SWOD48
SPC AC 010821
DAY 4-8 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0321 AM CDT TUE NOV 01 2011
VALID 041200Z - 091200Z
...DISCUSSION...
BEGINNING ON FRI/D4...AN ACTIVE AND PROGRESSIVE PATTERN WILL BE IN
PLACE. A LEAD TROUGH WILL BE LOCATED OVER THE SERN CONUS. MODELS
DIFFER ON HOW AMPLIFIED THIS TROUGH WILL BE AT THIS TIME...BUT IT
WILL BE IRRELEVANT IN TERMS OF SEVERE POTENTIAL AS INSTABILITY WILL
BE MINIMAL...AND...THE COLD FRONT SHOULD BE MOVING OFFSHORE. BEHIND
THIS TROUGH...A SPRAWLING AREA OF DRY HIGH PRESSURE WILL ENCOMPASS
THE ERN HALF OF THE CONUS.
THIS DRY AIR WILL BE IN PLACE AHEAD OF THE NEXT TROUGH...WHICH IS
FORECAST TO MOVE INTO THE PLAINS THE MORNING OF SAT/D5. THE ECMWF
MODEL HAS SLOWED DOWN THE SPEED OF THIS SYSTEM...NEARLY 12 HRS
SLOWER THAN THE GFS DETERMINISTIC MODEL. REGARDLESS OF WHICH
SOLUTION IS CLOSER TO REALITY...THERE WILL BE LITTLE MOISTURE AND
INSTABILITY ACROSS THE WARM SECTOR FOR SEVERE STORMS. FORECAST
SOUNDINGS SHOW ONLY 40S AND 50S F BOUNDARY LAYER DEWPOINTS OVER OK
AND KS. HIGHER DEWPOINTS WILL EXIST INTO CNTRL/SRN TX...BUT APART
FROM THE MAIN FORCING.
ON SUN/D6...THIS TROUGH WILL LOSE MOST OF ITS AMPLITUDE AS IT
CONTINUES NEWD ACROSS THE GREAT LAKES...LEAVING A BROAD AREA OF SWLY
FLOW BEHIND EXTENDING SWWD TO THE NEXT UPPER TROUGH FORECAST TO BE
OVER THE SWRN U.S. ON MON/D7. THIS WILL BE A MORE FAVORABLE REGIME
TO ADVECT SUBSTANTIAL LOW LEVEL MOISTURE NWD INTO THE PLAINS...WITH
AT LEAST LOWER 60S F DEWPOINTS LIKELY AS FAR N AS OK AND KS MON
AFTERNOON. LIFT ASSOCIATED WITH THIS RAPID WARM
ADVECTION...HOWEVER...WILL LEAD TO WIDESPREAD CLOUDS AND RAIN.
THUNDERSTORMS WILL BE LIKELY. SIGNIFICANT ENOUGH MODEL DIFFERENCES
EXIST AT D7 NOT TO INTRODUCE ANY SEVERE AREAS. THIS IS MAINLY DUE TO
THE POSSIBILITY OF WIDESPREAD CLOUDS AND RAIN...AND ALSO DIFFERENCES
IN MOISTURE RETURN MAGNITUDE...WITH THE GFS MUCH MORE BULLISH AND
THE ECMWF MUCH LESS SO.
THE UPPER TROUGH IS FORECAST TO MOVE ACROSS THE PLAINS MON NIGHT
INTO TUE/D8...AND THIS WOULD MOST LIKELY BE THE MOST ACTIVE SEVERE
DAY. THIS TYPE OF PATTERN WILL HAVE LESSER CHANCE FOR FAILURE GIVEN
A LONGER DURATION OF MOISTURE RETURN AND SUCH A BROAD BELT OF SWLY
FLOW/SHEAR FORECAST BY THE MODELS. AT THIS POINT...TIMING AND
AMPLIFICATION OF THE TROUGH IS THE MAIN ISSUE...WITH SEVERE WEATHER
POSSIBLE ON D7-D8 ANYWHERE FROM TEXAS NEWD INTO MO AND SRN IL. FOR
NOW...PREDICTABILITY IS TOO LOW TO CONFIDENTLY PLACE ANY SEVERE
AREAS.
..JEWELL.. 11/01/2011
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