822
FXUS63 KMQT 041119
AFDMQT

Area Forecast Discussion
National Weather Service Marquette MI
719 AM EDT Mon Aug 4 2025

.KEY MESSAGES...

- Mostly dry and warm weather persists into the first half of the
work week.

- Afternoon lake breeze development may kick off a few showers and
storms Monday and Tuesday.

- Smoke from Canadian wildfires will continue impacting air quality
and may locally reduce visibility at times. An Air Quality Alert
remains in effect for all of Upper Michigan.

&&

.SHORT TERM /THROUGH TUESDAY/...
Issued at 313 AM EDT Mon Aug 4 2025

Early this morning, midlevel ridging is situated from the Canadian
prairies southeast into the Great Lakes, with a weak shortwave
moving over IA. At the surface, high pressure is centered over
eastern Ontario, and this will continue sliding eastward today. The
aforementioned upstream shortwave slowly moves into western WI,
tossing some loosely organized vorticity into the western UP which
will help to increase cloud cover. With light southerly flow and sfc
high pressure influencing the area, CAMs suggest afternoon lake
breeze development will take place. Some CAMs do suggest some
convection firing along the lake breeze, especially in the central
and eastern UP, though model soundings show quite dry low levels
that may prevent convective initiation or hinder any developing
precip from reaching the ground. Opting to keep in some low chance
(generally >30%) PoPs along the typical central/east UP lake breeze
locations for the afternoon to account for this scenario, as well as
across the terrain of the western UP. If convection does fire,
nothing more than showers and maybe a rumble of thunder is expected
given weak shear and modest CAPE values below 1000j/kg.

Additionally, with generally light winds through much of the
atmospheric column, smoke and haze from Canadian wildfires will
continue to linger across the Great Lakes with air quality headlines
lingering through this evening. See the latest AQA for more details
and air quality information.

Tonight`s lows fall back a bit warmer than previous nights towards
the mid to upper 50s interior and low 60s lake shores, and should
likewise come in a couple degrees warmer on Tuesday. Expect highs in
the lower 80s across the area. Tuesday will otherwise be a repeat of
Monday, with sprawling high pressure centered over eastern Canada
extending ridging into the Great Lakes, and weak midlevel shortwave
action aloft. There remains a potential for some diurnal convection
in the higher terrain of the western UP and/or along any lake breeze
boundaries, but severe weather is not expected.

&&

.LONG TERM /TUESDAY THROUGH SATURDAY/...
Issued at 240 PM EDT Sun Aug 3 2025

Moving further into the work week, a rather complex setup emerges
that the ensembles and global deterministics are struggling to
define. The key elements at 500mb are a ridge moving over the
Canadian Prairie, a trough over the Mississippi River valley, semi-
permanent highs over the southwest US and Bermuda, and deep troughs
over British Columbia and Atlantic Canada. While all of these
features are large and slow-moving, their complex interactions are
handled differently depending on model of choice. Blending most
solutions together, the NBM, previously advertising low chance PoPs
Wednesday afternoon, now keeps the UP dry until Thursday and into
the following weekend with low chance (15-30%) PoPs hovering over
the central and western third. This reflects high certainty that the
pattern will break down to some degree but a low certainty in how it
will break down. Early indications are that the Canadian ridge will
go omega-shaped, and the western trough may pivot into the Upper
Great Lakes for the latter part of the work week.

Into next weekend, the pattern breakdown becomes chaotic, so further
shortwaves are possible but determining which one is the most likely
solution is difficult. With persistent diurnal heating and height
rises, and prevailing flow at mid to lower levels having a more
southerly component, temperatures will trend above normal with the
latest NBM showing widespread 30-60% chances of 90 degree highs by
Friday, and up to 90% chances for the downsloping Lake Superior
shores by Wed-Thurs. This in conjunction with a moistening trend in
dew points thanks to reestablished connection with Gulf or Corn Belt
moisture will increase instability through the week with mean LREF
SBCAPE values of over 1500 J/kg for the interior west by 00Z
Thursday, and 2000 J/kg Friday/Saturday. As a result, if given
forcing, thunderstorms will be back in the conversation for the
latter half of next week.

Additionally, while upcoming warming trend and temps pushing or
exceeding 90 degrees may be manageable for some, the combination of
above normal temperatures and increased humidity will put those
without efficient cooling at risk for heat related impacts. Current
NWS HeatRisk Tool suggests Moderate (level 2 of 4) to Major (3 of 4)
impacts by next weekend across the northern tier and western UP.

&&

.AVIATION /12Z TAFS THROUGH 12Z TUESDAY/...
Issued at 719 AM EDT Mon Aug 4 2025

VFR is the primary expected conditions at all TAF sites through the
12z TAF period under the influence of high pressure. That said, some
~6SM smoke is possible at all terminals this afternoon, with
visibility improving later this evening. A lake breeze is also
expected this afternoon. This lake breeze may kick off some -
shra/tsra at SAW/IWD, but confidence remains too low (<25% chance)
to include in the TAFs at this time.

&&

.MARINE...
Issued at 240 PM EDT Sun Aug 3 2025

Under primarily high pressure, winds will remain below 20 kt for
most of this forecast period. Otherwise, expect wildfire smoke to
cause poor air quality at least through Sunday. There will be some
chances of thunder next week, though model guidance is widely spread
in the timing and location details at this time.

&&

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

&&

$$

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