Sunrise 5:16 AM   Sunset 8:24 PM Moonrise 2:22 AM   Moonset 2:58 PM

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LMZ740 Winthrop Harbor To Wilmette Harbor Il- Wilmette Harbor To Northerly Island Il- Northerly Island To Calumet Harbor Il- 242 Pm Cdt Sat Jun 1 2024
Tonight - East winds around 10 kt becoming northwest 10 to 15 kt after midnight. Showers likely in the evening. Patchy fog. Waves 1 to 2 ft.Sunday - North winds 10 to 15 kt diminishing to 5 to 10 kt. Patchy fog in the morning. Waves 1 to 3 ft. Sunday night - East winds 5 to 10 kt becoming southeast overnight. Partly cloudy in the evening, then becoming mostly cloudy. Waves around 1 ft. Monday - Southeast winds 10 to 15 kt. Slight chance of showers and Thunderstorms late in the morning, then chance of showers and Thunderstorms in the afternoon. Waves 1 to 3 ft.

LMZ700
No data

FXUS63 KLOT 012352 AFDLOT

Area Forecast Discussion National Weather Service Chicago/Romeoville, IL 652 PM CDT Sat Jun 1 2024

KEY MESSAGES

- Showers continue into the early evening but become more scattered in nature. Main threat for an isolated storm west and south of Chicago.

- Patchy dense fog possible tonight.

- Periodic chances for showers and thunderstorms Monday into Wednesday morning.

DISCUSSION
Issued at 220 PM CDT Sat Jun 1 2024

Through Sunday Night:

Looking at decreasing coverage of a more cohesive region of showers/rain across NE IL and NW IN through mid afternoon as the primary region of low-level warm advection on the nose of a stout 40 knot southerly 850 mb jet moves east of the region. Through the rest of the afternoon: scattered showers and perhaps an isolated storm or two will develop, preferentially in the vicinity of a surface convergence axis which currently arcs from near Springfield, IL, northeastward to Pontiac. In this region, visible satellite shows a bit more vertical growth, with echoes evident off regional radar mosaics. This convergence axis will meander northeastward towards a La Salle to O'Hare line through the late afternoon as a diffuse low/surface circulation scoots into NW Illinois.

Did add a low mention (15-20 percent chance) for a storm or two in the vicinity of this convergence axis, and in particularly closer to central IL where mid-level temperatures will be the coolest. Given the moist-adiabatic nature to the thermal profile today with lapse rates generally near or under 6 C/km, not expecting much in the way of lightning, but there's just enough vertical growth to our southwest to support an isoT mention this afternoon. Given very weak flow in the column, cell motions will be slow, resulting in a threat for highly localized/isolated areas of more appreciable rainfall (on the order of 1-2 inches).
Finally, can't totally rule out a funnel cloud this afternoon in the vicinity of La Salle/Livingston counties where the low-level CAPE/lapse rate axis will impinge on the aforementioned convergence axis (have already seen a picture of one sent from far west-central Illinois).

Activity will diminish through the evening, although suspect we may not fully lose spotty shower activity until a cold front sweeps through the region overnight. With moist low-levels, fog development is possible although a recent trend towards somewhat stronger post-frontal northwest winds casts uncertainty on this part of the forecast. Did not make many changes to the inherited patchy fog grids, with pockets of dense fog possible overnight.

Sunday looks dry and pleasant, with highs in the mid 60s lakeside to the upper 70s/near 80 farther inland, and morning stratus should gradually erode, lift, and scatter. A complex of thunderstorms is forecast to press across Iowa Sunday evening and overnight but with little/no deep layer shear nearby and the primary MUCAPE axis relegated well to our west, any MCS should weaken appreciably as it approaches our W/NW towards daybreak Monday morning.

Carlaw

Monday through Saturday:

A slow-moving trough within relatively weak WSW flow aloft will track from the central Great Plains into the western Great Lakes through Monday night. While the evolution of upstream convection on Sunday will have bearing on the forecast across the area Monday into Monday night, some decaying convection should survive into the western CWA late Monday morning. The combination of a slightly capped environment and some forcing from the weakening wave suggests isolated to scattered thunderstorms should develop across most of the forecast area by late afternoon and into the evening hours. A few strong storms with small hail and gusty winds cannot be ruled out, particularly across the northern CWA and into Wisconsin conditional on any notable enhancement of mid-level flow ahead of the wave.

By Tuesday, subtle height rises, little organized forcing, and increasing low-level capping should keep most of the area dry through at least mid-afternoon before a modest mid-level wave fosters a band of showers and storms across the CWA Tuesday night. While dry conditions are likely for most of the day, have maintained chance PoPs in the forecast given the potential for upstream convective debris with weak MCVs to interact with steepening mid-level lapse rates. If a few storms were able to develop, locally strong winds would be possible.

The cold front will begin to usher in a cooler airmass and decreasing shower and storm chances on Wednesday. Deeper troughing across the far northern Great Plains will then expand into a broad upper-level low across Ontario and the Great Lakes region late in the week. Seasonably cool temps are likely Thursday through Sunday, with a period or two of diurnally enhanced showers possible during this time.

Kluber

AVIATION /00Z TAFS THROUGH 06Z MONDAY/
Issued at 652 PM CDT Sat Jun 1 2024

Forecast concerns include...

Ifr/lifr cigs/vis through daybreak Sunday.
Wind directions this evening.
Rain ending this evening.

A frontal boundary extends from near PIA to ARR to ORD and is expected to slowly shift southeast tonight as an area of low pressure moves along this boundary. Rain will slowly dissipate this evening but there will likely still be showers near the boundary through mid/late evening. Locally heavy rain will be possible with any of these showers.

South of this boundary, winds are generally southerly and gusting at times. North of the boundary, winds are generally light north/northeast. As this boundary transitions south, a period of variable winds can be expected at MDW and GYY. Winds may stay light northerly tonight and then drift to the north/ northeast Sunday morning and then more easterly Sunday afternoon into Sunday evening.

Ifr/lifr cigs are widespread north of the boundary and will spread south tonight. While visibilities have improved where the rain has stopped, areas of fog are expected to develop tonight but confidence remains low. If and where cigs clear, most likely across northwest IL and RFD, dense fog is possible.
Along the boundary, Chicago terminals and areas to the southeast, dense fog is also possible but with prevailing lifr cigs likely, vis may remain in the 1sm range. Confidence is too low to make changes to the current forecast, other than to add lower vis at RFD. Cigs/vis are expected to steadily improve after sunrise Sunday morning. cms

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

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