SWODY1
SPC AC 230059
DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0759 PM CDT MON AUG 22 2011
VALID 230100Z - 231200Z
...THERE IS A SLGT RISK OF SVR TSTMS ACROSS ERN ND...MUCH OF
MN...FAR WRN WI AND NRN IA...
...ERN DAKOTAS/MN/FAR WRN WI/NRN IA...
LATE AFTERNOON-EARLY EVENING SURFACE ANALYSES SHOWED A WARM
FRONT/DEWPOINT DISCONTINUITY BOUNDARY EXTENDING FROM CENTRAL MO NWWD
THROUGH FAR WRN IA INTO THE ERN DAKOTAS. THE NRN EXTENT OF THIS
BOUNDARY IS EXPECTED TO MOVE EWD INTO MN THIS FORECAST PERIOD AS LOW
LEVEL WINDS VEER TO SWLY AND INCREASE. THIS WILL SUBSEQUENTLY
RESULT IN BOTH LOW LEVEL MOISTURE/WARM AIR ADVECTION ACROSS THE ERN
DAKOTAS TO THE UPPER MS VALLEY. STEEP MIDLEVEL LAPSE RATES /PER NRN
PLAINS AND UPPER MIDWEST 00Z SOUNDINGS/ WILL CONTINUE TO SPREAD EWD
ATOP THE MOISTURE CORRIDOR RESULTING IN MODERATE TO STRONG MAINLY
ELEVATED INSTABILITY THROUGH THE OVERNIGHT FORECAST PERIOD.
A SHORTWAVE TROUGH MOVING INTO WRN ND AT THIS TIME WILL PROGRESS
ESEWD INTO THE UPPER MS VALLEY TONIGHT. ASCENT WITH THIS FEATURE
COMBINED WITH LOW LEVEL WAA SUGGESTS TSTMS WILL DEVELOP MAINLY OVER
THE MN PORTION OF THE SLIGHT RISK AREA...WITH THE GREATEST
CONCENTRATION AND FORECAST CONFIDENCE BEING OVER SRN MN/NRN IA PER
MODEL CONSENSUS OF CONVECTIVE QPF. THIS IS ALSO WHERE DEEP LAYER
ASCENT SHOULD BE BETTER FOCUSED ALONG THE NOSE OF A DEVELOPING SWLY
LLJ. THIS OUTLOOK HAS EXTENDED THE SLIGHT RISK WWD ACROSS EAST
CENTRAL/SERN ND DUE TO THE STEEPNESS LAPSE RATES ON THE 00Z BIS
SOUNDING AND INCREASING ASCENT SPREADING EWD WITH THE SHORTWAVE
TROUGH. SHORT TERM MESOSCALE DETAILS FOR SERN ND CAN BE FOUND IN
SPC MESOSCALE DISCUSSION #2039. OTHERWISE...GIVEN STEEP MIDLEVEL
LAPSE RATES ADVANCING INTO MN/NRN IA OVERNIGHT AND THE DEGREE OF
INSTABILITY AND STRONG EFFECTIVE BULK SHEAR...VERY LARGE HAIL WILL
BE POSSIBLE.
...ERN KS/WRN-SRN MO...
MODELS CONTINUE TO SUGGEST A SEPARATE VEERING/STRENGTHENING LLJ
EXTENDING INTO ERN KS/WRN MO OVERNIGHT. LOW LEVEL WAA ACROSS THIS
AREA AND MODERATE INSTABILITY/STRONG EFFECTIVE BULK SHEAR SUGGEST
TSTMS WILL BE POSSIBLE ACROSS THIS AREA. GIVEN LESS CONFIDENCE IN
OVERALL COVERAGE OF STRONGER CELLS THAN FARTHER N OVER THE UPPER
MIDWEST/UPPER MS VALLEY...LOW SEVERE PROBABILITIES WILL BE
MAINTAINED.
..PETERS.. 08/23/2011
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