DAY48SVR: Nws Storm Prediction Center Norman Ok

ACUS48 KWNS 250856
SWOD48
SPC AC 250855

DAY 4-8 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0355 AM CDT FRI MAY 25 2012

VALID 281200Z - 021200Z

...DISCUSSION...
THE MEDIUM RANGE MODELS BEGIN THE DAY 4 TO 8 PERIOD IN GOOD
AGREEMENT WITH AN UPPER-LEVEL TROUGH EXTENDING SWD THROUGH THE NRN
AND CNTRL PLAINS ON MONDAY/DAY 4. BY LATE MONDAY AFTERNOON...A COLD
FRONT IS FORECAST TO BE LOCATED FROM THE WRN GREAT LAKES SSWWD INTO
THE MID-MO VALLEY. THUNDERSTORM DEVELOPMENT WILL BE POSSIBLE ALONG
THIS BOUNDARY MONDAY AFTERNOON AND EVENING. GFS FORECAST SOUNDINGS
MONDAY EVENING FROM AROUND SPRINGFIELD MO NNEWD TO AROUND DAVENPORT
IA SHOW MODERATE TO STRONG INSTABILITY WITH AMPLE DEEP LAYER SHEAR
FOR SEVERE STORMS. WILL MAINTAIN AN ENHANCED SEVERE THREAT AREA
ALONG THIS CORRIDOR ON DAY 4. FOR TUESDAY/DAY 5...THE MODELS MOVE
THE UPPER-LEVEL TROUGH INTO THE GREAT LAKES REGION WITH THE COLD
FRONT ADVANCING QUICKLY SEWD ACROSS THE MID-MS VALLEY. AS THE FRONT
MOVES AWAY FROM THE STRONGER FORCING...THUNDERSTORM DEVELOPMENT
SHOULD BE MORE ISOLATED. THE GREATEST CONVECTIVE COVERAGE SHOULD
EXIST NEWD INTO THE CNTRL AND NRN APPALACHIAN MTNS WHERE STRONG
THUNDERSTORM ACTIVITY COULD OCCUR. A SEVERE THREAT MAY ALSO EXIST IN
THE SRN PLAINS AS MOISTURE RETURNS NWD DURING THE DAY. UNCERTAINTY
IS TOO GREAT TOO WARRANT A SEVERE THREAT AREA ON TUESDAY. ON
WEDNESDAY/DAY 6...BOTH THE GFS AND ECMWF BRING A SHORT-WAVE TROUGH
ESEWD ACROSS THE SRN PLAINS SUGGESTING A CONCENTRATED AREA OF SEVERE
THUNDERSTORM DEVELOPMENT WILL BE POSSIBLE ALONG AN AXIS OF STRONG
INSTABILITY WEDNESDAY AFTERNOON AND EVENING. HOWEVER...UNCERTAINTY
EXISTS CONCERNING THE TIMING AND AMPLITUDE OF THE SHORTWAVE TROUGH
AND WILL NOT INTRODUCE AN ENHANCED SEVERE THREAT AREA FOR WEDNESDAY.
BEYOND DAY 6...THE MODELS AMPLIFY AND MOVE THE SHORTWAVE TROUGH EWD
INTO THE MID-MS VALLEY. THUNDERSTORMS WILL AGAIN BE POSSIBLE AHEAD
OF THE SYSTEM BUT CONFIDENCE IS NOT VERY HIGH CONCERNING THIS LATE
IN THE PERIOD.

..BROYLES.. 05/25/2012

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