SWODY3
SPC AC 110718
DAY 3 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0218 AM CDT FRI MAY 11 2007
VALID 131200Z - 141200Z
..THERE IS A SLGT RISK OF SVR TSTMS ACROSS PORTIONS OF THE UPPER MS
VALLEY...
..THERE IS A SLGT RISK OF SVR TSTMS OVER THE NRN HIGH PLAINS OF MT
AND THE WRN DAKOTAS...
..UPPER MS VALLEY...
STRONG LOW LEVEL WARM ADVECTION WILL DOMINATE THE DAY3 PERIOD ACROSS
MN/WI AS UPPER RIDGE IS FLATTENED BY A FEW WEAK UPPER DISTURBANCES
AHEAD OF MAIN SHORTWAVE TROUGH OVER MT. MODELS ARE LIKELY
UNDERESTIMATING CAP DEVELOPMENT ACROSS THE WARM SECTOR AS FLOW VEERS
ALONG NE-SW ORIENTED SFC TROUGH OVER MN INTO SERN SD. LATEST
THINKING IS LLJ SHOULD AID CLUSTERS OF ELEVATED THUNDERSTORMS OFF
AND ON THROUGH THE PERIOD. TIMING OF INITIATION WILL PROVE
DIFFICULT WITHIN ZONE OF ISENTROPIC ASCENT. SOME HAIL MAY ACCOMPANY
THIS ACTIVITY BUT CONFIDENCE IN BOUNDARY LAYER DEVELOPMENT OVER SRN
MN INTO SERN SD IS QUESTIONABLE AT THIS TIME. GIVEN THE LIKELY
PRESENCE OF A CAP...AND THE PROSPECT FOR RELATIVELY WEAK CONVERGENCE
ALONG WIND SHIFT...CONVECTION MAY STRUGGLE TO SUSTAIN ITSELF. DEEP
LAYER SHEAR WOULD CERTAINLY SUPPORT SUPERCELL STRUCTURES IF UPDRAFTS
CAN MANAGE TO ROOT INTO HIGHER INSTABILITY AIRMASS.
..NRN HIGH PLAINS...
RELATIVELY HIGH CONFIDENCE IN STRONG THUNDERSTORM DEVELOPMENT WILL
BE NOTED ACROSS SRN MT DURING THE DAY3 PERIOD. BOTH THE NAM AND GFS
MOVE NWRN U.S. TROUGH INTO WRN MT BY 14/00Z. HEIGHTS WILL FALL
ACROSS THE NRN HIGH PLAINS AFTER DARK WHICH WILL PROVE BENEFICIAL IN
THE DEVELOPMENT OF AN EXPANSIVE AREA OF DEEP CONVECTION. FORECAST
SOUNDINGS ACROSS SRN MT SUGGEST ELY FLOW WILL DEEPEN AHEAD OF
SHORTWAVE TROUGH WITH NICE VEERING PROFILES EXPECTED ACROSS THE SERN
1/3RD OF THE STATE. IT APPEARS SFC DEW POINTS COULD EASILY APPROACH
50 F AS FAR WEST AS BIL...OR PERHAPS LVM AHEAD OF CONVECTIVE
DEVELOPMENT. AS A RESULT...STRONG THUNDERSTORMS SHOULD EASILY
DEVELOP OVER THE HIGHER TERRAIN OF SWRN MT BY MID AFTERNOON...THEN
SPREAD ENEWD WITHIN A VERY FAVORABLE SHEAR ENVIRONMENT FOR
SUSTAINING SUPERCELLS. IF MOISTURE DOES INDEED HOLD ACROSS THIS
REGION ISOLATED TORNADOES SHOULD BE NOTED IN ADDITION TO LARGE HAIL
AND DAMAGING WINDS. UPWARD EVOLVING SUPERCELL CLUSTERS MAY FORM AN
MCS BEFORE SPREADING INTO ERN MT/WRN ND AFTER DARK.
FARTHER SOUTHEAST ACROSS NEB...ISOLATED SUPERCELLS COULD EVOLVE
ALONG THE DRYLINE WHERE VERY STEEP LAPSE RATES SHOULD DEVELOP BY
LATE AFTERNOON. THIS ACTIVITY SHOULD PROVE DIURNAL IN
NATURE...THOUGH CERTAINLY COULD PRODUCE SOME SEVERE. LATER OUTLOOKS
MAY NEED TO ADDRESS THE DRYLINE IF IT APPEARS A MORE CONCENTRATED
ZONE OF DEEP CONVECTION COULD EVOLVE.
.DARROW.. 05/11/2007
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