Marine Weather and Tide Forecast for Lincolnwood, IL

DISCUSSION
Issued at 205 AM CST Wed Jan 15 2025

Through Thursday:

A recent hand surface analysis revealed a broad surface high pressure system centered over the Mid-Mississippi River Valley.
Clear skies, light winds, a fresh snowpack, and a resident dry airmass has allowed for temperatures to drop toward 0F this morning.
Throughout the day, the surface high pressure system will settle southward. The increasing pressure gradient along the northern flank of the surface high will accordingly allow for low-level southwesterly flow and warm air advection to gradually increase throughout the day. Assuming skies stay clear (which assumes the mass of clouds in Iowa doesn't make it here), highs this afternoon should top off in the upper teens to lower 20s. In all, it's looking like a quiet day.

Tonight, an upper-level shortwave (currently racing from Saskatchewan into southern Manitoba) will dive into the Great Lakes.
Increasing upper-level diffluence in the left exit region of an associated jet streak, modest DCVA ahead of the shortwave, and relatively steep mid-level lapse rates (including through the depth of the DGZ) will provide sufficient forcing for ascent to support widespread snow showers as the wave passes overhead. A dprog/dt on 500mb heights from a variety of deterministic and ensembles valid at daybreak Thursday reveals a subtle trend southwestward in the position of the upper-level wave, supporting increasing PoPs into the low to mid-range (20 to 50%) for show showers across our entire area, with the highest chances across northeastern IL and northwestern IN. Coverage of snow showers should be highest generally between midnight and daybreak. Compared to the past few rounds of snow, coverage of accumulations tonight into tomorrow morning should be less widespread and "streaky," with some areas picking up a quick few tenths of an inch right next to others that only see a dusting. Increasingly breezy northwest winds may also lead to pockets of low visibility overnight, as well.

Thursday will start relatively chilly with wind chills in the single digits. Flurries and isolated snow showers may very well prevail through early Thursday afternoon until the back edge of the upper- level cyclonic shear axis slides overhead. Mostly cloudy skies and highs in the lower 30s will mark the afternoon.

Borchardt

Thursday Night through Tuesday:

Mid-level ridging is expected to be building into the central CONUS and Great Lakes regions Thursday night into the day on Friday. This will result in stout warm advection across northern IL and northwest IN which will allow temperatures to warm nicely into the upper 30s to around 40 by Friday afternoon.
However, there has been some guidance that is showing more cloud cover advancing into the area on Friday ahead of a developing storm system (more on this below) which would mean cooler temperatures if it verifies. At this time, the guidance members with the higher cloud coverage and cooler temperatures appear to be outliers and thus have maintained the trend for Friday to be the warmest day of the week. Though, will keep an eye on trends in case things change.

While our area enjoys a break from the cold and active weather, an upper low is expected to move onshore in southern California and gradually broaden into a shortwave trough as it traverses across the southwest CONUS on Friday. At the same time, a broader trough associated with the Polar Jet is expected to be diving into the northern CONUS and eventually phasing with the southern shortwave Friday night into Saturday. Guidance (both ensemble and deterministic) remains in good agreement on the system evolution and a the development of a surface low near the lower Mississippi Valley that should lift into the Ohio River Valley Friday night through the day on Saturday. As this occurs, confidence is growing that our area should see at least some precipitation from this system Friday night through early Saturday, especially those southeast of I-55. However, there is still some lingering uncertainty on where exactly the surface low and northern edge of the precipitation shield will track so be mindful that subtle shifts may still occur.

That said, precipitation looks to start out Friday night in the form of rain as surface temperatures and the lower-atmosphere will be above freezing. Though, there has been a notable trend in guidance for the mid-levels to cool much quicker Friday night as a cold front swings through the area. Therefore, it appears that the transition from rain to either all snow or a rain-snow mix (pending surface temperature response) may be quicker than originally thought. With the duration of snow/wintry mix possibly lasting longer, there is a growing signal that some snow accumulations could occur before precipitation ends Saturday morning, particularly in the southeastern portions of the CWA Right now it is still far too early to discuss specific snow amounts and associated impacts, but this is something we will continue to monitor going forward.

Furthermore, there also remains the potential for some lake effect snow showers to develop on the backside of the system late Saturday into the day on Sunday. While initially it looks as if the lake effect should begin in portions of northwest IN due to northerly winds, it should quickly pivot into northern IN and lower MI as winds turn west-northwesterly on Sunday. That said, lake effect parameters do not look overly impressive despite the strong signal in guidance so there is the chance the lake effect could fail to materialize all together or be much weaker than some guidance depicts. For now have maintained some 15-20% POPs in northwest IN and points east to account for this possibility and will continue to watch trends as we get closer.

Finally, the phasing of the two aforementioned features will result in broad troughing establishing over the Continental United States from Sunday through at least the end of next week.
This troughing will allow lobes of Arctic air to dive into the region resulting in a return to below average temperatures and bitterly cold wind chills heading into next week. Guidance remains in great agreement that temperatures during the early part of next week may struggle to get out of the single digits during the Sunday to Tuesday timeframe. In fact, forecast highs on Monday are forecast to be solidly in the single digits with overnight lows Sunday night and Monday night well below zero.
Couple these temperatures with the modest northwest winds forecasted and conditions look to be in place to get wind chills in the -15F to -25F range. Additionally, any shortwaves that dive through the pattern could bring the chances for snow showers. While there is not any notable signals for such activity through at least the middle of next week, the pattern does look to become more favorable for shortwaves to pivot through our area so stay tuned.

Yack

AVIATION /12Z TAFS THROUGH 18Z THURSDAY/
Issued at 531 AM CST Wed Jan 15 2025

Forecast concerns for the terminals...

- Breezy southwest winds today becoming northwest on Thursday

- Scattered snow showers tonight which will produce reduced visibilities and some snow accumulation

- Potential for freezing drizzle early Thursday morning and associated lower ceilings

High pressure will remain in place today which will yield mostly clear skies. However, there is a plume of 6000-8000 ft clouds moving east across IA that may make it into the terminals between 17z and 20z. Since recent satellite trends show a hole developing in these clouds, confidence is low if they actually reach the terminals so have just added a SCT080 mention for now.
Otherwise expect light southwest winds this morning to increase this afternoon with gusts around 20 kts.

An upper-level disturbance is expected to pivot through the area tonight bringing with it scattered snow showers. While confidence is high on the showers occurring, the exact location of where they will track remains uncertain. Therefore, have maintained the PROB30 for these snow showers for now but did adjust the timing to reflect forecast trends. Anyone who sees a snow shower tonight can expect reduced visibilities (around 3-4 SM) and snow accumulations around 0.5 inches.

The snow should taper by daybreak Thursday morning, but forecast soundings do show a potential for freezing drizzle to develop as cloud ice is lost. However, there is some uncertainty as to whether or not the necessary forcing will intersect the saturated low-levels to actually produce any freezing drizzle making this a lower confidence scenario. That said, have decided to introduce a MVFR ceilings to the forecast Thursday morning which should occur regardless of any drizzle due to saturated low-levels. A SCT009 mention was also added to this group to hint at the potential for drizzle and associated lower ceilings. Obviously we will keep an eye on this possibility and make adjustments as needed to future TAFs.

Finally, the lower ceilings and any drizzle will conclude by mid-morning Thursday as the disturbance exits the area. Thus, conditions will improve back to VFR for the rest of the day on Thursday with otherwise breezy northwest winds gusting 20-25 kts.

Yack

LOT WATCHES/WARNINGS/ADVISORIES
IL...None.
IN...None.
LM...Small Craft Advisory from 3 PM this afternoon to 3 PM CST Thursday for the IL and IN nearshore waters.