ACUS03 KWNS 280728
SWODY3
SPC AC 280727

DAY 3 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0227 AM CDT THU JUL 28 2011

VALID 301200Z - 311200Z

....THERE IS A SLGT RISK OF SVR TSTMS ACROSS PORTIONS OF THE ERN
DAKOTAS AND MN...

....SYNOPSIS...
RELATIVELY STRONG SHORTWAVE TROUGH...MOVING RAPIDLY EWD THROUGH S
CENTRAL CANADA AND INTO WRN ONTARIO...WILL PUSH A COLD FRONT TO NEAR
A NWRN MN TO S CENTRAL SD LINE BY LATE SATURDAY AFTERNOON.
ELSEWHERE...LARGE UPPER RIDGE WILL COVER THE SRN TWO THIRDS OF THE
COUNTRY...WITH THE FLOW AROUND THIS SYSTEM FORECAST TO MOVE
TROPICAL STORM DON WWD/WNWWD THROUGH SRN TX.

....ERN DAKOTAS AND MN...
INCREASING SLY WINDS WILL ADVECT A MOIST BOUNDARY LAYER...MID TO
UPPER 60 DEWPOINTS...AHEAD OF THE APPROACHING COLD FRONT. THESE
DEWPOINTS COMBINED WITH STEEP MID LEVEL LAPSE RATES WILL RESULT IN A
VERY UNSTABLE AIR MASS SATURDAY AFTERNOON...WITH MLCAPES AOA 3500
J/KG. UNIDIRECTIONAL WLY WINDS ABOVE THE BOUNDARY LAYER WILL RESULT
IN EFFECTIVE SHEAR AT 30-40 KT...SUPPORTIVE OF SEVERE MULTICELLS AND
PERHAPS A SUPERCELL OR TWO. THE DEGREE OF INSTABILITY AND LAPSE
RATES WILL BE SUPPORTIVE OF BOTH A SEVERE HAIL AND WIND THREAT
DURING THE AFTERNOON AND EVENING HOURS.

....CAROLINAS WWD INTO THE SRN PLAINS...
DIFFUSE SURFACE TROUGH WILL MOVE SWD INTO THE CAROLINAS/TN VALLEY
....WHILE DRIFTING SWD INTO AR AND OK. WITH DIURNAL HEATING AND
HIGHER SURFACE DEWPOINTS NEAR BOUNDARY WILL YIELD MODERATE
INSTABILITY. SINCE THE UPPER RIDGE WILL BE SITUATED ACROSS THIS
REGION...THE DEEP LAYER SHEAR WILL BE QUITE WEAK. HOWEVER...THE
STEEP LOW LEVEL LAPSE RATES AND PW VALUES FROM 1.75 TO 2 INCHES MAY
SUPPORT A FEW STORMS WITH WET MICROBURSTS.

....SRN/CENTRAL TX...
AS REMNANTS OF DON MOVES WWD THROUGH SRN TX...WIND FIELDS MAY BE
STRONG ENOUGH TO SUPPORT A LOW TORNADO THREAT OR POSSIBLY STRONG
CONVECTIVE WIND GUSTS IN THE WEAKENING OUTER BANDS. REFERENCE THE
LATEST NATIONAL HURRICANE WATCHES/WARNINGS ON THIS TROPICAL SYSTEM
AS THE SEVERE WEATHER EXTENT WILL BE DEPENDENT ON HOW STRONG DON
BECOMES BEFORE MOVING INLAND.

...IMY.. 07/28/2011

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