Marine Weather and Tide Forecast for Munising, MI

SHORT TERM /THROUGH TONIGHT/
Issued at 259 AM EDT Fri May 16 2025

As the last of the rain showers moves through the central U.P.
behind the cold front boundary that's passing through the far east right now early this morning, satellite imagery shows clearing beginning to move into the area from Wisconsin. As this occurs, we could see temperatures take a quick dip into the 50s for a low this morning. However, with warm air advection already projected to move into the area before dawn, not too much of a dip is expected. As the parent low slowly rotates over the Northern Plains into Minnesota today, expect the warm air advection to accelerate over the central U.P. by the afternoon hours. With mostly sunny skies expected across the region until the mid-afternoon hours, model soundings show a deep boundary layer developing ahead of and during the increased cloud coverage this afternoon. With the accelerating warm air advection bringing a low-level jet into the area, expect to see southerly wind gusts of 30 to potentially even 40 mph develop across the area by this afternoon. CAMs and other model guidance show discrete rain showers and thunderstorms developing along a secondary cold front moving through the U.P. late this afternoon/early this evening beginning in the central U
P
While the threat for severe weather late this afternoon into early this evening remains marginal (5% chance) according to the Storm Prediction Center, severe winds of 60+ mph are possible in the central U.P. as thunderstorm downdrafts could bring the LLJ winds to the sfc. Should this occur, we could see isolated spots having snapped tree limbs and downed power lines. We could also see some isolated hail reports up to a quarter in diameter as the LLJ will bring strong shear to any thunderstorms that develop. As the storms traverse eastward across the U.P. this evening, the severe threat will diminish as the environment becomes less favorable with time and the area of instability shrinks; it currently looks like the severe weather threat will be over by midnight tonight. As the vertically-stacked low moves trough northern Wisconsin tonight, expect the wrap around moisture to initiate some light rain showers across the area behind the cold front, mainly along the northern tier.

Besides the marginal severe weather threat, another concern for the short-term is limited to potentially elevated fire weather concerns over Ontonagon, southern Houghton, and Baraga counties early this afternoon. Expect relative humidities to drop down to around 30% by the early afternoon hours, with highs getting into the mid to upper 70s and southerly winds gusting up to 30 to potentially 40 mph at times. However, as the cold front pushes through by the late afternoon hours, expect conditions to begin improving, with showers and even thunderstorms (some potentially strong to severe) being possible. Given the recent rainfall received over the area over the past 24 hours, will not issue an SPS for fire weather concerns this morning. However, should conditions be worse than forecasted for, this decision may need to be reevaluated.

LONG TERM /SATURDAY THROUGH THURSDAY/
Issued at 356 AM EDT Fri May 16 2025

The extended period is quite a bit calmer and cooler, with most of the period dominated by high pressure ridging from northern Ontario/Hudson Bay and low pressure missing us to our south. Thus, expect to see fairly dry conditions once we get through this weekend, but also below normal temperatures too.

Expect wrap around moisture from the low to continue light rain showers across the area Saturday, with the convection becoming more focused on the northern tier over the western U.P. by the afternoon hours as upslope enhancement becomes more evident. While the winds are expected to be lighter Saturday than today, we could still see some northwesterly gusts up to 30 mph at times by the afternoon hours as the low moves from the Upper Great Lakes towards the St.
Lawrence Seaway. With modest cold air advection cycling into the area Saturday, expect highs to be muted and below normal, only getting into the 50s across the area save for maybe the lower 60s in the far east and south central. A secondary trough behind the low is expected to bring reinforcing moisture and cold air advection to our region Saturday night and Sunday, allowing the upslope showers to continue as some lake enhancement may start to come into play. With some of the model guidance showing negative energy (below 0C) above the sfc, it's possible that we could see the light rain transition to snow, sleet, or even freezing rain; highs Sunday are only projected to get into the lower 40s along the northern tier near Lake Superior. While the NBM does not show this, I think that the greatest concern right now is the freezing rain potential, especially since some model soundings have the sfc temperature right at or below freezing Sunday. Now, with that being said, even if the freezing rain were to occur, I'd expect no more than a glaze to a couple of hundreths of an inch to accumulate (if that) as there won't be much moisture in the air to work with. While this would not cause any concerns for the power grid, it could create some travel concerns for the evening and overnight hours on untreated roadways; will need to monitor this in the future, even though I have low (less than 20%) confidence that this will happen.

The current model guidance has high pressure ridging from northern Ontario/Hudson Bay dominating the U.P. the rest of next week, keeping us dry and cooler than normal; expect highs to generally be limited to the 50s until we see a slight climb into the lower to mid 60s by the end of the week. We could see limited to potentially elevated fire weather concerns once again Monday and Tuesday across the interior west as the NBM shows relative humidities dropping down to as low as the mid 20 percents. However, given the recent rainfall, cooler temperatures, and lighter winds expected, leaning towards this being more of a limited fire weather threat at this time.

While a strong low pressure looks to develop over the Central Plains and meander eastward with time early next week, with the high pressure ridging overhead, I'm currently thinking that we will stay dry (even though the NBM is still giving us a chance for precipitation). However, should ridging in the lower levels be weaker than what's currently forecasted, there is a chance that we could get the northern flank of the precipitation associated with the low, especially since a mid to upper level low is already expected to be over the Ontario/Quebec border region near the Upper Great Lakes.

AVIATION /06Z TAFS THROUGH 06Z SATURDAY/
Issued at 116 AM EDT Fri May 16 2025

Showers and storms have exited the terminals, except for CMX where showers will linger through the first hour or so of the TAF period.
Brief MVFR expected at CMX/SAW for very early in the TAF period before VFR resumes. LLWS conditions expected to develop late tonight into Friday morning at IWD.

Main threats for Friday are gusty southerly winds and potential for thunderstorms. South to southwest winds are expected to gust around 30 kt from the late morning through the afternoon, with a 30% chance of up to 40 kt at IWD/SAW. There is about a 30% chance of thunderstorms at SAW in the 21Z-02Z timeframe. Any thunderstorm could result in briefly higher gusts to 50 kt. VFR expected to prevail the day, but cigs settle back to MVFR toward the end of the TAF period.

MARINE
Issued at 356 AM EDT Fri May 16 2025

Expect southeast to southerly winds to pick up to 30 knots with a few gale force gusts up to 35 knots possible this afternoon over the eastern lake as a LLJ moves into the area. As the sfc low moves over the lake today and tonight, expect the winds to become northwesterly at 20 knots or less behind it. However, as a secondary shortwave brings additional cold air advection into the region Saturday into Sunday, expect the northwesterly winds to pick up to 25 to 30 knots with a few gale force gusts up to 35 knots Saturday through Saturday night over the central and eastern lake. However, as high pressure ridging begins to move back in from the west and north on Sunday, expect the winds to become north to northeasterly at 20 to 25 knots Sunday morning before weakening to 20 knots or less late in the afternoon. A strong low meandering from the Central Plains into the Ohio Valley could create northeasterly winds of 20 to 30 knots across the western half of the lake Monday and Tuesday.

Some rain showers and thunderstorms are expected over the eastern half of Lake Superior late this afternoon into this evening, with some of the thunderstorms potentially bringing severe winds of 50+ knots and hail up to a quarter in diameter down to the water's sfc.
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MQT WATCHES/WARNINGS/ADVISORIES
Upper Michigan...
None.
Lake Superior...
None.
Lake Michigan...
None.