SWODY1
SPC AC 082332
DAY 1 CONVECTIVE OUTLOOK AMEND 1
NWS STORM PREDICTION CENTER NORMAN OK
0632 PM CDT SUN AUG 08 2010
VALID 082330Z - 091200Z
...THERE IS A SLGT RISK OF SVR TSTMS FROM THE CENTRAL PLAINS TO
UPPER MS VALLEY...
...THERE IS A SLGT RISK OF SVR TSTMS ACROSS PARTS OF ERN NV/WRN UT
AND NWRN AZ...
AMENDED FOR EXTENSION OF SLIGHT INTO NRN KS AS WELL AS INTO WRN WI
...NRN KS/WI...
THE SLIGHT RISK HAS BEEN EXTENDED INTO NRN KS TO ACCOUNT FOR
ACTIVITY CURRENTLY IN SEVERE THUNDERSTORM WATCH 590. THIS ACTIVITY
MAY PERSIST AS IT MOVES SLOWLY E WITH A THREAT OF WIND AND HAIL.
FARTHER N INTO WI...VIGOROUS ACTIVITY NOW EXTENDING FROM CNTRL MN
SWWD INTO NEB WILL CONTINUE EWD WITH A THREAT OF SEVERE WIND AND
HAIL.
...ERN NV/WRN UT/NWRN AZ...
A SLIGHT RISK ACROSS THIS REGION HAS BEEN EXPANDED SWD INTO PARTS OF
SWRN NV AND NWRN AZ. VISIBLE SATELLITE IMAGERY INDICATED MOSTLY
CLEAR SKIES HAVE DEVELOPED ACROSS MUCH OF THIS REGION WHERE CLOUDS
WERE LOCATED EARLIER TODAY. CONTINUED SURFACE HEATING ACROSS THIS
REGION COUPLED WITH COOLING MIDLEVEL TEMPERATURES/STEEPENING LAPSE
RATES SPREADING NE WITH ATTENDANT SHORTWAVE TROUGH THROUGH THE LOWER
CO VALLEY TO GREAT BASIN WILL RESULT IN FURTHER DESTABILIZATION.
DEEP LAYER SLY WIND FIELDS/EFFECTIVE BULK SHEAR AROUND 30 KT SUGGEST
MULTICELLS/LINE SEGMENTS WILL BE LIKELY. IN ADDITION TO STRONG WIND
GUSTS AS FORECAST IN THE PREVIOUS OUTLOOK...15 PERCENT HAIL
PROBABILITY HAS BEEN ADDED TO THE SRN TWO-THIRDS OF THE SLIGHT RISK
AREA. GIVEN STEEP LAPSE RATES...MODERATE INSTABILITY AND 500 MB
TEMPERATURES AOB -12 C...ORGANIZED STORMS WILL POSE A THREAT FOR
HAIL. STORMS IN FAR NWRN AZ/SWRN UT MAY PRODUCE A FEW HAIL EVENTS
POTENTIALLY APPROACHING A DIAMETER OF 2 INCHES GIVEN THE
AFOREMENTIONED FAVORABLE THERMODYNAMICS COMBINED WITH STRONGER SHEAR
SUPPORTING SUPERCELLS. OTHERWISE...THE FORECAST REMAINS THE SAME
WITH STORMS POTENTIALLY IMPACTING THE GSL AREA BY THIS EVENING.
...CENTRAL PLAINS TO UPPER MS VALLEY...
SLIGHT RISK HAS BEEN EXPANDED NWD INTO THE TWIN CITIES METRO AREA
GIVEN THAT A WARM FRONT HAS MOVED JUST N OF THIS REGION...WITH
STRONG SURFACE HEATING CONTRIBUTING TO VERY STRONG INSTABILITY.
THIS COMBINED WITH 40-50 KT OF EFFECTIVE SHEAR SUGGEST ANY STORMS
THAT CAN DEVELOP AND/OR MOVE THROUGH THIS ENVIRONMENT WILL POSE A
SEVERE WEATHER THREAT. RECENT STRONG TO SEVERE TSTM DEVELOPMENT WAS
OBSERVED OVER NORTH CENTRAL NEB...INVOF STRONGEST LOW LEVEL
CONVERGENCE JUST N OF A SURFACE LOW AND ALONG A BOUNDARY WHICH
EXTENDED EWD INTO NERN NEB TO CENTRAL IA. GIVEN VERY STRONG DEEP
LAYER SHEAR AND HIGH INSTABILITY...A THREAT EXISTS FOR SOME
SIGNIFICANT HAIL FROM NERN NEB/SERN SD INTO NWRN IA AND SWRN MN AND
10 PERCENT SIGNIFICANT HAIL PROBABILITY HAS BEEN ADDED TO THE
OUTLOOK. IN ADDITION...STRONGER LOW LEVEL SHEAR ALONG E-W SURFACE
BOUNDARY FROM NERN NEB INTO NWRN IA SUGGESTS POTENTIAL FOR A
TORNADO. THUS...5 PERCENT TORNADO PROBABILITY HAS BEEN ADDED TO THE
OUTLOOK.
..JEWELL.. 08/08/2010
.PREV DISCUSSION... /ISSUED 1122 AM CDT SUN AUG 08 2010/
...CENTRAL/UPPER MS VALLEY...
MAIN PLAYERS FOR SEVERE THUNDERSTORMS TODAY WILL BE THE DEVELOPMENT
OF AN EXTREMELY UNSTABLE AIRMASS AND ADEQUATE SHEAR FOR STORM
ORGANIZATION. FOCUS FOR INITIATION WILL BE THE SURFACE BOUNDARIES
AND WHERE THEY WILL BE LOCATED BY LATE THIS AFTERNOON WHEN
INITIATION IS MOST LIKELY.
OVERNIGHT MCS DECAYING CURRENTLY ACROSS SRN WI/NRN IL WITH A
TRAILING BOUNDARY WWD ACROSS SRN MN INTO A WEAK SURFACE LOW OVER
SERN SD. BY MID AFTERNOON AS TEMPS RISE THRU THE 90S COUPLED WITH
RICH PWAT TO 2 INCHES MLCAPES AOA 4000 J/KG WILL DEVELOP FROM SERN
SD/ERN NEB ACROSS IA/SRN MN.
WITH LITTLE AVAILABLE IN THE WAY OF UPPER SUPPORT...STORM INITIATION
WILL BE TIED TO WHERE THE CINH WEAKENS AND SURFACE CONVERGENCE WILL
BE LOCATED. ATTM BEST CONVERGENCE WOULD APPEAR TO BE JUST TO E OF
SURFACE LOW SD INTO SRN MN.
INITIAL STORMS LATE THIS AFTERNOON WILL POSE A RISK OF
BECOMING SUPERCELLULAR DUE TO STRONG EFFECTIVE SHEAR AND DEGREE OF
CAPE. LARGE HAIL AND DAMAGING WINDS APPEAR TO BE THE MAIN THREATS.
LATER TONIGHT...ACTIVITY MAY CONGEAL INTO A LARGER SCALE MCS/BOW AND
SPREAD EASTWARD INTO PARTS OF IA/WI/IL WITH A RISK OF DAMAGING
WINDS.
WILL MAINTAIN A RISK OF SEVERE WWD ACROSS NEB INTO NWRN KS GIVEN THE
STEEP LAPSE RATES AND CONVERGENCE VICINITY OF SURFACE TROUGH. WITH
DEEP LAYER SHEAR AROUND 30KT INITIAL PULSE ACTIVITY COULD FORM
CLUSTERS WITH ASSOCIATED WIND DAMAGE THREAT LATE THIS
AFTERNOON/EVENING.
...UT/NV...
THE UPPER LOW ALONG THE CENTRAL CA COAST WILL TRACK SLOWLY
EASTWARD AS ONE S/WV IMPULSE ROTATES NEWD ACROSS SRN NV INTO UT THIS
AFTERNOON AND EVENING. CURRENT OBSERVED CLOUD COVER MAY BE A PROBLEM
ACROSS THE RISK AREA...POTENTIALLY LIMITING DAYTIME HEATING AND LOW
LEVEL LAPSE RATES. HOWEVER HEATING COUPLED WITH COOLING MID LEVEL
TEMPERATURES SHOULD BE SUFFICIENT FOR AT LEAST ISOLATED
STRONG/SEVERE STORM DEVELOPING THIS AFTERNOON. THUNDERSTORMS WOULD
LIKELY DEVELOP FIRST ACROSS ERN NV/SWRN UT IN PROXIMITY TO THE S/WV
TROUGH WITH LOCALLY GUSTY/DAMAGING WINDS EXPECTED TO BE THE MAIN
THREAT. BY THIS EVENING STORMS COULD ALSO IMPACT FURTHER NE TO GSL
AREA.
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