SWODY1
SPC AC 201959
DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0259 PM CDT SUN MAR 20 2011
VALID 202000Z - 211200Z
...THERE IS A SLGT RISK OF SVR TSTMS FROM NERN KS THROUGH NRN MO/SRN
IA TO NRN IL AND FAR SRN WI...
...NERN KS TO NRN IL/FAR SRN WI...
NO CHANGES NEEDED FROM PREVIOUS OUTLOOK ISSUANCE FOR THE SLIGHT RISK
AREA. FOR SHORT TERM MESOSCALE DETAILS AND THREAT FOR SEVERE
STORMS...REFER TO SPC MESOSCALE DISCUSSION #241.
...ELSEWHERE...
SRN EXTENT OF THE GENERAL TSTM AREA HAS BEEN SHIFTED EWD GIVEN
RECENT EWD MOVEMENT OF THE DRY LINE. FARTHER WEST...THE GENERAL
TSTM AREA ALONG THE SRN CA COAST HAS BEEN EXPANDED INLAND SOME...
GIVEN AN EARLIER LIGHTNING STRIKE OBSERVED JUST OUTSIDE THE PREVIOUS
TSTM LINE AND EMBEDDED WITHIN CONVECTION ACROSS THIS AREA.
..PETERS.. 03/20/2011
.PREV DISCUSSION... /ISSUED 1127 AM CDT SUN MAR 20 2011/
SOUTHWESTERLY MID LEVEL FLOW IS PRESENT TODAY OVER MOST OF THE
PLAINS AND MS VALLEY...WITH WATER VAPOR IMAGERY SHOWING A
WELL-DEFINED SHORTWAVE TROUGH MOVING ACROSS SD/NEB. THIS FEATURE IS
EXPECTED TO MAINTAIN A RISK OF SHOWERS AND THUNDERSTORMS OVER
PORTIONS OF THE MIDWEST AND MID/UPPER MS VALLEY TODAY AND TONIGHT.
THIS IS ALSO THE AREA MOST LIKELY TO SEE ISOLATED SEVERE STORMS.
...IA/MO/IL/WI...
A LARGE CLUSTER OF SHOWERS AND THUNDERSTORMS HAS BEEN ONGOING FOR
MANY HOURS...MOVING FROM THE CENTRAL PLAINS INTO THE UPPER MS
VALLEY. STRONG HEATING HAS COMMENCED ALONG THE SOUTHERN EDGE OF
THIS PRECIP SHIELD OVER PORTIONS OF IA/MO AND INTO CENTRAL IL.
STRONG SOUTHERLY LOW LEVEL WINDS ARE ALSO HELPING TO
MOISTEN/DESTABILIZE THIS REGION WITH DEWPOINTS CLIMBING INTO THE 50S
ACROSS PORTIONS OF MO. THIS TREND WILL PERSIST THROUGH THE
AFTERNOON WITH HEATING/MOISTENING AND SOME DESTABILIZATION OCCURRING
AS FAR NORTH AS THE WI/IL BORDER.
MOST MODEL SOLUTIONS AGREE ON THE RE-DEVELOPMENT OF THUNDERSTORMS
THIS AFTERNOON IN THE WAKE OF THE MORNING MCS AND AHEAD OF THE
APPROACHING UPPER TROUGH. ACTIVITY SHOULD INTENSIFY ALONG THE
SURFACE BOUNDARY OVER CENTRAL IA AND SPREAD EASTWARD ACROSS PORTIONS
OF NORTHERN/CENTRAL IL. ALTHOUGH INSTABILITY WILL BE
LIMITED...FAVORABLE VERTICAL SHEAR AND COLD TEMPERATURES ALOFT WILL
PROMOTE A RISK OF HAIL AND GUSTY/DAMAGING WINDS IN THE STRONGEST
STORMS. THE EASTERN EXTENT OF THE SEVERE THREAT IS UNCERTAIN...BUT
LATEST HRRR SOLUTIONS SUGGEST SUFFICIENT DESTABILIZATION FOR A RISK
OF SEVERE WEATHER AS FAR EAST AS THE CHI AREA.
...KS/OK...
THE SURFACE DRYLINE WILL EXTEND SOUTH-SOUTHWESTWARD FROM IA INTO
CENTRAL KS AND NORTHWEST OK BY LATE THIS AFTERNOON. FULL SUNSHINE
AND STEEP MID LEVEL LAPSE RATES MAY BE SUFFICIENT TO LOCALLY
ELIMINATE THE CAP...ESPECIALLY OVER EASTERN KS WHERE WEAK UPWARD
FORCING IS ALSO EXPECTED. ANY STORMS THAT FORM ALONG THIS AXIS WILL
POSE A THREAT OF DAMAGING WINDS AND HAIL. THE MOST LIKELY TIME
WINDOW FOR THIS THREAT WOULD BE 23-02Z.
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