398
FXUS63 KMQT 181134
AFDMQT

Area Forecast Discussion
National Weather Service Marquette MI
734 AM EDT Mon Aug 18 2025

.KEY MESSAGES...

- There is a High Swim Risk this morning for the Lake Michigan
beaches of Schoolcraft County.

- Showers spread from west to east beginning this morning. Some non-
severe thunderstorms will be possible through early Tuesday. Heavy
rain will be possible, with a Marginal (category 1 of 5) for
excessive rainfall that may lead to localized flash flooding.

&&

.SHORT TERM /THROUGH TONIGHT/...
Issued at 420 AM EDT Mon Aug 18 2025

Early morning RAP analysis shows a shortwave (subtle at 500mb but
more pronounced at 700mb) over the eastern Dakotas moving into
Minnesota while longwave ridging prevails over much of central North
America. The UP is at the western periphery of the main surface high
pressure associated with said ridging, which at 08Z was centered
over the Ontario/Quebec line at around 1026 mb. Thus far, radar
returns have shown no precip over the UP with only light radar
returns over the far western open waters of Lake Superior. With the
delayed arrival of precipitation associated with the weakening
shortwave and nebulous forcing despite high PWATs (near 1.75 inches
by 00Z this evening is 97.5th+ percentile per the NAEFS) has lead to
a decreasing trend in QPF, with the HREF mean QPF by 12Z Tuesday
around a half inch for much of the UP. While a few embedded
thunderstorms are possible with these showers, HREF mean MUCAPE
throughout this event is less than 500 J/kg, so no severe weather is
expected. Excess cloudiness will flatten the diurnal temperature
curve somewhat with high temperatures today only expected to be in
the mid 60s to near 70. Gusty winds out of the southeast will force
prime conditions for rip currents along the Schoolcraft County
shorelines of Lake Michigan, so a Beach Hazard Statement will remain
in effect through the morning, with diminishing wind speeds in the
afternoon allowing for the rip current threat to similarly diminish.

As northwest flow sets up over the UP with ridging upstream, shower
activity will decrease from west to east overnight tonight. Low
temperatures wont fall far below the lower 60s tonight as abundant
moisture remains and cloud cover lingers.

&&

.LONG TERM /TUESDAY THROUGH SUNDAY/...
Issued at 324 PM EDT Sun Aug 17 2025

Showers taper off Tuesday as riding over the Northern Plains
supports surface high pressure building over the Great Lakes. High
pressure remains in place through midweek before ridge-riding
shortwaves cause the ridge to receded southwards by Friday. Expect
dry weather to persist to at least early Friday. Then, a deeper
trough and associated surface low move through Manitoba and Ontario
Friday into the weekend. This will bring in our next chances for
rain as a cold front sweeps through. Additionally, though a warming
trend is expected after Tuesday, temperatures may turn cooler than
average next weekend behind the front.

&&

.AVIATION /12Z TAFS THROUGH 12Z TUESDAY/...
Issued at 734 AM EDT Mon Aug 18 2025

While VFR conditions prevail at all TAF sites early this morning,
lowering ceilings and precipitation will move over all TAF sites
today, with some PROB30s for chances of non-severe thunderstorms
this morning at IWD and this afternoon at all sites. With abundant
moisture, even after precip ends, all sites will fall to MVFR with
IWD and CMX falling to IFR and occasionally LIFR, primarily in
ceilings but reductions in vis are also possible. Winds will be
occasionally gusty out of the southeast until a cold front pushes
through and shifts winds to be lighter and out of the northwest.

&&

.MARINE...
Issued at 324 PM EDT Sun Aug 17 2025

High pressure ridging centered across Ontario is keeping in gusty
northeast winds this afternoon - highest across the western arm of
the lake, where winds continue to gust to around 20-30kts. Winds
shift easterly, then to the southeast tonight into Monday, with 20-
25kt gusts becoming common across the whole lake. Some stronger
gusts to around 30kts will be possible along and north of the
Keweenaw. Meanwhile, a shortwave trough moving in will bring in
chances for showers and some rumbles of thunder. Winds gradually
lighten to 20 knots or less and more stable conditions return by the
middle of the week as high pressure ridging from Canada comes back
to the region.

&&

.MQT WATCHES/WARNINGS/ADVISORIES...
Upper Michigan...
  Beach Hazards Statement until noon EDT today for MIZ014.

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

&&

$$

SHORT TERM...GS
LONG TERM...LC
AVIATION...GS
MARINE...LC