SWODY2
SPC AC 201635
DAY 2 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1035 AM CST SAT NOV 20 2010
VALID 211200Z - 221200Z
...NO SVR TSTM AREAS FORECAST...
...SYNOPSIS...
A LARGE UPPER TROUGH WILL EXIST OVER MUCH OF THE WRN CONUS SUNDAY
WITH A BROAD SWLY FLOW REGIME ACROSS THE CNTRL STATES INTO THE UPPER
GREAT LAKES. ALTHOUGH LOW PRESSURE WILL DEEPEN FROM THE CNTRL
ROCKIES INTO THE PLAINS...LITTLE MOISTURE WILL BE AVAILABLE FOR
THUNDERSTORMS ALTHOUGH ISOLATED NON-SEVERE CONVECTION IS LIKELY
ACROSS THE W BENEATH STEEP LAPSE RATES ALOFT...AND PERHAPS OVER
PORTIONS OF THE UPPER MS VALLEY OVERNIGHT.
...COASTAL OREGON/NRN CA INTO THE SACRAMENTO VALLEY...
AN UPPER LOW CENTER WILL BE SITUATED OVER NRN CA AT THE BEGINNING OF
THE PERIOD...SHIFTING EWD ACROSS THE GREAT BASIN DURING THE DAY.
VERY COLD AIR ALOFT WITH 500 MB TEMPERATURES AROUND -30 C WILL FAVOR
WEAK LOW TOPPED CONVECTION CAPABLE OF PRODUCING LIGHTNING. THE MOST
LIKELY AREA WILL BE ALONG THE COAST...BUT A FEW STRIKES MAY OCCUR
WITH DAYTIME HEATING INTO THE CNTRL VALLEYS. VERY WEAK INSTABILITY
AND LOW LEVEL SHEAR PROFILES SUGGEST NO SEVERE THREAT.
...UT INTO CO...
COOLING ALOFT WILL ACCOMPANY AN EWD MOVING UPPER LOW CENTER DURING
THE DAY WITH SWLY LOW LEVEL UPSLOPE FLOW INTO UT/CO. MODEL FORECAST
SOUNDINGS SHOW STEEP LOW TO MID LEVEL LAPSE RATES DEVELOPING...AND
GIVEN LARGE SCALE LIFT AND AREAS OF HEATING...ISOLATED THUNDERSTORMS
ARE LIKELY. COOL AIR AND LOW PRECIPITABLE WATER VALUES WILL LIMIT
STORM INTENSITY.
...ERN IA INTO NRN IL LATE...
A SURFACE LOW PRESSURE TROUGH WILL REMAIN QUASISTATIONARY FROM THE
UPPER MS VALLEY SWWD INTO THE CNTRL PLAINS THROUGH THE PERIOD
BENEATH GRADUAL COOLING AND HEIGHT FALLS ALOFT. PERSISTENT SWLY LOW
LEVEL FLOW WILL ALLOW BOUNDARY LAYER DEWPOINTS INTO THE MID 50S F TO
ADVECT AS FAR N AS IA/IL OVERNIGHT. WEAK ISENTROPIC ASCENT AND
DEVELOPING WEAK INSTABILITY MAY BE ENOUGH TO PRODUCE AREAS OF
ELEVATED SHOWERS AND THUNDERSTORMS BY LATE EVENING INTO THE
OVERNIGHT HOURS. NEGATIVES TO INCIPIENT CONVECTION WILL BE PRESENCE
OF DRY AIR ALOFT AND HIGH SHEAR.
..JEWELL.. 11/20/2010
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