SWODY3
SPC AC 300720
DAY 3 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0220 AM CDT SUN AUG 30 2009
VALID 011200Z - 021200Z
...NO SVR TSTM AREAS FORECAST...
...SYNOPSIS...
MODELS INDICATE LITTLE CHANGE TO THE LARGE-SCALE UPPER FLOW PATTERN
ACROSS THE U.S. FROM MONDAY INTO TUESDAY. THE CLOSED LOW OVER THE
NORTHEAST PACIFIC MAY BEGIN TO SHIFT EAST/NORTHEAST TOWARD THE
BRITISH COLUMBIA/PACIFIC NORTHWEST COAST...AS A STRONG ZONAL JET
NOSES ACROSS THE MID LATITUDE PACIFIC. BUT...A GENERALLY
WEAK...BROADLY ANTICYCLONIC FLOW APPEARS LIKELY TO PERSIST ACROSS
THE WEST...WHILE A WEAK CYCLONIC FLOW LINGERS IN THE EAST. AS A
SMALL WEAK EMBEDDED CLOSED LOW MIGRATES EAST OF THE NORTHERN
ROCKIES...SOME SHARPENING OF THE RIDGE MAY OCCUR ACROSS THE
INTERMOUNTAIN WEST AND CANADIAN ROCKIES...AND THE CIRCULATION CENTER
IS FORECAST TO TURN SLOWLY SOUTHEASTWARD ACROSS THE NORTHERN PLAINS.
COOLING/DRYING ASSOCIATED WITH THE EASTERN TROUGH IS EXPECTED TO
CONFINE HIGHEST THUNDERSTORM PROBABILITIES TO THE FLORIDA
PENINSULA...WHERE UPPER FORCING AHEAD OF THE BASE OF THE TROUGH WILL
AID CONVECTIVE DEVELOPMENT AS THE BOUNDARY LAYER DESTABILIZES WITH
DAYTIME HEATING. OTHERWISE...SCATTERED THUNDERSTORMS WILL AGAIN BE
A POSSIBILITY ACROSS PARTS OF THE NORTHERN INTERMOUNTAIN REGION AND
ROCKIES INTO THE SOUTHERN PLATEAU.
...PARTS OF THE NORTHERN/CENTRAL HIGH PLAINS...
ADDITIONAL CONVECTIVE DEVELOPMENT WILL PROBABLY ACCOMPANY THE
DIGGING UPPER LOW/TROUGH INTO PARTS OF THE NORTHERN AND CENTRAL
PLAINS. HOWEVER...WITH A GULF MOISTURE RETURN STILL CUT-OFF...AND
MODELS FORECASTING A GRADUAL DRYING OF THE LOW-LEVEL ENVIRONMENT
NEAR THE LEE SURFACE TROUGH BY TUESDAY...BOUNDARY LAYER
DESTABILIZATION MAY BE LIMITED. EVEN SO...THE PRESENCE OF STEEP
LAPSE RATES AND SHEAR...ASSOCIATED WITH A MODEST NORTHWESTERLY
MID-LEVEL JET STREAK DEVELOPING ON THE SOUTHERN PERIPHERY OF THE
LOW...WILL PROBABLY BE SUFFICIENT FOR A FEW WIDELY SCATTERED
STRONG/SEVERE STORMS NEAR THE LEE TROUGH LATE TUESDAY AFTERNOON.
..KERR.. 08/30/2009
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