SWODY1
SPC AC 170059
DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0759 PM CDT SUN SEP 16 2007
VALID 170100Z - 171200Z
..NO SVR TSTM AREAS FORECAST...
..ERN/NRN AZ INTO ERN UT/CO...
EARLY EVENING WATER VAPOR IMAGERY INDICATED A MID/UPPER LEVEL TROUGH
MOVING EWD ACROSS CENTRAL/SRN CA AND NV. HEIGHT FALLS /30-50 METERS
AT H5/ AHEAD OF THIS TROUGH AS IT MOVES INTO THE GREAT BASIN...AND
JUXTAPOSED WITH MOISTURE PLUME STREAMING NNEWD FROM MEXICO TO THE
CENTRAL ROCKIES ARE EXPECTED TO SUPPORT ADDITIONAL CONVECTION THIS
FORECAST PERIOD FROM ERN AZ/UT INTO CO. ALTHOUGH INSTABILITY IS
EXPECTED TO BE WEAK...STRENGTHENING SWLY MID/UPPER LEVEL FLOW AS
TROUGH TRACKS FARTHER INLAND WILL MAINTAIN STRONG EFFECTIVE BULK
SHEAR VALUES FOR A FEW ORGANIZED TSTMS. STEEP MID LEVEL LAPSE RATES
AND INVERTED-V THERMODYNAMIC PROFILES...DESPITE SURFACE COOLING
INDICATE THE POTENTIAL FOR A FEW STORMS TO PRODUCE STRONG WIND GUSTS
THROUGH THE EVENING...AND POSSIBLY HAIL. SINCE THE WEAK INSTABILITY
SHOULD LIMIT SEVERE WEATHER COVERAGE DURING THIS FORECAST PERIOD...
SEVERE PROBABILITIES HAVE BEEN LOWERED.
..PARTS OF CENTRAL/NRN PLAINS TO UPPER MIDWEST...
WEAK HEIGHT FALLS ARE ALSO EXPECTED ACROSS THE NRN/CENTRAL PLAINS AS
A NRN STREAM TROUGH BECOMES MORE IN PHASE WITH GREAT BASIN SYSTEM
OVERNIGHT. IN THE LOW LEVELS...LEE TROUGH IS EXPECTED TO SPREAD EWD
INTO THE NRN PLAINS. MEANWHILE...WARM FRONT WHICH CURRENTLY
EXTENDED FROM WRN SD SSEWD INTO CENTRAL TO ERN KS IS EXPECTED TO
MOVE NWD TONIGHT IN RESPONSE TO SURFACE PRESSURE FALLS ACROSS THE
DAKOTAS/UPPER MS VALLEY AND STRENGTHENING SRN/CENTRAL PLAINS SWLY
LLJ. THIS BOUNDARY SHOULD EXTEND SEWD FROM A SURFACE LOW IN THE
CENTRAL DAKOTAS TO CENTRAL IA. INCREASING LOW LEVEL MOISTURE/WARM
AIR ADVECTION NWD FROM LOWER/MID MO RIVER VALLEY SUGGESTS SOME
POTENTIAL FOR CONVECTION INCREASING TONIGHT...ESPECIALLY ALONG NOSE
OF LLJ INTO IA WHERE WAA WILL BE STRONGEST.
FARTHER W...ONGOING CLUSTER OF TSTMS...CURRENTLY EXTENDING FROM NERN
CO TO FAR SWRN NEB...IS MOVING ENEWD TOWARD COOL SIDE OF WARM FRONT.
GIVEN THIS TRACK AND FURTHER BOUNDARY LAYER STABILIZATION WITH LOSS
OF DAY TIME HEATING...INCREASING WAA IN VICINITY OF STRENGTHENING
LLJ SUGGESTS THIS COMPLEX MAY BE SUSTAINED EWD OVERNIGHT ACROSS SRN
NEB. MARGINAL INSTABILITY SHOULD LIMIT THE EWD SEVERE THREAT...BUT
THIS OUTLOOK WILL EXTEND 5% SEVERE PROBABILITIES EWD.
.PETERS.. 09/17/2007
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