SWOD48
SPC AC 030900
DAY 4-8 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0400 AM CDT SUN APR 03 2011
VALID 061200Z - 111200Z
...DISCUSSION...
IN THE WAKE OF A TROUGH MOVING OFF THE EAST COAST...ZONAL FLOW IS
FORECAST ACROSS THE CONUS ON DAY 4 /WED APR 6/. AFTER DAY 4...THE
MID-UPPER LEVEL FLOW REGIME WILL TRANSITION TO SWLY...EXTENDING FROM
THE SWRN STATES THROUGH THE PLAINS TO OH VALLEY AND MID ATLANTIC
STATES. THIS EVOLUTION IS FORECAST TO OCCUR AS HEIGHTS RISE OVER
THE SERN STATES AND A LONGWAVE TROUGH DEEPENS WEST OF THE ROCKIES
THROUGH DAY 6 /FRI APR 8/. BEYOND DAY 6...THE GFS AND ECMWF DIFFER
WITH THE EWD PROGRESSION OF THIS LONGWAVE TROUGH.
...DAY 5 /THU APR 7/...
THE GFS/ECMWF ARE NOW IN BETTER AGREEMENT ON DAY 4...EJECTING THE
CLOSED LOW CURRENTLY LOCATED WELL WEST OF BAJA INTO THE SWRN STATES
ON WED APR 6...IN ADVANCE OF THE DIGGING WRN U.S. TROUGH THIS
FORECAST PERIOD. HOWEVER...THESE TWO MODELS DIFFER IN TIMING OF
THIS SYSTEM TRACKING ACROSS THE SRN PLAINS TO MID MS VALLEY ON DAY
5. TSTMS WILL BE POSSIBLE ON DAY 5...BUT UNCERTAINTY IN STORM
COVERAGE AND TIMING OF THE SYSTEM DOES NOT WARRANT A REGIONAL SEVERE
WEATHER THREAT AREA.
...DAY 7 /SAT APR 9/...
DESPITE MODEL DIFFERENCES BEYOND DAY 6 WITH THE EWD PROGRESSION OF
THE WRN STATES LONGWAVE TROUGH...THE GFS/ECMWF ARE IN FAIRLY GOOD
AGREEMENT WITH STRONGER LOW LEVEL MOISTURE RETURN DEVELOPING ON DAY
6 /FRI APR 8/ ACROSS THE SRN PLAINS. THIS WILL PERSIST INTO DAY 7
BENEATH STEEP MIDLEVEL LAPSE RATES. EACH MODEL INDICATES CONVECTIVE
INITIATION ALONG THE DRY LINE IN THE SRN PLAINS WITH STORMS
DEVELOPING TOWARD THE LOWER MO VALLEY SATURDAY NIGHT. GIVEN THAT
THIS IS THE FIRST OUTLOOK PERIOD WITH THE GFS/ECMWF IN GENERAL
AGREEMENT FOR A SEVERE WEATHER THREAT ACROSS TX/OK/KS SATURDAY
AFTERNOON/EVENING...CONFIDENCE REMAINS TOO LOW TO INCLUDE A REGIONAL
SEVERE WEATHER THREAT AREA AT THIS TIME.
..PETERS.. 04/03/2011
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