SWODY1
SPC AC 121613
DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1113 AM CDT SUN SEP 12 2010
VALID 121630Z - 131200Z
...NO SVR TSTM AREAS FORECAST...
...UPPER GREAT LAKES INTO THE MIDWEST...
A LOW-AMPLITUDE SHORT WAVE TROUGH AND ASSOCIATED 50-60 KT MIDLEVEL
JET STREAK NOW OVER THE RED RIVER VALLEY WILL RAPIDLY TRANSLATE
ESEWD THROUGH THE REGION TODAY...ENHANCING A BAND OF DYNAMIC FORCING
FOR ASCENT ALONG SYSTEM TRACK. AT THE SURFACE...LATEST MESOANALYSIS
INDICATES A WEAK COLD FRONT FROM WRN LAKE SUPERIOR SWWD INTO S-CNTRL
MN. BY MID AFTERNOON...THIS BOUNDARY IS EXPECTED TO BECOME ALIGNED
IN MORE OF AN ENE-WSW FASHION FROM THE UPPER PENINSULA OF MI INTO
NRN WI...AND WILL LIKELY SERVE AS THE FOCUS FOR A FEW STRONG TO
MARGINALLY SEVERE STORMS DURING THE LATTER HALF OF THE DIURNAL
HEATING CYCLE.
12Z OBSERVED SOUNDINGS AND SATELLITE-DERIVED PW IMAGERY SHOW THAT
PRE-FRONTAL AIR MASS IS RELATIVELY DRY WITH BOUNDARY LAYER DEW
POINTS IN THE 50S AND PW VALUES WELL BELOW AN INCH. HOWEVER...
UPSTREAM OBSERVATIONS SUGGEST THAT NOTABLE MID-TROPOSPHERIC COOLING
WILL SPREAD SEWD THROUGH THE REGION TODAY IN CONJUNCTION WITH
ABOVE-MENTIONED SHORT WAVE TROUGH. WHEN COUPLED WITH DAYTIME
HEATING AND SUBSEQUENT STEEPENING OF LOW-LEVEL LAPSE
RATES...PRE-FRONTAL AIR MASS IS EXPECTED TO BECOME MARGINALLY
UNSTABLE WITH MLCAPE APPROACHING 500 J/KG. GIVEN THE PRESENCE OF
40-50 KT OF DEEP WNWLY SHEAR...SETUP WILL FAVOR THE DEVELOPMENT OF
SOME STORM ORGANIZATION WITH A RISK FOR LOCALLY DAMAGING WIND GUSTS
AND MARGINALLY SEVERE HAIL THROUGH THIS EVENING.
A SECONDARY...WEAKER CONFLUENCE BAND DEVELOPING FROM NRN/CNTRL IA TO
ALONG THE WI/IL BORDER MAY ALSO SERVE AS THE FOCUS FOR ISOLATED
STORM FORMATION LATE THIS AFTERNOON INTO EVENING WITHIN A SIMILAR
THERMODYNAMIC AND KINEMATIC ENVIRONMENT. WHILE THIS AREA WILL BE
MORE WEAKLY FORCED THAN ALONG THE PRIMARY FRONT/WIND SHIFT...
ISOLATED OCCURRENCES OF MARGINALLY SEVERE WIND/HAIL WILL BE
POSSIBLE.
..MEAD/ROGERS.. 09/12/2010
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