221200Z - 231200Z

...THERE IS A SLGT RISK OF SVR TSTMS FOR PARTS OF THE NRN PLAINS...

...SYNOPSIS...
A LARGE-SCALE UPPER-LEVEL TROUGH OFF THE BRITISH COLUMBIA/PACIFIC NW
COAST WILL PROGRESS ACROSS SWRN CANADA/NWRN CONUS THROUGH EARLY
WED...AS AN INTENSE UPPER-LEVEL JET STREAK PENETRATES INLAND. THIS
WILL INDUCE CYCLOGENESIS OVER THE NRN PLAINS WITH PRIMARY SURFACE
LOW EXPECTED TO BE CENTERED OVER THE CNTRL DAKOTAS AT 23/00Z ALONG
AN E/SEWD MOVING COLD FRONT. LEE TROUGH/DRYLINE WILL BE DRAPED SWD
INTO THE SRN HIGH PLAINS. AS THE SURFACE CYCLONE DEVELOPS TOWARDS
SERN MANITOBA TUE NIGHT...THE COLD FRONT SHOULD REACH THE RED RIVER
VALLEY SWWD TO THE CNTRL HIGH PLAINS.

ELSEWHERE...A WEAK MID-LEVEL IMPULSE OVER THE MID-MS VALLEY WILL
DROP SEWD AND LIKELY SHIFT ACROSS THE DEEP SOUTH/SRN APPALACHIANS ON
TUE.

...NRN PLAINS...
PRIMARY LIMITING FACTOR TO A MORE ROBUST SEVERE THREAT WILL BE THE
LACK OF RICH BOUNDARY LAYER MOISTURE AHEAD OF THE COLD FRONT AND
DEEPENING CYCLONE...AS SYNOPTIC PATTERN SETUP FOR LIFT/INSTABILITY
APPEARS FAVORABLE FOR A CONCENTRATED SEVERE WEATHER EPISODE /MOST
PROBABLE IN ERN ND ON TUE EVENING/. LOW-LEVEL MOISTURE WILL INCREASE
WITHIN A RELATIVELY CONFINED CORRIDOR...DRAWING NWD A MARGINALLY
MOIST AIR MASS FROM THE SRN HIGH PLAINS. SURFACE DEW POINTS SHOULD
GENERALLY RISE INTO THE MIDDLE 50S TO AROUND 60. WITH A PRONOUNCED
EML RESULTING IN SUBSTANTIAL CAPPING...MLCAPE MAY REACH 2000-3000
J/KG ACROSS PARTS OF THE CNTRL DAKOTAS. A VERY DEEP MIXED BOUNDARY
LAYER WILL DEVELOP ACROSS PORTIONS OF WRN SD BETWEEN THE COLD FRONT
AND DRYLINE. AS MID-LEVEL HEIGHT FALLS OVERSPREAD THE REGION AND
LOW-LEVEL CONVERGENCE STRENGTHENS...ISOLATED TSTMS WILL LIKELY
DEVELOP ALONG THE ADVANCING COLD FRONT BY LATE AFTERNOON. INITIAL
TSTMS SHOULD BECOME SUPERCELLULAR WITH PRIMARY THREAT OF VERY LARGE
HAIL AS LARGE SURFACE DEW POINT DEPRESSIONS LIMIT TORNADIC
POTENTIAL. AS THE SLY LLJ STRENGTHENS DURING THE EVENING AMIDST
INTENSIFYING MID-LEVEL SWLYS...UPSCALE GROWTH INTO A SUPERCELL
CLUSTER/SMALL MCS APPEARS PROBABLE WITH PRIMARY THREATS OF LARGE
HAIL AND DAMAGING WINDS. GIVEN THE RELATIVELY NARROW WARM/MOIST
SECTOR...CONVECTION SHOULD BECOME INCREASINGLY ELEVATED...WITH A
WANING SEVERE THREAT OVERNIGHT TOWARDS THE UPPER MS VALLEY.

...SOUTHEAST...
A POCKET OF COLD MID-LEVEL TEMPERATURES...MINUS 14-16C AT 500
MB...WILL OVERSPREAD THE REGION DURING THE DAY WITH APPROACH OF THE
SHORT WAVE IMPULSE CURRENTLY OVER THE MID-MS VALLEY. THIS WILL AID
IN STEEPENING LAPSE RATES AMIDST A NEAR-NORMAL PW AIR MASS /VALUES
AROUND 1-1.25 IN/. HIGHER MOMENTUM FLOW SHOULD LARGELY REMAIN
CONCENTRATED AOA 500 MB...WHICH WOULD LIMIT THE MAGNITUDE OF
EFFECTIVE SHEAR. STILL...THE SETUP SHOULD YIELD ISOLATED ROBUST
STORMS DURING THE AFTERNOON CAPABLE OF MARGINALLY SEVERE HAIL AND
LOCALLY DAMAGING WINDS.

...CNTRL/SRN HIGH PLAINS...
ALONG THE SURFACE LEE TROUGH...ISOLATED HIGH-BASED TSTMS MAY FORM AT
PEAK HEATING. WITHIN A BELT OF CONFLUENT MID-LEVEL WLYS...MODERATELY
ELONGATED HODOGRAPHS WOULD FAVOR MARGINAL SUPERCELL STRUCTURES
CAPABLE OF SEVERE HAIL AND LOCALIZED DOWNBURSTS.

..GRAMS.. 05/21/2012

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