SWODY1
SPC AC 200038
DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0738 PM CDT FRI SEP 19 2008
VALID 200100Z - 201200Z
...NO SVR TSTM AREAS FORECAST...
...PARTS OF THE WESTERN/NORTHERN GREAT BASIN...
DESTABILIZATION IS ONGOING TO THE LEE OF THE NORTHERN SIERRA NEVADA
AND SOUTHERN CASCADES...WHERE COOLING /LIFT IN THE EXIT REGION OF A
MID-LEVEL JET STREAK NOSING ACROSS THE SAN FRANCISCO BAY/TAHOE
REGION IS OVERSPREADING A WARM AND DEEP MIXED BOUNDARY LAYER. THE
AIR MASS IS NOT PARTICULARLY MOIST...BUT CONDITIONS APPEAR
SUFFICIENT TO SUPPORT A FURTHER INCREASE/INTENSIFICATION OF
THUNDERSTORM ACTIVITY LATE THIS AFTERNOON/EARLY EVENING...
ESPECIALLY FROM PARTS OF NORTHWEST NEVADA INTO SOUTH CENTRAL OREGON.
SOME STORMS MAY BE CAPABLE OF PRODUCING LOCALLY DAMAGING WIND GUSTS
AND SMALL HAIL BEFORE WEAKENING LATER THIS EVENING.
...REMAINDER OF THE INTERMOUNTAIN WEST INTO THE HIGH PLAINS...
THE BULK OF ONGOING THUNDERSTORM ACTIVITY FROM THE REMAINDER OF THE
CENTRAL GREAT BASIN AND SOUTHERN PLATEAU...INTO THE CENTRAL/
SOUTHERN ROCKIES AND CENTRAL HIGH PLAINS...APPEARS LARGELY TIED TO
DAYTIME HEATING. AND...A RAPID DECREASE IN NUMBER/INTENSITY SEEMS
PROBABLE DURING THE 02-04Z TIME FRAME...IF NOT BEFORE.
...UPPER MISSISSIPPI VALLEY/UPPER GREAT LAKES REGION...
THE STRONG SHORT WAVE TROUGH...WHICH HAS BEEN DIGGING ACROSS
SOUTHERN HUDSON BAY/NORTHERN ONTARIO...IS PROGGED TO GRADUALLY TURN
EASTWARD TONIGHT. AS THIS OCCURS...STRONGER MID/UPPER FORCING FOR
UPWARD VERTICAL MOTION IS PROGGED TO BECOME FOCUSED NORTHEAST OF THE
UPPER GREAT LAKES REGION...ACROSS PARTS OF EASTERN/SOUTHERN ONTARIO
INTO WESTERN QUEBEC...WHERE HIGHEST THUNDERSTORM PROBABILITIES WILL
EXIST. ADDITIONAL STORM DEVELOPMENT APPEARS POSSIBLE FARTHER TO THE
WEST SOUTHWEST... ALONG/AHEAD OF A COLD FRONT EXPECTED TO ADVANCE
SOUTH OF THE CANADIAN/U.S. BORDER AREA. BUT...LOWER/MID
TROPOSPHERIC INHIBITION ALREADY PRESENT...COUPLED WITH BROADER SCALE
SUBSIDENCE ALOFT...AND PRE-FRONTAL BOUNDARY LAYER COOLING...PROBABLY
WILL MINIMIZE CONVECTIVE POTENTIAL OVERNIGHT ACROSS THIS REGION.
...MID/LOWER MISSISSIPPI VALLEY...
A MID-LEVEL CIRCULATION...EMBEDDED WITHIN A WEAK SOUTHERN BRANCH OF
THE POLAR WESTERLIES...IS PROGGED TO LINGER OVER SOUTHEAST
MISSOURI/NORTHEAST ARKANSAS OVERNIGHT. DESPITE STABILIZATION WITH
THE ONSET OF SURFACE COOLING...THE ENVIRONMENT APPEARS MOIST/
UNSTABLE ENOUGH...GIVEN FAVORABLE LARGE-SCALE FORCING...TO MAINTAIN
A RISK FOR THUNDERSTORM ACTIVITY NEAR/EAST THROUGH SOUTH SOUTHEAST
OF THE CIRCULATION CENTER.
..KERR.. 09/20/2008
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