Sunrise 6:01 AM   Sunset 7:37 PM Moonrise 3:37 PM   Moonset 4:26 AM

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LMZ742 Expires:202404191500;;003894 Fzus53 Klot 190815 Nshlot
nearshore marine forecast national weather service chicago/romeoville il 315 am cdt Fri apr 19 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>742-191500- winthrop harbor to wilmette harbor il- wilmette harbor to northerly island il- northerly island to calumet harbor il- 315 am cdt Fri apr 19 2024
.small craft advisory in effect from 10 am cdt this morning through this evening - .
Today - Northwest winds 15 to 25 kt becoming west this morning and increasing to 30 kt. Mostly Sunny. Waves 2 to 4 ft.Tonight - West winds 15 to 25 kt. Mostly clear. Waves 1 to 3 ft.Saturday - West winds 15 to 20 kt becoming northwest. Mostly Sunny in the morning, then becoming partly cloudy. Waves 1 to 3 ft.Saturday night - Northwest winds 10 to 15 kt becoming west. Partly cloudy. Waves 1 to 2 ft.

LMZ700
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FXUS63 KLOT 191122 AFDLOT

Area Forecast Discussion National Weather Service Chicago/Romeoville, IL 622 AM CDT Fri Apr 19 2024

KEY MESSAGES

- West winds gusting 35-40 mph with an elevated fire danger this afternoon.

- Patchy frost possible across the northwest cwa tonight.

- Much cooler temperatures are expected over the weekend with a threat for frost and sub-freezing temperatures, particularly on Saturday night outside of Chicago.

- The next opportunity for rain will arrive Monday night into Tuesday.

DISCUSSION
Issued at 201 AM CDT Fri Apr 19 2024

Through Saturday:

Westerly winds will steadily increase after sunrise and are expected to gust into the 35-40 mph range this afternoon and then will diminish with sunset this evening. Dewpoints are expected to drop into the mid 20s, possibly lower 20s and this will allow relative humidity levels to drop into the 25-30 percent range, resulting in an elevated fire danger.

These lower dewpoints will continue tonight which will allow low temps to drop into the mid 30s for most areas by Saturday morning, with some lower 30s possible. This presents the potential for frost to develop but northwest winds may remain in the 10 mph range for most of the night which may be too strong for frost to form. Maintained patchy frost mention across the northwest cwa, roughly from the Fox Valley west and then north of I-80. Confidence is low for how widespread any frost would become and trends will need to be monitored later today.

Saturday will still be breezy, with northwest winds possibly gusting into the 20-25 mph range. While dewpoints will generally be in the 20s, high temps look to be a few degrees cooler, perhaps only lower 50s for highs. Thus, relative humidity levels look to be a little higher, in addition to the expected lower wind speeds, thus an elevated fire danger is not expected. cms

Saturday Night through Thursday:

We're in for a quiescent stretch of weather through the weekend and the start of the work week as a sprawling surface high builds across the central CONUS. While the core of the high pressure won't ever build directly overhead, it looks like the gradient will relax sufficiently on Saturday night into Sunday to yield an effective radiational cooling setup, assuming a region of high cloud cover associated with an upper jet streak thins and diminishes as modeled. With dewpoints in the low to mid 20s, a potential for sub-freezing temperatures exists, particularly for outlying areas west and north of Chicago. No headlines just yet, but it's possible we'll need to consider freeze watches for this period.

We'll step into a brief warming trend Monday and Tuesday as the low-level flow turns southwesterly. A slightly elevated fire danger may evolve on Monday with breezy southwesterly winds and afternoon RH values dipping into the 30 to 35 percent range. The next precipitation chances arrive Monday night into Tuesday as a fairly robust upper vort approaches, driving a notable increase in warm advection across the region. Instability and overall moisture quality/depth don't look particularly impressive, however, with activity likely in the form of scattered showers.

A reinforcing shot of cooler air will arrive in the wake of a cold front Tuesday night and Wednesday before high temperatures once again warm back towards and into the 60s--at least away from the lake in northeast Illinois where persistent onshore flow will hold temperatures in the 50s. Thereafter, while timing and amplitude differences are evident, there seems to be a consistent signal in the deterministic and ensemble suite of a large trough developing across the Great Basin towards the end of next week, with embedded shortwaves shuttling east across the central CONUS into the weekend which could bring the next rounds of showers and storms to the region.

Carlaw

AVIATION /12Z TAFS THROUGH 18Z SATURDAY/
Issued at 622 AM CDT Fri Apr 19 2024

The aviation weather concerns are:

- Developing gusty WNW winds this morning and afternoon. Some occasional gusts up to 35 knots possible.

Northwesterly breezes will increase this morning, with gusts near 30 knots expected to develop towards midday and into the afternoon. There continue to be some indications that occasional gusts around 35 knots or even a bit higher may develop late this afternoon (20-23z timeframe). Winds will then gradually ease after sunset, although gusts on an intermittent basis look like they'll persist through much of the night and into Saturday morning.

VFR conditions are expected today, with FEW-SCT VFR cumulus developing during the afternoon. More expansive Cu is expected to develop on Saturday afternoon.

Carlaw

LOT WATCHES/WARNINGS/ADVISORIES
IL...None.
IN...None.
LM...Small Craft Advisory from 10 AM this morning to 7 PM CDT this evening for the IL nearshore waters.

Small Craft Advisory until 7 PM CDT this evening for the IN nearshore waters.

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