Sunrise 5:35 AM   Sunset 7:59 PM Moonrise 5:39 AM   Moonset 9:11 PM

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LMZ741 Expires:202405090330;;862416 Fzus53 Klot 082009 Nshlot
nearshore marine forecast national weather service chicago/romeoville il 309 pm cdt Wed may 8 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>742-090330- winthrop harbor to wilmette harbor il- wilmette harbor to northerly island il- northerly island to calumet harbor il- 309 pm cdt Wed may 8 2024
Tonight - Northeast winds 5 to 10 kt increasing to 10 to 20 kt in the evening. Slight chance of showers in the evening, then showers and slight chance of Thunderstorms after midnight. Waves 1 to 3 ft building to 2 to 4 ft. Thursday - Northeast winds 15 to 20 kt becoming north 20 to 25 kt. Showers and slight chance of Thunderstorms in the morning, then showers likely in the afternoon. Waves 3 to 5 ft. A small craft advisory will likely be needed. Thursday night - North winds 15 to 25 kt diminishing to 10 to 15 kt. Slight chance of showers in the evening. Waves 4 to 6 ft occasionally to 8 ft subsiding to 2 to 4 ft. A small craft advisory will likely be needed. Friday - North winds around 10 kt becoming east in the afternoon. Mostly Sunny in the morning, then becoming partly cloudy. Waves 2 to 4 ft subsiding to 1 to 3 ft.

LMZ700
No data

FXUS63 KLOT 081946 AFDLOT

Area Forecast Discussion National Weather Service Chicago/Romeoville, IL 246 PM CDT Wed May 8 2024

KEY MESSAGES

- Showers and a few thunderstorms are expected this evening and tonight. Some thunderstorms may feature small hail and gusty winds, primarily outside of the Chicago metro area.

- Cooler weather arrives Thursday, with periodic showers Thursday and again Friday night into the weekend.

DISCUSSION
Issued at 246 PM CDT Wed May 8 2024

Through Thursday night:

Today has been awfully pleasant for us so far with sunny skies and temperatures having reached the middle 70s to near 80 degrees area- wide. This is not the story across the rest of the Midwest, however.
Early this afternoon, we find two centers of surface low pressure in the region: one subtle little system in northwest IA and a broad, more prominent low marching across the Ozark Plateau. The former is producing nothing more than light showers out west while the latter is responsible for a swath of severe storms extending from western MO into south-central Kentucky. These two systems will phase into one over the next several hours before moving into central IL this evening. This will bring showers and likely a handful of storms to the area this evening through the better part of tomorrow.

We should begin to see isolated to widely scattered showers move into the SW CWA early-mid evening and progress across the rest of the area. With only a little bit of elevated instability squeezing into the CWA, thunderstorms look rather unlikely with this first little push any farther north than say the US Rt 24 corridor. More widespread activity will work in not long after midnight along the northern flank of the low as it passes through central IL. It looks like the overnight period will be our best chance at seeing embedded thunderstorms when several hundred joules of elevated CAPE look to build over parts of the area. The greatest thunder potential will exist in our western and southern CWA where we'll find the most appreciable instability with notably steeper low-mid level lapse rates. The environment becomes less and less favorable approaching the lake. While CAPE values certainly won't stand out tonight, most of it will be confined within the hail growth zone and we will have a respectable amount of mid level shear to work with, roughly 25-30 kt at 3-6 km. This means it's not out of the question to see some small hail develop within any relatively stronger elevated cores. Some dry air in the low levels and a ~30 kt LLJ could also promote some gusty winds with any thunderstorm or heavier shower tonight.

The instability will wane to the east early tomorrow pretty much driving the thunder potential out of here through the morning.
Scattered showers are expected to continue through much of the afternoon before high pressure builds in and clears conditions up during the evening. A tight pressure gradient on the backside of the system will bring breezy winds to the area during the day. Between the cloudy, rainy conditions and cold advection, tomorrow will be noticeably cooler with highs forecast near 60 south of I-80 and stuck in the 50s farther north.

Doom

Friday through Wednesday:

Shortwave ridging will produce stout mid-level warming through the day Friday, though low-level moisture will remain sufficient for a decent coverage of shallow cumulus during the afternoon.
On the heels of the ridge, a compact upper-level low will dig southeast over the western Great Lakes Friday night into Saturday. Earlier guidance had advertised a diurnally favorable passage of the low directly over our area midday Saturday, but has since supported a faster solution with the low passing to the northeast around daybreak. Additionally, more favorable thermodynamic profiles with anomalously cold mid-level temperatures will remain to the northeast. Have therefore continued to cap PoPs in the chance range with the expectation that shower coverage will be no greater than scattered.

Northwest flow aloft will persist Sunday into early next week.
Another shortwave trough is progged to cross the area sometime late Sunday afternoon through Sunday night. Low-level moisture availability looks marginal at best for any widespread precipitation as a sprawling surface ridge remains anchored in the Deep South, but an earlier arrival of the trough could support isolated to scattered storms in our forecast area during the late afternoon and evening.

Beyond Sunday night, substantial differences in guidance regarding the evolution of a building ridge across the eastern seaboard and a central CONUS trough support leaving the NBM's slight chance and chance PoPs untouched from Monday through Wednesday.

Kluber/Ogorek

AVIATION /18Z TAFS THROUGH 00Z FRIDAY/
Issued at 1218 PM CDT Wed May 8 2024

Aviation Forecast Concerns:

- Secondary low pressure system develops tonight into Thursday morning across central Illinois.

- Multiple rounds of precipitation expected late tonight through Thursday, bringing rainfall to northern IL terminals and reducing ceilings.

- Breezy conditions arrive this afternoon, with gusts increasing late Thursday morning as the low exits.

Low pressure system will begin to move into the Ohio River Valley this evening, with convective storms remaining south of the local area. A secondary low pressure system is modeled to develop overnight in the mid-Mississippi River Valley shifting slowly into central Illinois Thursday morning. This is expected to bring a wave of precipitation to northern Illinois terminals late tonight, lingering throughout much of Thursday. Model indication is for -SHRA chances throughout the event, with more steady RA coming in two waves early Thursday morning (07-14z)
and then again midday (16-22z) as the backside of the low pressure system exits the region. As this system develops across the region, ceilings are expected to decrease to MVFR with the early morning activity, with TEMPO LMVFR possible. Then LMVFR ceilings are forecast with the second wave midday into the afternoon.

Breezy conditions are anticipated to begin moving back across the area this afternoon into the evening with the leading low pressure system. As the secondary system begins to pull away from the northeast IL and northwest IN terminals Thursday, gusty winds are anticipated to pick up from the nne.

Baker

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

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