DAY1SVR: Day 1 Convective Outlook

ACUS01 KWNS 110035
SWODY1
SPC AC 110032

DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0732 PM CDT THU SEP 10 2009

VALID 110100Z - 111200Z

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

...NRN PLAINS...
A WELL-ORGANIZED UPPER-LEVEL TROUGH WILL CONTINUE TO APPROACH THE
REGION FROM THE WEST NORTHWEST THIS EVENING. AHEAD OF THE
SYSTEM...AN AXIS OF MODERATE INSTABILITY IS ANALYZED FROM CNTRL SD
EXTENDING NNEWD INTO SRN MANITOBA WITH A COLD FRONT LOCATED ACROSS
WRN ND. INCREASING LARGE-SCALE ASCENT AHEAD OF THE APPROACHING
UPPER-LEVEL TROUGH AND MORE FOCUSED LOW-LEVEL CONVERGENCE ALONG THE
FRONT SHOULD RESULT IN THUNDERSTORM INITIATION OVER THE NEXT 1-2
HOURS ACROSS WCNTRL ND. MODEL FORECASTS ARE IN AGREEMENT DEVELOPING
A CLUSTER OF THUNDERSTORMS THIS EVENING FROM ERN SD SWWD INTO PARTS
OF NWRN SD. THE 00Z SOUNDING FROM BISMARK SHOWS ABOUT 40 KT OF 0-6
KM SHEAR WITH A GRADUALLY VEERING WIND PROFILE BELOW 700 MB. THIS
ALONG WITH STEEP MID-LEVEL LAPSE RATES SHOULD SUPPORT ROTATING
STORMS WITH A THREAT FOR LARGE HAIL. AS STORMS INCREASE IN COVERAGE
ALONG THE BOUNDARY...A TRANSITION TO A MORE LINEAR MODE COULD OCCUR
RESULTING IN AN INCREASING THREAT FOR ISOLATED WIND DAMAGE LATE THIS
EVENING.

FURTHER SOUTHWEST ACROSS THE BLACK HILLS AND WRN NEB...MODEL
FORECASTS KEEP CONVECTIVE DEVELOPMENT MINIMAL DUE TO WEAKER
LARGE-SCALE ASCENT. A CAPPING INVERSION IS FORECAST TO STRENGTHEN
OVER WRN SD SUGGESTING ANY STORMS THAT CAN INITIATE WILL BECOME
ELEVATED LATE THIS EVENING INTO THE OVERNIGHT PERIOD. THE BEST
CHANCE FOR A SEVERE THREAT OVERNIGHT SHOULD BE WITH THE CLUSTER OF
THUNDERSTORMS ON THE NOSE OF THE LOW-LEVEL JET ACROSS WRN MN AND ERN
SD. ALTHOUGH INSTABILITY WILL BE DECREASING QUICKLY OVERNIGHT...A
MARGINAL SEVERE THREAT COULD LINGER AS A SFC LOW AND COLD FRONT
MOVES INTO THE ERN DAKOTAS.

...COASTS OF MD/DE AND NJ...
A LOW PRESSURE SYSTEM JUST OFF THE COASTAL WATERS OF VIRGINA WILL
MOVE SLOWLY NWWD TONIGHT ALLOWING FOR A BAND OF THUNDERSTORM
ACTIVITY TO MOVE ONSHORE INTO THE IMMEDIATE COASTAL AREAS OF MD...DE
AND NJ. THE LATEST WSR-88D VWP FROM DOVER DE SHOWS A VEERING
LOW-LEVEL WIND PROFILE WITH HEIGHT BELOW 3 KM WITH 25-30 KT OF 0-1
KM SHEAR. IN ADDITION LCL HEIGHTS MAY DROP AND PRECIPITABLE WATER
VALUES MAY INCREASE AS THE LOW MOVES TOWARD THE COAST. THESE FACTORS
ALONG WITH THE STRONG LOW-LEVEL SHEAR MAY SUPPORT A MARGINAL TORNADO
THREAT WITH ROTATING STORMS THAT MOVE INLAND THIS EVENING AND
OVERNIGHT.

..BROYLES.. 09/11/2009

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