DAY48SVR: Nws Storm Prediction Center Norman Ok

ACUS48 KWNS 270901
SWOD48
SPC AC 270901

DAY 4-8 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0401 AM CDT WED MAY 27 2009

VALID 301200Z - 041200Z

...DISCUSSION...
GFS AND ECMWF IN GOOD AGREEMENT AT LEAST THROUGH DAY 6...AFTER WHICH
SUBTLE DIFFERENCES IN THE MODELS BEGIN TO INCREASE. OVERALL
HOWEVER...MODELS CONTINUE TO POINT AT A FEW DAYS OF HEIGHTENED
SEVERE POTENTIAL OVER THE CENTRAL CONUS AND VICINITY. BOTH MODELS
CONTINUE TO FORECAST NW FLOW ACROSS THE CENTRAL US AND INTO THE
MIDWEST ON THE BACK SIDE OF A ERN NOAM UPPER LOW/TROUGH FOR DAY 4
/SAT. MAY 30/. AS A PORTION OF THIS TROUGH MOVES QUICKLY EWD AND
TAKES ON A NEGATIVE TILT DAY 5...FLOW ALOFT BECOMES MORE
NWLY/WLY...WITH SEVERAL SHORT-WAVE FEATURES MOVING THROUGH THE
RELATIVELY FAST FLOW FIELD OVER THE CENTRAL AND NRN
PLAINS/MIDWEST/OH VALLEY. FLOW ALOFT SLACKENS A BIT DAY 6...BUT
BOTH MODELS PROG A SHORT-WAVE TROUGH TO ENTER THE CENTRAL PLAINS
WHICH SHOULD MAINTAIN SEVERE POTENTIAL.

DAY 4 /SAT. MAY 30/...IT APPEARS THAT STORMS SHOULD EVOLVE ACROSS
THE NEB VICINITY...AS AMPLE MOISTENING/DESTABILIZATION OCCURS NEAR
AND S OF A NW-SE BAROCLINIC ZONE RETREATING NWD ACROSS THE CENTRAL
CONUS. STORMS SHOULD EXPAND INTO ONE OR MORE MCS LATE IN THE
DAY...AND THEN ACCELERATE SEWD TOWARD THE UPPER MIDWEST THROUGH THE
SECOND HALF OF THE PERIOD -- WITH DAMAGING WINDS EXPECTED TO BE A
MAIN THREAT.

DAY 5 /SUN. MAY 31/...A COLD FRONT IS FORECAST TO BEGIN MOVING SEWD
ACROSS THE PLAINS...PROVIDING A FOCUS FOR STORM DEVELOPMENT --
PARTICULARLY INVOF THE MID MO VALLEY REGION -- WITHIN DESTABILIZING
AFTERNOON AIRMASS. AGAIN...ONE OR MORE MCS SHOULD EVOLVE BY
EVENING...WITH A MORE EWD STORM TRACK INTO THE UPPER MIDWEST REGION.

DAY 6 /MON. JUN. 1/...CYCLOGENESIS ACROSS THE SRN HIGH PLAINS IS
HINTED AT ALONG THE TRAILING PORTION OF THE AFOREMENTIONED FRONT
MOVING SEWD ACROSS THE CENTRAL CONUS -- IN RESPONSE TO THE EJECTING
SHORT-WAVE TROUGH. WHILE FLOW ALOFT SHOULD BE WEAKER...A
PARTICULARLY MOIST/UNSTABLE AIRMASS ACROSS THE KS/OK REGION SHOULD
OFFSET THE SLIGHTLY-WEAKER FLOW FIELD...WITH THE SEVERE POTENTIAL
POSSIBLY INCLUDING TORNADOES NEAR AND NE OF THE LOW/INVOF THE WARM
FRONT WHICH IS PROGGED TO EXTEND ACROSS THE KS/NRN OK/MO VICINITY.

..GOSS.. 05/27/2009

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