Marine Weather and Tide Forecast for Lake Bluff, IL

DISCUSSION
Issued at 256 PM CDT Thu Oct 3 2024

Through Friday:

Through this evening, dry and pleasant conditions will continue with generally weak flow in the vicinity of a surface pressure col.

Overnight, a cold front will shift across the region, resulting in a slight uptick in northeasterly breezes and at least a chance for some light showers/sprinkles across the forecast area.
Guidance today suggest the main axis of enhanced dynamics (upper jet divergence, modest frontogenesis) and attendant moisture and instability will set up from northeast Missouri through central Illinois. This should tend to focus the greatest coverage of showers and even a few thunderstorms predominantly south and west of our forecast area for late tonight into Friday morning. The farther north you go, the more limited mid-level moisture profiles become, suggesting mainly light showers or sprinkles for locales north of about I-80. Can't rule out the potential for a few storms meandering into our southwest (La Salle, Grundy, Livingston county areas), but chances at this point still seem a bit too low to warrant a mention in the gridded forecast. Either way, overall precipitation amounts/coverage don't look particularly high in our area, and certainly not enough to help recover from ongoing drought conditions.

Clouds will gradually scatter out through the day on Friday, with high temperatures setting up a few degrees below today's with tranquil conditions continuing into Friday night.

Carlaw

Friday Night through Thursday:

Saturday morning, we'll find ourselves sandwiched between a departing high over the eastern Great Lakes and an approaching storm system/cold front to the west and northwest. Surface warm advection will be amplified during the day by a strengthening LLJ and should pull highs into the upper 70s and lower 80s. The LLJ along with a tight MSLP gradient near the system will bring breezy conditions to the area on Saturday which will carry on through Sunday following FroPa. A dry warm sector should provide us with mostly sunny skies as well.

This impending cold front is really the only feature of note here in the long term, and it's shaping up to be a rather fragile set up for parts of the area. This boundary looks to move across the CWA late Saturday evening and through the night.
The synoptic setup features a deep upper trough based immediately north of the CWA and an EML categorized by 8-9 K/Km lapse rates rooted at around 650 mb. A big majority of the more appreciable forcing and instability is found within the trough to our north. Convection looks likely across much of Wisconsin, but how far south the precip will reach remains in question.
Possibly the biggest factor to watch at this point and what seems to be driving discrepancies among models is how much moisture will gather ahead of the front to help destabilize the low levels. Unfortunately, there hasn't been any apparent trend among guidance or even between runs of the same model regarding low level moisture, but it's the runs with slightly higher sfc-800 RH that have been spitting out QPF across our north.
Even in the most unstable scenarios, storms should find it difficult to initiate beneath 850 mb. This means that they should avoid taking advantage of the impressive sfc-850 shear.
But any activity we see out of this could potentially be thunderous and a few deeper cores are not out of the question with that EML in place and still as many as around 30 kt of effective shear possible. Chances are highest the farther north you go with precip looking unlikely south of I-80. Accordingly, maintained slight chance PoPs near and north of I-80 with low end chances across our far north.

Any precip should clear the area by daybreak Sunday. Dewpoints look to plummet behind the front. While there is still some uncertainty in where dewpoints end up during the day, continued breezy conditions and very dry fuels will almost certainly set us up for a period of at least elevated fire weather concerns on Sunday, if not even nearing Red Flag criteria. Cloud cover should clear out nicely during the morning leaving us with more mostly sunny skies. Temperatures will cool back down a bit with highs forecast in the lower and middle 70s. Expansive surface high pressure will overspread the central CONUS throughout the upcoming week. This keeps precip chances minimal during the week with seasonable temperatures (60s and lower 70s) expected.

Doom

AVIATION /00Z TAFS THROUGH 06Z SATURDAY/
Issued at 643 PM CDT Thu Oct 3 2024

Forecast concerns include...

Chance of showers Friday morning.
Gusty northeast winds Friday morning.

Northeast winds are now expected through Friday evening, possibly becoming more northerly overnight. A cold front will move across the area early Friday morning and behind this cold front, there could be a brief period of gusts into the 20-25kt range. Gusts into the 15-20kt range are then possible for the rest of Friday morning and some periodic gusts may continue into early Friday afternoon.

There will be a chance of showers Friday morning, starting around daybreak and continuing through mid morning, though the best chance of showers looks to remain southwest of the terminals. The heaviest showers may briefly reduce vis to mvfr but cigs are expected to remain vfr. cms

LOT WATCHES/WARNINGS/ADVISORIES
IL...None.
IN...None.
LM...Small Craft Advisory from 3 AM to 1 PM CDT Friday for the IL and IN nearshore waters.