Marine Weather and Tide Forecast for Fox Lake, IL

DISCUSSION
Issued at 334 AM CDT Fri Apr 17 2026

Mesoscale high pressure centered over southern Lake Michigan is pushing a bank of fog and low stratus inland off the lake early this morning. Half mile or less visibilities are spreading around the interior Chicago metro area and farther west up near the WI state line. A Dense Fog Advisory is in effect through 10AM around the northeastern quadrant or so of our CWA
Southerly winds will ramp up quickly beyond sunrise as the high moves away and pressure falls begin ahead of an advancing low.
Strong warm advection ahead of the wave will allow for highs in the lower 80s around most of the area this afternoon. Relatively dry BL air today will promote deep mixing and encourage strong southerly winds with gusts to 30 to 35 mph, occasionally near 40 mph, during the afternoon.

Main focus for the forecast is the potential for severe thunderstorms this evening with the passage of a strongly-forced cold front. As a large upper trough scoots eastward from the Rockies into the central Plains, an EML will get advected into the region. The heart of the EML will focus just west of the Mississippi, but forecast soundings still depict a deep column of low to mid level lapse rates greater than 8 K/km allowing for anywhere from 1,500 to 3,000 Joules of afternoon MUCAPE. It's not entirely clear how much capping we'll maintain into the afternoon with some camps suggesting we may be largely uncapped.
However, dry low level air and weak ambient forcing in the open warm sector should do well to inhibit freely convecting storms even in a weakly capped environment. Only a couple of CAMs resolve isolated convection immediately ahead of the storm's cold front later in the day, but chances for free convection in the warm sector throughout the afternoon are seemingly low.
Should any afternoon free convection develop, they would have the ingredients necessary to quickly become severe and large hail and damaging winds would be the primary threat. Can't rule out a tornado threat with anything that might spawn during the afternoon either given elongating, looping low level hodographs, but high LCLs and low instability through the low levels are not favorable for tornadogenesis.

The primary window of concern for severe convection is this evening as the aforementioned low's cold front gets dragged across the area. A cluster of supercells is favored to form along the front across eastern IA during the afternoon before congealing into a strongly- forced line of convection across northern IL during the evening. Storms look to approach the I-39 corridor during the early evening and exit to the east early in the overnight, possibly with additional showers lingering late into the night. Guidance generally depicts storms on a weakening trend as they move into a thermodynamically less favorable environment across northern IL (and worsening with time via diurnal cooling). However, the environment will remain plenty supportive of strong to severe convection across our CWA, especially given the strong dynamic forcing at play with the front. The biggest concern with storms tomorrow is the damaging wind threat which recently prompted the Storm Prediction Center to drag the Day 1 Enhanced Risk (Level 3 of 5) east to the Indiana state line, including the city of the Chicago. BL CIN will be increasing through the evening, but can't rule out a spin up tornado threat along this line either given the strong forced ascent and impressive low level wind field.

Another big concern with rain and storms later today is the heavy rain and flooding threat. Area soils are especially moist from recent rains making them more susceptible to flooding and many local rivers and creeks, especially the Rock, Fox, and Des Plaines, are already well into flood stage. Near or over 1.5" of PWAT amid deep dynamic forcing and instability favors periods of heavy rainfall with the frontal passage. There is also a growing signal in model guidance for a shortwave impulse to track across the area and provide an additional period of moderate to heavy rain into the overnight in the wake of line of storms. Can't say for certain where this wave will track, but guidance likes near the I-80 corridor and near and south of I-80 is where the highest QPF is generally favored. Probs for 0.5" of rain from last evening's HRRR range from 60 to nearly 100% around the entire CWA and you won't find a piece of recent deterministic guidance without a swath of 1-2" across at least a small portion of the area. As little as 0.5" of rain could easily spell trouble for parts of the CWA from a flash flooding perspective, especially those north of I-80. Given the uncertainties and the fact that the highest amounts are generally favored outside of the more flood-sensitive areas, decided to hold off on issuing a Flash Flood Watch on this shift, but this is something the day shift will have to reconsider. A Hydrologic Outlook has been issued for these flooding concerns.

Behind the cold front, a much cooler airmass will settle into the region for this weekend. In fact, we'll likely see Saturday's high temperatures occur at midnight with cooler conditions expected during the day. Daytime highs are forecast in the middle 40s to lower 50s, a whole 30+ degrees cooler than today's high temperature forecast. Similar highs are expected for Sunday. Low temperatures are forecast in the 30s Saturday night into Sunday morning with some spots slated to get down to freezing. A modest westerly breeze may help mitigate frost/freeze impacts some, but we may be headed for our first frost/freeze headlines of the growing season this Saturday night. Better frost/freeze conditions will set up Sunday night/Monday morning with low temperatures forecast in the lower and middle 30s with calm winds and clear skies as surface high pressure centers over the region. Beyond tonight's rain chances which could stretch into early Saturday morning, no precip is anticipated over the weekend. In fact, conditions looks to remain largely quiet through early next week as we trend back toward unseasonably mild conditions.

Doom

AVIATION /06Z TAFS THROUGH 12Z SATURDAY/
Issued at 1226 AM CDT Fri Apr 17 2026

The key aviation weather messages are:

- LIFR/VLIFR cigs and vsbys through early morning, mainly at ORD, MDW, GYY, and possibly DPA. Conditions will improve rapidly after 12-13z.

- SE winds turning S to SSW this afternoon, with some occasional gusts greater than 30 knots possible.

- Line of thunderstorms--some severe--expected to impact all terminals this evening.

- Cold front arrives overnight with a breezy northwest wind shift and MVFR/brief IFR cigs.

An area of low stratus and fog continues to ooze westward off the lake. Over the past hour, cigs and vsbys have deteriorated at ORD/MDW, and expect that trend to continue overnight, with 200-300 foot cigs/VVs prevailing. With RVRs dropping, felt comfortable with continued TEMPO groups for 1/4SM FG through the night. Trends at DPA are more uncertain, with moist easterly trajectories evidently being blocked by high-rise structures in Chicago. It's unclear how cig/vsby trends will evolve as a result, but overall expectation is for eventual LIFR/VLIFR cigs and vsbys to develop overnight. Have left RFD VFR at this time given increasing low-level flow overnight and moist trajectories turning more northwesterly with time (into Wisconsin).

Conditions will rapidly improve in the 12-14z timeframe as SE breezes develop. Winds will eventually turn to a 180-190 direction during the afternoon with increasing gusts. There will be a potential for some intermittent 35 kt gusts towards mid afternoon, particularly INVOF RFD. Thereafter, a line of thunderstorms is expected to roll east across the region.
Confidence in overall storm timing is moderate-high. Some storms will be severe.

After storms clear, lingering showers and embedded TS will be possible through the late evening. A cold front will eventually shut any precipitation chances off with a gusty NW wind shift and developing MVFR cigs overnight into Saturday morning.

Carlaw

LOT WATCHES/WARNINGS/ADVISORIES
IL...Dense Fog Advisory until 10 AM CDT this morning for ILZ004- ILZ005-ILZ006-ILZ012-ILZ013-ILZ020-ILZ103-ILZ104-ILZ105- ILZ106-ILZ108.

IN...Dense Fog Advisory until 10 AM CDT this morning for INZ001- INZ002.

LM...Dense Fog Advisory until 7 AM CDT this morning for the IL and IN nearshore waters.