Sunrise 5:44 AM   Sunset 7:52 PM Moonrise 2:34 AM   Moonset 12:04 PM

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LMZ740 Winthrop Harbor To Wilmette Harbor Il- Wilmette Harbor To Northerly Island Il- Northerly Island To Calumet Harbor Il- 944 Am Cdt Wed May 1 2024
Rest of today - West winds 15 to 25 kt becoming northwest 10 to 20 kt late. Mostly Sunny late, becoming partly cloudy late afternoon. Waves 1 to 2 ft. Tonight - North winds 5 to 10 kt becoming northeast overnight. Chance of showers overnight. Waves around 1 ft. Thursday - East winds 10 to 15 kt. Chance of showers and slight chance of Thunderstorms. Waves 1 to 3 ft. Thursday night - Southeast winds 10 to 15 kt becoming south overnight. Chance of showers and Thunderstorms in the evening, then showers likely and a chance of Thunderstorms overnight. Waves 1 to 3 ft.

LMZ700
No data

FXUS63 KLOT 011143 AFDLOT

Area Forecast Discussion National Weather Service Chicago/Romeoville, IL 643 AM CDT Wed May 1 2024

KEY MESSAGES

- Widely scattered showers with a few embedded non-severe storms are expected late Wednesday night into Thursday morning.

- Another period of showers and storms is expected late Thursday into Friday. A few storms late Thursday afternoon into Thursday night could be strong to severe and produce locally heavy rainfall -- most likely near and west of the I-39 corridor.

DISCUSSION
Issued at 330 AM CDT Wed May 1 2024

Through Thursday:

A cluster of showers continues south of I-80 and east of I-55. A few cells have become more consolidated across Kankakee county and remain tall enough to produce occasional lightning strikes and gusty winds for the next hour or so as it moves east into Indiana along the Kankakee River Valley. The earlier concern about potential wake low winds developing thankfully haven't come to fruition though there have been sporadic gustiness in the 30-40 mph range.

The rest of the day looks dry across the area as surface high pressure settles over the region amidst slight mid-level height rises. Winds will be breezy out of the west to start the day with temperatures warming into the 70s this afternoon (warmest south of I-80).

Heading into tonight, modest warm advection and isentropic ascent sets up across the region well ahead of a weakening surface low cindered over eastern KS/NE. This should result in the development of widely scattered showers during the overnight hours and into Thursday morning (a few embedded non- severe elevated storms can't be ruled out). It is possible the late morning and early afternoon period is dry for much of the area though confidence is not especially high. Now that the convective allowing models are beginning to capture this period there are signs that isolated thunderstorms may attempt to develop within the warm sector near the warm front in the afternoon as it lifts north across the area. If this were to occur, a strong to severe storm couldn't be ruled out though the better potential exists west of I-39 toward early evening with the front and matches up with the latest SPC Day 2 Outlook highlighting a level 1 of 5 severe weather threat in those areas.

Temperatures on Thursday will be dependent on the placement of the warm front and how quickly it lifts to the north. Areas generally along/south of I-88/80 will be within the warm sector for the longest duration and could very well warm into the low to mid 80s! With a potentially slower arrival of the front and hence slower warming, areas along/north of I-88 may only warm into the 70s. Meanwhile, areas along the lakeshore in far northeast Illinois may struggle to warm out of the lower 60s!

Petr

Thursday Night through Tuesday:

Shower and storm coverage is likely to become increasingly numerous going into Thursday night as a cold front approaches from the west.
In addition to the threat for a few potentially strong to severe storms in our western CWA during the evening, a potential for locally heavy rainfall exists Thursday night into early Friday morning given the presence of climatologically high precipitable water values and that the mean storm motion relative to the orientation of the frontal zone will be conducive for training convective elements. EPS/GEFS ensemble QPF probabilities suggest that this potential appears to be maximized to the west of our forecast area, and rain rates may very well taper off as this corridor of showers and storms slides eastward into our forecast area Thursday night, but given the recent rainfall, it may not take a whole lot of rain to cause minor flooding here, so forecast trends in guidance still bear watching.

The rain is likely to linger into the daytime on Friday across at least eastern portions of our forecast area before ending as the cold front finally pushes east of here. When the rain and associated clouds will clear on Friday is still somewhat in question with guidance still offering mixed opinions on the overall progressiveness of the front. How quickly the rain and clouds clear the area will have an effect on high temperatures for Friday, with temperatures likely to climb into the low to mid 70s wherever some sunshine can be realized and remain in the 60s wherever the rain and stratus clouds remain pervasive. The exception to this will be areas closer to Lake Michigan, where the presence of onshore flow all day will keep temperatures in the 60s (and perhaps even the 50s along the immediate lakeshore) regardless of when the rain and clouds clear out.

A signal for another round of precipitation in the area remains for the late Saturday through early Sunday time period as a shortwave impulse tracks into the region, though it's not an overly coherent one with lots of variance still present in medium range guidance regarding the overall strength of this disturbance and what sort of surface response it might induce. Temperatures over the weekend are favored to be near to slightly above normal and again will be cooler closer to Lake Michigan, before most signs point towards another warm-up early to mid-week next week. The overall weather pattern across the central part of the CONUS also looks to be quite stormy during the first half of next week, and thus, there will likely be additional opportunities for us to see showers and storms towards the end of the current forecast period.

Ogorek

AVIATION /12Z TAFS THROUGH 18Z THURSDAY/
Issued at 643 AM CDT Wed May 1 2024

Key Messages:

- Westerly winds gusting to around 25 kts today.

- Showers and possibly a few storms arriving towards the end of the TAF period.

A narrow band of stratus with cloud bases between 2500 and 4000 ft AGL should clear the Chicago metro terminals by about 13 or 14Z this morning, leaving only some high cirrus clouds overhead for the remainder of the day. Otherwise, for today, westerly winds will gust to around 25 kts before subsiding late this afternoon and turning northeasterly/easterly tonight.

Overnight into tomorrow morning, scattered showers are likely to spread into the area as a warm front lifts northward. There may be just enough instability available to support a few thunderstorms as this activity passes by the terminals, but confidence in this is relatively low. Elected to add a PROB30 for TSRA to the ORD, MDW, and RFD TAFs for now to highlight this possibility.

Ogorek

LOT WATCHES/WARNINGS/ADVISORIES
IL...None.
IN...None.
LM...Small Craft Advisory until 4 PM CDT this afternoon for Winthrop Harbor IL to Gary IN.

Small Craft Advisory until 10 AM CDT this morning for Gary to Burns Harbor IN-Burns Harbor to Michigan City IN.

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