SWODY1
SPC AC 061951
DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0251 PM CDT SUN SEP 06 2009
VALID 062000Z - 071200Z
...NO SVR TSTM AREAS FORECAST...
...LOWER OH VALLEY...
ONLY SMALL ADJUSTMENTS TO LOW WIND/HAIL PROBABILITIES HAVE BEEN
MADE.
A BROKEN BAND OF STRONG TO MARGINALLY SEVERE STORMS HAS DEVELOPED
TODAY ACROSS THE REGION WITH THE MOST INTENSE ACTIVITY LOCATED FROM
JUST W OF HOP SWWD TO NEAR JBR AS OF 1930Z. THESE STORMS APPEAR TO
BE ASSOCIATED WITH A WEAK VORTICITY MAXIMUM ROTATING AROUND PRIMARY
DEEP-LAYER CYCLONE SITUATED FARTHER N NEAR STL. INFLOW AIR MASS IS
WARM AND MOIST WITH MLCAPE OF 1500-2000 J/KG. WHILE THE STRONGER
STORMS WILL BE CAPABLE OF LOCALLY STRONG WIND GUSTS AND PERHAPS HAIL
INTO THIS EVENING...VERTICAL SHEAR REMAINS QUITE MARGINAL BASED ON
AREA PROFILERS/VWPS...AND NO ORGANIZED SEVERE WEATHER IS EXPECTED.
...ERN CO/WRN KS...
TSTMS CURRENTLY DEVELOPING ALONG THE FRONT RANGE MAY INCREASE IN
COVERAGE THIS AFTERNOON INTO EVENING WHILE PROGRESSING EWD INTO THE
HIGH PLAINS IN ASSOCIATION WITH WEAK MIDLEVEL IMPULSE MOVING THROUGH
THE CNTRL ROCKIES. THE COMBINATION OF STEEP LOW TO MIDLEVEL LAPSE
RATES AND MLCAPE OF 1000-2000 J/KG SHOULD SUPPORT STRONG PULSE OR
LOOSELY-ORGANIZED STORM CLUSTERS CAPABLE OF GUSTY WINDS.
HOWEVER...THE VERY WEAK TROPOSPHERIC WIND FIELD /REF. PLATTEVILLE CO
PROFILER/ WILL LIMIT ANY MORE SUBSTANTIAL SEVERE THREAT.
..MEAD.. 09/06/2009
.PREV DISCUSSION... /ISSUED 1057 AM CDT SUN SEP 06 2009/
...MID MS VALLEY TO LOWER OH VALLEY...
LIFT WITH PERSISTENT VORT CENTER OVER MO/IL TODAY WILL ACT ON MOIST
AND UNSTABLE AIRMASS ACROSS THE LOWER OH VALLEY AND CONTINUE TO
SUPPORT CLUSTERS OF SLOW-MOVING STORMS. POCKETS OF GREATER SURFACE
HEATING/DESTABILIZATION AND EFFECTIVE SHEAR ON THE ORDER OF 20-30KT
COULD ALLOW A FEW STORMS TO BRIEFLY ATTAIN MORE ORGANIZED STRUCTURE
AND PERSISTENCE...PERHAPS LEADING TO A COUPLE OF MARGINAL HAIL/WIND
EVENTS. THIS POTENTIAL SEEMS SUFFICIENT ENOUGH TO JUSTIFY THE
INTRODUCTION OF LOW SEVERE PROBABILITIES THIS AREA.
...MT...
STRONG MID/UPPER TROUGH TRANSLATING EWD ACROSS THE NWRN U.S AND WRN
CANADA WILL PRODUCE GREATEST HEIGHT FALLS ACROSS PARTS OF BC AND AB
CANADA....LIFT WITH LEE LOW AND ADVANCING PACIFIC FRONT WILL
CONTRIBUTE TO SOME TSTM DEVELOPMENT ACROSS THE ROCKIES LATER TODAY
THROUGH TONIGHT. STORMS ARE LIKELY TO BE MAINTAINED INTO ERN/NERN MT
LATE TONIGHT GIVEN MODEST DYNAMIC FORCING ACCOMPANYING THE LOW/FRONT
AND UPPER TROUGH. WHILE INSTABILITY AVAILABLE TO THIS ACTIVITY IS
EXPECTED TO REMAIN LIMITED DUE TO LACK OF GREATER LOW LEVEL
MOISTURE...EVAPORATIVE COOLING AMIDST DEEPLY MIXED BOUNDARY
LAYER...EVEN AFTER DARK...COULD CONTRIBUTE TO A FEW STRONG WIND
GUSTS AS STORMS MOVE ACROSS THE REGION THROUGH EARLY MONDAY.
...SOUTHWEST TO INTERMOUNTAIN REGION...
DECAYING SHORT WAVE DISTURBANCE/PV ANOMALY WILL CONTINUE DRIFTING
EWD FROM AZ AND THE FOUR CORNERS REGION TODAY. BACKGROUND ASCENT
ASSOCIATED WITH THIS SYSTEM...AND DIURNAL AND DIFFERENTIAL HEATING
ACROSS THE MOUNTAINS...WILL AGAIN PROMOTE TSTM DEVELOPMENT. LACK OF
STRONGER FLOW/FORCING SHOULD KEEP ORGANIZED SEVERE WEATHER THREAT TO
A MINIMUM.
...ERN NC...
CHANCES FOR DEEP CONVECTION ARE FORECAST TO INCREASE OVER COASTAL
AREAS LATE IN THE FORECAST PERIOD AS MARGINALLY ORGANIZED AND
PERSISTENT MCS NOW SOUTH OF CAPE FEAR DRIFTS NWD. WHILE FORECAST
SOUNDINGS DEPICT LOW LEVEL DIRECTIONAL SHEAR ASSOCIATED WITH THIS
DISTURBANCE INCREASING ACROSS THE OUTER BANKS THROUGH EARLY
MONDAY...THE MAGNITUDE OF RESULTING SHEAR/SRH REMAINS TOO WEAK TO
JUSTIFY INTRODUCING SEVERE PROBABILITIES AT THIS TIME.
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