SWODY1
SPC AC 280056
DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0756 PM CDT THU AUG 27 2009
VALID 280100Z - 281200Z
...NO SVR TSTM AREAS FORECAST...
...ND THROUGH NWRN MN AREA...
WINDOW OF OPPORTUNITY APPEARS TO BE CLOSING FOR AN ORGANIZED SEVERE
EVENT...THOUGH IT IS STILL POSSIBLE THAT A STRONG STORM OR TWO COULD
DEVELOP THIS EVENING AND PRODUCE MAINLY HAIL.
EARLY THIS EVENING A COLD FRONT EXTENDS FROM NWRN MN SWWD THROUGH
CNTRL ND WHERE IT INTERSECTS A N-S ORIENTED CONVERGENCE BOUNDARY
THAT STRETCHES SWD TO JUST WEST OF BISMARK THEN SWD INTO NWRN SD.
DEEP CONVECTION HAS BEEN TRYING TO DEVELOP OVER S CNTRL ND WITHIN
ZONE OF MESOSCALE LIFT ALONG THESE BOUNDARIES. HOWEVER...00Z RAOB
DATA FROM BISMARK...WHICH SHOULD BE REPRESENTATIVE OF THE NEAR STORM
ENVIRONMENT...SHOWS THAT INSTABILITY IS A MAJOR LIMITING FACTOR DUE
TO MEAGER LOW LEVEL MOISTURE. CAPE COMPUTED FROM ML PARCELS SHOWS
ONLY A SMALL SLIVER OF INSTABILITY BETWEEN 700 AND 500 MB. THE ONSET
OF NOCTURNAL COOLING AND LIKELIHOOD THAT COOLER TEMPERATURES ALOFT
ASSOCIATED WITH THE SEWD MOVING IMPULSE WILL REMAIN IN POST FRONTAL
REGION SUGGEST THAT ANY REMAINING SEVERE POTENTIAL WILL PROBABLY BE
SOMEWHAT LIMITED.
...EXTREME SERN IA THROUGH NRN IL...
VEERING LOW LEVEL WIND PROFILES IN VICINITY OF WARM FRONT AND JUST
EAST OF SURFACE LOW IS RESULTING IN AUGMENTED LOW LEVEL SHEAR AND
0-1 KM HELICITY ON THE ORDER OF 200 M2/S2 FROM EXTREME SERN IA INTO
NRN IL. SOME UPDRAFT ROTATION AND A WEAK LOW LEVEL MESOCYCLONE OR
TWO REMAIN POSSIBLE THIS EVENING. HOWEVER...VERY POOR LAPSE
RATES...MARGINAL INSTABILITY AND THE ONSET OF NOCTURNAL COOLING WILL
CONTINUE TO BE A LIMITING FACTOR FOR A SEVERE THREAT IN THIS AREA.
...CNTRL THROUGH WRN TX AND ERN NM...
WIDELY SCATTERED STORMS DEVELOPING FROM ERN NM THROUGH WRN TX MAY
REMAIN CAPABLE OF PRODUCING MAINLY ISOLATED DOWNBURSTS NEXT COUPLE
HOURS. HOWEVER...THE LIMITED SEVERE THREAT IS PRIMARILY DIURNAL IN
NATURE AND SHOULD GRADUALLY WANE AS THE BOUNDARY LAYER BEGINS TO
STABILIZE.
..DIAL.. 08/28/2009
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