SWODY1
SPC AC 051954
DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0254 PM CDT SUN SEP 05 2010
VALID 052000Z - 061200Z
...NO SVR TSTM AREAS FORECAST...
...MT INTO THE WRN DAKOTAS...
STORMS HAVE BEEN INCREASING IN INTENSITY ACROSS N CNTRL MT BEHIND
THE COLD FRONT AND BENEATH VERY COOL AIR ALOFT WITH 500 MB
TEMPERATURES AROUND -20 C. SOME OF THESE STORMS MAY PRODUCE
MARGINALLY SEVERE HAIL AT TIMES...BUT INSTABILITY WILL REMAIN WEAK.
FARTHER E...CONVERGENCE ALONG THE FRONT IS INCREASING ACROSS SWRN
MT/NWRN WY...AND A GRADUAL INCREASE IN STORM COVERAGE AND INTENSITY
IS ANTICIPATED AS THE FRONT DEEPENS. ACTIVITY MAY EVOLVE INTO A
CLUSTER WITH A THREAT OF STRONG TO SEVERE WIND GUSTS AND MARGINAL
HAIL AS IT TREKS EWD ACROSS SRN/ERN MT...FAR NRN WY...AND INTO THE
WRN DAKOTAS.
..JEWELL.. 09/05/2010
.PREV DISCUSSION... /ISSUED 1130 AM CDT SUN SEP 05 2010/
...NRN HIGH PLAINS TO THE UPPER MS VALLEY THROUGH TONIGHT...
A PRONOUNCED MIDLEVEL TROUGH OVER THE NRN ROCKIES WILL MOVE ESEWD TO
THE CENTRAL AND NRN HIGH PLAINS BY TONIGHT...WHILE DOWNSTREAM LEE
CYCLOGENESIS OCCURS INVOF WRN NEB. SUBSTANTIAL MOISTENING HAS
OCCURRED FROM IA NWWD INTO THE DAKOTAS IN THE ZONE WHERE
LOW-MIDLEVEL WAA COINCIDES WITH THE MOISTURE PLUME ORIGINATING FROM
THE NRN ROCKIES YESTERDAY. THIS MOISTENING IS ALSO OCCURRING ON THE
ERN EDGE OF THE STEEPER LAPSE RATES AND WARMER EML...SUCH THAT A FEW
ELEVATED THUNDERSTORMS WILL CONTINUE TO BE POSSIBLE THROUGH THE
PERIOD. SOME SMALL HAIL CANNOT BE RULED OUT TONIGHT INVOF SE MN/NE
IA/SW WI/NW IL...THOUGH ONLY WEAK MIDLEVEL INSTABILITY SUGGESTS THAT
SEVERE HAIL IS IMPROBABLE.
EVAPOTRANSPIRATION HAS CONTRIBUTED TO SKIN LAYER MOISTENING ACROSS
THE MID MO VALLEY OF NEB/IA/SD...BUT THE RICHER BOUNDARY LAYER
MOISTURE IS CONFINED TO A STALLED FRONT ACROSS THE N/NW GULF OF
MEXICO. CONTINUED EWD EXPANSION OF THE EML WILL LIKELY MAINTAIN A
CAPPED BOUNDARY LAYER ACROSS THE LOWER PLAINS OF NEB/SD INTO
IA...WITH THE ONLY POTENTIAL EXCEPTION BEING A SMALL CHANCE OF
HIGH-BASED STORMS LATE THIS AFTERNOON ACROSS CENTRAL NEB WHERE DEEP
MIXING WILL LARGELY REMOVE CONVECTIVE INHIBITION.
THE GREATER RISK FOR STORM DEVELOPMENT...HOWEVER...WILL BE FARTHER
NW INTO S CENTRAL/SE M...NRN WY...AND WRN SD WHERE LARGE SCALE
ASCENT WILL BE STRONGEST ALONG A COLD FRONT AND IMMEDIATELY
DOWNSTREAM FROM THE MIDLEVEL TROUGH. DESPITE SOMEWHAT LIMITED
LOW-LEVEL MOISTURE /BOUNDARY LAYER DEWPOINTS ONLY IN THE
40S/...AFTERNOON TEMPERATURES IN THE 70S AND STEEP LAPSE RATES WILL
SUPPORT MLCAPE OF 500-1000 J/KG. DEEP-LAYER VERTICAL SHEAR WILL BE
SUFFICIENT FOR ORGANIZED LINE SEGMENTS AND SUPERCELLS...WITH AN
ATTENDANT RISK FOR ISOLATED DAMAGING GUSTS AND MARGINALLY SEVERE
HAIL THIS AFTERNOON INTO EARLY TONIGHT. THE SOMEWHAT LIMITED
INSTABILITY SUPPORTS MAINTAINING ONLY LOW WIND/HAIL PROBABILITIES.
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