Marine Weather and Tide Forecast for Lake Koshkonong, WI

UPDATE
Issued 1001 PM CST Mon Jan 20 2025

Winds have diminished significantly across southern Wisconsin as a ridge of high pressure builds across the region. Isobaric packing should increase once again into the early morning hours Tuesday as high pressure sinks into the Middle Mississippi Valley and low pressure ejects from the Canadian Rockies.
Therefore, still expecting wind chill values to plummet to negative 30 degrees and below into the early morning hours.
Extreme Cold Warnings are in effect from late tonight and very early Tuesday morning through noon CST Tuesday for these concerns. As temperatures rise into Tuesday afternoon, winds remain gusty and keep wind chill values low. Therefore, Cold Weather Advisories may be issued after the Extreme Cold Warnings end.

Patchy low clouds continue to progress southeastward across southern Wisconsin, but are transient and patchy enough to pose a minimal threat to falling temperatures overnight.

MH

SHORT TERM
Issued 309 PM CST Mon Jan 20 2025

Tonight through Tuesday night:

Area of light snow showers and flurries may linger into early this evening across southern and central portions of the area, as some weak low level frontogenesis shifts southeast through the area. Not expecting any accumulations, as the gusty west northwest winds should blow anything off of surfaces. There may be a very brief visibility reduction at times, but nothing impactful.

The coldest temperatures and wind chills of the cold snap arrive tonight into Tuesday morning.

Have added Waukesha and Walworth Counties into the Extreme Cold Warning starting at midnight CST until noon CST Tuesday, and Milwaukee, Racine and Kenosha Counties starting at 3 AM CST until noon CST Tuesday. Wind chills should reach the 30 below zero threshold in these areas during these periods. They may rise above this an hour or two before noon CST Tuesday in these areas.

In addition, extended the Extreme Cold Warning for southwestern parts of the area until noon CST Tuesday, as wind chills may take another few hours to rise above 30 degrees below zero. The Cold Weather Advisory remains in effect until the start of the Extreme Cold Warnings.

There may be additional Cold Weather Advisories issued after noon CST Tuesday, depending on how quickly wind chills rise.
Will let later shifts determine this timing.

There may be some clouds that move through the area from the west northwest into tonight. Some uncertainty with how much cloud cover is expected, so may need to add more clouds into the forecast later tonight.

Warm air advection begins Tuesday night, as winds shift to the south and southwest. This may keep wind chills in the 10 to 20 below zero range in the evening, before slowly rising after midnight, as temperatures slowly hold steady or rise.

Wood

LONG TERM
Issued 309 PM CST Mon Jan 20 2025

Wednesday through Monday:

Models are still showing some warm air advection brining in some deep moisture for Wednesday into Wednesday evening, as low pressure passes to the north and drags a surface trough through the area. There is a broad 500 mb trough that shifts through the region, with individual shortwaves either moving by to the southwest or shifting through the area. All in all, there should be a period of light snow during this time, with accumulations under an inch. Not expecting big impacts from this system.

Temperatures are expected to moderate more toward seasonal normals by the end of the week and into the weekend, per ensemble trends.

Wood

AVIATION
Issued 1001 PM CST Mon Jan 20 2025

Steady northwesterly winds with occasional gusts up to 15 kt will continue through much of tonight, with widespread gusts closer to 20 kt redeveloping around sunrise. Winds shift to become westerly into Tuesday morning, with gusts continuing.
Winds then shift to southwesterly Tuesday afternoon and evening, and southerly overnight Tuesday. Winds remain gusty around 20 kt regardless of direction.

A few transient areas of clouds around 2500 ft will progress southeastward across southwestern to far south-central Wisconsin, with brief periods of broken ceilings possible.
Clouds dissipate by early Tuesday morning, with VFR conditions expected Tuesday through Tuesday night.

MH

MARINE
Issued 309 PM CST Mon Jan 20 2025

Arctic high pressure around 30.9 inches will shift into the Central Plains tonight and the Middle Mississippi River Valley Tuesday. It will shift further east into the middle of the week.
The progression of the high will help to maintain breezy west northwest winds across Lake Michigan through the first half of this week.

The breezy west northwest winds will combine with elevated wave heights and frigid air temperatures to support heavy freezing spray through Tuesday afternoon.

Heavy Freezing Spray Warnings remain in effect for the southern open waters of Lake Michigan through 6 PM CST Tuesday. A Heavy Freezing Spray Warning is also in effect for the northern third of the open waters until 6 AM CST Tuesday morning. It is possible that areas of heavy freezing spray could continue longer over portions of the warned area, with trends being monitored over coming forecasts for any potential extensions.

Low pressure around 29.8 inches will move southeast into the Western Great Lakes region Tuesday night into Wednesday, promoting a southwest wind shift over Lake Michigan. Southwest winds will become breezy on Wednesday. This will support continued freezing spray potential into Wednesday, with any freezing spray expected to be lighter relative to earlier in the week.

For the nearshore waters of Lake Michigan, a Small Craft Advisory is in effect until 3 AM CST Tuesday morning. Gusty west northwest winds will gust up to 25 knots at times during this period. Additional periods of Small Craft Advisory conditions are likely again Tuesday night through Wednesday, for gusty winds.

Wood

MKX WATCHES/WARNINGS/ADVISORIES
WI
Cold Weather Advisory
WIZ046-WIZ047-WIZ051-WIZ052-WIZ056- WIZ057-WIZ058-WIZ059-WIZ060-WIZ062-WIZ063-WIZ064-WIZ065- WIZ067-WIZ068-WIZ069-WIZ070 until midnight Tuesday.

Extreme Cold Warning...WIZ046-WIZ047-WIZ051-WIZ052-WIZ056- WIZ057-WIZ058-WIZ059-WIZ060-WIZ062-WIZ063-WIZ064-WIZ065- WIZ067-WIZ068-WIZ069-WIZ070 until noon Tuesday.

Cold Weather Advisory...WIZ066-WIZ071-WIZ072 until 3 AM Tuesday.

Extreme Cold Warning...WIZ066-WIZ071-WIZ072...3 AM Tuesday to noon Tuesday.

LM
Heavy Freezing Spray Warning
LMZ080-LMZ567-LMZ669-LMZ671- LMZ673-LMZ675-LMZ777-LMZ779-LMZ868-LMZ870-LMZ872-LMZ874- LMZ876-LMZ878 until 6 PM Tuesday.

Heavy Freezing Spray Warning...LMZ261-LMZ362-LMZ364-LMZ366- LMZ563-LMZ565 until 6 AM Tuesday.