573
FXUS63 KMQT 171924
AFDMQT

Area Forecast Discussion
National Weather Service Marquette MI
324 PM EDT Sun Aug 17 2025

.KEY MESSAGES...

- There is a High Swim Risk today for the beaches of Marquette and
Alger counties.

- Showers spread from west to east beginning early Monday morning.
Some thunderstorms, likely non-severe, 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 flash
flooding.

&&

.SHORT TERM /THROUGH MONDAY NIGHT/...
Issued at 324 PM EDT Sun Aug 17 2025

Afternoon RAP analysis has high pressure centered over Ontario, with
ridging southward into the Great Lakes. Meanwhile, just to the west,
a midlevel shortwave is seen moving through the Dakotas with
convection already kicking off across western MN. Closer to home,
skies remain mostly clear - apart from right along the Superior
shoreline. Cool, northeast upslope flow is keeping in low-topped
stratocumulus across far northern Marquette county. Temperatures are
staying on the chilly side, peaking only in the lower 60s lakeside
and in the lower 70s inland.

Tonight, winds shift to be out of the east as the aforementioned
embedded shortwave moves to the northern MN vicinity and surface low
pressure in the 1005-1010mb range moves into MN. This will continue
to track eastward either right over the Upper Peninsula or over Lake
Superior. PoPs will slowly increase over the far west after 06Z and
only progress to the central UP by 12Z. Extremely meager instability
(mean MUCAPE in the HREF of maybe 250 J/kg) will limit nocturnal
thunderstorm potential. Instability remains limited into the daytime
hours as rain chances continue to spread eastward. Even if thunder
is only isolated in nature, heavy rainfall cannot be ruled out as
significant moisture advection will allow PWATs to climb to over 1.5
across the entire UP. Showers and storms finally wrap up late Monday
night into early Tuesday morning as the cold front moves in; by
then, a widespread quarter- to half-inch of rain is expected across
the area, but some spots may see higher totals of 0.75-1.0in. This
higher QPF would be possible especially where we can get multiple
rounds of rainfall (as suggested by some of the CAMS). WPC has us in
a Marginal risk for excessive rainfall.

Otherwise, expect temperatures to come in a couple degrees warmer
than today owing to weak warm advection; highs Monday reach into the
upper 60s to lower 70s area-wide, falling back into the upper 50s
and lower 60s Monday night.

&&

.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 /18Z TAFS THROUGH 18Z MONDAY/...
Issued at 126 PM EDT Sun Aug 17 2025

Cool onshore flow continues to lead to low strato-cumulus at CMX and
SAW, with MVFR restrictions possible at times over the next few
hours before cloud cover diminishes into the evening. Chances of
rain then overspread the TAF sites from west to east overnight
tonight into Monday morning, with about 30 percent chances of TSRA
at IWD prior to 12Z and otherwise VFR conditions at all terminals.
However, ceilings then lower to MVFR towards the end of the forecast
period. Expect winds to shift from the northeast to be primarily out
of the southeast by Monday morning.

&&

.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 8 PM EDT this evening for MIZ005-
     006.

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

&&

$$

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