Marine Weather and Tide Forecast for Munising, MI

DISCUSSION
Issued at 246 AM EDT Mon Apr 20 2026

Clear skies early this morning have allowed temperatures to plunge into the teens already as longwave radiation escapes from Earth into space; we may even have a few of the typical cold spots in the interior areas get into the positive single digits before sunrise this morning. As this happens, we may see some frost form across the area as widespread sub-freezing temperatures continue until after sunrise. After sunrise, expect the high pressure ridging over the U.P. to allow RHs to tank into the 20 percents to potentially teens over the west half by late this afternoon as a dry cold front from northern Ontario prepares to drop across the U.P. late tonight. With a LLJ moving in ahead of the cold front, expect to see winds to start increasing from the south as the day goes on; we could even see southerly gusts up to 30 mph in the downslope areas near Lake Superior by early this evening (up to a 40% chance). In addition, warm air advection begins to move into U.P. today ahead of the dry cold front, allowing temperatures to rise above freezing into the 40s to potentially even lower 50s over the west by late this afternoon. Thus, given the potentially low RHs, increasing winds late in the day, and warming temperatures, we could see elevated fire weather conditions over the west half of the U.P. late this afternoon into early this evening. However, one of the limiting factors for elevated fire weather potential is the winds not coming in until very late in the day; because the cold front won't push through the U.P. until late tonight, the LLJ ahead of it won't enter into the U.P. until late this afternoon/early this evening; by the time that happens, mixing starts to become limited in the boundary layer as temperatures start to lower due to the loss of sunlight.
Another limiting factor is the ongoing snowmelt over much of the area as well as the moist soils; with ongoing snowmelt over the north central, Keweenaw, and east during the day today, and with the ground across the area still being fairly saturated from the recent snowmelt and rain from last week, there may be more moisture available at the sfc than what guidance is suggesting, even despite the VERY dry air that's able to be mixed down throughout the daylight hours. And finally, another factor is the 'cool' temperatures; highs are only expected to get into the lower 50s over the interior west today, which isn't exactly conducive for increasing the vapor pressure deficit. Therefore, while some limited elevated fire weather concerns could be seen today, expect the factors listed above to keep fire elevated fire weather concerns in check.

Expect warmer low temperatures tonight as higher-level cloud cover keeps us somewhat insulated. Behind the dry cold front, expect clear/sunny skies through the mid-week as temperatures progressively warm each day. While RHs could drop into the 20 percents on Tuesday and Wednesday, and highs could get into the 60s on Tuesday and 70s on Wednesday, thinking fire weather concerns will be limited as winds will be light and snowmelt will still be ongoing over the northern tier of Upper Michigan. Nevertheless, the drier conditions may dry out the interior west near Wisconsin and south central throughout the week.

Our next chance of rain showers and thunderstorms looks to come around Thursday night/Friday as a robust cold front punches through Upper Michigan. The synoptic setup of the cold front moving through actually looks fairly similar to the cold front that passed us this past Friday. However, severe weather potential is looking muted at this point as not much CAPE will be available for convection; that being said though, there will be plenty of shear in the atmospheric profile and the hodograph does look supportive for stronger thunderstorms; should the forecast change and more energy become available for the potential convection, then expect the severe potential to increase. As of right now though, things look pretty tame save for maybe some heavy downpours.

Behind the cold front, drier weather returns as temperatures around normal hang around the U.P. thanks to the upper-level low responsible spinning over central Canada.

AVIATION /12Z TAFS THROUGH 12Z TUESDAY/
Issued at 705 AM EDT Mon Apr 20 2026

VFR conditions continue over the terminals today through tonight as a dry cold front passes through late tonight/early Tuesday morning.
Ahead of the cold front, expect high-level clouds to move into the area today. In addition, a LLJ is projected to move overhead tonight, bringing LLWS to each of the terminals. While the incoming LLJ is expected to increase winds later in the day across the terminals, the strongest winds will not arrive until after sunset; this will thus keep the strongest winds aloft tonight.

MARINE
Issued at 246 AM EDT Mon Apr 20 2026

Light winds of 20 knots or less this morning give way to increasing south to southwesterly winds this afternoon into this evening as a dry cold front drops over Lake Superior tonight. With a LLJ potentially bringing higher wind speeds to the lake's sfc tonight, there is a 40 to 50% chance that low-end gales to 35 knots will be seen tonight over the eastern open lake (chances highest near the International Border). Therefore, decided to keep the inherited Gale Watch going from 8 PM EDT this evening to 5 AM EDT Tuesday morning as there is still a lot of uncertainty on whether some of the higher winds in the LLJ will be able to mix down to the water, or if the stable layer caused by the cold water temperatures will prevent this from occurring.

Behind the dry cold front, expect winds to drop down to 20 knots or less again by Tuesday morning and to remain that way until Wednesday night/Thursday. As we head into Wednesday night/Thursday, expect increasing warm air advection from the Gulf to begin increasing winds from the southeast to south ahead of a stout cold front moving in from the west. Southeast to south winds increase to 20 to 30 knots over at least the eastern half of the lake by Thursday, with a 20% chance for low-end gales starting in the afternoon. The gale chances increase up to 40 to 50% by Thursday night as the cold front begins to push into the far western lake. Some rain showers and thunderstorms could be seen with the cold front's passage Thursday night through Friday. Behind the cold front, expect the winds to become westerly to 20 to 25 knots by Friday night.

MQT WATCHES/WARNINGS/ADVISORIES
Upper Michigan...
None.
Lake Superior...
Gale Watch from this evening through late tonight for LSZ266- 267.

Lake Michigan...
None.