SWODY1
SPC AC 251621
DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1121 AM CDT THU JUN 25 2009
VALID 251630Z - 261200Z
...THERE IS A SLGT RISK OF SVR TSTMS OVER A LARGE PART OF THE
CENTRAL/ERN GREAT LAKES INTO THE OH/MID MS VALLEYS...
...THERE IS A SLGT RISK OF SVR TSTMS OVER THE CENTRAL HIGH PLAINS...
...THERE IS A SLGT RISK OF SVR TSTMS ACROSS PORTIONS OF THE NRN HIGH
PLAINS...
...MID-UPPER MS RIVER VALLEY/CENTRAL-ERN GREAT LAKES/OH VALLEY...
SURFACE FEATURES WILL REMAIN DIFFUSE ACROSS THE REGION TODAY WITH
VERY LITTLE LOW LEVEL FLOW TO FOCUS DEVELOPMENT. THIS REMAINS
PRIMARY CONCERN TODAY REGARDING LOCATION OF GREATER SEVERE COVERAGE
AS AIR MASS BECOME VERY UNSTABLE AMONGST WARM/MOIST SUMMER-TIME
BOUNDARY LAYER. ACTIVITY WILL LIKELY INCREASE ACROSS A RELATIVELY
LARGE AREA FROM THE MID/UPPER MS RIVER VALLEY AND CENTRAL GREAT
LAKES DURING THE AFTERNOON AS CAP ERODES AHEAD OF NRN STREAM
SHORTWAVE TROUGH NOW MOVING ACROSS THE NRN/WRN GREAT LAKES. DESPITE
THE WEAK LOW LEVEL FLOW...MID LEVEL FLOW WILL REMAIN MORE THAN
SUFFICIENT FOR ORGANIZATION INTO LINES/CLUSTERS WITH STRONGER SHEAR
SUPPORTIVE OF SUPERCELLS ACROSS THE CENTRAL/ERN GREAT LAKES. LARGE
HAIL AND DAMAGING WINDS ARE EXPECTED TO BE PRIMARY SEVERE THREATS
WITH ACTIVITY PERSISTING INTO THE EVENING SEWD TOWARDS THE OH RIVER
VALLEY AND EWD INTO PORTIONS OF PA/NY.
ADDITIONAL CLUSTER OF STRONG/SEVERE STORMS SHOULD INCREASE WITH
DIURNAL HEATING INTO PORTIONS OF MO/MID MS RIVER VALLEY AS SUBTLE
MID LEVEL IMPULSE CONTINUES SSEWD AROUND SRN PLAINS UPPER RIDGE.
THIS WILL PROVIDE SUFFICIENT MEAN FLOW FOR SOME CLUSTERING OF THE
MORE ROBUST CORES ALONG A COMMON OUTFLOW AND PERHAPS A MORE
PERSISTENT WIND DAMAGE THREAT...DRIVEN MAINLY BY STEEPENING LOW
LEVEL LAPSE RATES.
...NRN/CENTRAL HIGH PLAINS...
SEVERE THREAT WILL LIKELY EVOLVE WITHIN SEPARATE REGIMES ACROSS THIS
AREA LATE TODAY AND THIS EVENING. NRN PORTION OVER CENTRAL MT WILL
BE DRIVEN MORE BY LARGE SCALE FORCING AHEAD OF STRENGTHENING SURFACE
COLD FRONT MOVING ACROSS THE NRN ROCKIES THIS AFTERNOON. DESPITE
ONLY MODEST INSTABILITY...STEEP LAPSE RATES AND STRENGTHENING WLY
WINDS ALOFT SHOULD SUPPORT THREATS OF DAMAGING WINDS AND HAIL WITH
THE STRONGER STORMS SPREADING QUICKLY ENEWD THROUGH THE EVENING.
ACROSS THE CENTRAL HIGH PLAINS...SEVERE THREAT WILL BE MORE DRIVEN
BY WEAK UPSLOPE FLOW AND SUBTLE IMPULSES EVIDENT ON WV IMAGERY
ROTATING ACROSS THE GREAT BASIN/CENTRAL ROCKIES. THIS ACTIVITY WILL
LIKELY SPREAD EWD OFF THE HIGHER TERRAIN DURING THE MID/LATE
AFTERNOON AND LIKELY EVOLVE AS A FEW CLUSTERS OF STRONG TO SEVERE
STORMS. LARGE HAIL AND DAMAGING WINDS SHOULD BE PRIMARY SEVERE
THREATS OVER THIS REGION...WITH POSSIBLE MCS PERSISTING INTO THE
CENTRAL PLAINS OVERNIGHT.
..EVANS/HURLBUT.. 06/25/2009
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