textproduct: Marquette

KEY MESSAGES

- The combination of warm, moist air contributing to snowmelt and moderate to locally heavy rain Thursday night into Friday will result in renewed flooding concerns for low-lying areas, streams, and rivers over the western half of the UP. A Flood Watch has been issued.

- Unseasonably warm temperatures continue through Thursday, settling to near to slightly above normal Friday into the weekend. The next period of widespread precipitation is expected Monday into Monday night.

- There is a 50% chance for low-end gales over eastern Lake Superior near the international border Thursday evening through Friday morning.

DISCUSSION

Issued at 350 PM EDT Wed Apr 22 2026

Temperatures in the interior UP are reaching into the high 60s and lower 70s this afternoon in the midst of mid-level ridging extending across the Northern Great Plains and Great Lakes. Thanks to radiational heating and low moisture in the low-levels, dewpoint values inland have reached down into the 20s and 30s. Closer to Great Lake shorelines, temperatures are remaining lower, in the 50s and lower 60s, and dewpoints higher, tending to be above 30. While the low-level dryness and sunshine offers welcome relief for snow- free saturated soils, risk of river flooding in localized areas remains as snowpack continues to melt out of upland, forested areas. Modeled NOHRSC SWE shows remaining snowpack contains mostly between 2" and 10" of water equivalent in the upstream areas of the Sturgeon, Escanaba, and Michigamme, Menominee River basins. with pockets of higher amounts possible. Though dewpoints may well continue to drop into the teens through the remainder of today, creating even drier surface conditions, only limited fire weather concerns exist in the short-term given nonexistent to light breezes across the CWA.

Conditions look to begin to shift tonight as a mid-level trough deepens and progresses eastward across the Northern Great Plains; its accompanying surface low organizes throughout Wednesday night and begins to lift through North Dakota to southern Manitoba by Thursday morning. On the backside of today's ridging and ahead of this incoming low, theta-E advection aloft leads to weak elevated instability, Isle Royale may see a band of low-QPF (<0.2") showers and perhaps a thunderstorm or two. Surface moisture recovers substantially Thursday morning as a plume of warm Gulf moisture wraps into the incoming low; RH's reach into the 60s and 70s mid- morning.

By Thursday, midlevel ridging crests over the local area while troughing approaches from the west. A surface low will occlude over southern Manitoba. Warmth and moisture will increase on strong southerly winds in the surface to 850 mb layer. With precipitation not expected until late Thursday evening, a deepening boundary layer will contribute to high temperatures well above normal, especially in the western half where the airmass will not be modified by Lake Michigan, with highs well into the 70s and possibly touching 80 (50s and 60s in the east half where winds will be off Lake Michigan). An axis of PWAT of 1-1.25 inches will approach from the west in the evening, which is +2 to +3 sigma per the NAEFS. The approaching frontal boundary will slow as the low occludes, with the possibility of weak waves developing along the front, which could prolong the heavier rainfall in the far west. Latest probs of > 1" in 24 hours are up to 40% per the REFS. There is also modest instability with 500-750 J/kg MUCAPE which could result in convective downpours. The combination of accelerated snowmelt and moderate to locally heavy rainfall has prompted the issuance of an Areal Flood Watch from Thursday evening through Saturday morning for the western half of the UP (see hydro section below for more details). The QPF will be reduced with eastward extend owing to the lack of instability, but there is still some uncertainty here with a 10-20% of exceeding an inch during the day on Friday. With deep layer shear increasing to near 30 kt there is a marginal risk of a stronger storm or two producing gusty winds and hail, although the marginal parameters and unfavorable time of day limit this potential.

As the upper low stays fairly stationary over southern Canada Friday into the weekend, cold air advection will be rather gradual, with the core of coldest air remaining west. So temperatures will just be knocked down closer to normal for the weekend. A dry weekend is favored as the deep moisture plume exits east. Additional troughing emanating from the desert Southwest will eject into the Plains and Great Lakes early next week, with the next period of organized precip likely Monday into Monday night. Near to below normal temperatures are favored thereafter.

AVIATION /18Z TAFS THROUGH 18Z THURSDAY/

Issued at 113 PM EDT Wed Apr 22 2026

VFR prevails through the rest of today courtesy of high pressure over the area and mostly sunny skies. Tonight, ahead of a weak front (chances of precipitation under 15%), southerly flow becomes gusty at IWD, and LLWS is present at IWD and CMX. Should the front be stronger than expected, IWD has a ~25% chance of falling to MVFR at 11Z Thursday. There is also a 25% chance for MVFR ceilings at SAW by mid-morning as southeast winds may bring in lower-level marine moisture off of Lake Michigan.

MARINE

Issued at 350 PM EDT Wed Apr 22 2026

Winds will become southeasterly and increase to 20 to 25 knots over the north central and eastern lake tonight ahead of an approaching frontal boundary. The winds continue to build from the southeast Thursday into Thursday night as a cold front approaches from the west. Eventually, southeast gales up to 35 knots could start to occur Thursday evening over the eastern open lake, with chances for low-end gales becoming maximized to up to 50% late Thursday night, with highest probabilities near the international border. A Gale Watch was not issued due to the limited area of higher gale probabilities. While some rain showers are expected along and ahead of the cold front's passage Thursday night through Friday, no severe weather is expected save for maybe a low-end chance for some stronger storms containing gusty winds and hail closer to Duluth early Thursday evening.

Behind the cold front, expect the winds to become westerly gusting up to 20 to 25 knots Friday night into early Saturday. After that, expect light winds of 20 knots or less to return to Lake Superior for the rest of the weekend thanks to a weak pressure gradient and high pressure ridging.

HYDROLOGY

Issued at 350 PM EDT Wed Apr 22 2026

Dewpoints will climb into the 40s and 50s Thursday which, combined with significantly warmer than normal temperatures and breezy conditions, will result in accelerating melting of the snowpack Thursday and Friday. Latest projections suggest an average of 2" per day of snow water equivalent could melt during this time. An approaching frontal boundary will slow as it approaches the UP, which could prolong the heavier rainfall in the far west. Latest probs of > 1" in 24 hours are up to 40% in the west Thursday night into Friday, decreasing to 20% in the central and east mainly on Friday. There is also potential for thunderstorms in the west half which could result in locally heavier downpours. The combination of accelerated snowmelt and moderate to locally heavy rainfall has prompted the issuance of an Areal Flood Watch from Thursday evening through Saturday morning for the western half of the UP. There is uncertainty on impacts given that the highest probability of heavy rainfall are south of the existing snowpack. However, renewed rises on area rivers and streams can be expected Thursday into the weekend, and flooding of low-lying areas, creeks, and streams can also be expected.

MQT WATCHES/WARNINGS/ADVISORIES

Upper Michigan... Flood Watch from Thursday evening through Saturday morning for MIZ001>005-010-011-084.

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