SWOD48
SPC AC 180853
DAY 4-8 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0353 AM CDT MON APR 18 2011
VALID 211200Z - 261200Z
...DISCUSSION...
A RELATIVELY LOW AMPLITUDE/FAST MOVING BELT OF WEST-SOUTHWESTERLY
MID/UPPER FLOW IS EXPECTED TO PREVAIL THROUGH THE MIDDLE/LATE PART
OF THE WEEK PER 00Z ECMWF/GEFS/UKMET GUIDANCE. AS TYPICAL OF SUCH A
LOW AMPLITUDE LONGWAVE REGIME...SPECIFIC PREDICTABILITY REMAINS
LIMITED WITH A FAIR AMOUNT OF SPREAD/ASSOCIATED UNCERTAINTY
REGARDING SHORTWAVE-TYPE FEATURES. THE 00Z GEFS/DETERMINISTIC GFS
CONTINUE TO REFLECT A BIT MORE AMPLIFICATION WITH A DAY 4-5
WESTERN/CENTRAL CONUS UPPER TROUGH AS COMPARED TO THE 00Z
ECMWF/UKMET...WHILE THE 00Z ECMWF/UKMET ARE INDICATIVE OF A MORE
SUBSTANTIAL WESTERN STATES TROUGH EVOLVING THIS WEEKEND AS COMPARED
TO THE 00Z GEFS. WHILE SEVERE WEATHER THREATS WILL UNDOUBTEDLY EXIST
DURING THE PERIOD...CONFIDENCE IN THE DELINEATION OF ANY 30 PERCENT
CALIBER SEVERE RISK AREAS IS CURRENTLY LIMITED.
FOR DAY 4/THURSDAY...THE SOUTH-CENTRAL PLAINS SHOULD BE A FOCUS FOR
SEVERE TSTMS AS LOW LEVEL MOISTURE GRADUALLY RETURNS TOWARD A
DEVELOPING SOUTH-CENTRAL PLAINS SURFACE LOW/DRYLINE TRIPLE POINT.
HOWEVER...THE DEGREE OF LARGE SCALE FORCING /AMID LOW AMPLITUDE
SOUTHWESTERLY FLOW ALOFT/ COINCIDENT WITH THE WARM/MOIST SECTOR IS A
BIT UNCERTAIN...BUT AT LEAST SOME SEVERE THREAT SEEMS PROBABLE
INCLUDING A RISK FOR SUPERCELLS. A SEVERE RISK /MAINLY HAIL/ COULD
DEVELOP INTO THE LOWER MO VALLEY/MIDDLE MS VALLEY THURSDAY NIGHT.
BY DAY 5/FRIDAY...ESPECIALLY IF A MORE AMPLIFIED WESTERN TO CENTRAL
STATES TROUGH MATERIALIZES AS PER 00Z GEFS GUIDANCE...A MORE
SIGNIFICANT/WIDESPREAD SEVERE THREAT MAY EVOLVE WITHIN A CORRIDOR
FROM THE SOUTH-CENTRAL PLAINS NORTHEASTWARD INTO THE MIDDLE MS RIVER
VALLEY/MIDWEST/LOWER OH VALLEY. WHILE THE MAGNITUDE/SPECIFIC AREAL
DELINEATION OF THE SEVERE RISK IS STILL A BUT UNCERTAIN PENDING
NUMERICAL GUIDANCE VARIABILITY...AN APPRECIABLE SEVERE THREAT DOES
SEEM LIKELY FRIDAY/FRIDAY NIGHT WITHIN THE AFOREMENTIONED CORRIDOR.
..GUYER.. 04/18/2011
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