DAY48SVR: Nws Storm Prediction Center Norman Ok

ACUS48 KWNS 150859
SWOD48
SPC AC 150858

DAY 4-8 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0358 AM CDT FRI MAR 15 2013

VALID 181200Z - 231200Z

...DISCUSSION...
THE MEDIUM RANGE MODELS BEGIN THE DAY 4 TO 8 PERIOD WITH AN
UPPER-LEVEL TROUGH IN THE GREAT PLAINS AND MOVE THIS FEATURE EWD
ACROSS THE MID TO UPPER MS VALLEY ON MONDAY/DAY 4. THE MODELS SHOW A
CORRIDOR OF LOW-LEVEL MOISTURE EXTENDING NWD FROM THE CNTRL GULF
COAST STATES INTO THE OH VALLEY WHERE THUNDERSTORMS COULD DEVELOP
DURING THE DAY ON MONDAY. THE MODELS ARE IN DECENT AGREEMENT WITH
THE MID-LEVEL JET FORECAST TO COUPLE WITH THE LOW-LEVEL JET ACROSS
THE OH VALLEY. THIS SCENARIO WOULD RESULT IN STRONG SHEAR PROFILES
WITH SEVERE THUNDERSTORMS POSSIBLE DURING THE AFTERNOON AND EVENING.
THE SEVERE THREAT SHOULD EXTEND SWD FROM KY INTO TN AND NRN AL WHERE
MODEL FORECASTS SHOW 60+ SFC DEWPOINTS AND MODERATE INSTABILITY. ON
TUESDAY/DAY 5...THE MODELS MOVE THE UPPER-LEVEL TROUGH ACROSS THE
ATLANTIC SEABOARD WITH A COLD FRONT MOVING OFFSHORE INTO THE
ATLANTIC. ON WEDNESDAY/DAY 6...THE MODELS DEVELOP ZONAL FLOW ACROSS
THE CONUS WITH THE MOIST SECTOR LOCATED FROM EAST TX EWD ACROSS LA.
THUNDERSTORMS COULD OCCUR DURING THE DAY ON WEDNESDAY OR DURING THE
OVERNIGHT PERIOD ALONG THE MOISTURE GRADIENT FROM NE TX EWD INTO THE
CNTRL GULF COAST STATES. AT THIS POINT...ANY SHORTWAVE TROUGH THAT
MOVES ACROSS THE SCNTRL U.S. ON WEDNESDAY WILL BE LOW-AMPLITUDE. FOR
THIS REASON...THE MODELS DIFFER ON THE SCENARIO WITH THE GFS SHOWING
A CONVECTIVE POTENTIAL MUCH FURTHER EAST THAN THE ECMWF.

CONCERNING THE DAY 4 TO 8 PERIOD...A SEVERE THREAT WILL CERTAINLY BE
POSSIBLE ACROSS THE OH AND TN VALLEYS ON MONDAY AFTERNOON AND
EVENING. WILL ADD A 30 PERCENT SEVERE PROBABILITY AREA ACROSS PARTS
OF THE SRN OH VALLEY AND TN VALLEY WHERE THE MODELS ARE IN DECENT
AGREEMENT THAT THE COMBINATION OF INSTABILITY...SHEAR AND LIFT WILL
SUPPORT AN ENHANCED SEVERE THREAT.

..BROYLES.. 03/15/2013

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