AREAS AFFECTED...CNTRL/ERN IA...NRN/CNTRL IL...NWRN IND
CONCERNING...SEVERE THUNDERSTORM WATCH 437...
VALID 300033Z - 300200Z
THE SEVERE WEATHER THREAT FOR SEVERE THUNDERSTORM WATCH 437
CONTINUES.
SUMMARY...THE SVR THREAT ACROSS WW 437 WILL LIKELY HAVE DIMINISHED
BY THE SCHEDULED EXPIRATION TIME OF 02Z. REMAINING VALID PORTIONS OF
THE WW BEHIND ERN/SRN-FLANKING OUTFLOW BOUNDARY MAY BE CANCELLED
PRIOR TO EXPIRATION TIME. AREAS DOWNSTREAM ACROSS NRN/CNTRL IL INTO
NWRN IND WILL CONTINUE TO BE MONITORED FOR ADDITIONAL WW ISSUANCE
THROUGH THE NIGHT.
DISCUSSION...CONVECTION HAS BECOME LARGELY DISORGANIZED ACROSS WW
437 DURING THE LAST COUPLE OF HOURS...AFTER OUTFLOW FROM THE SMALL
SVR COMPLEX THAT CROSSED THE CEDAR RAPIDS AREA SURGED AHEAD OF
PARENT CONVECTION. THIS OUTFLOW BOUNDARY NOW EXTENDS WSWWD FROM 35
ENE MOLINE IL TO 45 E LAMONI IA. ISOLATED ELEVATED CONVECTION WITHIN
30 MILES N/W OF THIS BOUNDARY MAY POSE A MARGINAL SVR
THREAT...THOUGH THIS THREAT MAY SUBSIDE AS OUTFLOW SURGES AHEAD OF
THE CONVECTION. FARTHER WEST...WEAK ISENTROPIC ASCENT ATOP THE COLD
POOL IS SUPPORTING SCATTERED ELEVATED STORMS INTO WRN PARTS OF THE
WW AREA...AND AN ISOLATED MARGINALLY SVR HAIL THREAT CANNOT BE RULED
OUT. OVERALL...HOWEVER...THIS LOOSELY ORGANIZED CONVECTIVE SYSTEM
APPEARS TO BE EXHIBITING MORE ANAFRONTAL CHARACTERISTICS...WITH A
DIMINISHING SVR THREAT ANTICIPATED THROUGH 02Z.
MEANWHILE FOR DOWNSTREAM AREAS...A CONVECTIVELY AUGMENTED BOUNDARY
IS ADVANCING NEWD ACROSS IL INTO IND...WITH VERY UNSTABLE AIR
OBSERVED TO ITS SOUTH -- REF. CENTRAL ILLINOIS 00Z RAOB FEATURING
3260 J/KG OF MLCAPE /THOUGH WITH SUBSTANTIAL DRY AIR ALOFT/.
HOWEVER...MODEST MIXED-LAYER INHIBITION IS PRESENT...AND IS FORECAST
TO INCREASE THROUGH THE NIGHT OWING TO NOCTURNAL/DIABATIC COOLING.
REGARDLESS...WITH A NOCTURNAL INCREASE IN WAA COMMENSURATE WITH
STRENGTHENING WSWLY 700-850 MB FLOW/STRENGTHENING BOUNDARY-LAYER
WIND MAXIMUM...ADDITIONAL STORMS -- LIKELY INITIALLY ELEVATED --
MIGHT DEVELOP ACROSS PARTS OF IL/IND. SHOULD A SUFFICIENT NUMBER OF
STORMS MATERIALIZE WITH COLD POOL DEVELOPMENT/UPSCALE GROWTH
ENSUING...A MORE WIDESPREAD SVR THREAT WARRANTING WW ISSUANCE COULD
CONDITIONALLY DEVELOP LATER IN THE NIGHT DOWNSTREAM OF WW 437
PROVIDED 30-45 KT OF EFFECTIVE BULK SHEAR. HOWEVER...LARGE
UNCERTAINTY IN THIS THREAT REMAINS OWING TO THE AFOREMENTIONED
INHIBITION/LACK OF STRONGER DEEP FORCING FOR ASCENT.
..COHEN.. 06/30/2012
...PLEASE SEE WWW.SPC.NOAA.GOV FOR GRAPHIC PRODUCT...
ATTN...WFO...IND...LOT...ILX...DVN...DMX...
LAT...LON 42319237 42309060 42058897 41618777 41038739 40288749
39948786 39808823 39778889 39888922 40579071 40709213
41069314 41819327 42319237
