DAY48SVR: Nws Storm Prediction Center Norman Ok

ACUS48 KWNS 220901
SWOD48
SPC AC 220900

DAY 4-8 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0400 AM CDT MON OCT 22 2012

VALID 251200Z - 301200Z

...DISCUSSION...
00Z ECMWF/GEFS/UKMET ARE IN AMPLE GENERAL AGREEMENT WITH THE
EXPECTED EVOLUTION AND GRADUAL EASTWARD-SHIFT OF A LONGWAVE TROUGH
OVER THE WESTERN/CENTRAL CONUS THROUGH LATE WEEK. A COLD FRONT IS
EXPECTED TO SPREAD EAST-SOUTHEASTWARD ACROSS THE EAST-CENTRAL CONUS
THROUGH DAYS 4-6 /THURSDAY-SATURDAY/.

ON DAY 4/THURSDAY...THIS UPPER TROUGH AND COLD FRONT WILL INITIALLY
ENCOUNTER A RELATIVELY MOIST AIRMASS FOR THE SEASON ACROSS THE
MIDDLE/UPPER MS RIVER VALLEY. WHILE THE EXACT DEGREE OF
DESTABILIZATION IS UNCERTAIN...AMPLE FORCING FOR ASCENT/VERTICAL
SHEAR MAY OVERSPREAD THE MOIST AXIS NEAR/AHEAD OF THE COLD FRONT FOR
SOME ORGANIZED SEVERE TSTMS ON DAY 4/THURSDAY. PENDING SUFFICIENT
DESTABILIZATION...SUCH SEVERE POTENTIAL COULD INCLUDE PORTIONS OF
WI/EASTERN IA/WESTERN IL TO MO...PERHAPS AS A FAST-MOVING/LOW-TOPPED
SQUALL LINE ESPECIALLY WITH NORTHERN EXTENT. WHILE AT LEAST SOME
SEVERE TSTMS WILL BE POSSIBLE...LINGERING GUIDANCE VARIABILITY
REGARDING UPPER TROUGH AMPLITUDE/TIMING...AND UNKNOWNS REGARDING THE
EXACT DEGREE OF DESTABILIZATION...PRECLUDE A 30 PERCENT SEVERE RISK
AREA.

THEREAFTER...TSTMS WILL REMAIN POSSIBLE ALONG THE COLD FRONT INTO
DAY 5/FRIDAY. A PARTICULARLY ORGANIZED/CONSEQUENTIAL SEVERE RISK IS
NOT CURRENTLY ANTICIPATED...BUT SOME STRONG/POSSIBLY SEVERE TSTMS
MIGHT BE POSSIBLE FOR AREAS SUCH AS THE ARKLATEX VICINITY NEAR THE
COLD FRONT. OTHERWISE...RELATIVELY BENIGN CONDITIONS WITH RESPECT TO
DEEP CONVECTION ARE GENERALLY ANTICIPATED THROUGH THE WEEKEND INTO
EARLY NEXT WEEK AS DRY/COLD CONDITIONS PREVAIL EAST OF THE ROCKIES.

..GUYER.. 10/22/2012

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