DAY 4-8 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0359 AM CDT THU APR 21 2011
VALID 241200Z - 291200Z
...DISCUSSION...
WHILE SOME DETAILS VARY...THE 00Z ECMWF/GEFS/UKMET ARE IN AMPLE
GENERAL AGREEMENT WITH THE EXPECTED AMPLIFICATION OF THE LARGE SCALE
PATTERN LATE THIS WEEKEND/EARLY NEXT WEEK...HIGHLIGHTED BY A
PROMINENT WESTERN/CENTRAL CONUS UPPER TROUGH.
ON DAY 4/SUNDAY...THE SOUTHERN HIGH PLAINS WILL LIKELY BE A FOCUS
FOR AT LEAST SOME SURFACE BASED SEVERE THREAT NEAR/EAST OF A DRYLINE
ACROSS WEST TX AND PERHAPS INTO OK. OTHER ELEVATED STORMS CAPABLE OF
SEVERE HAIL ARE PROBABLE SUNDAY NIGHT FROM OK INTO THE OZARKS/LOWER
MO VALLEY. BUT GIVEN LINGERING UNCERTAINTY REGARDING THE EXTENT OF
PRE-DARK SURFACE BASED DEEP CONVECTION...LARGELY OWING TO
ANTICIPATED MODEST LARGE SCALE FORCING FOR ASCENT/ONLY WEAK HEIGHT
FALLS...TOO MUCH UNCERTAINTY CURRENTLY EXISTS TO DELINEATE A 30
PERCENT EQUIVALENT SEVERE RISK AREA.
FOR DAY 5/MONDAY...HAVE INTRODUCED A SEVERE RISK AREA FOR PORTIONS
OF THE SOUTHERN PLAINS TO THE ARKLATEX/OZARKS. WHILE TIMING/SPATIAL
DETAILS VARY TO A DEGREE...REASONABLE CONFIDENCE EXISTS THAT A
SOUTHERN STREAM SHORTWAVE TROUGH WILL OVERSPREAD A MOIST AIRMASS TO
THE EAST OF THE DRYLINE/COLD FRONT. AS SUCH...SEVERE STORMS SEEM
LIKELY MONDAY/MONDAY NIGHT ACROSS THIS REGION.
INTO DAYS 6/7 TUESDAY/WEDNESDAY...AS THE NEXT PORTION OF THE CENTRAL
CONUS UPPER TROUGH PIVOTS EASTWARD...A RELATIVELY
WIDESPREAD/MULTI-ROUND SEVERE THREAT IS EXPECTED FROM THE SOUTHERN
PLAINS EAST-NORTHEASTWARD INTO THE MIDWEST AND LOWER/MIDDLE MS RIVER
VALLEY. WHILE SEVERE STORMS SEEM LIKELY EACH OF THESE
DAYS...SPECIFIC PREDICTABILITY IS STILL QUITE LIMITED IN THIS TIME
FRAME.
..GUYER.. 04/21/2011
