DAY3SVR: Nws Storm Prediction Center Norman Ok

ACUS03 KWNS 200706
SWODY3
SPC AC 200705

DAY 3 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0205 AM CDT SUN MAY 20 2012

VALID 221200Z - 231200Z

...NRN PLAINS...

00Z MODEL GUIDANCE IS IN REASONABLE AGREEMENT REGARDING THE
EVOLUTION OF UPPER TROUGH OVER THE WRN U.S. NAM/GFS/ECMWF ALL
SUGGEST A SIGNIFICANT MID LEVEL SPEED MAX WILL EJECT ACROSS THE NRN
ROCKIES INTO THE DAKOTAS DURING THE LATTER HALF OF THE PERIOD. AS A
RESULT A PRONOUNCED SFC COLD FRONT WILL SURGE ACROSS MT/WY INTO THE
WRN DAKOTAS DURING THE AFTERNOON HOURS. IN RESPONSE TO THE UPPER
TROUGH LLJ WILL INCREASE ACROSS THE PLAINS AND STRENGTHEN INTO THE
EVENING HOURS WHICH WILL ALLOW A NARROW AXIS OF ENHANCED MOISTURE TO
RETURN AHEAD OF THE COLD FRONT. AT THIS TIME IT APPEARS BOUNDARY
LAYER MOISTURE SHOULD BE A BIT MARGINAL WITH SFC DEW POINTS LIKELY
APPROACHING THE MID-UPPER 50S...OR PERHAPS EVEN 60 DEG F PRIOR TO
THE WIND SHIFT. ADDITIONALLY...PRE-FRONTAL CAPPING WILL BE OF SOME
CONCERN...ESPECIALLY GIVEN THE EXPECTED MARGINAL WARM SECTOR
MOISTURE. AT THIS TIME IT APPEARS VERY STRONG HEATING WILL
CONTRIBUTE TO NEAR DRY ADIABATIC LAPSE RATES ACROSS WRN NEB INTO
EXTREME SRN SD. IF TEMPERATURES CAN WARM INTO THE LOWER 90S THEN
INHIBITION SHOULD BE REDUCED ENOUGH FOR SFC-BASED CONVECTION ALONG
THE COLD FRONT. ADDITIONALLY...ALTHOUGH CONVECTIVE TEMPERATURES MAY
NOT BE BREACHED ACROSS ND STRONGER FORCING SHOULD ENCOURAGE TSTM
DEVELOPMENT. AT THIS TIME WILL ONLY INTRODUCE 5% PROBS TO ACCOUNT
FOR A THREAT OF DAMAGING WINDS AND LARGE HAIL WITH CONVECTION THAT
DEVELOPS ALONG THE COLD FRONT DURING THE LATE AFTERNOON INTO THE
EVENING HOURS. HOWEVER...THE STRENGTH OF THE UPPER SYSTEM MAY
REQUIRE AN INCREASE TO SEVERE PROBS ACROSS THE NRN PLAINS AS
VERTICAL SHEAR PROFILES WOULD CERTAINLY SUPPORT ORGANIZED STORMS.

..DARROW.. 05/20/2012

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