


Area Forecast Discussion
Issued by NWS Central Illinois
Issued by NWS Central Illinois
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410 FXUS63 KILX 172306 AFDILX Area Forecast Discussion...Updated Aviation National Weather Service Lincoln IL 606 PM CDT Fri Oct 17 2025 .KEY MESSAGES... - Showers and storms producing locally heavy rain will be possible Saturday afternoon and evening, particularly across east central and southeast Illinois, where isolated rainfall totals could exceed 1 to 2 inches in spots. - The risk for severe thunderstorms remains low, but a 5-14% chance of severe weather is possible Saturday afternoon/evening across east central and southeast Illinois. - Strong northwest winds with gusts of 30-40 mph are likely on Sunday, and a 30-50% chance exists for isolated gusts to reach or exceed 45 mph. && .DISCUSSION... Issued at 138 PM CDT Fri Oct 17 2025 This afternoon, high pressure stretches along the eastern seaboard while low pressure is moving east across the Canadian Prairies. Modest southerly flow across central Illinois ahead of the low and attendant cold front along with increasing cloud cover will result in mild conditions overnight with lows in the low to mid 60s. Showers and thunderstorms are expected to increase in coverage across Iowa/Missouri late this afternoon into the evening, then will track into west central Illinois late tonight. Convection will likely be in a decaying phase owing to the poor diurnal timing. Through 12 UTC / 7 AM CDT Saturday morning, precip is expected to advance as far east as the Illinois River to I-55 corridor. The initial wave of precip will continue to track east across the state through the remainder of the morning and early afternoon Saturday, but expect precip to expand in coverage late afternoon and evening as a pair of phasing mid level shortwaves push across the mid Mississippi Valley. PWats increase up to around 1.5 inches ahead of these features, which is above the 90th percentile for GEFS re-forecasts for mid October. In addition to the high moisture content, mean cloud-bearing flow (850-300mb) looks to be fairly parallel to the surface front which could result in some training of storms. Some locally heavy rain could develop as a result. HREF LPMM indicates some swaths of 1 to 2 inches (locally higher) of rain will be possible, especially in portions of SE and east central Illinois where precip timing better aligns with peak heating. The severe threat remains a bit uncertain Saturday, mainly due to concerns around the amount of instability. GFS advertises only modest instability Saturday afternoon with MLCAPE values less than 1000 J/kg. If we do realize the instability, shear will be favorable to support a severe weather threat. 0-6km shear vectors are expected to increase to around 30-40 kt in magnitude with 15-25 kt in the lowest 0-1km. Poor lapse rates resulting in "skinny" CAPE profiles do not appear overly supportive of hail, and only marginally supportive of damaging wind gusts. Wouldn`t be surprised to see the severe outlook for Saturday be further trimmed from the northwest with additional updates, but a 5% risk seems reasonable still, especially across east central and southeast Illinois. In response to the aforementioned shortwaves, surface low will deepen to our east Saturday night into Sunday resulting in a tight pressure gradient and 2-4mb/3hr pressure rises overspreading central Illinois in its wake Sunday. Moderately strong winds will be the result Sunday. Cold-air-advection driven steep low level lapse rates will also be in place allowing mixing down of winds aloft in the 35-40 kt range Sunday afternoon. A few wind gusts reaching or exceeding wind advisory criteria (45 mph) cannot be ruled out (30-50% probability from the NBM roughly along east of I-55). The breezy northwest wind will keep temperatures suppressed through the day Sunday with highs struggling to reach the low 60s. Another upper level disturbance, at times a closed upper low, is expected to dig across the Great Lakes Monday night into Tuesday. Strong warm air advection ahead of this system will briefly drive temps back up to around 70 degrees Monday afternoon. A few showers are possible within the mid level WAA Monday evening, followed by additional precip chances Tuesday as cold air advection again drives steep low level lapse rates and weak diurnal instability. The ECMWF is most bullish on precip chances as far south as central Illinois, while the GFS and GEM favor precip mainly to our north. Deubelbeiss && .AVIATION... (For the 00z TAFs through 00z Saturday Evening) Issued at 606 PM CDT Fri Oct 17 2025 Lowering/thickening high to mid level clouds and south winds around 10 kt will prevail over the central IL terminals this evening. By late tonight, scattered showers/storms associated with a pre-frontal trough will begin to move into central IL, gradually shifting east through Saturday morning. TSRA coverage is expected to be fairly low so kept the thunder mention to PROB30. Most CAMs show a general lull in activity late morning through much of the afternoon. However during this period ceilings will be lowering, with MVFR becoming more likely by early evening. More widespread SHRA with embedded TSRA are likely to move in from the south just beyond 00z/Sunday, when low pressure approaches and deepens across the region. 25 && .ILX WATCHES/WARNINGS/ADVISORIES... None. && $$