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LMZ741 Expires:202312101645;;217273 Fzus53 Klot 100855 Nshlot
nearshore marine forecast national weather service chicago/romeoville il 255 am cst Sun dec 10 2023
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>743-101645- winthrop harbor to wilmette harbor il- wilmette harbor to northerly island il- northerly island to calumet harbor il- calumet harbor il to gary in- 255 am cst Sun dec 10 2023
.small craft advisory in effect until 9 am cst this morning...
Today..West winds 20 to 25 kt becoming northwest and diminishing to 15 to 20 kt by mid morning. Cloudy. Waves 2 to 4 ft subsiding to 1 to 3 ft.
Tonight..Northwest winds 10 to 15 kt. Mostly cloudy. Waves 1 to 3 ft.
Monday..West winds 10 to 15 kt becoming southwest in the afternoon. Partly cloudy in the morning then clearing. Waves 1 to 2 ft.
Monday night..Southwest winds 10 to 20 kt. Mostly clear. Waves 1 to 3 ft.

LMZ700
No data

FXUS63 KLOT 101145 AFDLOT

Area Forecast Discussion National Weather Service Chicago/Romeoville, IL 545 AM CST Sun Dec 10 2023

SHORT TERM
Issued at 235 AM CST Sun Dec 10 2023

Through Monday...

Key Messages:

* Cooler more seasonable temperatures with easing winds

* Mainly dry conditions forecast other than maybe a few flurries in northwest Indiana this afternoon and a brief period of lake effect snow showers for northeast Porter County

Blustery conditions continue early this morning with temperatures in the lower to mid 30s with winds gusting to around 25-30 mph resulting in wind chills in the 20s. Winds gradually ease with time through the daylight hours as the pressure gradient begins to relax and the low-level jet weakens. Widespread low clouds combined with continued cold air advection should limit our warming to just a few degrees today with temperatures holding fairly steady through the day in the 30s.

The upper trough beings to narrow as its axis pivots overhead today with a trailing shortwave moving through during the afternoon and evening hours. This could bring with it the potential for a few flurries if cloud temperatures cool enough for ice nuclei to be present. The best potential for this is in portions of northwest Indiana (20% chance). Additionally a few lake effect showers may dip into northeastern portions of Porter county though no accumulation is expected.

The temperature forecast for tonight will be highly dependent on the sky cover forecast and how quickly the stratus clears out. In the wake of the upper through and associated shortwave the expectation is that clouds will attempt to clear out from west to east overnight, though there is some hi-res guidance that hangs onto clouds through Monday morning. If this were to occur, forecast low temperatures may be too cold (currently in the low to mid 20s) and may need to be nudged up by a few degrees. In contrast, an earlier more widespread clearing would lead to colder temperatures, potentially dipping into the teens across portions of interior northern Illinois.

The surface ridge axis shifts east of the area by Monday morning turning winds back out of the southwest which, combined with clearing skies will help temperatures warm a bit more than seen today, into the mid 30s to lower 40s.

Petr

LONG TERM
Issued at 235 AM CST Sun Dec 10 2023

Monday night through Saturday...

Key Messages:

* No impactful weather is expected in the long-term period.

* Return to above average temps late in the week into next weekend.

Long wave troughing will persist over the Great Lakes and New England through Wednesday locking in the current outbreak of near average temperatures. Encroaching upper ridge is progged to build east into the region late in the week and into the weekend allowing unseasonably mild Pacific origin air to flood eastward across much of the country, including locally. There is a small chance of some showers Saturday as a northern stream shortwave is progged to move across the region. At this distance, a lot could change with a small wave like next weekend's, so slight chance pops offered up by NBM are plenty for now.

It's simply too hard *not* to talk about the signal for no impactful snow between now and late December. Of the 100 EPS/GEFS/CMCE members from the 12Z suite, only 30 to 40 show >0.1" of a snow, and fewer than 5 show more than 2", through December 24th at both Chicago O'Hare and Rockford. There are no signs of an impactful winter storm in the region anytime soon.

Borchardt/Izzi

AVIATION
For the 12Z TAFs...

* MVFR CIGS expected to persist into this evening, probably through much of tonight/early Monday morning

Large shield of stratus blankets much of the western Great Lakes and mid to upper Mississippi Valley early this morning. CIGS with this stratus vary mostly between FL015-FL022 and there could be a slight diurnal lifting of bases during the day today, but generally anticipate CIGS to remain MVFR. Guidance varies considerably with timing of clearing out of the stratus at the terminals, with a number of models suggesting clearing today or this evening. Generally this time of year, stratus tends to linger much longer than forecast, so trended the 12Z TAFs toward the slowest clearing guidance which keeps it around until Monday morning.

Only other item of note is the west-northwest winds gusting above 20kt early this morning. Anticipate the frequency of the gustiness to decrease this morning, likely becoming fairly infrequent this afternoon. Later amendments will likely be able to move up the end time of the gustiness, but for now maintained gusts into the afternoon.

- Izzi

LOT WATCHES/WARNINGS/ADVISORIES
IL...None.
IN...None.
LM
Small Craft Advisory
Winthrop Harbor IL to Gary IN until 9 AM Sunday.

Small Craft Advisory...Gary to Michigan City IN until 9 PM Sunday.

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