Sunrise 5:52 AM   Sunset 7:45 PM Moonrise 9:59 PM   Moonset 6:27 AM

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LMZ740 Winthrop Harbor To Wilmette Harbor Il- Wilmette Harbor To Northerly Island Il- Northerly Island To Calumet Harbor Il- 907 Am Cdt Thu Apr 25 2024
Rest of today - Southeast winds 5 to 10 kt this morning becoming east 10 to 15 kt this afternoon. Mostly Sunny. Waves 1 to 2 ft. Tonight - East winds 10 to 20 kt becoming southeast overnight. Clear. Waves 1 to 2 ft building to 2 to 4 ft. Friday - Southeast winds 15 to 25 kt increasing to 20 to 25 kt in the afternoon. Showers in the afternoon. Waves 3 to 5 ft. A small craft advisory may be needed.Friday night - Southeast winds 20 to 25 kt becoming south. Showers and a chance of Thunderstorms. Waves 4 to 6 ft occasionally to 8 ft. A small craft advisory will likely be needed.

LMZ700
No data

FXUS63 KLOT 251132 AFDLOT

Area Forecast Discussion National Weather Service Chicago/Romeoville, IL 632 AM CDT Thu Apr 25 2024

KEY MESSAGES

- Periods of showers and thunderstorms expected starting Friday and continuing at times through the weekend, with some threat for severe weather, particularly later in the weekend. Locally heavy rainfall possible as well.

- Gusty southerly winds to 40 mph Saturday and Sunday.

DISCUSSION
Issued at 224 AM CDT Thu Apr 25 2024

Through Friday:

After a cool start, temperatures will jump a few degrees compared to Wednesday as high pressure begins to depart to the north and east. A lake breeze will push inland towards midday resulting in lake cooling with high temperatures for lakeside communities only in the upper 40s to near 50 degrees. Tonight, temperatures will fall into the upper 30s and lower 40s, with a smattering of mid 30s possible in the typical cool spots. Increasing low-level warm advection and 5 to 10 mph surface winds will likely preclude much of a frost threat.

Friday will be a transition day towards a more active period of weather heading into the weekend. A tightening pressure gradient will drive increasing southeasterly breezes through the morning and afternoon. Eventually, shower and thunderstorm chances will also increase, particularly during the afternoon, as a lead impulse drives a more notable increase in warm advection overhead although the severe threat during this period appears low.

Carlaw

Friday Night through Wednesday:

Showers and scattered thunderstorms are expected to be ongoing Friday evening across much of the area and will be ending early Saturday morning, from west to east. A warm front will be lifting north across the area Friday night, shifting winds to the south/southwest and they may gust into the 30-35 mph range.
This will likely allow temps to level off in the upper 50s to around 60 in the evening and then possibly slowly rise into the lower 60s during the overnight hours.

As the first surface low lifts north across the upper Great Lakes on Saturday, there remains little focus for new thunderstorm development during much of the daylight hours on Saturday. There could be some lingering precipitation in the east Saturday morning and perhaps an isolated storm across far northwest IL along a cold front by evening. Lowered pops to low chance for most of the area. Southerly winds may gust as high as 40 mph on Saturday and with the expected lack of precip and warming temps prior to sunrise, highs should easily reach upper 70s for most areas and lower 80s are looking possible.

A second area of low pressure will move from the Plains Sunday to the upper Great Lakes Monday along the cold front noted above left behind from the first system. Convection is expected to develop northeast of this second low and along the cold front Saturday night. There remains quite a bit of uncertainty for where exactly this will occur and how far into the cwa it may move or develop. Nevertheless, increasing pops Saturday evening through Sunday morning look reasonable, especially for the northwest half of the cwa. There would be some severe potential during this time as well as the potential for heavy rain.

Precip trends for Sunday become fairly uncertain and likely dependent on what does or does not occur Saturday night. While there will likely be some dry periods Sunday into Sunday night, difficult to make any changes to the higher blended pops. There will be a continued threat of severe weather and heavy rain on Sunday, perhaps a better chance with any convection Sunday afternoon. Assuming there is some dry hours and some sunshine, highs on Sunday may be similar to Saturday, in the upper 70s with 80 possible.

The slower evolution/movement of the second system has continued, resulting in the cold front not moving across the local area until Monday afternoon with a continued chance for showers/scattered thunderstorms on Monday, mainly across the eastern half of the area. Confidence is fairly low for how convective trends will evolve on Monday. cms

AVIATION /12Z TAFS THROUGH 18Z FRIDAY/
Issued at 632 AM CDT Thu Apr 25 2024

Forecast concerns include...

Lake breeze early this afternoon.
Gusty southeast winds Friday morning.

Light and variable winds will become southeast this morning with speeds under 10kts. A lake breeze will move inland early this afternoon, shifting winds easterly at ORD/MDW/GYY with speeds to 10kts. Winds will turn back southeasterly this evening and remain southeast into Friday morning. Speeds will increase into the 10-15kt range by daybreak Friday morning with gusts into the lower 20kt range by mid/late Friday morning. cms

LOT WATCHES/WARNINGS/ADVISORIES
IL...Freeze Warning until 8 AM CDT this morning for ILZ003-ILZ004- ILZ005-ILZ006-ILZ008-ILZ010-ILZ011-ILZ012-ILZ013-ILZ103.

Frost Advisory until 8 AM CDT this morning for ILZ019-ILZ020- ILZ021-ILZ023-ILZ032-ILZ033-ILZ039-ILZ105-ILZ106-ILZ107- ILZ108.

IN...Frost Advisory until 8 AM CDT /9 AM EDT/ this morning for INZ001-INZ002-INZ010-INZ011-INZ019.

LM...None.

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