[SWODY1] SWODY1

[Severe Weather Outlook Day 1]

ACUS01 KWNS 030541
SWODY1
SPC AC 030540

DAY 1 CONVECTIVE OUTLOOK  
NWS STORM PREDICTION CENTER NORMAN OK
1240 AM CDT SUN SEP 03 2006

VALID 031200Z - 041200Z

...THERE IS A SLGT RISK OF SVR TSTMS THIS AFTERNOON AND EVENING OVER
THE MID MO VALLEY...

...SYNOPSIS...

COMPLEX BLOCKING PATTERN WILL CONTINUE THIS PERIOD WITH THE PRIMARY
FEATURES BEING AN AMPLIFIED RIDGE FROM THE SWRN DESERTS INTO THE
CANADIAN PRAIRIES AND A MID TO UPPER-LEVEL LOW WHICH WILL TRANSLATE
SLOWLY SEWD THROUGH THE MIDDLE AND LOWER MO VALLEY.  IN THE
LOW-LEVELS...SURFACE LOW ATTENDANT TO THE UPPER LOW WILL
CONCURRENTLY DEVELOP SEWD FROM SERN SD ALONG THE MO VALLEY OF ERN
NEB/WRN IA.  ATTENDANT FRONTAL BOUNDARY /THE NRN EXTENT OF WHICH
BEING OCCLUDED AND PRECEDING SURFACE LOW/ WILL GENERALLY EXTEND FROM
ERN IA/WRN IL SWWD INTO SERN OK/NRN TX BY AFTERNOON.

...MID MO VALLEY...

IT APPEARS DEEP...MOIST CONVECTION WILL BECOME FOCUSED IN TWO AREAS
THIS AFTERNOON...1) ALONG OCCLUDED FRONTAL ZONE FROM SERN MN/WRN WI
SWD INTO ERN IA AND WRN IL...AND 2) INVOF THE SURFACE AND UPPER LOWS
OVER ERN NEB/WRN IA.  THE GREATER POTENTIAL FOR SEVERE STORMS
CAPABLE OF MAINLY SEVERE HAIL IS FORECAST TO EXIST WITH THE LATTER.

03/00Z UPPER AIR OBSERVATIONS INDICATE THAT A POCKET OF RELATIVELY
COLD MID-LEVEL TEMPERATURES /I.E. -18 TO -20 C AT 500 MB/ ARE
ASSOCIATED WITH THE UPPER LOW. DAYTIME HEATING COUPLED WITH THESE
COLD TEMPERATURES WILL RESULT IN THE DEVELOPMENT OF STEEP LOW TO
MID-LEVEL LAPSE RATES WITH AFTERNOON SBCAPES INCREASING TO AROUND
1000 J/KG.

EXPECT TSTMS TO INCREASE IN COVERAGE THROUGH THE AFTERNOON ACROSS
ERN NEB/WRN IA...FOCUSED LARGELY BY LOW-LEVEL CONVERGENCE INVOF
ATTENDANT SURFACE LOW. WHILE STORMS SHOULD REMAIN RELATIVELY
LOW-TOPPED...STRENGTHENING MID AND HIGH-LEVEL FLOW AROUND SRN
PERIPHERY OF UPPER LOW MAY BE SUFFICIENT TO SUPPORT SOME UPDRAFT
ROTATION WITH SEVERE HAIL BEING THE PRIMARY SEVERE THREAT. 
HOWEVER...SHOULD STRONG DIABATIC HEATING OCCUR NEAR SURFACE
LOW...POTENTIAL WILL EXIST FOR A BRIEF TORNADO OWING TO THE
CO-LOCATION OF STEEP LOW-LEVEL LAPSE RATES AND CONCENTRATED ZONE OF
VORTICITY.

...LOWER CO VALLEY...

LOW-LEVEL MOISTURE SURGE FROM THE GULF OF CA WILL BE MAINTAINED
THROUGH THE PERIOD...SUPPORTING DEWPOINTS IN THE 60S.  THIS MOISTURE
IN CONJUNCTION WITH ANTICIPATED STRONG DAYTIME HEATING WILL ONCE
AGAIN CONTRIBUTE TO POCKETS OF MODERATE INSTABILITY LATER TODAY WITH
SBCAPES OF 1000-1500 J/KG.  FORECAST SOUNDINGS SUGGEST THAT VERTICAL
SHEAR WILL REMAIN RELATIVELY WEAK...HOWEVER THE STEEP LOW-LEVEL
LAPSE RATES AND MODERATE INSTABILITY SHOULD BE SUPPORTIVE OF
ISOLATED STRONG TO SEVERE STORMS CAPABLE OF MAINLY LOCALLY DAMAGING
WIND GUSTS.

..MEAD/GRAMS.. 09/03/2006