textproduct: Marquette

KEY MESSAGES

- Rain and snowmelt will continue to lead to rises on area rivers and possible minor flooding on typically flood-prone rivers, especially early to mid next week during and after a strong low pressure brings additional rainfall to the area.

- An active and warmer pattern is expected for early next week. Some strong to severe thunderstorms are possible (15% chance), with severe hail being the primary threat; severe winds are a less likely secondary threat.

- There is a non-zero chance for flash flooding across our area Monday into Tuesday morning, with the highest chance of occurrence currently over the west (5% according to WPC).

SHORT TERM /THROUGH THIS AFTERNOON/

Issued at 212 AM EDT Sat Apr 26 2025

Upper air pattern consists of a 500 mb closed low off the CA coast and a shortwave trough across the upper Great Lakes. The shortwave trough moves to New England by 00z Sun. Basically, quiet weather for this forecast period. Drizzle and showers will continue to move out and drier air and weather will move in. Did not make too many changes to the going forecast.

LONG TERM /TONIGHT THROUGH FRIDAY/

Issued at 252 AM EDT Sat Apr 26 2025

Sunday, look for cloud cover to increase as the ridge axis shifts eastward and low pressure organizes over the Plains. While we could see RHs drop down into the lower 30 percents again in the interior east, given the cloud cover overhead, expect conditions at the surface to be a little more moist on Sunday in comparison to Saturday for most of the area. Southerly flow will see temperatures rising well into the 50s for most of the UP, apart from the shorelines of Lake Michigan where temperatures may even struggle to crack the 50 degree mark.

Active weather then returns for the beginning of the work week. Model guidance remains in fairly good agreement on the deepening trough over the Rockies Sunday night lifting northward towards the Great Lakes Monday. A strengthening southerly LLJ will be directed into the Upper Midwest Sunday night, with strengthening WAA aloft in response. PWATs increase to around an inch over the Great Lakes Sunday night, but as we head into the daytime hours Monday, a Gulf connection will funnel in even higher PWAT air (as much as 1.25in over the Great Lakes). Meanwhile, a surface low closes off somewhere over western NE or SD closer to 06Z Monday, and deterministic and ensemble guidance are narrowing in on a track that has this moving northeast through MN Monday to reach western Lake Superior around 06Z Tuesday. Thus, the UP will be in the warm sector of the system for most of the day as the warm front becomes directed from the Northern Plains to northern Ontario. Will note that this means that our strengthening southerly flow will be directed largely parallel to the warm front. Low pressure moves into northern Ontario late Monday night, with the associated cold front tracking through the UP early in the day Tuesday.

So, what? An initial batch of rain, perhaps with some embedded thunder, develops over the Plains late Sunday and may reach us Sunday night into Monday morning. However, our main batch of rain and potentially severe convection develops by Monday evening and continues through the first half of the night. MUCAPE increases to 1000-2000j/kg, with deep layer shear up to 50+kts. While the severe threat will be lessened during the overnight hours, given that we will be in the warm sector ahead of the low's cold front Monday night, some embedded energy aloft and strong shearing could very well allow strong to severe thunderstorms to continue across the region until the cold front moves through Tuesday morning. With cloud cover remaining over us throughout the day Monday via the warm front moving over us, no surface-based CAPE is projected; thus, tornadoes are not expected for our area. However, with convection being elevated in nature and strong shear keeping mesocyclones going, we could see severe hail across our area, with severe thunderstorm winds being a possibility too (albeit with a lower possibility of occurrence); currently, the SPC shows the U.P under a 15% chance for severe weather late Monday through Monday night.

Meanwhile, with showers and storms continuing over the area Monday into Tuesday morning, some training of convection may occur. Taking this into account, and ensemble guidance showing PWATs increasing up to around the 95th percentile modeled climatology, there is a non- zero chance that we could see some flash flooding across the area late Monday into Tuesday morning, particularly over the western U.P. where guidance is highlighting higher QPF returns (WPC also shows a 5% chance for flash flooding for late Monday over the western U.P.). As far as totals, guidance shows a widespread quarter to half-inch of rain across the UP Monday through Monday night, with around a 30- 40% chance for higher rainfall amounts in excess of an inch.

As the cold front of the low pushes through on Tuesday morning, expect a progressive end to the rainfall from the northwest to southeast. We could see a quick transition over to some snowfall at the end, but with temperatures still being above freezing, nothing should stick. We could see some more river rises in response to the rainfall into the middle of next week though, particularly if this is a soaking rainfall event.

The active weather pattern continues into the latter half of next week, with drier weather on Wednesday being replaced by more rainfall over the area sometime late next week. Expect the temperatures to be fairly seasonable from Wednesday onwards.

AVIATION /06Z TAFS THROUGH 06Z SUNDAY/

Issued at 1219 AM EDT Sat Apr 26 2025

High pressure will gradually build into the region tonight, resulting in all sites trending toward VFR conditions. MVFR ceilings will still be possible early in the period tonight at KCMX and through the night at KSAW. Additionally, MVFR visibilities will also be possible at KSAW. Winds will be mainly northerly, with gusts to 20kts possible Saturday at KSAW.

MARINE

Issued at 252 AM EDT Sat Apr 26 2025

Northerly winds continue to gust to around 20-25kts across the east half of the lake this morning, but will slowly fall back below 20kts this afternoon. The winds remain light until a low lifting from the Northern Plains approaches on Monday. As it does so, some thunderstorms could move into the western lake Monday afternoon, followed by the eastern half Monday evening. Some of the storms could be strong to severe ahead of the low's passing Monday night, with severe hail being the primary threat; severe winds are a secondary threat and will be dependent on if they can make it to the surface. If the winds can reach the surface, the erratic and strong winds could make sailing dangerous underneath the thunderstorms. Ahead of the low's passage, expect winds to increase from the southeast and south to 20 to 30 knots over the eastern half of the lake Monday afternoon and evening. Behind the low's passage, expect winds to pick up from the northwest and north, potentially gusting up to gales of 35 knots over the north central and eastern lake on Tuesday. As high pressure moves back in on Wednesday, expect the winds to diminish back down to 20 knots or less again by Wednesday morning, remaining below 20kts through the rest of the work week.

MQT WATCHES/WARNINGS/ADVISORIES

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