Sunrise 5:42 AM   Sunset 7:54 PM Moonrise 3:06 AM   Moonset 1:21 PM

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LMZ646 Wind Point Wi To Winthrop Harbor Il- 505 Pm Cdt Thu May 2 2024
Tonight - South wind 10 to 15 knots easing to 5 to 10 knots late in the evening, then veering southwest after midnight becoming southwest 5 to 10 knots early in the morning. Chance of Thunderstorms through around midnight. Chance of showers through the night. Slight chance of Thunderstorms after midnight. Waves 2 to 4 feet subsiding to 1 to 2 feet in the late evening and overnight. Friday - Northwest wind 5 to 10 knots veering east late in the afternoon. Partly Sunny in the morning then clearing. Waves around 1 foot. Friday night - East wind 5 to 10 knots backing northeast late in the evening, then becoming northeast 5 to 10 knots after midnight. Mostly clear. Waves around 1 foot. Saturday - Northeast wind 5 to 10 knots becoming east 10 to 15 knots in the late morning and afternoon. Slight chance of showers and Thunderstorms in the afternoon. Waves 1 to 2 feet.

LMZ600
No data

FXUS63 KLOT 022357 AFDLOT

Area Forecast Discussion National Weather Service Chicago/Romeoville, IL 657 PM CDT Thu May 2 2024

KEY MESSAGES

- Scattered showers and thunderstorms will increase in coverage this afternoon, and continue through the overnight hours.

- A few storms may be severe this afternoon with hail up to 1 inch in diameter, 60 mph winds, and soaking downpours. The severe threat should wane after sunset.

- Periodic chances for showers and thunderstorms will continue from this weekend onward, with some potential for severe weather on Tuesday.

DISCUSSION
Issued at 253 PM CDT Thu May 2 2024

Through Friday night:

Showers and thunderstorms are off to an early start along the I-55 corridor, seemingly due to the interaction with an eastward-moving mid-level gravity wave and the northward-moving warm front.
Additional showers and storms are expected to develop throughout the afternoon and especially after sunset as the right entrance region of an upper-level jet streak moves over the Great Lakes.
As we already saw with the first batch of showers and thunderstorms, a few may pulse to severe levels with 1" hail and 60 mph "splat" downbursts through about midnight thanks to MLCAPE 1000-1250 J/kg and meager deep layer shear. With that said, widespread severe weather is not expected today, and the threat should wane with the loss of heating after sunset (though a few non-severe thunderstorms may continue through the overnight hours).

Showers will likely continue through daybreak Friday as a cold front sweeps across the area. Chances for rain will then end from west to east Friday morning behind the front as drier air works into the region. Clearing skies and highs in the lower 70s are expected tomorrow afternoon, though stout northerly winds off Lake Michigan will keep lakeshore locations some 10 to 15 degrees colder, particularly in northwestern Indiana.

As a surface high pressure system slides overhead tomorrow night, slacking winds and clear skies will allow for efficient radiational cooling. Overnight lows should dip into the upper 40s with locally cooler readings in typical cold spots. If drier guidance verifies (allowing for even more efficient radiational cooling), some lower 40 degree readings cannot be ruled out.

Borchardt

Saturday through Thursday:

Primary forecast concerns are the potential for severe thunderstorms Tuesday and possibly isolated strong/severe thunderstorms Saturday afternoon/evening.

The models are now showing a compact system moving across the local area Saturday afternoon/evening with a chance for thunderstorms. The ensembles are in reasonable agreement for this potential and there is some instability. There will be the potential for a few strong/severe storms during peak heating in the afternoon/early evening. Blended pops are generally in the low chance range but these may need to be increased if these trends continue.

Sunday looks mainly dry and there is quite a bit of uncertainty for precip chances Sunday night into Monday morning with the Canadian/ECMWF fairly dry with only the GFS showing precipitation. After the wave on Saturday afternoon/evening and as the pattern shifts into early next week, this time period may end up being dry but made no changes to the blended pops which are likely too high, in the chance range, for Sunday night into Monday.

By Monday afternoon into Monday night, convection is expected to develop well west of the area and possibly reach northwest IL by daybreak Tuesday and if it does, most likely in a decaying phase. With temps likely to reach 80 and dewpoints in the 60s on Tuesday, this will provide plenty of instability for additional thunderstorms to form Tuesday afternoon and evening and some of these thunderstorms may become severe. Precipitable water values look to reach into the 1.5 to 1.75 inch range, which will allow for heavy rain.

The pattern stays unsettled into the end of next week with periodic chances for showers and thunderstorms, though there will also be several dry periods. cms

AVIATION /00Z TAFS THROUGH 06Z SATURDAY/
Issued at 657 PM CDT Thu May 2 2024

Forecast concerns for the terminals...

- Scattered showers and thunderstorms this evening give way to widespread showers and isolated embedded storms overnight

- Ceilings lowering to MVFR after midnight into Friday morning

- Winds become west-northwest overnight then gradually turn northeasterly Friday afternoon

Scattered showers and thunderstorms continue to fester across northeast IL this evening along remnant outflow boundaries form earlier storms. While observed soundings out of MDW do show a modest cap developing, scattered showers and storms are expected to persist through the evening as the aforementioned boundaries interact with the waning instability. A wider coverage of showers is expected to develop along the cold front in eastern IA and spread into the terminals around 03z this evening. Since the instability should be rather weak by this point I suspect very little in terms of thunderstorm activity, but given the strong frontal forcing and modest instability aloft a stray embedded storm through midnight cannot be ruled out. The cold front is expected to push east of the terminals early Friday morning which will bring an end to the showers and allow dry conditions to prevail through the rest of the period.

Aside from the showers, ceilings will also be lowering into the 1500 to 2000 ft range overnight as rain saturates the lower atmosphere. As the front exits Friday morning ceilings will gradually improve back to VFR conditions by midday. Otherwise, light south-southeast winds this evening will veer to westerly as showers return and then northwesterly behind the cold front late tonight into Friday morning. Directions will then settle into an east-northeast orientation Friday afternoon as high pressure builds into the area with speeds remaining generally under 10 kts.

Yack

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

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