Severe Storm Outlook Narrative (AC)
Issued by NWS

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000
ACUS48 KWNS 250853
SWOD48
SPC AC 250852

DAY 4-8 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0352 AM CDT SAT MAY 25 2013

VALID 281200Z - 021200Z

...DISCUSSION...
THE GFS/ECMWF ARE IN GENERAL AGREEMENT ON TUESDAY /DAY 4/ IN SHOWING
STRONG SWLY FLOW OVER THE SRN HIGH PLAINS NEWD INTO THE
MIDWEST...SUPPORTING AT LEAST ISOLD SEVERE WITHIN THIS CORRIDOR
AHEAD OF THE AMPLIFYING WRN U.S. UPPER TROUGH.  MODELS DIVERGE
SUBSTANTIALLY BY WEDNESDAY /DAY 5/ IN THE EVOLUTION OF THE WRN U.S.
UPPER TROUGH AS IT MOVES INTO THE CNTRL U.S.  THE 00Z/25 GFS SHOWS A
LESS AMPLIFIED SOLUTION VS. THE 00Z/25 ECMWF EXHIBITING A MORE
MERIDIONAL/HIGHER AMPLITUDE SCENARIO AS A NEGATIVELY-TILTED TROUGH
EJECTS INTO THE CNTRL STATES.  ALTHOUGH IT SEEMS PROBABLE AN
ELONGATED MID LEVEL LOW WILL BECOME CENTERED OVER THE NWRN CONUS BY
MID-LATE WEEK...CONSIDERABLE SPREAD IS NOTED IN THE ECMWF/GEFS
ENSEMBLE MEMBERS IN THE EVOLUTION OF EJECTING SHORTWAVE FEATURES.
AS A RESULT...CONSIDERABLE UNCERTAINTY EXISTS FROM WEDNESDAY /DAY 5/
INTO NEXT WEEKEND AND PRECLUDES THE HIGHLIGHT OF POSSIBLE 30 PERCENT
SEVERE PROBABILITY AREAS AT THIS TIME.  DESPITE THE AFOREMENTIONED
MODEL PREDICTABILITY CONCERNS AND PRIOR DAY/S STORM ACTIVITY
EXERTING INFLUENCE ON SUBSEQUENT DAY/S...A POTENTIALLY ACTIVE
SEVERAL DAY PERIOD FOR SEVERE WEATHER IS POSSIBLE.  THEREFORE...AN
INCREASED RISK FOR ORGANIZED SEVERE STORMS SEEMS PLAUSIBLE FOR PARTS
OF THE PLAINS AND MIDWEST ON TUESDAY /DAY 4/...OVER A LARGER PORTION
OF THE PLAINS ON WEDNESDAY /DAY 5/ AND THEN POSSIBLY IN PARTS OF THE
PLAINS AND UPPER MIDWEST ON THURSDAY /DAY 6/.

..SMITH.. 05/25/2013
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