Sunrise 5:41 AM   Sunset 7:54 PM Moonrise 3:32 AM   Moonset 2:39 PM

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LMZ740 Winthrop Harbor To Wilmette Harbor Il- Wilmette Harbor To Northerly Island Il- Northerly Island To Calumet Harbor Il- 314 Am Cdt Fri May 3 2024
Early this morning - Southwest winds 5 to 10 kt. Patchy fog. Showers likely and slight chance of Thunderstorms. Waves around 1 ft. Today - Northwest winds 10 to 15 kt becoming northeast by noon. Patchy fog in the morning. Chance of showers through mid morning. Waves 1 to 2 ft. Tonight - Northeast winds 5 to 10 kt. Mostly clear. Waves around 1 ft. Saturday - East winds 5 to 10 kt increasing to 10 to 15 kt. Slight chance of showers and Thunderstorms in the afternoon. Waves 1 to 2 ft. Saturday night - North winds 5 to 10 kt becoming northwest 10 to 15 kt. Showers likely and a chance of Thunderstorms in the evening, then slight chance of showers and Thunderstorms overnight. Waves 1 to 2 ft.

LMZ700
No data

FXUS63 KLOT 031122 AFDLOT

Area Forecast Discussion National Weather Service Chicago/Romeoville, IL 622 AM CDT Fri May 3 2024

KEY MESSAGES

- Increasing chances of showers and thunderstorms capable of producing gusty winds Saturday afternoon and evening.

- Periodic shower and thunderstorm chances next week, with some potential for strong to severe storms Tuesday.

DISCUSSION
Issued at 335 AM CDT Fri May 3 2024

Through Saturday:

Ongoing convective activity across portions of northern Illinois and northwest Indiana continues to wane early this morning as remaining instability and associated mid-level lapse rates decrease. In fact, as of 3am CT, very little lightning has been observed in the forecast area over the past hour. While a few lightning strikes are still possible through sunrise, a departing mid-level wave will limit remaining deeper-layer support. Meanwhile, a cold front roughly parallel to the Mississippi River will continue to shift a band of shallow showers across the area into mid-morning.

High pressure will quickly settle across the western Great Lakes through tonight. The combination of a rather dry airmass evident by upstream dew points generally in the 30s along with fairly clear skies today should allow seasonably warm conditions in the 60s along the shore and lower 70s inland today.

Today's cold front will stall across the south half of Illinois, allowing for a return of low-level moisture behind the surface high on Saturday. A small mid-level wave lifting northeast across the far Upper Mississippi River Valley Saturday morning may brush the northwest CWA Return of sufficient moisture by this point remains in question, though an isolated storm cannot be ruled out for areas west of I-39 late morning into early afternoon. A disjointed trough passage into the western Great Lakes later Saturday and into Saturday night should better align with increasing shallow moisture to produce scattered showers and storms as far east as around I-57 by sunset. However, fairly shallow low-level moisture return and a deep reservoir of dry mid-level air may limit storm coverage but also support gusty winds with any convection.

Kluber

Saturday Night through Thursday:

Showers and thunderstorms should be ongoing along and ahead of a cold front Saturday evening. Some of these storms could be strong to severe early in the evening, with mainly localized gusty winds, though this threat should diminish with eastward extent due to diurnal loss of low-level instability and generally weak deep-layer shear. Sunday through Sunday night looks to be largely dry and cooler, as Saturday night's cold front settles toward the Ohio Valley and surface high pressure builds east across the upper Midwest and western Great Lakes region. Temperatures will be limited to the lower 70s well inland Sunday afternoon, while northeast winds off of Lake Michigan will keep highs only in the upper 50s near the lake.
Lows will dip into the mid-upper 40s in most spots Sunday night.

Ensemble guidance depicts deep upper level trough developing across the western and central CONUS heading into next week, with a closed upper low developing across the Northern Plains Monday. A series of mid-level short waves are progged to rotate around the south and southeast periphery of the circulation as it slowly drifts east, eventually lifting the front across the lower Ohio Valley northward as a warm front later Monday night into Tuesday. Some spotty elevated showers are possible as early as Monday afternoon and evening as warm/moist advection develops atop the warm frontal slope, though really becomes more focused into the local area Tuesday into Tuesday night. This appears to be the period with the greatest potential for thunderstorms, some potentially strong to severe given strong mid-level wind fields and warm/moist/conditionally unstable low levels. Temperatures looks to surge back into the upper 70s/around 80 Tuesday afternoon, with surface dew points rising into the 60s as the warm front lifts across the area.

Periodic shower and thunderstorm chances linger through the mid-week period, as ensembles continue to indicate the upper trough drifting east across the upper Midwest/Great Lakes region through the end of the forecast period. Blended NBM guidance maintains chance pops both Wednesday and Thursday, especially during the more diurnally-favored afternoon/evening hours.
Higher low-level Theta-E air mass gradually gets shunted east of the area during this time, with temperatures gradually settling into the lower 70s by Thursday.

Ratzer

AVIATION /12Z TAFS THROUGH 18Z SATURDAY/
Issued at 612 AM CDT Fri May 3 2024

Key Aviation Messages...

- Period of low-MVFR and IFR ceilings early this morning, scattering to VFR by mid-morning.

- North-Northwest winds 10-15 kts early, becoming northeast around 10 kt late morning/midday.

- Low-confidence potential for MVFR ceilings at KMDW/KORD early Saturday morning.

Surface cold front was pushing through northeast IL early this morning. A fairly narrow band of low-MVFR and patchy IFR ceilingswas along/behind the front, and will affect the Chicago terminals for a few hours this morning before moving east and allowing VFR conditions to prevail. A few spotty sprinkles may linger for an hour or so, though no impactful showers are expected. With the front, winds shift north- northwest 10-15 kts, and these will persist through late morning before winds veer northeast at around 10 kts. High-res model guidance has shown quite a bit of spread as to just when the shift to northeast will occur, but should occur in the late morning to midday time frame. Winds will then remain northeast through this evening, eventually becoming light east late tonight and southeast Saturday morning.

Guidance continues to suggest some low-MVFR stratus may form over Lake Michigan and northern Indiana early Saturday morning, and could possibly spread west into KMDW/KORD around sunrise.
Confidence is low at this distance, but will continue to monitor with later forecasts.

Ratzer

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

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