SPC AC 181244
DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0744 AM CDT MON APR 18 2011
VALID 181300Z - 191200Z
...NO SVR TSTM AREAS FORECAST...
...SYNOPSIS...
ZONAL FLOW NOW PRESENT ACROSS THE LWR 48 WILL UNDERGO GRADUAL
AMPLIFICATION THIS PERIOD AS A TROUGH DEEPENS SEWD ACROSS THE WRN
U.S. AND HEIGHTS REBOUND OVER THE SOUTHEAST.
AT LWR LVLS...AN ELONGATED LEE LOW LIKELY WILL PERSIST TODAY FROM
ERN CO SE INTO WRN OK. THE LOW MAY STRENGTHEN SOMEWHAT TONIGHT IN
RESPONSE TO AMPLIFYING TROUGH IN THE WEST. FRONTAL ZONE EXTENDING
ENE FROM THE LOW INTO THE OH VLY SHOULD INTENSIFY THROUGH THE
PERIOD...AND SERVE AS A FOCUS FOR STORM DEVELOPMENT...ESPECIALLY
THIS EVE AND TONIGHT.
...NE KS E INTO THE MID MS/LWR OH VLYS...
SSWLY LOW-LVL FLOW HAS BECOME ESTABLISHED OVER THE S CNTRL U.S... E
OF CO/OK LEE CYCLONE. THIS FLOW SHOULD PERSIST THROUGH THE
DAY...ALLOWING INCREASINGLY MOISTURE-RICH AIR /PW AOA 1.25 INCHES/
TO SPREAD NNEWD TO VICINITY OF STRENGTHENING FRONT OVER
KS/MO/IL/IND. AT THE SAME TIME...HOWEVER...WSWLY MID-LVL FLOW WILL
MAINTAIN/EXPAND EML ENEWD ACROSS THE REGION.
CAPPING BY THE EML SHOULD PROHIBIT DEEP CONVECTIVE DEVELOPMENT OVER
MOST OF REGION S OF THE FRONT THROUGH THE PERIOD...
ALTHOUGH A SMALL WINDOW OF OPPORTUNITY WILL EXIST FOR
STORM OR TWO S OF THE BOUNDARY THIS AFTN OVER SRN/ERN MO.
INCREASING CINH AND LIMITED MOISTURE AVAILABILITY ALSO SHOULD
PROHIBIT STORM DEVELOPMENT ALONG AND N OF THE FRONT THROUGH THE DAY.
BUT BY THIS EVE/EARLY TONIGHT...COMBINATION OF INCREASING MOISTURE
AND NOCTURNAL STRENGTHENING OF LLJ EXPECTED TO FOSTER STORM
DEVELOPMENT ALONG AND N OF THE BOUNDARY...ESPECIALLY FROM CNTRL MO
INTO CNTRL/SRN PARTS OF IL AND IND.
ALTHOUGH MOST OF THE STORMS SHOULD BE ELEVATED...SUFFICIENT CLOUD
LAYER CAPE/SHEAR MAY DEVELOP TO FOSTER A THREAT FOR SVR
HAIL...ESPECIALLY TONIGHT THROUGH EARLY TUE. THERE ALSO WILL EXIST
A LOW PROBABILISTIC THREAT FOR SOME OF THE STORMS TO BECOME
SURFACE-BASED LATE TONIGHT OR EARLY OVER SRN IL AS MOISTURE
CONTINUES TO INCREASE OVER REGION...AND THE ELEVATED STORMS BEGIN TO
PRODUCE EWD-MOVING COLD POOLS. THIS ACTIVITY COULD YIELD LOCALLY
DMGG WIND. AT THE SAME TIME...OTHER STORMS MAY FORM WWD INTO PARTS
OF KS.
SATELLITE AND MODEL DATA DO NOT SHOW AN IDENTIFIABLE UPR LVL IMPULSE
TO ENHANCE STORM DEVELOPMENT ALONG AND S OF THE FRONT. FOR THIS
REASON...AND BECAUSE LOW-LVL MOISTURE IS NOT YET IN PLACE ALONG THE
BOUNDARY...HAVE OPTED NOT TO DEPICT A SLIGHT RISK AREA ATTM.
HOWEVER...PARTS OF THE LOW PROBABILISTIC CORRIDORS DEPICTED MAY
REQUIRE UPGRADE TO SLIGHT RISK IN LATER OUTLOOKS SHOULD IT APPEAR
THAT UPLIFT WILL BE STRONGER AND MORE FOCUSED THAN IS NOW EXPECTED.
..CORFIDI/HURLBUT.. 04/18/2011
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NOTE: THE NEXT DAY 1 OUTLOOK IS SCHEDULED BY 1630Z
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