NOTE: Some of the data on this page has not been verified and should be used with that in mind. It may and occasionally will, be wrong. The tide reports are by xtide and are NOT FOR NAVIGATION. Privacy and Cookie policy

LMZ740 Winthrop Harbor To Wilmette Harbor Il- Wilmette Harbor To Northerly Island Il- Northerly Island To Calumet Harbor Il- 857 Am Cdt Sat Sep 23 2023
Rest of today..Southeast winds around 15 kt becoming east late. Partly cloudy early, then becoming mostly Sunny. Waves 2 to 4 ft.
Tonight..East winds 15 to 20 kt becoming southeast overnight. Mostly clear. Waves 2 to 4 ft.
Sunday..Southeast winds 10 to 20 kt becoming east in the afternoon. Partly cloudy in the morning, then becoming mostly cloudy. Waves 2 to 4 ft.
Sunday night..East winds 10 to 15 kt becoming southeast overnight. Chance of showers. Waves 2 to 4 ft.

LMZ700
No data

FXUS63 KLOT 231121 AFDLOT

Area Forecast Discussion National Weather Service Chicago/Romeoville, IL 621 AM CDT Sat Sep 23 2023

SHORT TERM
Issued at 218 AM CDT Sat Sep 23 2023

Through Sunday Night...

Main forecast concern is precip chances Sunday afternoon into Sunday night.

A few lingering sprinkles will be possible through daybreak across the far northern cwa. Otherwise, expecting clouds to continue to scatter/dissipate through the morning hours with mostly sunny skies expected today. Even though temps may fall several more degrees through sunset, they are still much warmer than previously expected for right now, in the mid 60s and even lower 70s in Chicago. Thus, temps will likely start at a higher level and upper 70s/lower 80s are expected except near the lake and its possible many areas will see lower 80s for highs today.

A cold front will move across IA tonight into Sunday morning and begin to slow as it moves into northwest and western IL Sunday.
There remains quite a bit of uncertainty regarding how far east the associated precip with this front will move. Some of the CAMS are quite aggressive with showers and even a few thunderstorms moving into the western third of the cwa by late morning/early afternoon. There had been reasonable agreement that the bulk of the precip would be in a weakening/dissipating stage as it entered northwest IL and that is still possible. However, given the uncertainty and proximity to the local area, increased chance pops into the 40 percent range for the western third of the area Sunday. With the eastern third likely staying dry. Suspect there will still be changes to the forecast for this time period over the next 24-30 hours as trends emerge. With expected increasing clouds, perhaps even cloudy skies across the west Sunday, this will likely keep temps down some, perhaps only lower 70s northwest to upper 70s southeast. There seems to be a better chance, still low, of isolated/scattered showers Sunday night. While confidence is still low, maintained low chance blended pops for the entire area. cms

LONG TERM
Issued at 218 AM CDT Sat Sep 23 2023

Monday through Saturday...

Ensemble models are displaying a weakening negatively tilted trough at 500 mb through the day Monday over Minnesota. With a weak wind gradient aloft over Illinois suggesting the potential for upper level convergence, Monday is looking drier with additional subsidence over the area. However, surface winds out of the south-southeast will still advect higher precipitable water values into Illinois, just no lifting mechanism to result in precipitation.

Both the GFS and Euro ensemble models are suggesting that on Tuesday, the trough starts to shift from a negative tilt to a positive tilt by Wednesday morning, and to dip down from Minnesota toward lower Michigan. With the probability of p-wat values at or just above an inch (slightly anomalous for this time of year), and a weak wave of vorticity descending down, it is no surprise that a few more ensemble members (compared to yesterday) are suggesting chances for precipitation on Tuesday. Confidence in timing and magnitude is still low so the forecast was kept at slight to low end chance PoPs (20 to 35 percent) for Tuesday. Deterministic models are suggesting at some CAPE to be present which would lead to an isolated rumble of thunder, but uncertainly still remains on the strength of forcing given that projections of the surface thermal gradient does not look overly impressive; likely the reason not all ensemble members are biting on the precip chances.
That being said, models are trending slightly wetter for Tuesday compared to 24 hours ago. Increasing clouds are expected with the chance an umbrella may be handy to keep nearby.

An upper level ridge is forecast to grow over the Southern Plains and shift and drift east over Illinois mid to late next week.
Wednesday looks a bit drier, but chances for rain linger Wednesday morning depending on how slow the upper low tracks east. In its wake Wednesday afternoon and through the rest of the week, higher pressure grows with drier conditions and seasonable temperatures in the 70s.

DK

AVIATION
Issued at 0621 AM CDT Sat Sep 23 2023

For the 12Z TAFs...

Despite weak showers along the Wisconsin/Illinois state border, no major impacts to area terminals. VFR conditions through the TAF period. Winds will be more southeasterly Saturday morning, shifting slightly to the east in the afternoon, then back to the southeast at night.

DK

LOT WATCHES/WARNINGS/ADVISORIES
IL...None.
IN...None.
LM...None.

toggle option: (graph/table)

Full Color Weather Map

Link to Loop


Other links: GEOS-West     Contential US     Full GOES-East

Chicago, IL,