


Area Forecast Discussion
Issued by NWS Chicago, IL
Issued by NWS Chicago, IL
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103 FXUS63 KLOT 162339 AFDLOT Area Forecast Discussion National Weather Service Chicago/Romeoville, IL 639 PM CDT Thu Oct 16 2025 .KEY MESSAGES... - Periods of showers and possible thunderstorms expected late Friday night through Sunday morning. - Windy and much cooler Sunday. - Another period of rain possible towards the middle of next week. && .DISCUSSION... Issued at 308 PM CDT Thu Oct 16 2025 Through Friday: A surface high continues to reside over the Great Lakes this afternoon which has maintained a warm and partly sunny day for us. However, there has been an area of showers moving across northeast IA and southern WI associated with a plume of warm advection and mid-level moisture. While these showers are expected to meander across south-central WI this evening and overnight, some modest moisture may ooze into far northern and northeast IL and result in a brief period of light showers and/or sprinkles this evening and overnight. For now have opted to maintain the 20% POPs for areas near the IL-WI line and near the IL lake shore but suspect most will remain dry. The surface high and the associated mid-level ridge will begin to get pushed eastward on Friday as the broad trough currently over the Rockies ejects into the Midwest. Though, the lingering subsidence will support one more dry and warm afternoon for us with highs forecast to top out in the mid to upper 70s areawide (some spots could even tag 80 near I-39). Winds will be breezy however, as the tightening pressure gradient generates some 20-25 mph gusts Friday afternoon. Friday night through Thursday: The weather will turn more active as we head into the weekend as the aforementioned broad trough continues to move east and phase with a secondary shortwave (currently off the coast of the Pacific Northwest) on Saturday. At the same time, a cold front is expected to be draped from the northern Great Lakes to the south-central Plains and begin to get pushed east by the trough Friday night. Locally the front should begin to arrive after midnight Friday night and then slowly meander across northern IL and northwest IN on Saturday. Therefore, showers and perhaps even a few thunderstorms are expected to develop across the area Friday night through Saturday. While forecast soundings continue to show very limited instability present on Saturday (around 300-500 J/kg), the strong forcing with the front and trough in addition to the 35-45 kts of effective shear may be sufficient to support a stronger storm or two mainly across eastern IL and northwest IN Saturday afternoon/evening where the greatest instability is forecast. If a stronger storm does materialize it seems the main threat would be gusty winds, but there is some indication that perhaps an isolated spin-up could occur. That said, the Storm Prediction Center does have portions of our south and southeast CWA in a marginal (level 1 of 5) risk for Saturday but given the limited instability still think the severe threat is rather low at this time. Heading into Saturday night, a surface low is forecast to develop somewhere in the Great Lakes region as the phasing trough pivots into the region. Initially it looked as if this developing surface low would occur over northeast IL and northwest IN, but guidance has trended away from that solution and now has the low forming over WI and Lower MI. While the overall result from the surface low will be more or less the same for our area (continuing rain chances Saturday night into Sunday morning), the low track will ultimately dictate where the heaviest rainfall axis occurs and how strong the winds are. That said, guidance remains in fairly good agreement that northern IL and northwest IN should see around an inch or so of rainfall in total (from Friday night through Sunday morning) with some spots possibly picking up close to 2 inches if they get under the heavier axis. Since these rain amounts should fall over a 36-48 hour period the risk for flooding appears lows especially given the antecedent dry conditions. Though, if a stronger storm trains over an area than some localized ponding could be seen. In addition to the rain, winds will become gusty on Sunday as the low deepens with gusts in the 30-35 mph range likely and localized gusts near 40 mph a possibility if the deeper low solutions verify. The low and associated trough are forecast to pivot east of the area Sunday afternoon which should allow drier conditions to close out the weekend and kick off next week. Though, temperatures behind this system will be more typical for late October with highs in the upper 50s to lower 60s forecast for Sunday and low to mid-60s for Monday. Another storm system looks to pivot through the area during the Monday night into Wednesday time frame but uncertainty remains as to how strong the system will be and its exact track. For now have maintained the 20-40% POPs offered by the NBM but suspect further refinement will be needed over the coming days. Regardless, it does look as if more seasonable October temperatures will persist through much of next week. Yack && .AVIATION /00Z TAFS THROUGH 06Z SATURDAY/... Issued at 639 PM CDT Thu Oct 16 2025 VFR conditions are forecast through the TAF period. ESE winds will gradually turn SSE through the evening remaining generally light (around 5-10 kt). Winds are then expected to continue veering to the SSW Friday morning, though confidence on the exact timing remains on the lower-end and could occur as early as 12-13Z. Opted to hang on to the inherited 14Z timing for now. Winds will then steadily increase through the rest of the morning hours with gusts in the lower 20kt range expected by the afternoon. Petr && .LOT WATCHES/WARNINGS/ADVISORIES... IL...None. IN...None. LM...None. && $$ Visit us at weather.gov/chicago