Marine Weather and Tide Forecast for Fox Lake, IL

MESOSCALE
Issued at 1208 PM CDT Fri May 16 2025

Main focus for severe thunderstorms late this afternoon and early this evening continues to be across my southeastern counties of eastern central IL into northwestern IN. This includes areas generally along and east of I-55 and along and south of I-80. Prior to the severe storm threat, strong gusty winds and low afternoon RH's will promote a high fire danger for portions of northern IL.

Mainly clear skies and a parched airmass overhead is fostering deep boundary layer mixing that is allowing temperatures to quickly warm through the lower 80s as of 11 AM. Continued mixing of this very warm and dry boundary layer is expected this afternoon, likely mixing in excess 8,000 ft. This deep mixing will promote steady (or even falling) surface dewpoints in the 40s as surface temperatures warm into the middle to upper 80s, and will also result in increasingly gusty south-southwest winds through the day. The strongest wind gusts this afternoon and evening are generally expected along and northwest of the I-55 corridor, where gusts of 45 to perhaps as high as 55 mph are anticipated. This has prompted the recent issuance of a wind advisory for this area, as well as a targeted Red Flag Warning within portions of this wind advisory.

While a parched and very deeply mixed boundary layer is not typically associated with storm development, we are expecting a rather impressive northward surge of low-level moisture (surface dew points up around 60) along and east of the I-55 corridor very late this afternoon (after 4 PM) and into the evening just in advance of an eastward shifting cold front/dryline feature.
This corridor of better low-level moisture currently resides across southern MO and IL, and is noted by a late morning uptick in CU development on regional Satellite imagery.

This increasingly moist and unstable airmass is expected to foster isolated to widely scattered thunderstorm development across parts of eastern MO and southwestern IL into early this afternoon. Thereafter, storm coverage is expected increase as large scale forcing for ascent increases in response to a notable mid-level impulse over the mid-Missouri Valley quickly swinging eastward along the southern periphery of the upper low residing in the Upper Midwest. As storm coverage increases, severe storms will develop northward across IL through the afternoon ahead of the dry line feature within the northward surging airmass. The area we are most concerned with for these severe thunderstorms are in areas generally along and east of I-55 and along and south of I-80, with the main timeframe looking to be from 4 to 10 pm this evening. More isolated storm coverage is possible northwest of this area.

The presence of very steep low-to-mid level lapse rates and inverted V-type soundings with high DCAPE (in excess of 1,000 j/kg) will foster very strong downdrafts and outflow with these storms. Accordingly, the primary severe weather threat with this activity looks to be damaging winds, some perhaps destructive (75+ mph). Some instances of large hail also cannot be ruled out. Expect the storm threat to wane by mid to late evening as the cold front/dry line shifts east of the area.

KJB

DISCUSSION
Issued at 247 AM CDT Fri May 16 2025

Through Saturday:

Two primary forecast concerns through early this evening, severe weather potential and windy, dry conditions for possible wildfires.
Please see the fire weather section below.

Much drier air has spread across western and northern IL with dewpoints in the upper 40s. The models are in good agreement with low level moisture surging back north late this afternoon into early this evening, with dewpoints back into the upper 50s to possibly lower 60s along and east of I-55. A cold front will be approaching from the west and scattered thunderstorms are expected to develop east of I-55. Coverage further north into the Chicago Metro area is more uncertain with perhaps only isolated thunderstorms. Strong winds aloft along with ample instability will allow any storms that develop to quickly become severe with large hail and damaging winds the main threats.
Given the wind profiles in the soundings, isolated damaging gusts into the 60-65kt range will be possible.

Before the storms, southwesterly winds will steadily increase this morning with gusts into the 40-45 mph range expected. There is a narrow window this afternoon, where gusts could frequently be at or above 45 mph, which is wind advisory criteria.
Confidence is too low to issue a windy advisory at this time, but trends will need to be monitored. Gusts will diminish a bit this evening, into the 25-30 mph range but will remain gusty through sunset Saturday evening. Another period of higher gusts in the 35-40 mph is possible as the colder air spreads into the area late this evening.

Previous forecast included patchy blowing dust for today for the western cwa and made no changes. There were stripes of heavier rainfall from the storms Thursday afternoon that will limit this potential for those areas.

High temperatures today are expected to reach into the middle, to perhaps upper 80s for most locations. Wind directions may remain southerly enough to keep temps cooler along the north lakeshore. Low temps will drop into the lower/mid 50s Saturday morning. High temps will be cooler on Saturday ranging from mid 60s north to around 70 south. cms

Saturday Night through Thursday:

A sprawling ~1030 mb high will build east across Ontario and the Hudson Bay on Sunday with mid-level shortwave ridging forecast to build in across the local forecast area. This high to our north with send a robust afternoon and evening lake breeze/backdoor front through the entire region. This will end up holding lakeside highs in the mid/upper 50s, while inland locales will likely warm into the 70s prior to the lake breeze push. While some guidance hints at the potential for some intermittent lower cloud cover on Sunday, most indications are that any morning cloud cover should scatter into the afternoon.

On Sunday night into Monday, a sharpening warm frontal zone well to our south will slowly advance northward into southern Iowa, northeast Missouri, and southern Illinois. Increasing low-level warm advection in response to strengthening 925-850 mb southwesterlies overtopping this frontal zone will lead to the development of showers and thunderstorms, but given the current location of the aforementioned boundary and MUCAPE gradient, most/all of this activity through Sunday night looks to remain well to our south. Even into the day on Monday any activity locally currently looks like it should remain isolated to scattered, with deeper moisture still relegated to our south.
Forecast soundings off the GFS in particular look like they'd be more supportive of intermittent drizzle/showers as opposed to thunderstorms.

On Monday night into Tuesday, guidance pushes a modest surface low (near 1000 mb) towards northern Missouri/southern Iowa as a robust shortwave pivots across the central plains. During this time, the northward progress of the returning warm front is forecast to slow, with the boundary overall becoming quasistationary across central to downstate Illinois. Isentropic upglide will increase once again, likely leading to a nocturnal expansion of showers and storms which--depending on the precise location of the stalled front--may begin to push into our forecast area, particularly south of about I-80. Could end up being a locally heavy rainfall threat somewhere in the vicinity with this setup.

Thereafter, guidance generally depicts a complex upper pattern developing, with a series of upper lows/gyres pinwheeling around one another into the middle of the week. This general evolution will keep the threat for intermittent periods of rain with embedded thunderstorms going in the vicinity, at least into Wednesday.
There's a signal for things to dry out into the end of the week.

Carlaw

AVIATION /18Z TAFS THROUGH 00Z SUNDAY/
Issued at 1258 PM CDT Fri May 16 2025

Forecast concerns for the terminals...

- Gusty south-southwest winds this afternoon with 35-40 kt gusts likely.

- Scattered thunderstorms expected late this afternoon and evening (22-02z). A few storms may be severe with damaging winds and hail as the main threat.

- Period of MVFR ceilings tonight into Saturday morning.

- Winds become westerly behind cold front with gusts in the 25-30 kt range tonight through Saturday.

Winds have continued to increase as diurnal mixing has commenced across the area this afternoon. While gusts have generally be around 30 kts thus far, gusts are expected to peak in the 35-40 kt range this afternoon and early evening. A cold front will move through the area this evening which will turn winds from south-southwest to westerly where they will remain through the rest of the period. Gusts are expected to subside a bit overnight as diurnal mixing weakens, but 28-30 kt gusts should prevail overnight before easing into the 25-30 kt range on Saturday.

Outside of the winds, there is also the potential for scattered thunderstorms to develop later this afternoon and evening (between 22z and 02z) especially over far northeast IL and northwest IN. Confidence on storms occurring has increased slightly since this morning as a plume of low-level moisture has started to move towards the area from southern MO. However, a fair amount of uncertainty remains in storm coverage particularly with northward extent. Therefore, have maintained the TEMPO groups at the Chicago area terminals but did decided to include a VCSH mention at RFD. Given that the threat for storms is around 20% at RFD and most guidance has storms developing east of the airport, feel the confidence is still to low for a formal TS mention. Additionally, any storms that develop will have the capability of producing winds in excess of 50 kts and large hail possibly up to golf ball size. The greatest severe threat is maximized southeast of a ORD to PNT line.

Finally, a period of MVFR ceilings is expected to develop tonight as the upper low over the Dakotas swings overhead.
Ceilings should generally be in the 2500-3000 ft range but lower clouds may develop in southern WI and near RFD. MVFR conditions should lift back to VFR by mid-morning on Saturday with skies gradually clearing through the end of the period.

Yack

MARINE
Issued at 245 AM CDT Fri May 16 2025

Southerly winds are expected to gust to gales to 35 kt this afternoon for mainly the IL nearshore waters and through Gary in the IN nearshore. Winds will shift westerly this evening as a cold front moves across southern Lake Michigan. Winds may continue to gust to near gale force with and just behind this cold front. Gusts will then diminish slightly, into the 25-30kt range which will continue through early Saturday evening. cms

FIRE WEATHER
Issued at 245 AM CDT Fri May 16 2025

A fire weather watch remains in effect for all of northeast IL this afternoon.

Much drier air has spread across western and northern IL and is expected to remain in place through mid afternoon. Dewpoints may lower a few more degrees, into the mid 40s and combined with high temperatures in the middle, to perhaps upper 80s, minimum relative humidity levels in the 20 to 25 percent range are possible this afternoon. Southwesterly winds will steadily increase this morning into this afternoon with gusts into the 40-45 mph range expected this afternoon. This combination of low relative humidity and strong winds will create the potential for rapid wildfire spread. A limiting factor is that some areas received heavier rainfall from the storms Thursday afternoon.

Low level moisture is expected to surge back north late this afternoon into early this evening, with dewpoints in the upper 50s, perhaps lower 60s, east of I-55. There will also be a chance of thunderstorms late this afternoon into early this evening for areas along and east of I-55. The combination of rising relative humidity levels as well as possible rainfall will end the wildfire risk by early this evening. cms

LOT WATCHES/WARNINGS/ADVISORIES
IL...Wind Advisory until midnight CDT tonight for ILZ003-ILZ004- ILZ005-ILZ006-ILZ008-ILZ010-ILZ011-ILZ012-ILZ013-ILZ019- ILZ020-ILZ021-ILZ032-ILZ103-ILZ104-ILZ105-ILZ106-ILZ107.

Red Flag Warning until 7 PM CDT this evening for ILZ010-ILZ011- ILZ012-ILZ019-ILZ020-ILZ021.

IN...None.
LM...Gale Warning until 10 PM CDT this evening for Winthrop Harbor IL to Gary IN.

Small Craft Advisory until 10 PM CDT this evening for Gary to Burns Harbor IN-Burns Harbor to Michigan City IN.