858 FXUS63 KILX 120505 AFDILX Area Forecast Discussion...Updated Aviation National Weather Service Lincoln IL 1205 AM CDT Tue Aug 12 2025 .KEY MESSAGES... - Daily chances for showers and thunderstorms will continue through midweek with the highest chances on Tuesday afternoon (40-60%) as a cold front slowly works through the area. - Seasonable temperatures are expected this week with things turning hot by the weekend. There is a 30-50% chance for heat indices over 100 degrees Friday through Sunday with the higher probabilities in west-central and southern Illinois. && .DISCUSSION... Issued at 149 PM CDT Mon Aug 11 2025 ...Daily Precipitation Chances Through Midweek... Upper analysis shows a large upper trough positioned over the north- central CONUS/south-central Canada with a blocking high over the Atlantic Ocean. At the surface, ridging in place from the Mid- Atlantic states westward into the middle Mississippi Valley. A nearly stationary front remains positioned northwest of here and stretches from central Wisconsin into south-central Iowa. Widely scattered showers and thunderstorms will be common once again today, especially this afternoon into early evening with the focus being near/west of I-55. Storms have the potential to develop fairly quickly due to strong instability, but will struggle to remain organized under a weakly sheared environment. Similar to previous days, slow storm motions and high PWATs will lead to the threat for locally heavy rainfall with any storms. By Tuesday, a shortwave trough will allow the parent trough to begin pivoting eastward into the Great Lakes Region and push the previously mentioned front into central Illinois as a cold front. This will support higher precipitation chances across the area (40- 60%), especially during the peak heating of the afternoon into early evening hours. Strong instability and slightly better shear with the front may lead to the development of few stronger thunderstorms. However, better chances for severe storms will be confined north of here, closer to the upper wave. Storm motions will once again be slow on Tuesday with even higher PWATs due to dewpoints pooling near the front. Because of this, a threat for heavy rainfall/localized flooding will once again be a concern, especially where heavy rain has fallen in previous days. The front will slowly exit the area later Wednesday, with some lingering shower/storm chances continuing in southeast parts of the state through Wednesday afternoon. ...Drier, Then Heating Up... A drier period looks to take shape for the end of the week into the start of the weekend as flow aloft transitions to upper ridging. Forecast guidance depicts a few overnight MCS`s working across the Northern Plains into the Upper Mississippi Valley late this week into the weekend. These look to stay north of us with our next chance for rain holding off until later in the weekend or early next week tied to a cold front. Until then, temperatures will gradually climb underneath the building ridge. High temperatures Friday through the weekend peaking in the upper 80s to low 90s with heat indices flirting with Heat Advisory criteria (105 degrees) on Saturday and Sunday. There is 30-50% chance heat indices rise above 100 degrees Friday through Sunday, with the higher probabilities being in west-central and southern parts of the state. NMA && .AVIATION... (For the 06z TAFs through 06z Tuesday Night) Issued at 1205 AM CDT Tue Aug 12 2025 Batch of convection currently over far northeast MO will shift northeast through early morning, possibly clipping KPIA. Added a PROB30 group to account for this 08-12z. Beyond that, a line of thunderstorms is expected to develop this afternoon along a slow moving cold front. Most convective allowing guidance shows initiation near the I-55 corridor mid afternoon, gradually advancing east through early evening. MVFR to IFR conditions will be associated with any storms, otherwise VFR will dominate the forecast. 25 && .ILX WATCHES/WARNINGS/ADVISORIES... None. && $$