SWODY1
SPC AC 221616
DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1116 AM CDT SUN MAR 22 2009
VALID 221630Z - 231200Z
...NO SVR TSTM AREAS FORECAST...
...SYNOPSIS...
INTENSE/COLD TROUGH AND ASSOCIATED VERY STRONG POLAR JET MAX
CURRENTLY MOVING EWD THRU CA BY 12Z MON WILL BE ENTERING CENTRAL
HIGH PLAINS. COMPLEX SURFACE PATTERN AS LOW CENTER OVER SERN MT
REFLECTING LEAD S/WV TROUGH NOW LIFTING NEWD INTO NRN PLAINS WILL
REDEVELOP SWD IN LEE TROUGH TONIGHT WHERE STRONG CYCLOGENESIS WILL
BE UNDERWAY CENTRAL HIGH PLAINS.
WHILE GULF MOISTURE STILL LIMITED THE COMBINATION OF STEEP MID LEVEL
LAPSE RATES AND WARM ADVECTION ASSOCIATED WITH 50KT LLJ THRU THE
PLAINS WILL SUPPORT LARGE AREA OF MDT/STG CONVECTION WITH HAIL
POTENTIAL.
...NRN/CENTRAL PLAINS...
WITH MID LEVEL LAPSE RATES IN EXCESS OF 8C/KM MUCH OF AREA FROM KS
NWD THRU THE DAKOTAS ALONG WITH THE LARGE SCALE ASCENT ASSOCIATED
WITH BOTH WARM ADVECTION AND S/WV LIFTING NEWD FROM THE
ROCKIES...THE ONLY LIMITING PARAMETER PRECLUDING AN UPGRADE IN THE
SEVERE THREAT IS THE INSTABILITY. WITH MUCAPES ABOVE THE STRONG
WARM FRONTAL INVERSION EXPECTED TO REMAIN GENERALLY LESS THAN 500
J/KG...HAIL WHICH WILL BE COMMON IN STRONGEST UPDRAFTS SHOULD MOSTLY
REMAIN ONLY MARGINALLY SEVERE. MODELS IN BASIC AGREEMENT THAT
THUNDERSTORMS WILL CONTINUE TO EXPAND IN AREAL COVERAGE IN THE WARM
ADVECTION ZONE ASSOCIATED WITH LOW LEVEL JET AND SHIFT GRADUALLY EWD
ACROSS DAKOTAS/NEB INTO WRN MN/IA DURING THE AFTERNOON.
THERE IS SOME POTENTIAL FOR NEAR SURFACE BASED CONVECTIVE
DEVELOPMENT LATER THIS AFTERNOON PORTIONS OF SD/NE GIVEN SUFFICIENT
HEATING. IF THIS OCCURS THEN GREATER INSTABILITY WILL BE AVAILABLE
FOR THUNDERSTORMS AND A POTENTIAL UPGRADE TO A SLIGHT RISK IN 20Z
OUTLOOK MAY BE REQUIRED.
OVER THE CNTRL HI PLNS EARLY MON...EXPECT STORMS TO FORM ON
LEADING EDGE OF STRONG ASCENT/DPVA ASSOCIATED WITH GRT BASIN TROUGH.
COMBINATION OF ASSOCIATED DESTABILIZATION ALOFT...LOW LVL
CONVERGENCE N-NE OF DEEPENING NE CO SFC LOW...AND FRONTOGENETIC
FORCING MAY SUPPORT A LINE OF STRONG TO POSSIBLY SVR STORMS LATE IN
THE PERIOD OVER SW SD AND WRN/NRN NEB SE INTO NW KS. STEEPENING MID
LVL LAPSE RATES WILL BOOST MUCAPE TO AOA 1000 J/KG...ALTHOUGH
TEMPORAL BACKING OF LOW TO MID TROPOSPHERIC FLOW SUGGESTS STORMS
WILL QUICKLY ASSUME A LINEAR ORGANIZATION.
ATTM IT APPEARS THAT GREATEST BLOSSOMING OF STORMS WILL OCCUR JUST
AFTER 12Z. BUT IF IT APPEARS THAT GRT BASIN VORT WILL PROGRESS MORE
RAPIDLY THAN NOW EXPECTED...A CATEGORICAL SLIGHT RISK MAY
ALSO BE REQUIRED.
...PORTIONS OF NRN INTERMOUNTAIN REGION...
COLD FRONT IS INTENSIFYING FROM JUST E OF BYI SWD ALONG NV/UT BORDER
THIS AM AS UPSTREAM CA TROUGH MOVES RAPIDLY EWD. STEEP LAPSE RATES
IN ADVANCE OF THE FRONT COMBINED WITH OROGRAPHIC ENHANCEMENT SHOULD
RESULT IN THUNDERSTORMS DEVELOPING ALONG AND JUST W OF FRONT BY
EARLY THIS AFTERNOON. WHILE MLCAPES EXPECTED TO BE NO GREATER THAN A
COUPLE HUNDRED J/KG...SOME HAIL AND GUSTY WINDS ARE
EXPECTED...PARTICULARLY ALONG THE WASATCH FRONT WITH THE FROPA.
..HALES/HURLBUT.. 03/22/2009
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