textproduct: Marquette

KEY MESSAGES

- Cooler than normal temperatures through the rest of the work week. Frost is possible the next few nights.

- A dry work week is followed up by light rain this weekend.

UPDATE

Issued at 246 AM EDT Wed May 20 2026

The going forecast remains on track this morning as GOES-East Nighttime Microphysics RGB imagery shows some pockets of low stratus and some high cirrus but otherwise unimpactful weather over the UP. RAP analysis shows expansive 1024 mb high pressure centered over the eastern Dakotas yet covering most of the north-central CONUS. Anywhere not affected by low stratus will see efficient radiational cooling tonight with decreasing northwest winds in addition to the ongoing 850mb cold advection. This 1-2 punch of cooling will bring lows near freezing this morning for most. While a slackening pressure gradient from the approaching high and low pressure over Quebec getting further away will result in decreasing winds, the long fetch of the NW winds will keep wave heights in excess of 4 feet for the nearshore Lake Superior waters adjacent to Alger and Luce counties into this afternoon, which may be hazardous to small craft.

For the week ahead, with the only precipitation chances in the forecast having low impacts associated with them, the two biggest areas of impactful weather will be the potential for particularly dry weather this work week and frost impacting the beginning of growing season. With high pressure dominating the forecast for the rest of the work week, RHs will fall in the afternoon hours, with some spots seeing minimum RHs Thursday and Friday well into the mid- 20s. Thankfully, light winds mainly gusting under 15 kt will limit any wildfire concerns. With Friday beginning frost/freeze headlines, the LREF has increased chances of the interior UP seeing sub-36 degree lows Friday morning, now as high as 55%. A hard freeze is not expected as chances of sub-freezing lows sub-10%.

DISCUSSION

Issued at 220 PM EDT Tue May 19 2026 Amended at 246 AM EDT Wed May 20 2026

High pressure and dry air building in from the west behind the previous day's cold front sets up a quiet pattern for the remainder of the work week as it slides over the Great Lakes region. Precipitation does not return until this weekend as a trough over the Plains pivots northeast over the region. Details around this are murky, but impacts likely will be low as instability is nil and probabilities of exceeding 0.5 inches of rain in 24 hours holds at 10% of less. Drier and warmer weather is progged to return early next week with high pressure possibly returning. This quieter period is captured in the CPC precipitation outlooks with near normal for the 6-10 day and slightly below normal for the 8-14 day.

Despite zonal flow developing aloft by this afternoon, low level CAA into today yields temps between 5-15F below normal. Lows in the 30s to low 40s this morning will only warm into the 40s to mid 50s for most today, save for a few spots reaching low 60s south-central. Temps dip even lower tonight into the upper 20s to upper 30s. While it is still early for growing season, some patchy frost is possible tonight and widespread frost is anticipated Wednesday night. A ridge over the southeast CONUS begins to build late week while a trough deepens over the Rockies. This strengthens southerly flow and WAA increasing temps closer to normal by this weekend with highs in the 50s and 60s and lows in the 40s to low 50s. Patchy frost is possible again Thursday night, but no headlines are planned yet this week given slow start to growing season. In the wake of the weekend system, a strong mid level ridge looks to build over the Midwest, favoring the warming trend to continue into next week. CPC temperature outlooks both show the UP under ~65-70% chances for above normal temps to close out the month.

AVIATION /12Z TAFS THROUGH 12Z THURSDAY/

Issued at 653 AM EDT Wed May 20 2026

Besides some transient MVFR ceilings this morning at IWD and SAW, VFR conditions prevail over the TAF sites through the period. Expect light winds out of the northwest to veer to the north to northeast through today and the evening, becoming south-southeasterly at IWD and CMX early tomorrow morning.

MARINE

Issued at 220 PM EDT Tue May 19 2026 Amended at 246 AM EDT Wed May 20 2026

Winds over the east settle below 20 kts this morning and likely remain sub-20 kts across the lake through Friday as high pressure persists over the Great Lakes and eastern Canada. Significant wave heights of 4-6 ft over the east settle below 4 ft by this afternoon and likely remain 4 ft or less the remainder of the forecast period. This light wind pattern may even persist into next week with no significant systems on the horizon this weekend and high pressure favored to return next week.

MQT WATCHES/WARNINGS/ADVISORIES

Upper Michigan... Beach Hazards Statement until 5 PM EDT this afternoon for MIZ006.

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