textproduct: Marquette

KEY MESSAGES

- Sub-freezing temperatures this morning will result in a hard freeze for much of the UP and a frost for the remainder of the UP. Freeze Warnings have been expanded and Frost Advisories remain in effect this morning.

- Temperatures approaching freezing Friday morning will result in another frost away from the Great Lakes.

- Borderline fire weather conditions are possible on Friday as winds gusts are over 50% likely to exceed 25 mph with RHs falling into the 20s% range in the afternoon, though high temperatures are not expected to widespread exceed 65 degrees.

- Dry weather through Friday is followed up by light rain this weekend.

UPDATE

Issued at 250 AM EDT Thu May 20 2026

The going forecast remains mostly on track this morning as GOES-East Nighttime Microphysics RGB imagery shows a virtually clear sky save for a few pockets of high cirrus. This with light winds will allow efficient radiational cooling with KSAW, KERY, and KISQ already falling sub-freezing along with a smattering of mesonet sites across the UP. As temperatures are pacing well cooler than the NBM (5Z RTMA shows around 5 degrees cooler than hourly NBM temps), the resulting forecast edits result in an expanded area of temperatures staying sufficiently sub-freezing to expand the Freeze Warning to include the entire UP except the Keweenaw Peninsula, the far west, and Menominee County (though north of US-2 will experience sub-freezing conditions).

For the rest of today and Friday, the two biggest areas of impactful weather will be the potential for particularly dry weather and a return of frost. With high pressure dominating the forecast for the rest of the work week, RHs will fall in the afternoon hours, with much of the interior UP seeing minimum RHs today and Friday well into the mid-20s. Thankfully, light winds mainly gusting under 10 kt will limit any wildfire concerns for today. Friday will have some concern as winds begin to gust to around 20 kt (LREF chances of exceeding 25 mph are 50+%) ahead of precip after sunset, though high temperatures perhaps not exceeding 65 as well as too low of certainty in the exact RH and wind forecast is too low to categorize the level of fire weather concern just yet. Friday morning, LREF probabilities of temperatures below 36 degrees continue to trend higher, with now up to 70% chances of such conditions in the interior central and eastern UP, though chances of sub- freezing lows are still 10% or less. Following the conclusion of ongoing frost/freeze headlines, another batch of Frost Advisories will be likely with the afternoon forecast package. The latest ensembles do not provide enough clarity on the weather pattern beyond Friday evening to deviate from the NBM.

DISCUSSION

Issued at 323 PM EDT Wed May 20 2026 Amended at 250 AM EDT Thu May 20 2026

High pressure has moved in over the UP and will continue to reside over the Great Lakes into the weekend. This keeps dry weather going through Friday. The cooler than normal airmass will reside overhead into the weekend, keeping highs in the 50s and 60s today through Saturday. Lows Friday morning will be slightly warmer in the 30s; additional Frost Advisories may be needed. The other thing to monitor is fire weather conditions. Mixing on Thursday and Friday suggest RH in the interior dipping into the 20s. That said temps are marginal both days and wind gusts only reach 20 mph on Friday, so borderline elevated fire weather conditions are the high-end solution.

Attention then turns to the troughing over the Plains on Friday. This collection of waves pivots northeast Friday, moving overhead on Saturday. At the surface a weak low moves from the Southern Plains into the Lower MI vicinity while a secondary low moves from the Central Plains to MN/IA before dissipating. Better ascent straddles the UP, but some light showers are likely. NBM probabilities of 0.25 inches of rain in 24 hours are 25-50%, highest near Lake MI, south- central, and along the western Spine of the UP.

Next week brings a warming trend as a strong mid level ridge builds over the Great Lakes. A trailing shortwave on Sunday leaves 15-25% PoPs in the forecast before favoring drier weather high pressure returns to the Great Lakes on Monday. Expect highs to warm back into the 70s and 80s for most early next week, cooler 60s by the lakeshores. Lows rise into the mid 40s to 50s. Forecast confidence quickly falls off by late next week as models struggle to resolve a closed low that develops over the west CONUS.

AVIATION /12Z TAFS THROUGH 12Z FRIDAY/

Issued at 716 AM EDT Thu May 21 2026

High pressure over the region is leading to P6SM and SKC conditions, with VFR forecast to prevail throughout the period. While winds will remain light with sustained winds only rarely exceeding 5 kt, wind directions may change significantly especially in the vicinity of the lake breeze.

MARINE

Issued at 323 PM EDT Wed May 20 2026

High pressure keeps winds variable below 20 kts through Friday morning. A low pressure system lifting into the Great Lakes on Saturday increases easterly winds between 15-25 kts late on Friday, continuing through much of Saturday. Winds settle below 20 kts Saturday night, once again remaining light and variable below 20 kts into next week as high pressure returns to the Great Lakes.

MQT WATCHES/WARNINGS/ADVISORIES

Upper Michigan... Frost Advisory until 9 AM EDT /8 AM CDT/ this morning for MIZ001>003-009-012.

Freeze Warning until 9 AM EDT /8 AM CDT/ this morning for MIZ004>007-010-011-013-014-084-085.

Lake Superior... None. Lake Michigan... None.