Sunrise 5:41 AM   Sunset 7:53 PM Moonrise 3:30 AM   Moonset 2:38 PM

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LMZ742 Expires:202405032115;;535321 Fzus53 Klot 030814 Nshlot
nearshore marine forecast national weather service chicago/romeoville il 314 am cdt Fri may 3 2024
for waters within five nautical miles of shore on lake michigan
waves are provided as a range of significant wave heights, which is the average of the highest 1/3 of the waves, along with the average height of the highest 10 percent of the waves which will occasionally be encountered.
lmz740>742-032115- 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 030835 AFDLOT

Area Forecast Discussion National Weather Service Chicago/Romeoville, IL 335 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 /06Z TAFS THROUGH 12Z SATURDAY/
Issued at 1220 AM CDT Fri May 3 2024

Aviation Key Messages:

- SHRA persist through pre-dawn hours. Embedded TSRA threat diminishing but non-zero, especially toward KGYY.

- Period of MVFR ceilings develops pre-dawn and lingers until a cold front passes after sunrise.

- Winds shift NNW with cold front after sunrise, then turn NNE- NE by mid-morning. NE winds persist through remainder of period.

Somewhat diffuse area of low pressure was lifting north- northeast across eastern WI as of midnight, with a cold front trailing through far western IL into western MO. This low was associated with a mid-level disturbance over central IL, and will continue to lift northeast with the cold front moving across the terminals by sunrise. SHRA and embedded TSRA will persist ahead of the front, with TSRA growing more isolated with time, with greatest coverage of TS likely toward KGYY. MVFR ceilings along the cold frontal zone will spread across the terminals pre-dawn, eventually scattering out to VFR by mid- morning.

Winds, while somewhat disorganized by earlier stronger convection, will be generally light W-SW ahead of the cold front, then shift NNW behind the front by sunrise. Winds will then continue to veer northeast by mid morning behind the front, and will generally remain northeast through the day.

Winds turn light easterly Friday evening, and there is some model guidance indication that MVFR stratus may form east of the area across Lake Michigan and IN, which could drift west into the terminals later in the night. Confidence is low this far out, but have included a FEW020 mention in TAFs.

Ratzer

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

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