SPC AC 221259
DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0759 AM CDT TUE JUN 22 2010
VALID 221300Z - 231200Z
...THERE IS A MDT RISK OF SVR TSTMS OVER PARTS OF
NEB...SD...IA...SRN MN...SW WI...AND NRN IL...
...THERE IS A SLGT RISK OF SVR TSTMS SURROUNDING THE MDT RISK
AREA...FROM THE CNTRL HI PLNS TO THE OH VLY AND MID ATLANTIC
STATES/NORTHEAST...
...SYNOPSIS...
PERSISTENT SRN PLNS/OZARKS UPR RIDGE WILL BE SUPPRESSED SOMEWHAT S
LATER THIS PERIOD AS A PAIR OF POTENT SHORTWAVE IMPULSES NOW OVER
THE GRT BASIN SHEAR NE INTO THE CNTRL HI PLNS BY EVE...AND REACH THE
UPR MS VLY EARLY WED. AT THE SAME TIME...SYSTEM THAT CROSSED THE
GRT LKS LATE YESTERDAY WILL CONTINUE E INTO NEW ENGLAND.
AT LWR LVLS...COLD FRONT NOW EVOLVING OVER THE WRN DAKOTAS AND WY
SHOULD CONTINUE E/SE THROUGH THE PERIOD...WHILE STNRY FRONT NOW
EXTENDING ROUGHLY W-E FROM SRN NEB TO CNTRL IL...DISJOINTED IN
SEVERAL PLACES BY CONVECTIVE OUTFLOW...ADVANCES NEWD INTO SE SD/NRN
IA.
SEVERAL CORRIDORS OF SVR WEATHER ONCE AGAIN APPEAR LIKELY IN A BROAD
SWATH FROM THE NRN/CNTRL HI PLNS TO THE MID/UPR MS VLY AND THE NERN
STATES. POTENTIALLY THE MOST SIGNIFICANT/WIDESPREAD THREAT...MAINLY
IN THE FORM OF HIGH WIND...MAY EVOLVE LATE TONIGHT/EARLY WED OVER
PARTS OF NEB/SE SD/IA/SRN MN/SRN WI AND NRN IL.
...CNTRL HI PLNS TO MID/UPR MS VLY TODAY THROUGH WED MORNING...
SCTD SMALL CLUSTERS OF STRONG/BRIEFLY SVR ELEVATED STORMS MAY
PERSIST THROUGH THIS MORNING ALONG STNRY/WARM FRONT FROM ERN NEB
INTO CNTRL IL/IND...SUPPORTED BY LOW LVL WAA/MOISTURE INFLOW.
SFC HEATING SHOULD FOSTER THE DEVELOPMENT OF SCTD SFC-BASED BY EARLY
AFTN ALONG THE FRONT IN IL/IND...AND PERHAPS A BIT LATER ALONG THE
BOUNDARY IN IA AND SE SD. OTHER STORMS LIKELY WILL FORM BY MID-LATE
AFTN ALONG DEVELOPING COLD FRONT IN ERN SD/WRN MN...ALONG LEE TROUGH
IN ER CO/WRN KS....AND IN POST-FRONTAL UPSLOPE FLOW IN ERN WY/SW SD.
GIVEN 40-50 KT DEEP SW TO WLY SHEAR ACROSS THE ENTIRE REGION... AND
SBCAPE RANGING FROM AOA 2500 J/KG IN THE HI PLNS TO ABOVE 4000 J/KG
IN THE MS VLY...SUSTAINED SUPERCELLS APPEAR LIKELY. IN ADDITION TO
POSING A THREAT FOR VERY LARGE HAIL...ESPECIALLY IN THE HI PLNS E
INTO CNTRL NEB/SE SD...A THREAT ALSO WILL EXIST FOR TORNADOES. THE
LATTER THREAT SHOULD BE GREATEST DURING THE EARLY STAGES OF STORM
DEVELOPMENT IN THE HI PLNS...AND INVOF WARM FRONT FROM SE SD ESE
INTO IA/SRN MN.
AFTN STORMS LIKELY WILL MERGE INTO SEVERAL CLUSTERS THIS EVE...ALONG
THE COLD FRONT AND LEE TROUGH IN PARTS OF SD...WRN/NRN NEB AND NW
KS...AND ALONG WARM FRONT IN IA/MN/IL. THE POTENTIAL WILL EXIST FOR
ONE OF THESE CLUSTERS TO GROW INTO A DERECHO LATE TONIGHT/EARLY
WED....MOST LIKELY OVER NERN NEB OR SE SD...AS 50+ KT 500 MB SPEED
MAX ASSOCIATED WITH THE GRT BASIN OVERSPREADS THE REGION. THIS
CONVECTIVE SYSTEM COULD PRODUCE A SWATH OF DMGG WIND E/ESE INTO NRN
IL/SRN WI BY 12Z WED.
...UPR OH VLY INTO MID ATLANTIC ...
MOIST...WSWLY LOW LVL MOISTURE INFLOW ON SRN FRINGE OF GRT LKS
SHORTWAVE TROUGH...AND SFC HEATING...WILL DESTABILIZE THE MID
ATLANTIC STATES AND PARTS OF THE NORTHEAST TODAY. COUPLED WITH
ASCENT PROVIDED BY TROUGH...EXPECT SCTD CLUSTERS/BANDS OF STORMS BY
MID AFTN ALONG LOW LVL CONFLUENCE AXIS/WEAK FRONT EXTENDING FROM SRN
OH/NRN KY INTO WV/MD AND VA. A BAND OF STORMS ALSO MAY FORM ALONG
WAA AXIS THROUGH CNTRL NY/PA. DAMAGING WIND SHOULD BE THE PRIMARY
CONCERN FROM OH/KY INTO WV. A MORE STRONGLY SHEARED ENVIRONMENT
WILL EXIST OVER AND E OF THE MOUNTAINS FROM MD/NRN VA INTO
NY/PA...CLOSER TO UPR TROUGH. THERE...A FEW SUPERCELLS MAY WILL BE
POSSIBLE...WITH AN ATTENDANT THREAT FOR A TORNADO OR TWO IN ADDITION
TO LOCALLY DMGG WIND/MARGINALLY SVR HAIL.
..CORFIDI/GARNER.. 06/22/2010
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