857
FXUS63 KMQT 202317
AFDMQT

Area Forecast Discussion
National Weather Service Marquette MI
717 PM EDT Thu Aug 20 2026

.KEY MESSAGES...

- Scattered showers and a few thunderstorms move west to east
  this evening into tonight. Rainfall amounts will be light,
  generally around 0.1" or less, though some higher amounts are
  possible in storms.

- Showers and storms re-develop along the cold front over the
  central UP Friday afternoon, then move eastward into the
  evening. Additional rainfall totals are expected to be 0.1" or
  less, though higher amounts are possible in storms.

&&

.DISCUSSION...
Issued at 304 PM EDT Thu Aug 20 2026

Afternoon water vapor imagery shows nicely the midlevel shortwave
over North Dakota, with RAP analysis showing surface low pressure
over the ND/MN border region. WAA out ahead of this, coincident with
a 30-40kt LLJ, has touched off convection over eastern MN and
western Lake Superior. Associated midlevel cloud cover continues to
work eastward into the UP, and though some weak radar returns have
drifted over the western UP at times, dry air is winning out so far
(dewpoint depressions on the order of 20 degrees) and preventing
anything from reaching the ground. With that, have pulled back the
onset timing of convection over the western UP closer to 00Z. By
then, a few hundred j/kg of CAPE indicate that some thunder will be
possible, and this continues overnight as the initial batch of
showers and storms works eastward. Heavy rainfall is not expected,
with most spots seeing a tenth of an inch or less. However, higher
totals of a quarter-inch would be possible in storms (HREF showing
embedded 30-50% probability of such totals per 6-hourly period
tonight). Otherwise, expect temperatures, rising comfortably through
the 70s this afternoon, to fall back into the 50s to near 60
overnight.

Friday, the surface low off to our west tracks through the UP
(perhaps opening up into a surface trough). This brings a cold front
through the area, which looks to be draped somewhere across the
central UP by mid-morning. Destabilization ahead of the front over
the central and eastern UP will allow showers and storms to
redevelop into the afternoon, but with very limited shear and MUCAPE
below 1000j/kg, strong to severe storms are not expected. This
should not be a washout, again with most areas receiving additional
rainfall totals of a tenth of an inch or less. However, ensembles
show as much as a 50% chance for higher embedded totals in excess of
a quarter-inch in heavier downpours. Friday is looking otherwise
breezy ahead of the front, with southerly wind gusts to around 20mph
over the eastern UP. Temperatures peak in the lower to mid 70s
behind the front, and the mid to upper 70s ahead of it.

Additional chances for showers and storms return for Saturday as a
midlevel low drops into northern Ontario, sending additional
shortwaves and a shot of cold air advection into the Great Lakes.
That said, the main story will be marine hazards and gusty northerly
winds Saturday/Sunday. Modest pressure rises coupled with cold air
advection (850 mb temps between 3-6C Sunday) will create northerly
gusts 20-30 kts with a 40-50% chance of gales to 35 kts over the
eastern portions of the lake.

Model discrepancies follow into next week, though Sunday and Monday
looks mainly dry, followed by on and off rain chances the rest of
the forecast period as a series of shortwaves drop through the Great
Lakes.

&&

.AVIATION /00Z TAFS THROUGH 00Z FRIDAY/...
Issued at 716 PM EDT Thu Aug 20 2026

Showers and storms continue to push into the area tonight through
Friday with the passage of a shortwave low. While generally VFR
conditions are expected through the evening hours, low MVFR to IFR
cigs are expected to roll-in Friday morning across the west and
central U.P. as the low`s center moves into the area. While some
lake effect/enhanced rain showers could be seen behind the low on
Friday, thinking the best chances for showers and storms will be
relegated to SAW by the afternoon hours once some diurnal
instability comes into play. Generally southerly winds tonight give
way to northwesterly winds by Friday afternoon behind the low, with
skies clearing out and becoming VFR again by the late afternoon
hours.

In addition to the above, some marginal LLWS could be seen over the
terminals. However, because chances are too low (<30%), decided to
not have mentions of it in the TAFs.

&&

.MARINE...
Issued at 304 PM EDT Thu Aug 20 2026

Lake Superior - ESE wind gusts pick up to around 20kts over the east-
central portions of the lake tonight, then gusts fall back below
20kts Friday afternoon while a passing cold front causes winds to
shift over to the NW. The main marine hazards return Saturday and
Sunday as a pair of systems bring modest pressure rises and cold air
advection over the Lake resulting in gusty N to NW winds upwards of
20-30 kts beginning Saturday morning through Sunday night. At this
time, there is a low chance (30-50%) for a few gales to 35 kts
mainly between Marquette and Whitefish Point. Winds fall back below
20kts Sunday night, and stay mainly below 20kts through early next
week.

Northern Bay of Green Bay and northern Lake Michigan - Southerly
wind gusts up to 15-20kts will be possible over the Bay beginning
later this evening, but become more common over the Bay and northern
Lake Michigan late tonight and linger through Friday as low pressure
traverses the area. This results in waves building between 1-3 ft
(greatest in the open waters closer to Lake Michigan). A brief
reprieve in winds comes Friday night behind a weak cold front,
however, two systems then dive into the area Saturday and Sunday,
resulting in gusty north to northwest winds 15-25 kts through Sunday
night. Wind gusts briefly fall back below 20kts for Monday before
potentially increasing again into the midweek period.

&&

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

&&

$$

DISCUSSION...LC
AVIATION...TAP
MARINE...LC