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LMZ745 Expires:202312091015;;143945 Fzus53 Klot 090314 Nshlot
nearshore marine forecast national weather service chicago/romeoville il 914 pm cst Fri dec 8 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.
lmz744-745-091015- gary to burns harbor in-burns harbor to michigan city in- 914 pm cst Fri dec 8 2023
.small craft advisory in effect through late Sunday night...
Rest of tonight..South winds 15 to 20 kt increasing to 30 kt after midnight. A few 35 kt gale force gusts possible late. Scattered showers in the evening, then periods of showers after midnight. Waves 1 to 3 ft building to 2 to 4 ft.
Saturday..Southwest winds to 30 kt diminishing to 20 to 25 kt. A few 35 kt gale gusts possible early. Showers likely in the morning. Waves 3 to 5 ft.
Saturday night..West winds 20 to 25 kt. Slight chance of rain and snow showers overnight. Waves 3 to 6 ft occasionally to 8 ft.
Sunday..Northwest winds 20 to 25 kt diminishing to 15 to 20 kt. Slight chance of rain and snow showers. Waves 4 to 7 ft occasionally to 9 ft.

LMZ700
No data

FXUS63 KIWX 090828 AFDIWX

Area Forecast Discussion National Weather Service Northern Indiana 328 AM EST Sat Dec 9 2023

SYNOPSIS
Issued at 328 AM EST Sat Dec 9 2023

Light rain showers move across the area today with highs near 60. It will also be windy with a few gusts up to 40 mph possible. Colder air returns for Sunday with some light lake effect snow possible into Sunday night. Any accumulation will be less than an inch. Quiet weather is then expected for the bulk of next week.

SHORT TERM
(Today)
Issued at 328 AM EST Sat Dec 9 2023

Light rain showers finally beginning to spread across our CWA given better low level theta-e surge and increasing isentropic ascent on the nose of a 45-50 kt LLJ. Mid/upper levels remain relatively dry though with far better CVA and left exit upper jet dynamics passing to our northwest. This will keep showers relatively light and scattered through the early morning. Upstream obs indicate a line of convection with a few embedded storms that may clip our far western counties later this morning but no significant impacts anticipated.
Cold front crosses the CWA roughly 15-19Z today with another minor uptick in shower activity. Here again, precip chances and amounts will be limited by poor mid/upper level support for ascent and limited moisture/instability this far north. Best chances for moderate rain will be in our far SE counties late this afternoon and evening where slightly better prefrontal instability will develop (highs in low 60s) along with an increasing fgen response to elongated trough. Will continue to hold off on thunder mention though and a very brief window for moderate rain will limit overall amounts regardless.

Most noteworthy aspect of sensible weather today may end up being wind. Far better gradient is ahead of the front in unfavorable WAA regime but forecast soundings now hint at potential to briefly mix into strong gusts immediately along and just ahead of the front. If model soundings verify...some peak gusts near 40mph may be possible.
Confidence in 45+ mph gusts is too low for an advisory but the area should be prepared for some brief windy conditions roughly 13-19Z.
The best chances for stronger gusts will be in our NW CWA closer to the surface low.

LONG TERM
(Tonight through Friday)
Issued at 328 AM EST Sat Dec 9 2023

Apart from aformentioned rain in our far SE this evening, most of the area will be dry tonight given some postfrontal dry air in westerly flow. Precip chances don't return until around 12Z Sun as flow veers more NW, CAA ramps up, and another shortwave passes. Have therefore made further cuts to PoP's tonight. Low temps near 32F will not arrive until 12Z Sun.

Difficult forecast for Sun with both marginal lake effect parameters and marginal thermal profiles (during the day). CAA will steadily increase through the day with 850mb temps dropping to near -10C by late afternoon. NW flow trajectories support a moderate fetch but very dry air over WI will limit the response with 0-2km theta-e lapse rates barely favorable for lake effect precip. A few weak vorticity maxima rotate through the area but forecast soundings show inversion heights barely reaching 5 kft, which just barely reach ice- producing layer of -12C. Surface temps hold in the mid/upper 30s for much of the day but low dewpoints yield wet-bulb temps near to just slightly above freezing. All of this points to a messy, low confidence forecast for precip coverage and types. SCT showers are expected but with little/no organization and overall light rates.
Suspect wet-bulb cooling will yield primarily snow as the precip type where precip manages to occur but any accumulation will quickly melt during the day. Best chance for accumulation will be Sun night but still marginal parameters suggest generally less than an inch confined to areas north of US-30. Temps do drop well into the 20s Sun night so isolated accumulations on the roads are possible and may lead to a few slick spots for the morning commute.

Rest of the period remains extremely quiet as split flow keeps low level ridge locked over the Ohio Valley. Temps remain near average through Wed then warm slightly for Thu/Fri. SW CONUS closed low eventually ejects east and brings the next chance for rain at the end of next week.

AVIATION
(For the 06Z TAFS through 06Z Saturday Night)
Issued at 1240 AM EST Sat Dec 9 2023

A warm front will lift northward through the next few hours, bringing showers south of US 30 northward. As the LLJ begins to saturate the airmass we'll see showers become more widespread, with gusty southwest winds ahead of the approaching cold front that will pass through this morning (at KSBN) into the early afternoon (at KFWA). Precipitation should be fairly light overnight, with more impactful precipitation moving in with the cold front (perhaps lower MVFR/even brief IFR ceilings/5-6SM visibility). Have a lull in precipitation behind the warm front this morning, mainly in the 10-14z time frame, though it's possible KSBN sees more impactful conditions (some of the guidance has 700 ft ceilings with light drizzle in this time period, but left out for now). Most of the guidance keeps heavier precipitation to the northwest tight along the cold front.
Otherwise, LLWS at KSBN as we decouple, with some gusts still up to around 30 knots (LLJ around 50-55 knots). Expect gusts to become more prevalent as the cold front approaches and we get some daytime mixing. Can't rule out a few gusts up to around 35 knots.



IWX WATCHES/WARNINGS/ADVISORIES
IN...NONE.
MI...NONE.
OH...NONE.
LM...Small Craft Advisory until 7 AM EST Monday for LMZ043-046.

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