SWOD48
SPC AC 070842
DAY 4-8 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0342 AM CDT TUE SEP 07 2010
VALID 101200Z - 151200Z
...DISCUSSION...
AMPLE LARGE SCALE AGREEMENT CONTINUES THROUGH LATE WEEK AMONG 00Z
ECMWF/GEFS GUIDANCE. THE INITIAL/MAIN FOCUS WILL BE ON THE EJECTING
MID-WEEK WESTERN STATES TROUGH...WHICH AFOREMENTIONED GUIDANCE
INDICATES WILL BE STEADILY ADVANCING EAST-NORTHEASTWARD FROM THE
NORTHERN HIGH PLAINS TO THE UPPER MS RIVER VALLEY ON DAY 4/FRIDAY.
AS THIS OCCURS...AT LEAST SOME SEVERE RISK IS PROBABLE ACROSS
PORTIONS OF THE MIDDLE/PERHAPS LOWER MO RIVER VALLEY...TO THE UPPER
MIDWEST AND PERHAPS UPPER MS VALLEY. CURRENT THINKING IS THAT SUCH A
SEVERE THREAT COULD BE CENTERED ACROSS EASTERN NEB/WESTERN IA...AND
PERHAPS ADJACENT EASTERN KS/NORTHERN MO AS WELL AS SOUTHERN MN. THE
POSSIBILITY OF AN ANA-FRONTAL TYPE SCENARIO...WITH MODEST
FORCING/VERTICAL SHEAR JUXTAPOSED WITH THE WARM SECTOR...PRECLUDES
CONSIDERATION OF A HIGHER PROBABILITY /30 PERCENT AND GREATER/ RISK
AREA AT THIS JUNCTURE.
INTO DAY 5/SATURDAY...CURRENT INDICATIONS ARE THAT NOTHING BEYOND AN
ISOLATED/MARGINAL SEVERE RISK WOULD EXIST ALONG THE EASTWARD
ADVANCING COLD FRONT ACROSS THE MIDWEST/OHIO VALLEY...GIVEN THAT THE
BRUNT OF THE PARENT UPPER TROUGH SHOULD BE MINORING/SPREADING INTO
CANADA.
OTHERWISE...THE LARGE SCALE PATTERN SHOULD DEAMPLIFY THIS
WEEKEND...WITH RESULTANT LOW AMPLITUDE/MODERATELY STRONG WESTERLIES
PREVALENT ACROSS THE NORTHERN TIER OF THE CONUS. THERE ARE EARLY
INDICATIONS THAT SOME SEVERE THREAT COULD INCREASE ACROSS THE MIDDLE
MO VALLEY/UPPER MIDWEST/UPPER MS VALLEY VICINITIES BY AROUND DAY
6/DAY 7. THIS WOULD BE AS MOISTURE RETURNS NORTHWARD ACROSS THE
REGION...AS A RELATIVELY LOW AMPLITUDE TROUGH CROSSES THE NORTHERN
TIER OF THE CONUS LATE THIS WEEKEND/EARLY NEXT WEEK PER 00Z
ECMWF/GEFS GUIDANCE. HOWEVER...CONSIDERABLY LIMITED PREDICTABILITY
EXISTS GIVEN THE LOW AMPLITUDE NATURE OF THE LARGE SCALE REGIME BY
THAT JUNCTURE.
..GUYER.. 09/07/2010
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