448
FXUS63 KMQT 011907
AFDMQT

Area Forecast Discussion
National Weather Service Marquette MI
307 PM EDT Mon Jul 1 2024

.KEY MESSAGES...

- Our next round of rain showers, with some rumbles of thunder,
moves in by early Tuesday morning.


- Next rounds of showers and thunderstorms arrive Monday night,
continuing into Wednesday. Gusty southerly winds up to 25-35 mph are
also expected on Tuesday.

- Low chance (~25%) of afternoon and low to medium chance (25-40%)
of evening showers/storms across the western half of Upper Michigan
on July 4th. Rain spreads over the region Thursday night and Friday.

&&

.SHORT TERM /THROUGH TONIGHT/...
Issued at 306 PM EDT Mon Jul 1 2024

The upper ridge axis is sliding across the Great Lakes this
afternoon, with surface high pressure centered over the Lower
Peninsula. With increasing southerly winds over the UP and a warmer
airmass working in, temperatures have been able to climb into the
70s across the UP; some spots in the western half of the UP, where
southerly winds are downsloping, are even flirting with the 80
degree mark.

Clouds will gradually spread in through the first half of the night
ahead of a shortwave that is currently ejecting out of the Plains.
Not far behind will be the next round of rain showers by Tue 06Z. As
the showers track eastward across the UP tonight, also cannot rule
out a few rumbles of thunder...but will note that instability
remains quite limited with capped soundings. Meanwhile, much warmer
lows can be expected tonight unlike the last few nights as the
clouds/rain limit radiational cooling. Widespread 50s will prevail
Tuesday morning.

&&

.LONG TERM /TUESDAY THROUGH SUNDAY/...
Issued at 320 AM EDT Mon Jul 1 2024

Primary focus in the extended forecast period continues to be the
broad mid-upper level trough shifting out of the northern Rockies
beginning tonight. This system will amplify and support a surface
low developing this afternoon over eastern Montana/western Dakotas.
As the main trough axis/closed low aloft shifts east into Manitoba
tonight, the surface low will lift to near Lake Winnipeg, and then
to northeastern Manitoba/far northwestern Ontario by Tuesday
afternoon. Its expected to continue lifting north Tuesday night.
This progression will result in two waves of precip lifting through
our forecast area, in addition to a strong low level jet and
tightening pressure gradient resulting in gusty winds.

The first wave of precip is expected to slide east late tonight and
Tuesday as a surface trough rotates through. Models continue to
highlight an environment lacking much in the way of instability, but
the elevated MUCAPE of ~200j/kg means a thunderstorm can`t be ruled
out. A lull is expected by afternoon in the west, which will shift
east through the evening as the initial swath of precip exits into
Ontario. As this initial wave moves through, a strengthening
pressure gradient over the region will ensue as a strong 925-850mb
40-50kt low level jet presses overhead. Even with modest dinural
mixing, gusty southerly winds will develop, particularly near the
Bay of Green Bay, Lake Michigan, and the downslope and higher
terrain locations in the Gogebic Range, Michigamme Highlands, and
lakeshore areas of Marquette and Alger counties. NBM appears certain
of 25-30 mph wind gusts in these locations and eastern Upper
Michigan and suggests ~25% chance of exceeding 35 mph. Model
soundings that suggest effective mixing suggest potential upwards of
40 mph. The second wave will lift northeast into the U.P. Tuesday
night ahead of the eastward migrating cold front. Between guidance
available last night and tonight, there appears to be a better
handle on when precip should end, with most now ending precip in the
east Wednesday morning.

A surface ridge extending northwest should help support a mostly dry
day on Wednesday, although there is a brief period in the east that
could destabilize enough for afternoon showers/storms to develop
before the cold front clears. The 4th of July should start off dry
thanks to the lingering effects of the surface ridge and a meso high
developing over Lake Superior. Upstream though, another trough exits
the northern Rockies and presses through the Plains. Guidance
amplifies the shortwave and lifts a surface low through the eastern
Dakotas and into Minnesota in the afternoon/evening. There`s good
agreement among the guidance packages that this wave will shift east
through Minnesota and Wisconsin through the day Friday, then lift
northeast through Upper Michigan Friday night into early Saturday.
Best chances for precip with this wave will be Thursday night and
Friday. Its unclear if it will remain dry Thursday afternoon and
evening in the western half of Upper Michigan. While probability is
currently low (~25%), Thursday afternoon destabilization could result
in convection developing. Additionally, increasing isentropic ascent
may support showers lifting into the region during the evening hours
(25-40%). Anyone with evening firework plans across the western half
of Upper Michigan should continue monitoring the forecasts.

&&

.AVIATION /18Z TAFS THROUGH 18Z TUESDAY/...
Issued at 133 PM EDT Mon Jul 1 2024

VFR conditions will prevail today into tonight, but ceilings lower
into the early hours of Tuesday as a disturbance moving through
brings in our next round of rain beginning between -9-12Z in the
western UP. Ceilings lower to MVFR by 09Z at IWD, and at CMX and
possibly SAW by mid morning. Ceilings may lower further to IFR at
IWD by mid morning as well. A period of LLWS is also expected
beginning late tonight, ending Tuesday morning from west to east.
Otherwise, expect winds out of the south to turn gusty tonight into
Tuesday, with gusts up to 30 kts becoming common.

&&

.MARINE...
Issued at 320 AM EDT Mon Jul 1 2024

Light winds will persist over Lake Superior today with high pressure
continuing to influence the region.

A system will begin lifting from the Plains into Canada tonight,
then continue lifting northward Tuesday into Wednesday. The passage
of this system will result in at least 2 rounds of rain and storms
and two periods of stronger winds. Expecting the first round of
showers, maybe with a thunderstorm embedded within to shift through
Lake Superior late tonight and Tuesday. These showers may support
fog developing and periods of low visibility on the lake. As the
system approaches tonight, tightening pressure gradient will develop
while a strong 40-50kt 925-850mb low level jet moves over eastern
Lake Superior. There`s still a great deal of uncertainty in how much
of these stronger winds will mix to down to the surface given the
increasing stability of the over lake environment. However, recent
internal probabilistic tools are beginning to highlight nearshore
areas downwind of the Michigan lakeshores and the stretch from
Marquette northward into Canadian waters as those most likely to
experience low end gales. This tool is only suggesting a 20-40%
chance, which is in the middle of the road of probabilities when
comparing to the HREF and the NBM. These ~40% values may also be
somewhat representative downwind of the lakeshores east of Marquette
and along the northern shores of the Keweenaw, where models struggle
with the land/lake interface and localized terrain driven influences
have been known to mix down stronger winds to the surface. At this
point, given the uncertainty and the isolated nature of the stronger
mixing downwind of the lakeshores, will hold off on a gale watch and
allow the next shift to reexamine it again.

Another round of moisture will lift through Tuesday night into
Wednesday while the effects of the low level jet wane. The cold
front presses through west to east Tuesday night into Wednesday
morning, allowing winds to become westerly/southwesterly for
Wednesday. Another period of stronger winds up to 20-30kts, looks
possible between the Keweenaw and Isle Royale Wednesday in this
southwesterly flow. High pressure returns briefly for Thursday with
a weaker low pressure system expected to pass over the Upper Great
Lakes late Friday and Saturday. Light winds below 20 kts returns
Wednesday night, continuing likely into the weekend.

&&

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

&&

$$

SHORT TERM...LC
LONG TERM...JTP
AVIATION...LC
MARINE...JTP