229
FXUS63 KMQT 181850
AFDMQT

Area Forecast Discussion
National Weather Service Marquette MI
250 PM EDT Tue Aug 18 2026

.KEY MESSAGES...

- Isolated showers and thunderstorms this afternoon and evening,
  mainly near Lake Michigan.

- Temperatures will be close to seasonal averages most days
  through the week, with highs in the 70s and lows in the 40s
  and 50s.

- Showers and thunderstorms are possible (40-70% chance) late
  Thursday into Friday as a weak system moves through the area.

&&

.DISCUSSION...
Issued at 249 PM EDT Tue Aug 18 2026

The general pattern through the forecast period and toward the end
of August places the UP under northwest flow aloft. This yields
seasonal to slightly cooler than normal temps, captured by the CPC 6-
10 day temp outlook. The mid level closed low over northern Ontario
and Hudson Bay gradually makes its way to northern Quebec for
Thursday into the weekend, but likely will be replaced by another
deep trough early next week. Model discrepancies exist regarding the
timing and placement of this trough (or if another closed low
develops), but this currently does not yield significant changes to
the northwest flow anticipated for over the Upper Great Lakes.

Afternoon observations have placed the cold front now over central
and eastern Upper MI with temps in the 70s to low 80s ahead of it.
Tds in the upper 50s to low 60s and PWATs struggling to reach 1.2
inches are not terribly impressive, but steep low level lapse rates
and SBCAPE values up to 1500 J/kg are present over parts of the east
half. Strong bulk shear is present up to 50 kts on the latest SPC
mesoanalysis page. As low level f-gen increases with colder 925 mb
temps pressing south from eastern Lake Superior, isolated convection
continues. These could bring gusty winds and small hail, but severe
weather is not expected until outside the CWA.

A much drier airmass moves in tonight behind the cold front. Mostly
clear skies and light winds support (between 5-10F) colder than
normal temps. Lows are expected in the 40s to mid 50s, coldest
interior west where upper 30s are anticipated. High pressure builds
in over the Great Lakes through Wednesday, keeping dry and
comfortable conditions going. The blended guidance mean has been
running several degrees too warm during recent cool nights, thus
have opted for the lower end of the distribution, 10th percentile
for low temps tonight and tomorrow night. Highs in the 70s on
Wednesday will once again be followed by lows in the 40s to mid 50s,
coldest interior west where temps dip into the mid to upper 30s.

High pressure over the Great Lakes Thursday morning shifts
southeast, giving way to a shortwave and weak sfc trough the west.
WAA reintroduces rain chances into Thursday night and a trailing
shortwave continues PoPs on Friday. Strong to severe storms are not
expected given that probabilities of 1000 or greater CAPE values
struggle to reach 30% until Friday when bulk shear falls off. As far
as rainfall amounts go, 24 HR NBM probabilities for 0.25 inches or
more are in the 30-60% range with 15-25% chances for at least 0.75
inches. While any storms that do form could put down locally heavy
rainfall, a widespread heavy rainfall is not expected. Thus not
expecting appreciable improvements to the ongoing drought conditions
over the south and west. A cold front on Saturday yields one more
day of showers and non severe storm chances (15-30%) before high
pressure returns with mostly dry weather into early next week.

&&

.AVIATION /18Z TAFS THROUGH 18Z WEDNESDAY/...
Issued at 119 PM EDT Tue Aug 18 2026

VFR will be the predominant flight category for the duration of the
TAF period. The only exception could be brief MVFR conditions at SAW
later this afternoon, but with most if any convection expected south
and east of the area, will leave out of the TAF. Meanwhile, winds
are veering northwesterly with the passing front, with gusts up to
20kts possible mainly at SAW and CMX through the rest of the
afternoon.

&&

.MARINE...
Issued at 217 PM EDT Mon Aug 17 2026

Lake Superior - Southwesterly winds 20-25kt are expected through the
early evening between Isle Royale and the Canadian shore where winds
are being funneled. Over the rest of the lake southwest winds of 15-
20kt can be expected. Winds will shift northwest wind and
increase to 25kt near/east of the Keweenaw late tonight into
Tuesday. Thereafter winds will generally be less than 20kt
through the remainder of the week. A few thunderstorms will be
possible tonight and again on Thursday night and Friday but
strong thunderstorms are not expected. Another period of
northwest winds are expected on Saturday, 20-30kt, mainly along
and east of the Keweenaw.

Northern Bay of Green Bay and northern Lake Michigan - Overall
expect winds less than 20kt trough Thursday. Showers and
thunderstorms are possible tonight into Tuesday (50% chance) as a
cold front pushes through the area. Isolated thunderstorms Tuesday
afternoon could produce gusty winds. Another front is expected to
bring showers and thunderstorms into the area Friday night into
Saturday. Southwest winds to 25kt are expected ahead of the front on
Friday near and east of Manistique. Winds diminish Friday night,
then shift northwest on Saturday increasing to 25kt.

&&

.MQT WATCHES/WARNINGS/ADVISORIES...
Upper Michigan...
None.
Lake Superior...
None.
Lake Michigan...
None.

&&

$$

DISCUSSION...77
AVIATION...LC
MARINE...NL