166
FXUS63 KMQT 131906
AFDMQT

Area Forecast Discussion
National Weather Service Marquette MI
306 PM EDT Sun Sep 13 2026

.KEY MESSAGES...

- Chilly tonight with frost in the interior west. A Frost
  Advisory is in effect for several counties of the western UP.
  Patchy frost is possible elsewhere across the interior central
  and east.

- Widespread rain moves into the UP from west to east late
  Monday through Tuesday morning. There is a 40-70% chance for
  rainfall amounts >0.5", mainly across the southern half of the
  UP.

- A Gale Watch remains in effect for the Upper Great Lakes
  Monday night through Tuesday. Southerly gales 35-40 kts turn
  westerly Tuesday afternoon. Westerly gusts 40-45 kts will be
  common with a few gusts to 50 kts possible (50-70% chance)
  near the Keweenaw Peninsula.

- Strong westerly winds are expected Tuesday afternoon,
  especially in the Keweenaw where frequent gusts near 45 mph
  are possible (60- 90% chance).

&&

.DISCUSSION...
Issued at 305 PM EDT Sun Sep 13 2026

Afternoon satellite imagery imagery reveals troughing stretching
down from the Hudson Bay down through the Great Lakes. Cold air
advection characterized by 850 mb temperatures falling into the
single digits has been able to kick off scattered lake effect rain
showers for the NE UP. So far temperatures have only managed to peak
in the low 60s to upper 50s this afternoon under gusty NW winds.
Tonight, lake effect showers dwindle in the east as drier air works
into the region. Under mostly clear skies, building high pressure,
and diminishing winds, efficient radiational cooling will allow the
interior west to cool into the upper 20s to low 30s. Frost
Advisories have been expanded for most of the western UP save for
the Keweenaw. Elsewhere, patchy frost and upper 30s may be found
across the interior central and east, but confidence is lower on
frost potential there. Even the lakeshores may be able to enjoy a
cool night in the 40s!

Our attention then turns to a period of active weather tomorrow
night through Tuesday. High pressure overhead will keep the region
dry through most of the day tomorrow, however, widespread rain is
anticipated Monday night through Tuesday morning as a deep moves
from the Northern Rockies into the High Plains. Moist return flow
(PWATs climbing near the 95-99th percentile of climo) and strong
isentropic ascent will be the focal point for a wave of showers and
maybe a few embedded thunderstorms moving west to east across the UP
ending early Tuesday. Ensembles still present some uncertainty
regarding QPF amounts and where the greatest amounts will be found.
The tail end of this morning`s HREF and REFS run suggest a 40-70%
chance for rainfall amounts >0.5" largely confined to the southern
UP while global ensembles like the NBM and LREF are happy to paint
greater probs of >0.5" (60-90%) across the entire region.
Regardless, any meaningful rain is welcome to help curtail ongoing
drought. Strong southerly winds accompanying a 45-55kt LLJ and
pressure falls ramp up late Monday to early Tuesday. Widespread 30-
40 mph wind gusts will be common. NBM and CAM guidance is a little
too hot with the upper end of wind gust potential, suggesting
favorable probability for 40-45 kt gales on the lakes. Pattern
recognition tells us that this is not likely to happen, as mixing
into the 45-55 kt LLJ doesn`t often occur given early fall over-lake
stability. A few gusts >40 kts are possible, but widespread gusts
>30-40 kts are hard to achieve in a southerly wind regime. What is
more likely to happen is strong westerlies on Lake Superior and in
the Keweenaw Tuesday afternoon as pressure rises (~1 mb/hr) and cold
air advection contribute to gusts reaching 40-50 kts. Ensembles
suggest high probability (60-90% chance) for frequent gusts >45 mph
(Wind Advisory criteria) in the Keweenaw.

Zonal flow and height rises contribute to drier and more seasonable
weather heading into the mid to late week.

&&

.AVIATION /18Z TAFS THROUGH 18Z MONDAY/...
Issued at 137 PM EDT Sun Sep 13 2026

VFR conditions continue through the forecast period, with high
ceilings and no visibility limitations. Some lake effect showers are
ongoing over southeastern Lake Superior. SAW may see a very brief,
light rain shower or two this afternoon if a shower strays inland,
but confidence is too low for inclusion in the TAF. Winds are
expected to remain gusty and northwesterly this afternoon, reducing
to ~5kts overnight as a high pressure center moves across the U.P.
Monday morning, winds will increase to ~10kts and  become southerly
on the back side of the high pressure center.

&&

.MARINE...
Issued at 305 PM EDT Sun Sep 13 2026

Lake Superior: Gusty W to NW winds 20-30 kts have been common
through this morning and afternoon with a few gales to 35 kts mixed
in at Stannard Rock and Granite Island. Building high pressure will
act to weaken winds back down to 20 knots or less again tonight and
to remain that way until Monday afternoon. As a warm front
approaches the area on Monday, expect the winds to increase from the
southeast and south ahead of it later in the day, with southerly
gales of 35 to 40 knots being seen across the east half of the lake
Monday night. A few southerly gales 40 to 45 knots may be realized
if mixing can tap into a 45-55 kts low level jet, but pattern
recognition tells us that this is hard to achieve in a southerly
wind regime in the early fall given over lake stability. Winds veer
westerly behind a cold front Tuesday morning. Strong pressure rises
and cold air advection will work to increase west gales of 40 to 45
knots across most of the lake, especially closer to the Keweenaw
Peninsula where there is a 60-90% for gales between 45-50 kts
Tuesday afternoon. As a flattening high pressure ridge begins to
move into the area for the middle of the week, expect the winds to
weaken back down to 20 knots or less by late Tuesday night,
remaining that way until potentially next weekend.

Northern Green Bay and northwestern Lake Michigan: WNW winds of 15
to 25 knots this afternoon fall back down to 15 knots or less again
late tonight. The lighter winds remain until an approaching warm
front on Monday increases winds from the south during the afternoon
hours. As the front occludes Monday night, expect the southerly
winds to become maximized to gales near 35 to 40 knots. In addition
to the gale potential, some rumbles of thunder could be heard during
the overnight hours. However, no severe weather is expected. While
cold air advection does work into the area on Tuesday, with the
better CAA over Lake Superior, expect the winds to slowly dwindle
with time as they veer, eventually becoming 15 knots or less again
Tuesday night as flattening high pressure ridging builds into the
Upper Great Lakes.

&&

.MQT WATCHES/WARNINGS/ADVISORIES...
Upper Michigan...
  Frost Advisory from 2 AM EDT /1 AM CDT/ to 9 AM EDT /8 AM CDT/
     Monday for MIZ002-004-009>011-084.

  Beach Hazards Statement until 9 PM EDT this evening for MIZ006.

Lake Superior...
  Gale Watch from late Monday night through Tuesday afternoon
     for LSZ162.

  Gale Watch from Monday evening through Tuesday evening for
     LSZ240>251-263>267.

Lake Michigan...
  Gale Watch from Monday evening through Tuesday morning for
     LMZ221-248-250.

&&

$$

DISCUSSION...BW
AVIATION...LH
MARINE...BW