Sunrise 5:37 AM   Sunset 7:58 PM Moonrise 5:08 AM   Moonset 7:52 PM

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LMZ741 Expires:202405071515;;774447 Fzus53 Klot 070853 Nshlot
nearshore marine forecast national weather service chicago/romeoville il 353 am cdt Tue may 7 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>742-071515- winthrop harbor to wilmette harbor il- wilmette harbor to northerly island il- northerly island to calumet harbor il- 353 am cdt Tue may 7 2024
Today - Southeast winds 10 to 15 kt increasing to 15 to 20 kt this morning, then becoming southwest at 10 to 20 kt this afternoon. Showers and Thunderstorms likely in the morning, then a chance of Thunderstorms in the afternoon. Waves 3 to 5 ft subsiding to 2 to 4 ft this afternoon. Tonight - Southwest winds 10 to 15 kt. Chance of showers and Thunderstorms in the evening. Waves 1 to 3 ft subsiding to around 1 ft. Wednesday - Southwest winds 5 to 10 kt becoming southeast 10 to 15 kt in the afternoon. Slight chance of showers and Thunderstorms in the afternoon. Waves around 1 ft. Wednesday night - Northeast winds 10 to 20 kt. Showers and slight chance of Thunderstorms in the evening, then showers likely and a chance of Thunderstorms overnight. Waves 1 to 3 ft building to 2 to 4 ft.

LMZ700
No data

FXUS63 KLOT 071107 AFDLOT

Area Forecast Discussion National Weather Service Chicago/Romeoville, IL 607 AM CDT Tue May 7 2024

KEY MESSAGES

- Thunderstorms expected this morning, which may produce gusty winds and/or small hail.

- A second round of scattered thunderstorms is likely this afternoon, with the highest confidence east and southeast of the I-55 corridor. A few of these afternoon storms could become severe with large hail and damaging winds as the primary hazards.

- Another round of storms may develop late Wednesday, some of which could be strong to severe, mainly south of I-80 into central IL/IN.

DISCUSSION
Issued at 344 AM CDT Tue May 7 2024

Through Wednesday Evening:

Early morning Midwest radar mosaic depicts an extensive north- south linear MCS propagating east-northeast across eastern IA/MO. This MCS, associated with a potent negative-tilt mid- level short wave and surface cold front spreading east from the mid/upper Missouri Valley, will continue to push into northern IL and the WFO LOT forecast area after 5 am. The surface cold front was in the process catching up to a warm front stretching from IA into central IL, which should allow storms to become slightly elevated farther east into IL, which along with the gradual diurnal decrease in low-level instability should result in a slow weakening trend as it moves into our area. Despite these trends, localized sub-severe gusty surface winds up to 50 mph will likely still be possible across our western cwa as this line arrives. While a few isolated to widely scattered cells may develop ahead of the line within increasing warm advection flow, the main line of storms should reach the Chicago metro area around 7-8 am.

The convective outflow/cold pool footprint from these morning storms will stabilize low levels through midday, with some question remaining regarding location/extent of diurnal destabilization across the forecast area this afternoon.
Kinematics certainly favor the potential for strong to severe storms, with the mid-level short wave trough steepening mid- level lapse rates and a 75+ kt mid-level jet spreading across the area. Guidance continues to indicate the bulk of morning convection clearing the area around noon, with around 1000 J/kg of MLCAPE developing by early afternoon. CAMs depict at least widely scattered to scattered thunderstorm redevelopment early- mid afternoon, though location and evolution is of somewhat low confidence. Severe storms are possible area-wide this afternoon with all hazards possible, though areas east/southeast of the I-55 corridor look to have a higher overall and higher tornado threat better low-level instability and stronger shear as the mid-level jet spreads east. The window for greatest severe threat is roughly from 1-2 pm through about 5 pm, with storms becoming more isolated thereafter. Coverage may be a bit better across northwest IL and along the IL/WI border late in the afternoon.

Generally quiet weather is expected tonight into Wednesday morning, as the mid-level short wave lifts northeast of the area and short wave mid-level ridging develops overhead. Breezy southwest winds later today will diminish overnight, as weak surface high pressure slides across the area.

Another round of showers and thunderstorms is expected to develop Wednesday afternoon into Wednesday night, as the next short wave approaches the area. A surface low pressure wave is expected to develop along the cold/stationary front which will trail across the southern Plains in association with this wave, which will then propagate northeast into the mid-Mississippi Valley by Wednesday evening. Renewed warm advection return flow will help push the front north across central IL/IN as a warm front during the period, with showers and thunderstorms developing northeast into the forecast area during the afternoon. Details remain somewhat unclear with the track of the surface wave and frontal position by Wednesday evening, with various guidance showing quite a bit of spread. A more northerly low/warm front track into our southern cwa would likely present a greater severe weather threat.

Ratzer

Late Wednesday Night through Monday:

A mid-level trough extending southwest across Quebec and southern Ontario will phase with a mid-level low over the Missouri Valley Wednesday night. As the phasing wave crosses the area on Thursday, a residual low to mid-level TROWAL combined with PWATs around 1" and a deep layer favoring warm rain processes supports the potential for a low-end localized band of heavy rain (1-2") across portions of northern Illinois into southern Wisconsin late Wednesday night into Thursday. Outside of this band, scattered diurnally enhanced showers and perhaps a few storms are expected.

After a quick-moving ridge yields dry and seasonable temps on Friday, another upper-level low is progged to cross the western Great Lakes on Saturday. Anomalously cold mid-level temps shifting across the area through the day will yield scattered showers and storms, with some stronger cores likely producing locally strong wind gusts. Diverging solutions by early next week with regards to handling of the departure of Saturday's upper low and a building ridge to the west greatly diminishes the forecast by early next week.

Kluber

AVIATION /12Z TAFS THROUGH 18Z WEDNESDAY/
Issued at 605 AM CDT Tue May 7 2024

Key Aviation Messages: - Line of TSRA with potential gusts to 30 knots 13-15Z - SE winds shifting SW and gusting over 20 knots around 19Z - Scattered TSRA, possibly locally severe, mid-afternoon

A line of TS moving across northern Illinois will reach ORD/MDW roughly around 1330Z, with an expected duration one hour or less. While these storms are gradually weakening, locally higher wind gusts to 30 knots are possible.

Behind the initial line of TS, BKN MVFR ceilings are expected to develop as isolated -SHRA persist through the remainder of the morning. SE winds will then veer SW and gust to 25 knots beginning around 19Z.

Confidence continues to increase with another round of TS mid to late afternoon. TS may be in the vicinity of northeast Illinois for several hours, but the most likely window of direct impacts to ORD/MDW is from 19-22Z. These storms may be strong to severe and capable of wind gusts over 30 knots and hail.

Beyond the second round of TS, VFR conditions and SW winds are expected through tonight.

Kluber

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

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