<pre>ACUS11 KWNS 031821 SWOMCD
Mesoscale Discussion 1418 NWS Storm Prediction Center Norman OK 0120 PM CDT Mon Sep 03 2018
Areas affected…Portions of central/eastern IA…northern IL…and far southern WI
Concerning…Severe potential…Watch unlikely
Valid 031820Z – 032045Z
Probability of Watch Issuance…5 percent
SUMMARY…A marginal strong/gusty wind threat should continue through the rest of the afternoon. Watch issuance is not expected.
DISCUSSION…18Z surface analysis shows a convectively reinforced boundary extending from far southern WI into northern IL and central/eastern IA. Water vapor satellite imagery shows a low-amplitude shortwave trough moving over IA this afternoon, and scattered thunderstorms have already formed across northern IL ahead of this feature. Relatively strong diurnal heating has occurred to the south of the boundary/front, with temperatures in the mid 80s to lower 90s away from ongoing convection. The low-level airmass is also very moist per 12Z soundings from KDVN and KILX and recent surface observations. Even though mid-level lapse rates remain poor, MLCAPE of 1500-2500 J/kg will likely exist through peak heating along and south of the boundary. VWPs from the KLOT and KDVN radars show modestly strengthening southwesterly flow through mid levels, which is resulting in around 25-35 kt of effective bulk shear across the warm sector. This shear coupled with steepening low-level lapse rates should be enough to support occasional multicells capable of producing mainly isolated strong wind gusts up to 50-60 mph as they move east-northeastward. With somewhat stronger mid-level winds expected to remain just to the north of the boundary through the rest of the afternoon, the overall severe threat will likely remain too isolated/marginal to justify watch issuance.
..Gleason/Guyer.. 09/03/2018
…Please see www.spc.noaa.gov for graphic product…
ATTN…WFO…LOT…ILX…MKX…DVN…ARX…DMX…
LAT…LON 41579255 41879225 42539058 42838772 42528774 42228775
41938762 41618754 41198759 40759043 40879161 41139244 41579255 </pre>
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