963 FXUS63 KMQT 200509 AFDMQTArea Forecast Discussion National Weather Service Marquette MI 109 AM EDT Sat Sep 20 2025
.KEY MESSAGES...
- Off and on showers and thunderstorms are expected Saturday through early next week.
- Seasonable temperatures continue through next week.
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.DISCUSSION... Issued at 304 PM EDT Fri Sep 19 2025
Afternoon water vapor and RAP analysis reveal broad troughing over the Northern Plains, with an embedded closed midlevel low spinning over eastern South Dakota and additional shortwaves rotating around the parent trough. At the surface, low pressure is analyzed over the eastern Dakotas and western Minnesota, with an associated stalled front extending out from it into MN and southern WI and another cold front extending into IA. Closer to home, spotty showers continue across the western half of the UP courtesy of some weak shortwave action, but drier midlevel air is moving into northern WI ahead of the aforementioned stalled front; this will help to bring a brief pause in shower activity into the evening hours.
Tonight through Sat, the closed low unravels while the parent trough begins to move towards the Great Lakes, and a somewhat more vigorous shortwave currently moving into eastern NE swings towards the UP with the stalled front slowly lifting northward through WI. So, while dry weather will persist for most through tonight, chances for scattered showers return for the daytime hours Saturday. Our best window for showers will be Saturday night as the more vigorous shortwave ripples through. Another trailing shortwave moves through Sunday, keeping PoPs in the forecast for the remainder of the weekend. Some thunder will not be ruled out given some modest instability (a few to several hundred j/kg of MUCAPE) but weak forcing and limited shear will preclude any risk for severe storms. Where we can get any heavier showers or storms, guidance favors the occasional quarter-inch of QPF. Otherwise, look for temperatures to continue to come in more or less near normal through the weekend with highs ranging generally in the mid/upper 60s and lows in the 50s.
Chances for showers and perhaps a non-severe storm linger Monday as the trough slowly moves through. From there, high pressure builds in with diminishing cyclonic flow aloft bringing back drier weather for Tuesday and Wednesday. However, forecast confidence wanes from this point onwards as synoptic features are poorly resolved by guidance after Wednesday. The general trend is for a shortwave to move onshore of the Pacific NW early in the week, drop into the Plains by midweek. Some of the guidance closes off a midlevel low over the Midwest or Great Lakes by this point. Then, the trough or midlevel low finally drops south of the Great Lakes by late Friday. A ridge looks to build in over the W in the trough`s wake, traversing E toward the Canadian Prairie into the weekend. How that feature gets affected by a closed low developing somewhere over the Central U.S. or several messy shortwaves across the CONUS is not clear. Opted to leave the NBM as is, favoring drier weather and rather steady temps with highs in the mid 60s to low 70s and lows in the mid 40s to mid 50s.
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.AVIATION /06Z TAFS THROUGH 06Z SUNDAY/... Issued at 109 AM EDT Sat Sep 20 2025
SAW and CMX have already made the transition from MVFR to VFR early this morning, but IWD is still holding steady at MVFR. However, IWD should also become prevailing VFR in the next few hours with a MVFR tempo to then account for the next round of showers and isolated thunderstorms expected to overspread Upper Michigan. PROB30 groups have also been inserted at CMX and SAW throughout the TAF period to capture periods of MVFR/IFR conditions in any heavier downpours. Meanwhile, southeast winds will be an impact at CMX with gusts up to 25 kts at times through the TAF period.
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.MARINE... Issued at 304 PM EDT Fri Sep 19 2025
Northeast winds remain elevated across the western arm of the lake through this evening and into the first half of the night, with 20- 30kt gusts common. There remains around a 20-40% chance of some gale- force gusts closer to the Duluth harbor. This builds significant wave heights up to 3-4 ft SW of Stannard Rock and between 4-9 ft over the W half through this evening. Winds veer ESE tonight into early Sat with 20-30kt gusts continuing; this time the strongest winds will be over the eastern half of the lake. This results in waves of 3-6 ft over the N-Central waters and along the international border on Sat. Winds gradually settle below 20 kts from W to E late in the day Sat through Sun morning, likely remaining below 20 kts through much of next week. Otherwise, expect on and off showers and thunderstorms this weekend.
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.MQT WATCHES/WARNINGS/ADVISORIES... Upper Michigan... None. Lake Superior... None. Lake Michigan... None.
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DISCUSSION...LC AVIATION...JTP MARINE...LC
NWS mqt Office Area Forecast Discussion