DAY1SVR: Day 1 Convective Outlook

ACUS01 KWNS 221631
SWODY1
SPC AC 221629

DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1129 AM CDT TUE MAY 22 2012

VALID 221630Z - 231200Z

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

...THERE IS A SLGT RISK OF SVR TSTMS OVER THE SERN STATES...

...NRN PLAINS...
BROAD UPPER TROUGH OVER THE PACIFIC NW WILL MOVE EWD ACROSS THE NRN
ROCKIES DURING THE PERIOD AS A BAND OF STRONG MID/UPPER WINDS
TRANSLATES ACROSS THE NRN ROCKIES INTO THE PLAINS. SURFACE LOW OVER
SERN MT IS EXPECTED TO MOVE INTO SWRN ND BY LATER THIS AFTERNOON AND
CONTINUE NEWD TOWARD EXTREME SERN MANITOBA LATE TONIGHT. AS THE LOW
MOVES INTO THE WRN DAKS BY EVENING...A COLD FRONT WILL PROGRESS EWD
BEFORE REACHING THE ERN DAKS BY THE END OF THE PERIOD. A WARM FRONT
EXTENDING EWD FROM THE LOW ACROSS ND WILL LIFT SLOWLY NWD. DYNAMIC
FORCING FOR LARGE SCALE ASCENT WILL INCREASE OVER THE NRN PLAINS AND
ND IN PARTICULAR WITHIN THE LEFT EXIT REGION OF THE UPPER JET AS IT
MOVES TOWARD THE REGION TONIGHT.

THIS WILL RESULT IN A FAVORABLE SYNOPTIC/MESOSCALE PATTERN FOR
SEVERE STORMS...WITH THE PRIMARY LIMITING PARAMETER BEING MARGINAL
LOW LEVEL MOISTURE AS RETURN FLOW FROM THE GULF OF MEXICO CONTINUES
TO BE INHIBITED. 12Z RAOBS OVER THE CENTRAL/NRN PLAINS SUGGEST THAT
MOISTURE ABOVE THE GROUND WILL MIX DOWNWARD WITHIN THE PBL AS
HEATING OCCURS...WITH SURFACE DEW POINTS REACHING THE LOW/MID 50S.
STRONG DIABATIC HEATING /ESPECIALLY OVER THE CENTRAL AND ERN DAKS/
WILL RESULT IN CONSIDERABLE INSTABILITY WITH MLCAPE REACHING 2000
J/KG THIS AFTERNOON. THE CAPPING INVERSION ASSOCIATED WITH EML IS
EXPECTED TO INHIBIT SURFACE-BASED CONVECTIVE DEVELOPMENT THROUGH
MUCH OF THE AFTERNOON IN THE WARM SECTOR.

STORMS ARE MORE LIKELY TO INITIATE NEAR AND NORTH OF THE SURFACE LOW
BY LATE AFTERNOON AS LOW LEVEL CONVERGENCE INCREASES AND LARGE SCALE
ASCENT BEGINS TO OVERSPREAD THE AREA FROM THE WEST. ACTIVITY IS
LIKELY TO GRADUALLY INCREASE IN COVERAGE THIS EVENING AS THE
SOUTHERLY LOW LEVEL JET STRENGTHENS INTO THE NRN PLAINS. DEEP LAYER
SHEAR OF 35-45 KT WILL SUPPORT ORGANIZED CONVECTIVE STRUCTURES
INCLUDING A FEW SUPERCELLS. STEEP LAPSE RATES INDICATE POTENTIAL
FOR STORMS TO PRODUCE VERY LARGE HAIL IN ADDITION TO DAMAGING WIND
GUSTS...ALTHOUGH A FEW TORNADOES MAY ALSO BE POSSIBLE ESPECIALLY
NORTH OF THE WARM FRONT WHERE LOWER LCL HEIGHTS AND BACKED NEAR
SURFACE WINDS WILL EXIST. STORMS MAY GRADUALLY GROW UPSCALE INTO
ONE OR MORE LINEAR MCS/S DURING THE EVENING THAT HAVE POTENTIAL TO
DEVELOP SMALL BOWING SEGMENTS...WITH THE WIND DAMAGE THREAT POSSIBLY
INCREASING AFTER 03-6Z.

FARTHER SOUTH INTO SD AND POSSIBLY NRN NEB...MORE ISOLATED STORM
COVERAGE IS EXPECTED BUT STRONG INSTABILITY AND SHEAR WILL STILL
FAVOR A FEW SUPERCELL STRUCTURES WITH ATTENDANT RISK OF LARGE HAIL
AND DAMAGING WIND GUSTS.

...SERN STATES...
COLD UPPER TROUGH WITH 500 MB TEMPERATURES NEAR -15C IS PROGRESSING
EWD ACROSS AL ATTM. VISIBLE IMAGERY INDICATES NUMEROUS AREAS WITH
LIMITED CLOUD COVER WHERE STRONG DIABATIC HEATING/DESTABILIZATION IS
OCCURRING...AND MUCAPE IS EXPECTED TO REACH 1500-2000 J/KG THIS
AFTERNOON. STORMS ARE EXPECTED TO INCREASE THIS AFTERNOON
ESPECIALLY OVER PARTS OF GA...SC...AND POSSIBLY NRN FL IN ADVANCE OF
THE UPPER TROUGH...WITH STRONGER CELLS CAPABLE OF PRODUCING LARGE
HAIL AND DAMAGING WIND GUSTS.

......CNTRL AND SRN PLAINS...
ISOLATED HIGH-BASED SUPERCELL STORMS ARE FORECAST TO DEVELOP NEAR
THE LEE TROUGH/DRYLINE FROM WRN NEB SOUTH TO TX. PRIMARILY NEUTRAL
MID-LEVEL HEIGHT TENDENCIES WILL BE ASSOCIATED WITH LIMITED
CONVECTIVE COVERAGE. HOWEVER...STEEP LOW/MID-LEVEL LAPSE RATES AND
MODEST DEEP SHEAR SHOULD YIELD AN ISOLATED SVR WIND/HAIL THREAT.

..WEISS/GARNER.. 05/22/2012

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