937
FXUS63 KMQT 300719
AFDMQT

Area Forecast Discussion
National Weather Service Marquette MI
319 AM EDT Mon Sep 30 2024

.KEY MESSAGES...


- Dry weather gives way to spotty rain chances tonight into early
Tuesday as a cold front moves through.

- Patchy frost or a freeze is possible early Wednesday with a 20-50%
chance for sub-freezing lows in the interior-western UP.

- Gusty west/northwest winds upwards of 35 mph possible (40-60%
chance) over and along Lake Superior Monday night through Tuesday
night. Winds shifting to the SW remain gusty for Wednesday.

&&

.SHORT TERM /THROUGH TONIGHT/...
Issued at 254 AM EDT Mon Sep 30 2024

Water vapor imagery and RAP analysis show a vigorous shortwave trof
across Alberta/Saskatchewan/MT and mid-level ridging from the
southern Rockies to the Great Lakes. Under the mid-level ridging,
it`s yet another quiet night across Upper MI. A somewhat drier
column compared to last night is enhancing radiational cooling under
clear skies and calm conditions. Temps have fallen into the 40s F
across most of the fcst area with many of the traditional interior
cool spots down into the mid/upper 30s F. Where winds are stirring,
temps are in the 50s to around 60F. Ironwood is the warm spot at
60F. The quiet conditions have allowed areas of fog to form. Much of
the fog is rather shallow. This fog will dissipate within about 2hrs
after sunrise.

Aforementioned vigorous shortwave trof to the w will herald a change
in the weather from the recent period of warmth to conditions more
typical of this time of year, but for today, Upper MI will remain
ahead of the trof and its associated cold front. Thus, one more warm
day under sunny skies is on the way to round out was has been a warm
Sept. Mid morning 850mb temps today are indicated to be similar to
mid-morning yesterday. So, high temps today will be similar to
yesterday. However, yesterday, ne winds kept conditions cooler near
Lake Superior. Today, s to sw winds will bring warmer conditions
back to that area. Expect highs across the fcst area to be mostly 75-
80F. The s to sw winds will result in coolest conditions near Lake
MI where highs lakeside will be around 70F. Tightening pres gradient
and building mixed layer will result in winds becoming gusty to 20-
25mph across the w to n central this aftn.

&&

.LONG TERM /TONIGHT THROUGH SUNDAY/...
Issued at 318 AM EDT Mon Sep 30 2024

An upper trough and deepening low pressure moving through the
Canadian Prairies today stall out around Hudson Bay tonight into
Tuesday, with an associated cold front sweeping through the UP
tonight and Tuesday morning. A surface high will pass south of the
UP Tuesday and Wednesday, helping counteract the potential for any
lake effect precipitation following the cold front. A shortwave
pivoting around the larger trough will usher in another cold front
later in the week, though by the end of the week, differences in the
global deterministic and ensemble guidance leaves high uncertainty
in the late portions of the forecast.

Simulated reflectivity shows a broken line of showers quickly moving
through the UP after 00Z tonight courtesy of a passing cold front.
Any rain should be moving out of the eastern UP after sunrise
Tuesday. That said, much of the UP may in fact remain dry. Rather
dry soundings and the quick fropa indicate that QPF will not be
particularly high; HREF probabilities of over a tenth of an inch of
precip by 12Z Tuesday are only 20-40%, highest in the east.

Tuesday will be much cooler behind the front with temperatures
slightly below normal at around 60 degrees. With a tight pressure
gradient over the area, expect breezy conditions - particularly
closer to Superior where NW winds may gust to around 30mph. The cold
advection and sinking air behind the front as well as a 1022mb high
sliding south of the UP will suppress cloud cover overnight Tuesday
into Wednesday, allowing for the coldest air of the season to be
observed in the interior west. Guidance continues to favor
widespread lows in the 30s and 40s across the UP (warmest near the
lakeshores), with the coldest model guidance highlighting sub-
freezing temperatures in the interior-western UP. Agricultural
interests should take note of the forecast over the next couple of
days in case a frost or freeze product is needed.

Temperatures return to normal and slightly above normal for the
remainder of the week as flow goes mainly zonal aloft with the
trough becoming a cutoff low over Hudson Bay. Another wave rounding
out the northern low will increase the pressure gradient over the
Great Lakes Wednesday, which should help to keep winds elevated
through midweek. Guidance continues to struggle on the timing of
another shortwave dropping through sometime in the Thursday-Friday
timeframe, but this would present our next opportunity for some
light rain before a ridge builds in again next weekend. Towards the
end of the forecast period, most of the global deterministic and
ensemble guidance are keying in on another wave dropping into the
Great Lakes, but there are significant differences regarding the
exact track, strength, and timing of this next potential rain-maker.

&&

.AVIATION /06Z TAFS THROUGH 06Z TUESDAY/...
Issued at 129 AM EDT Mon Sep 30 2024

Quiet conditions and strong radiational cooling are allowing
fog patches, mostly shallow, to form. SAW will be affected
overnight with vis likely to fluctuate btwn MVFR and LIFR, as
low as airfield landing mins. Fog is also forming along the
Portage Canal and Torch Lake area to the s and se of CMX. Light
se winds will likely transport this fog to the terminal,
resulting in conditions falling to LIFR in the next few hrs. Fog
affecting both terminals will dissipate within a couple of hrs
after sunrise. Light downslope winds at IWD should allow VFR to
prevail overnight. All terminals will be VFR today thru this
evening. Approaching cold front will lead to gusty s winds to
around 20kt or so developing today. A period of LLWS is then
expected tonight at CMX/SAW.

&&

.MARINE...
Issued at 318 AM EDT Mon Sep 30 2024

Southerly winds are starting off below 20kts early this morning, but
winds pick up to around 20-25kts especially across the eastern half
of the lake later this morning as a cold front begins to approach
the Great Lakes. As the cold front passes over the lake tonight into
Tuesday, southerly winds veer northwesterly and gust up to 30 kt
with a 20-30% chance of exceeding gales. While the forecast gets
more uncertain Wednesday and beyond, another frontal passage is
expected in the back half of the week, and some guidance suggests up
to 50% chances of gales at some point Wed-Fri associated with that
second frontal passage. The highest chances of gales will be
Wednesday afternoon when pre-frontal southwesterly winds are
funneled between Isle Royale and Thunder Bay.

&&

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

&&

$$

SHORT TERM...Rolfson
LONG TERM...LC
AVIATION...Rolfson/Voss
MARINE...LC