SPC AC 211233
DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0733 AM CDT MON MAR 21 2011
VALID 211300Z - 221200Z
...THERE IS A SLGT RISK OF SVR TSTMS THIS EVENING INTO TONIGHT FOR
E/NE NEB...WRN/NRN IA...SE SD...SW MN...
...THERE IS A SLGT RISK OF SVR TSTMS THIS AFTERNOON/EVENING FOR THE
SE OH/WV AREA...
...SYNOPSIS...
THE DEEP MIDLEVEL TROUGH OVER CA THIS MORNING WILL EJECT NEWD OVER
THE CENTRAL ROCKIES TO THE HIGH PLAINS BY TUESDAY MORNING. AN
ASSOCIATED LEE CYCLONE IS EXPECTED TO FORM TODAY INVOF NE CO...AND
THEN DEVELOP EWD ALONG A WARM FRONT THAT WILL MOVE NWD FROM KS/MO
INTO NEB/IA.
...MID MO VALLEY AREA THIS EVENING THROUGH TONIGHT...
MID-UPPER 50S BOUNDARY LAYER DEWPOINTS WILL SPREAD NWD WITH THE WARM
FRONT FROM I-70 THIS MORNING IN KS/MO TO JUST S OF I-80 IN NEB/IA BY
LATE EVENING. THE MOISTURE ADVECTION WILL OCCUR BENEATH STEEP
MIDLEVEL LAPSE RATES...AND WILL COMBINE WITH STRONG DAYTIME HEATING
TO SUPPORT LATE AFTERNOON MLCAPE NEAR 1500 J/KG ALONG AND S OF THE
WARM FRONT. HOWEVER...SURFACE-BASED THUNDERSTORM DEVELOPMENT
APPEARS QUESTIONABLE ALONG THE WARM FRONT THROUGH THE DAYLIGHT HOURS
AS A RESULT OF SLOWLY WARMING TEMPERATURES ABOVE THE BOUNDARY LAYER
AND LINGERING CONVECTIVE INHIBITION. IF A SURFACE-BASED STORM
MANAGES TO FORM THIS EVENING ALONG THE WARM FRONT...THE ENVIRONMENT
WILL SUPPORT SUPERCELLS CAPABLE OF PRODUCING LARGE HAIL AND PERHAPS
A TORNADO.
THE MORE PROBABLE SCENARIO WILL BE FOR ELEVATED THUNDERSTORMS TO
FORM TONIGHT IN THE ZONE OF WAA N OF THE WARM FRONT ACROSS
IA/NEB/SD/SRN MN...AS THE LLJ STRENGTHENS AND PARCELS REACH
SATURATION ON THE NE EDGE OF THE EML PLUME. STEEP MIDLEVEL LAPSE
RATES...COOL MIDLEVEL TEMPERATURES...MUCAPE IN EXCESS OF 1000
J/KG...AND EFFECTIVE BULK SHEAR AOA 40 KT COULD SUPPORT A COUPLE OF
ELEVATED SUPERCELLS WITH THE POTENTIAL TO PRODUCE LARGE HAIL.
...SE OH/WV AREA THIS AFTERNOON/EVENING...
AN INITIAL BELT OF ELEVATED THUNDERSTORMS IS MOVING ESEWD OVER
VA/MD/DE AS A SHORTWAVE TROUGH MOVES OVER THE LOWER GREAT LAKES. IN
THE WAKE OF THIS MIDLEVEL TROUGH AND AN ASSOCIATED SURFACE
CYCLONE...A SLOW-MOVING E-W ORIENTED FRONT WILL PERSIST THROUGH THE
EVENING ACROSS THE OH VALLEY. BOUNDARY LAYER DEWPOINTS IN THE 50S
AND AFTERNOON SURFACE TEMPERATURES IN THE 70S WILL CONTRIBUTE TO
MLCAPE VALUES NEAR 500 J/KG WITH MINIMAL CONVECTIVE INHIBITION. A
SECONDARY MIDLEVEL SPEED MAX IS FORECAST TO MOVE FROM IA THIS
MORNING TO OH/WV LATE THIS AFTERNOON...WHICH WILL COMBINE WITH
DAYTIME HEATING AND WEAK ASCENT ALONG THE FRONT TO SUPPORT
THUNDERSTORM DEVELOPMENT BY LATE AFTERNOON. VERTICAL SHEAR WILL BE
FAVORABLE FOR SUPERCELLS...AND THE STRONGER STORMS COULD PRODUCE
DAMAGING GUSTS AND LARGE HAIL.
..THOMPSON/GRAMS.. 03/21/2011
CLICK TO GET WUUS01 PTSDY1 PRODUCT
NOTE: THE NEXT DAY 1 OUTLOOK IS SCHEDULED BY 1630Z
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