843
FXUS63 KMQT 161828
AFDMQT

Area Forecast Discussion
National Weather Service Marquette MI
228 PM EDT Tue Jul 16 2024

.KEY MESSAGES...

- Low impact showers with perhaps a rumble of thunder this evening.

- A 20% to 40% chance for scattered light showers on Wednesday.

- Cooler and drier for midweek with the arrival of high pressure.

- Next chances for showers and maybe some thunder return on
Saturday.

&&

.SHORT TERM /THROUGH WEDNESDAY NIGHT/...
Issued at 227 PM EDT Tue Jul 16 2024

GOES-16 Day Cloud Phase imagery shows an agitated cu fiueld across
much of the central and western UP with clear skies over the
Keweenaw and otherwise fair weather cu over the eastern UP. A line
of showers briefly passed over Isle Royale and some thunderstorms
look to be following the US/Canada maritime border over Lake
Superior. Radar returns show a couple isolated showers among the cu
field but nothing of particular note otherwise.

HREF guidance shows the pattern of isolated to scattered light rain
showers persisting until sunset when diurnal heating ceases. SBCAPE
maximum in the HREF is maybe 1,000 J/kg and is more likely closer to
250 J/kg. Therefore, a rumble of thunder cannot entirely be ruled
out but precip totals should be low today, which will provide some
relief to the basins that are still draining from yesterday`s
convection. Overnight should remain dry until the very early morning
hours, when PoPs increase gradually as the base of an upper trough
over northern Ontario swings south to be over the UP by 09Z
Wednesday. Once again, impacts should be low as no HREF members show
an inch of rainfall over the UP prior to 12Z Wednesday.

&&

.LONG TERM /TONIGHT THROUGH MONDAY/...
Issued at 443 AM EDT Tue Jul 16 2024

Starting tonight, the mid level trough over northern Ontario pivots
over the Upper Great Lakes. With the associated PVA, northwest
upslope flow, and a reinforcing cold front dropping sough late
tonight into Wednesday morning, light showers/sprinkles are expected
to touch off in the west after midnight. Temps turn cooler tonight
with upper 40s to 50s, warmer by the lakeshores. As the trough
continues over the area and the front pushes south through Wednesday
morning, precip expands southwest across the UP. Afternoon highs
will be cool in the 60s to low 70s. With high pressure building in
from the west and PVA diminishing, dry weather returns from west to
east. That said, the broken stratocumulus deck looks to lasting well
into the afternoon and possibly the evening hours. Mixing behind
the cold front will result in light northwest winds with gusts
expected up to 20 mph. Model soundings and the 7/16 0Z HREF indicate
a 30-50% chance for gusts up to 25 mph in the Keweenaw and eastern
UP.

The cooler pattern holds through Wednesday night as high pressure
and a drier airmass builds in. In turn, subsidence increases, winds
tapper off, and radiative cooling under clear skies brings temps
down into the 40s with low 50s near the lakeshores.

High pressure continues to shift east-southeast over the Great Lakes
through the rest of the week into next weekend, yielding more
seasonable temps with plenty of sunshine. Also during this period,
the mid level ridge over the western CONUS amplifies, deepening the
trough over northern Ontario/Quebec. A shortwave trough dropping
south across the Upper Great Lakes Friday night into Saturday brings
a cold front with it for Saturday, supporting the next chances for
showers and thunder. This also likely brings a brief period of
cooler temps, especially near Lake Superior. From there, ensemble
guidance continues to indicate that another high pressure pressure
builds back in from northwestern Canada as the amplified ridge
eventually gives way late next week and shifts eastward across the
CONUS. This means that outside any additional shortwaves, precip
will be largely driven by diurnal heating or lake breeze convergence
moving into next week. Temps look to return to normal moving into
next week.

&&

.AVIATION /18Z TAFS THROUGH 18Z WEDNESDAY/...
Issued at 130 PM EDT Tue Jul 16 2024

VFR prevails at all TAF sites through tonight under mainly light
northwesterly winds except for some gusty conditions at CMX. A few
-SHRA may impact SAW this afternoon, but chances of precipitation
are only around 25%.

Overnight, a shortwave swinging through from the north will bring
more 15-25% chances of rain but over 50% chance of cigs falling to
MVFR at all sites.

&&

.MARINE...
Issued at 443 AM EDT Tue Jul 16 2024

West to northwest winds are generally expected to remain below 20
kts through this evening. Northwest winds increase to 20-25 kts late
tonight, holding into Wednesday as a cold front pushes south across
the lake; the strongest winds are expected over the central zones
(LSZ263-266) of the lake. During this period, waves build up to 3-5
ft over the east half of the lake, particularly in the waters
between Marquette, Grand Marais, and Stannard Rock.

With high pressure building in from the west on Wednesday and
continuing east-southeast over the Great Lakes into this weekend,
winds are expected to remain below 20 kts into next week. A cold
front moving southward from Ontario will yield a wind shift to the
north for Saturday/Sunday, otherwise winds will be predominantly
from a west and southwest direction though the forecast period.

&&

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

&&

$$

SHORT TERM...GS
LONG TERM...Jablonski
AVIATION...GS
MARINE...Jablonski