Subj : MESO: Mesoscale Discussion 0577 To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Thu Apr 20 2023 18:51:16 ACUS11 KWNS 201851 SWOMCD SPC MCD 201850=20 ILZ000-WIZ000-IAZ000-202015- Mesoscale Discussion 0577 NWS Storm Prediction Center Norman OK 0150 PM CDT Thu Apr 20 2023 Areas affected...Far eastern IA...Northern IL...Southern WI Concerning...Severe potential...Tornado Watch likely=20 Valid 201850Z - 202015Z Probability of Watch Issuance...80 percent SUMMARY...Thunderstorms capable of all severe hazards, including tornadoes, are expected to develop across far eastern IA, northern IL, and southern WI this afternoon and evening. DISCUSSION...Recent surface analysis places a low about 45 miles east-northeast of ALO in far northeast IA. A warm front extends eastward from this low across southern IL, while a cold front extends southwestward across eastern IA through northeast, central, and southwest MO. Temperatures have climbed into the upper 60s/low 70s ahead of this front, with dewpoints generally in the upper 50s. Convective inhibition currently remains in place, but is expected to gradually erode as additional heating increases surface temperatures and modest low-level moisture advection persists. This low-level moisture advection may not result in an increase in dewpoints, but should help offset the effects of boundary-layer mixing.=20 Most forecast soundings suggest temperatures in the mid 70s and dewpoints in the upper 50s, combined with modest mid-level cooling/moistening, will sufficiently reduced the convective inhibition enough to allow for thunderstorm initiation. Whether or not these conditions occur across far east IA before the front moves through remains uncertain, given the lower temperatures and greater cloud cover. Once initiation occurs, strong vertical shear should result in organized storms, including some initially discrete supercells. In addition to strong deep-layer flow, DVN VAD has already sampled 50 kt at 1 km AGL. This intense low-level flow supports the potential for supercells capable of producing tornadoes. Large hail and damaging gusts are also possible. Given the linear forcing, uncertainty exists regarding the duration of truly discrete storms, with a trend towards a more cell-in-line mode or even purely linear possible with time. Even so, embedded tornadoes would still be possible, in addition to damaging gusts and isolated hail. ...Mosier/Grams.. 04/20/2023 ....Please see https://urldefense.com/v3/__http://www.spc.noaa.gov__;!!DZ3fj= g!-bp6_6IZ0tj6Cqa_VpFw_C-IYNqSo3Fsg1gQm6T5ErHnrK6M7W22hKIa2O-ouHldquAYsAagL= kBJ4C8RPITrixy6cb4$ for graphic product... ATTN...WFO...LOT...ILX...MKX...DVN...ARX... LAT...LON 42519140 43059106 43599006 43658898 43558834 43148786 41428783 40758955 40559158 42519140=20 =3D =3D =3D To unsubscribe from WX-STORM and you already have a login, go to https://lists.illinois.edu and use the "Unsubscribe" link. Otherwise email Chris Novy at cnovy@cox.net and ask to be removed from WX-STORM. --- SBBSecho 3.14-Linux * Origin: capitolcityonline.net * Telnet/SSH:2022/HTTP (1:2320/105) .