


Area Forecast Discussion
Issued by NWS Central Illinois
Issued by NWS Central Illinois
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168 FXUS63 KILX 090510 AFDILX Area Forecast Discussion...Updated Aviation National Weather Service Lincoln IL 1210 AM CDT Wed Jul 9 2025 .KEY MESSAGES... - There will be daily chances (20-50% coverage) for showers and storms through the remainder of the week and into the weekend. Storms will generally be favored during the afternoon and evening hours, except for Friday night as a warm front lifts across the region. There is a marginal risk (level 1 of 5) for severe storms this afternoon and evening. - Seasonable heat and humidity will remain in place the remainder of the week into this weekend with afternoon highs generally in the mid to upper 80s and dew points in the 70s. A few spots may tag 90 degrees Friday. && .DISCUSSION... Issued at 135 PM CDT Tue Jul 8 2025 This afternoon, water vapor imagery shows a shortwave trough digging across the Upper Midwest and into the western Great Lakes region while another more subtle shortwave trough is digging across central Missouri. Ahead of these features, broad ascent should be able to tap into an unstable and uncapped air mass in place across central Illinois allowing for thunderstorms to develop. RAP suggests around 2000 J/kg MLCAPE will be present across much of central Illinois this afternoon along with minimal MLCin. Despite the mid level features, deep layer shear is expected to be weak, around 20 kt or less which will keep a more organized severe threat in check. As such, a pulse severe threat with isolated, damaging downburst winds will be the primary concern this afternoon and evening. In addition, 12Z HREF LPMM continues to suggest that some localized pockets of very heavy rain of 3-5 inches will be possible. Wednesday and Thursday will see much of the same across central Illinois with seasonably warm and humid conditions along with weakly forced convective chances which will peak during the afternoon and evening hours. GFS suggests both days will see moderate instability with MLCAPE values around 1500 J/kg and weak deep layer shear of 15-20 kt or less. As such, disorganized and scattered convection with a pulse severe wind threat will again be concerns. Slow storm motions could lead to some additional isolated pockets of very heavy rain. That being said, given the scattered nature of storms it`s important to remember that many areas will not see rain. Friday into Saturday, a more robust shortwave trough is progged to dig across the northern Great Plains into the Upper Midwest with a surface low deepening over the Upper Midwest Friday evening. A warm front will lift across central Illinois as a result and Friday looks to be the best day to see some locations tag 90 degrees again. Shear and instability parameters look to be more supportive of severe weather Friday. GFS advertises around 2500 J/kg MLCAPE with modest capping (40-50 J/kg) and around 30 kt of 0-6km shear. This would support some scattered strong to severe storms during the afternoon, but a greater severe threat may materialize Friday evening as a low level jet develops resulting in upscale growth of storms as they track east along the warm front/instability gradient. There remains a high degree of uncertainty with placement and timing of these storms with the latest GFS a couple hundred miles further east compared to yesterday`s run. Additional storms will be possible Saturday associated with the remnant outflow or trailing cold front, although the faster GFS suggests the threat Saturday may set up just to our east. As timing details are yet to be resolved, Friday and Saturday will bear close watching in the meantime. Frontal boundary will stall near the Ohio Valley late this weekend with Sunday having the best chance to stay dry within the post frontal air mass. Highs will be slightly lower Sunday, topping out in the lower to mid 80s. The frontal boundary lifts back north early next week with daily chances for precip returning as the hot and humid conditions overspread central Illinois once again. Deubelbeiss && .AVIATION... (For the 06z TAFs through 06z Wednesday Night) Issued at 1210 AM CDT Wed Jul 9 2025 Main aviation concerns will be in the first 6-8 hours of the forecast. An area of clearing along the Illinois River is showing signs of developing low stratus and dense fog, with the 05Z observation at KPIA coming in at 1/4SM. The extent of the stratus and fog will depend on how far east the clearing makes it, which may not make it much further than KBMI/KSPI as the stratus takes over. Will keep the IFR/LIFR conditions confined to these three sites, though ceilings below 2000 feet will make it further east with time. Ensemble probabilities show significant improvement in the 14-15Z time frame, with any lingering ceilings after that mainly around 4-5kft. Geelhart && .ILX WATCHES/WARNINGS/ADVISORIES... None. && $$