FXUS63 KILX 191727 AFDILX Area Forecast Discussion...Updated Aviation National Weather Service Lincoln IL 1227 PM CDT Tue Aug 19 2025 .KEY MESSAGES... - Hot and humid conditions continue south of I-70 today, where afternoon heat indices of 100 to 105 are expected. A cold front will move through today though, resulting in temperatures returning to near normal for the rest of the work week. - Scattered storms are possible (20-40% chance) through the afternoon, mainly south of I-72/Danville. Isolated strong wind gusts are possible with these storms. && .DISCUSSION... Issued at 242 AM CDT Tue Aug 19 2025 A convective complex was ongoing at 2am/07z, with outflow draped between the I-55 and I-72 corridors and storms located to the immediate west of the OFB. The main forecast change is a faster southward progression of the frontal boundary, due in part to these ongoing storms. The 19.00z guidance suite generally had a good handle on these expectations. While the front will push south of the area today, the air immediately behind the front will still be muggy with dewpoints staying in the mid 70s for much of the day (although slightly lower dewpoint air should start to push in from the north tonight). The expectation is that temps will still warm into the 90s south of I-70 ahead of the front, although the ongoing convection does add a layer of uncertainty as to whether or not these temps are reached. The 19.00z HREF had a 60-80% probability of heat indices reaching at least 100 south of I-70, so opted to hoist one last heat advisory for Effingham to Crawford county and southward. The faster frontal progression should also mean a faster end to precip across the area, with chances ending from NW to SE through the day. For the daytime hours, scattered precip will mainly be focused south of I-72/Danville (20-40%), shifting south of I-70 by early evening, and out of the area by late evening. Similar to previous days, a few storms could produce strong to severe wind gusts owing to strong instability, but weak shear will limit a more organized severe threat. Once this front departs, the rest of the week should be dry (precip chances below 10%) with seasonable temperatures (highs in the mid 80s). While NNE sfc winds on Wed could enhance low-level moisture in east-central IL due to fetch off Lake Michigan, fcst soundings show modest capping in place to stymie any shower activity, at least in our CWA. Dewpoints gradually trend lower and are expected to fall into the mid 60s by Thurs-Fri. *** THIS WEEKEND INTO NEXT WEEK *** There is still a strong signal for below normal temps in the extended as an upper wave pushes across the northern Great Lakes and sends a cold front through IL late Fri or during the day Sat. Still think there is a some precip potential with this front, although it's unlikely to amount to much as synoptic forcing aloft will be quite limited and the best instability trails behind the front. Blended guidance still has PoPs at just 10%, with the low values likely due in part to timing differences with the front, as well as placement differences and limited precip coverage. This post-frontal airmass should provide an early taste of fall, with high temperatures likely falling into the 70s. The NBM has a 20- 40% chance for highs above 80F north of I-70 on Sun, and just a 10- 30% chance area-wide next Mon. The cooler temps will also be accompanied by lower dewpoints, with the model blend dropping dewpoints into the mid 50s. Erwin && .AVIATION... (For the 18z TAFs through 18z Wednesday Afternoon) Issued at 1223 PM CDT Tue Aug 19 2025 A cold front has pushed south of the terminals leaving a modest northerly breeze in its wake. MVFR ceilings are in place near and north of the I-74 corridor early this afternoon, but are expected to lift/scatter to VFR over the next few hours. MVFR ceilings may redevelop as diurnal cumulus develops mid to late Wednesday morning, especially along the I-74 corridor. Deubelbeiss && .ILX WATCHES/WARNINGS/ADVISORIES... Heat Advisory until 7 PM CDT this evening for ILZ066>068-071>073. && $$