Sunrise 5:16 AM   Sunset 8:21 PM Moonrise 1:58 AM   Moonset 1:42 PM

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LMZ741 Expires:202406010445;;214016 Fzus53 Klot 312008 Nshlot
nearshore marine forecast national weather service chicago/romeoville il 308 pm cdt Fri may 31 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>742-010445- winthrop harbor to wilmette harbor il- wilmette harbor to northerly island il- northerly island to calumet harbor il- 308 pm cdt Fri may 31 2024
Tonight - East winds 10 to 15 kt becoming south 5 to 10 kt late. Partly cloudy in the evening, then becoming mostly cloudy. Waves 1 to 2 ft. Saturday - South winds 10 to 15 kt becoming southeast in the afternoon. Showers likely. Waves 1 to 2 ft. Saturday night - Southeast winds 5 to 10 kt becoming northeast overnight. Slight chance of showers in the evening. Waves 1 to 2 ft. Sunday - Northeast winds 5 to 10 kt becoming east in the afternoon. Mostly cloudy in the morning, then becoming partly cloudy. Waves around 1 ft.

LMZ700
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FXUS63 KLOT 312342 AFDLOT

Area Forecast Discussion National Weather Service Chicago/Romeoville, IL 642 PM CDT Fri May 31 2024

KEY MESSAGES

- Rainy Saturday.

- Periodic shower and thunderstorm chances Monday-Wednesday.

DISCUSSION
Issued at 312 PM CDT Fri May 31 2024

Through Saturday Night:

Upper trough over the southern Plains this afternoon will move northeast and across the mid Mississippi Valley Saturday. Dry conditions are expected this evening and most of the overnight hours with some rain possibly moving into southwestern portions of the CWA toward dawn Saturday. Showers are expected to overspread the remainder of the CWA Saturday morning and continue much of the day.

Cloud cover and widespread rain look to prevent any meaningful destabilization, so thunder chances appear quite low with this system. Despite that lack of thunder, rather strong forcing, a moist air mass (PWATs >150% of normal), and the slow moving nature of the trough could result in some formidable rainfall totals. Widespread rainfall of a half inch to around an inch and a quarter are likely, with some locally heavier totals possible.
The steadier nature of the rain should limit any significant flooding concerns, but a many areas will see a good soaking with standing water in typical poor drainage areas. Rain should end from west to east late Sat afternoon into Saturday evening.

Given the expected cloud cover and rain, have lowered high temps for Saturday, with highs now generally expected to be in the mid- upper 60s (possibly still a bit generous). Given the expected rainfall and likelihood of winds going calm, will need to watch for some patchy fog overnight Saturday night.

- Izzi

Sunday through Friday:

Weak high pressure over Lake Michigan will bring seasonable weather to the area on Sunday. Cloud cover will decrease throughout the day with temperatures rising into the high 70s and low 80s. Winds will be light, however, onshore flow will allow for the development of a lake breeze, keeping temperatures a little cooler along the lakeshore (high 60s to low 70s).

Late Sunday evening, a shortwave will move across the Plains with an associated surface low lifting through the northern Plains and into Canada. Convection will fire along the cold front of this system well to our west and begin advancing east overnight. The instability gradient appears to be fairly sharp and with the surface low and cold front lifting into Canada, the storms will be in the weakening phase by the time they reach the western portions of the CWA early Monday morning. The precipitation will continue to dissipate as it advances eastward and it appears possible that areas in the eastern portion of the CWA may not see any precipitation Monday morning.

Monday's forecast has a lot of uncertainty still remaining with it due to the remnant convection that will be present Monday morning and the associated leftover cloud cover from the dissipating showers and storms. A warm front will lift across the area on Monday with southerly flow bringing increased dew points. If the sun is able to peak out for a bit then pockets of 1000-1500 J/kg of CAPE may be able to develop along the frontal boundary. Forcing for convection looks uncertain as large scale forcing appears to be limited and poorly placed with the instability as the shortwave continues to lift northeast. Any storms that are able to develop will likely not be strong as deep layer shear will be weak, however, it cannot be ruled out that storm is able to produce some strong winds or small hail.

Diurnal heating and moisture return on Tuesday will once again allow for CAPE values to grow Tuesday afternoon. However, pretty stout capping appears to be in place. If the cap is able to erode throughout the afternoon, it is possible that some storms may be able to form, however, deep layer shear will not be present, so there will not be any severe storms.

On Tuesday another shortwave will push across the Northern Plains and Canada with a surface low in southern Canada. A cold front will push east across the Mississippi River Valley bringing convection into the area late Tuesday night. The exact timing is still uncertain, but it appears that the cold front and associated convection will move through later Tuesday night or early Wednesday morning. There appears to be potential for severe storms across the Mississippi Valley Tuesday afternoon and evening, however, instability will be quickly decreasing after dark Tuesday night, so the convection will likely be weakening as it reaches the CWA

Following the passage of the cold front early Wednesday morning, storm chances look marginal Wednesday afternoon. PoPs chances were left in the forecast, but it looks possible that Wednesday could be a completely dry day following the overnight convection and cold frontal passage. The overall synoptic pattern will shift to a primarily northwest flow pattern as the low gets stuck in southern Canada, near Lake Superior. This will allow cooler temperatures and dry conditions through the remainder of the work week.

Carothers

AVIATION /00Z TAFS THROUGH 06Z SATURDAY/
Issued at 642 PM CDT Fri May 31 2024

Forecast concerns include...

Rain developing Saturday morning.
Mvfr/Ifr cigs Saturday afternoon/evening.
Possible fog Saturday evening/early Sunday morning.

Areas of rain are expected to spread across the area after sunrise Saturday morning and start times will likely need some refinement as trends emerge. The rain is expected to continue through mid/late afternoon and then taper off to showers by sunset. The rain may be moderate/heavy at times. There is a small chance for thunder, especially Saturday afternoon, but confidence is too low to include mention in the tafs.

Cigs will lower through mvfr and likely into ifr Saturday afternoon. Only medium confidence for timing for ifr cigs, which could remain sct/bkn in the afternoon, with prevailing ifr cigs expected through most Saturday evening. Mvfr vis is expected with the rain Saturday afternoon but after the rain ends Saturday evening, some fog development is possible. Confidence is low, but after sunset Saturday evening into early Sunday morning will need to be monitored for the potential for areas of fog and possibly dense fog.

Southeast winds around 10kt with a few higher gusts will continue through sunset this evening then speeds will diminish under 10kts. Winds will turn more easterly Saturday and then there is uncertainty for wind directions Saturday evening, which will be dependent on where an area of low pressure tracks. cms

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

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