Sunrise 5:35 AM   Sunset 8:00 PM Moonrise 5:39 AM   Moonset 9:12 PM

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LMZ740 Winthrop Harbor To Wilmette Harbor Il- Wilmette Harbor To Northerly Island Il- Northerly Island To Calumet Harbor Il- 950 Pm Cdt Tue May 7 2024
Rest of tonight - Southwest winds 5 to 10 kt. Isolated showers. Waves 1 to 2 ft.Wednesday - Southwest winds 5 to 10 kt becoming east 10 to 15 kt in the afternoon. Mostly Sunny. Waves 1 to 2 ft. Wednesday night - Northeast winds 15 to 25 kt. Showers likely and slight chance of Thunderstorms. Waves 2 to 4 ft building to 3 to 5 ft. Thursday - North winds 15 to 25 kt increasing to 30 kt. Showers likely in the morning, then chance of showers in the afternoon. Waves building to 4 to 7 ft occasionally to 9 ft. A small craft advisory will likely be needed.

LMZ700
No data

FXUS63 KLOT 080602 CCA AFDLOT

Area Forecast Discussion...CORRECTED National Weather Service Chicago/Romeoville, IL 102 AM CDT Wed May 8 2024

KEY MESSAGES

- A round of thunderstorms may develop late Wednesday into Wednesday night, some of which could be strong to severe, mainly south of I-80 into central Illinois and Indiana

- Cooler with periodic showers Thursday and then Friday night into the weekend

DISCUSSION
Issued at 338 PM CDT Tue May 7 2024

Tonight through Wednesday Evening:

A post cold frontal short-wave may touch off a few showers and thunderstorms across portions of far northern Illinois through the early to mid evening, with slight chance (~15-20%) PoPs for this activity. Generally quiet weather is then expected tonight into Wednesday morning, as the mid-level short wave lifts northeast of the area and short wave mid-level ridging develops overhead. Winds will become light to calm tonight as weak surface high pressure slides across the area. Forecast lows tonight are in the mid to upper 50s, locally lower 50s.

The most recent guidance has trended drier through much of Wednesday afternoon, enabling another warm day (mid 70s to lower 80s F) despite increasing cloud cover. The exception to the warmth once to the early afternoon will be lakeshore areas due to winds turning onshore synoptically and aided by lake influence.

From late Wednesday afternoon through Wednesday night, another round of showers and thunderstorms is expected to develop. Some scattered showers may develop across far northern Illinois and across the state line into Wisconsin in the late afternoon. More notably, the approach of the next short-wave will result in a gradual uptick in showers and thunderstorms to the south of I-80 prior to sunset, and then spreading northward in the evening and overnight.

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.
Overall, the guidance has come into better agreement in barely returning the front northward into our far southern CWA (south of US-24) as a warm front by Wednesday evening. This is where some potential may exist for surface based severe weather threats, primarily damaging winds and hail.

Otherwise, as most of our area will be on the cool side of the front, the main concern will be elevated hail producing thunderstorms , some of which may become marginally severe (hail up to 1" diameter) as mid-level lapse rates steepen amidst supportive effective bulk shear. In addition, seasonably high PWATs may present a localized ponding or even flooding threat, primarily near and south of I-80.

Castro/Ratzer

Late Wednesday Night through Tuesday:

A mid-level trough extending southwest across Quebec and southern Ontario will phase with a mid-level low over the Missouri Valley late 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" totals by mid day Thursday) across portions of northern Illinois into southern Wisconsin. Outside of this band, scattered diurnally enhanced showers and perhaps a few storms are expected. Much cooler conditions are in store, with highs only in the upper 50s to lower 60s inland and lower to mid 50s near Lake Michigan. Adding to the cool feel, northerly winds will gust up to 25-35 mph, strongest near the lake.

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. It appears temperatures will trend back to above normal by the end of the period.

Kluber/Castro

AVIATION /06Z TAFS THROUGH 12Z THURSDAY/
Issued at 1259 AM CDT Wed May 8 2024

Key Aviation Messages: - Wind shift from SW to E early this afternoon - Scattered SHRA tonight (20% chance of elevated TS), with MVFR ceilings developing toward sunrise Thursday

VFR conditions are expected through at least this evening, with generally FEW/SCT mid-level clouds. SW winds under 10 knots early this morning may become somewhat VRB under 5 knots as a weak surface ridge crosses northern Illinois. Winds are then expected to shift E around 10 knots with lake-enhanced boundary ahead of a surface low nearing central Missouri. E to NE winds 10-15 knots are then favored through the remainder of the period.

A band of SHRA and perhaps isolated elevated TS is expected to drift northward over the terminals late this evening and overnight. TS potential of around 20% chance remains low enough to keep TS mention out of the TAF this far out, but future TAF updates may require introduction of TS if expected SHRA coverage also increases. Otherwise, MVFR ceilings should advect into the area late tonight, with some IFR ceilings possible Thursday morning beyond the current forecast period (12Z Thursday).

Kluber

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

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