SWODY2
SPC AC 140550
DAY 2 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1250 AM CDT TUE SEP 14 2010
VALID 151200Z - 161200Z
...THERE IS A SLGT RISK OF SVR TSTMS ACROSS THE MID MO VALLEY AND
VICINITY...
...SYNOPSIS...
WHILE A LOW AMPLITUDE -- NEARLY ZONAL -- FLOW FIELD ALOFT WILL
PREVAIL ACROSS MOST OF THE U.S. THIS PERIOD...A PRONOUNCED
SHORT-WAVE TROUGH IS FORECAST TO MOVE EWD THROUGH THE FLAT MEAN
RIDGE SITUATED OVER THE CENTRAL PORTION OF THE COUNTRY. THIS
FEATURE WILL DRIVE SURFACE CYCLOGENESIS OVER THE MID MO VALLEY
REGION...WITH THE LOW PROGGED TO SHIFT ENEWD TO THE IL VICINITY
OVERNIGHT. THIS LOW -- AND ASSOCIATED SEWD-MOVING COLD FRONT --
WILL FOCUS THE MAIN AREA OF ROBUST CONVECTION DURING THE DAY 2
PERIOD.
...MID MO VALLEY/CENTRAL PLAINS...
OVERNIGHT CONVECTION WILL LIKELY REMAIN ONGOING ACROSS PARTS OF THE
CENTRAL PLAINS AND VICINITY AT THE START OF THE PERIOD...AND MAY
CONTINUE INTO THE AFTERNOON AS EWD-MOVING SHORT-WAVE TROUGH HELPS TO
MAINTAIN A SLY LOW-LEVEL JET AND ATTENDANT WARM ADVECTION REGIME.
AS THE UPPER SYSTEM CONTINUES EWD...CYCLOGENESIS IS FORECAST ACROSS
THE MID MO VALLEY REGION THROUGH THE AFTERNOON...WITH THE DEVELOPING
LOW SHIFTING SLOWLY ENEWD WITH TIME. AS THIS
OCCURS...HEATING/DESTABILIZATION IS FORECAST ACROSS THE WARM
SECTOR...WITH 1000 TO 2000 J/KG MIXED-LAYER CAPE EXPECTED BY MID
AFTERNOON ACROSS THE SLIGHT RISK AREA. AS THE LOW DEEPENS...EXPECT
STORM DEVELOPMENT TO OCCUR INVOF THE LOW...AND ALONG THE
STRENGTHENING/SEWD-MOVING COLD FRONT AS IT MOVES OUT OF NEB AND
INTO/ACROSS KS WITH TIME.
ALONG WITH FAVORABLE INSTABILITY...SHEAR BY AFTERNOON WILL SUPPORT
SEVERE/SUPERCELLS STORMS...AS ENHANCED LOW-LEVEL SLYS/SELYS INVOF
THE SURFACE LOW VEER/INCREASE WITH HEIGHT TO WLY AT 40 TO 50 KT AT
H5 AS THE MID-LEVEL JET STREAK MOVES ACROSS THIS REGION. ATTM...IT
APPEARS THAT THE POTENTIAL FOR A COUPLE OF TORNADOES WILL EVOLVE --
PARTICULARLY INVOF ERN NEB/IA/NRN MO WHERE A WARM FRONT IS EXPECTED
TO RESIDE -- WITHIN THE BROADER AREAL THREAT FOR LARGE HAIL AND
LOCALLY-DAMAGING WINDS.
AS THE LOW DEEPENS OVERNIGHT AND SHIFTS ACROSS THE MS VALLEY INTO
THE IL VICINITY...THE SEWD-SURGING COLD FRONT WILL CONTINUE TO
SUPPORT INCREASINGLY-LINEAR CONVECTION. MEANWHILE...THE
REDEVELOPING LOW-LEVEL JET WILL ALSO FAVOR AN ELEVATED CONVECTIVE
INCREASE INTO THE UPPER MS VALLEY/SRN UPPER GREAT LAKES REGION.
THOUGH DIURNALLY-DECREASING INSTABILITY SUGGESTS A SLOW WANE IN
SEVERE POTENTIAL...WIND/HAIL THREAT MAY LINGER WELL INTO THE
OVERNIGHT HOURS ALONG/AHEAD OF THE COLD FRONT.
..GOSS.. 09/14/2010
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