Note: A severe weather area depicted in the Day 4-8 period indicates a 30% or higher probability for severe thunderstorms within 25 miles of any point.
PREDICTABILITY TOO LOW is used to indicate severe storms may be possible based on some model scenarios. However, the location or occurrence of severe storms are in doubt due to: 1) large differences in the deterministic model solutions, 2) large spread in the ensemble guidance, and/or 3) minimal run-to-run continuity.
POTENTIAL TOO LOW means the threat for a regional area of organized severe storms appears highly unlikely during the entire period (e.g. less than a 30% probability for a regional severe storm area across the CONUS through the entire Day 4-8 period).
Forecast Discussion
ZCZC SPCSWOD48 ALL
ACUS48 KWNS 260852
SPC AC 260852
DAY 4-8 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0352 AM CDT SAT MAY 26 2012
VALID 291200Z - 031200Z
...DISCUSSION...
THE MEDIUM RANGE MODELS BEGIN THE DAY 4 TO 8 PERIOD WITH AN
UPPER-LEVEL TROUGH OVER THE NCNTRL U.S. WITH WLY FLOW LOCATED ACROSS
THE SCNTRL STATES. ALTHOUGH THE MODELS DO NOT IDENTIFY A SHORTWAVE
TROUGH...MODEL FORECASTS DO DEVELOP THUNDERSTORMS ON TUESDAY/DAY 4
ALONG AN AXIS OF STRONG INSTABILITY ACROSS TX AND OK. ANOTHER AREA
WITH CONVECTIVE POTENTIAL SHOULD EXIST IN THE CNTRL AND NRN
APPALACHIAN MTNS AHEAD OF AN UPPER-LEVEL TROUGH WHERE THE GFS SHOWS
MODERATE INSTABILITY TUESDAY AFTERNOON. ON WEDNESDAY/DAY 5...THE
MODELS AGAIN DEVELOP THUNDERSTORMS IN THE SRN AND CNTRL PLAINS WITH
THE GFS AND ECMWF MOVING A SHORTWAVE TROUGH SEWD ACROSS THE REGION.
THE MODELS THEN MOVE A COLD FRONT SEWD ACROSS THE SRN PLAINS AND
GULF COAST STATES ON THURSDAY/DAY 6. THUNDERSTORM ACTIVITY MAY OCCUR
ALONG THE FRONT THURSDAY AFTERNOON AND EVENING AND NWD INTO THE MID
MS VALLEY NEAR AN UPPER-LEVEL LOW. BEYOND DAY 5...THE MODEL
SOLUTIONS DIVERGE SHARPLY AND A LOT WILL DEPEND ON THE AMPLITUDE OF
AN UPPER-LEVEL TROUGH IN THE OH AND TN VALLEYS. IF THE GFS IS
SOMEWHAT CLOSE TO BEING CORRECT...THEN THUNDERSTORM ACTIVITY WILL BE
POSSIBLE ALONG THE ERN SEABOARD FRIDAY AFTERNOON/DAY 7. AT THIS
POINT...WEDNESDAY APPEARS TO BE THE DAY WITH THE GREATEST SEVERE
THREAT POTENTIAL WITH SEVERE STORMS POSSIBLE IN THE SRN AND CNTRL
PLAINS. HOWEVER...SUBSTANTIAL UNCERTAINTY EXISTS CONCERNING THE
EXACT LOCATION AND MAGNITUDE OF THE THREAT. WILL NOT INTRODUCE A
SEVERE THREAT AREA ATTM.
..BROYLES.. 05/26/2012
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