textproduct: Marquette

KEY MESSAGES

- Showers and thunderstorms move in from west to east late tonight into Wednesday, persisting into Thursday morning. Greatest coverage of rainfall will be in the west half.

- Temperatures remain below normal through Thursday.

- Above normal temperatures and increased humidity return early next week, along with periodic showers and thunderstorms.

DISCUSSION

Issued at 149 PM EDT Tue Jun 23 2026

As of early Tuesday afternoon, midlevel shortwave ridging over the upper Mississippi Valley continues to result in subsidence over the UP today. It's another dry and seasonable day, but seasonably cool closer to Lake Superior with a northerly component to the low-level flow. A closed midlevel low over Saskatchewan will be the main player in the local weather for the midweek period. A shortwave trough along the southern periphery of the low is forcing a band of showers and thunderstorms pushing into western MN, while stratiform rain extends to the north and west into the southern Canadian prairies. CAM consensus is that the MN storms will weaken with eastward extend as they lose instability and encounter a progressively drier airmass. However, moistening will continue with time tonight as the shortwave works east and the UP becomes positioned in the poleward exit region of a seasonably strong 300 mb jet. This will result in a broken band of showers and embedded thunderstorms (MUCAPE values increasing up to 500 J/kg in the west) late tonight into Wednesday morning moving from the western into the central UP.

During the day Wednesday, the midlevel low opens up as it shifts a bit southeastward into the upper Great Lakes. Resulting midlevel height falls should result in continuing scattered to numerous shower and thunderstorm activity through the day, again with greatest coverage over the central and west but also spreading into the east. There exists a window for modest surface destabilization in the west by the afternoon, although the degree of insolation/warming is unclear. Per the 12Z HREF, nonzero probability of > 1000 J/kg SBCAPE is confined to areas near the WI border and tops out at around 40%, so the overall severe weather threat is low. Deep layer shear is also modest at 20-25 kt. Locally heavy rainfall will be possible in the west due to potential repeated rounds of rain and relatively slow-moving cells, and per the HREF LPMM, can't rule out locally up to 2" amounts. However, PWATs remain modest at just over an inch, and overall the flood threat is low.

The midlevel trough shifts over the UP Wednesday night into early Thursday, with the surface reflection moving into northern lower. This appears to be a decent pattern for some lingering shower activity in at least the morning (possibly into the afternoon in the east) with moisture not scouring out until later in the day as high pressure builds in from the west. Highs remain in the mid-60s to low 70s both Wed/Thu.

Confidence continues to grow in a long-awaited pattern change this weekend into early next week, as ridging builds over the Upper Midwest in response to an anomalous midlevel low lifting from the Pacific Northwest/northern Rockies into the Canadian Prairies. The trend among the ensembles has been for a less progressive ejection of height falls from the trough and a stouter ridge, so accordingly, chances are increasing that the entire coming weekend will be dry. It's becoming more likely that we'll see a return to above-normal temperatures along with increasing humidity and bouts of thunderstorms by early next week as the ridge axis shifts east and midlevel southwesterly flow evolves.

AVIATION /00Z TAFS THROUGH 00Z THURSDAY/

Issued at 822 PM EDT Tue Jun 23 2026

A mid level trough is still on track to bring scattered showers and thunderstorms from west to east late tonight into tomorrow morning. Until then, VFR conditions will prevail at all TAF sites. However, will lean toward TEMPOS and PROB30s after that to account for periods of MVFR conditions in heaviest rain showers and thunderstorms. First tempo, though, will be at IWD in the Wed 02-06Z time frame to highlight approaching showers with PROB30s after Wed 06Z. Elsewhere, onset of any flight restrictions with showers and storms will be after Wed 10Z at CMX and SAW. For now, will continue to omit thundestorm mention at CMX where probabilities are too low.

MARINE

Issued at 149 PM EDT Tue Jun 23 2026

Light winds persist into early tonight due to high pressure. An approaching low will result in a modest increase in southeasterly winds over the east half of the lake, and northeasterly over the west half, gusting to near 20 kt late tonight into Wednesday. Isolated thunderstorms are possible over the lake during this time period as well. Winds will be less than 20 kt Wednesday night through the rest of the week.

MQT WATCHES/WARNINGS/ADVISORIES

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