351
FXUS63 KMQT 081744
AFDMQT

Area Forecast Discussion
National Weather Service Marquette MI
144 PM EDT Tue Jul 8 2025

.KEY MESSAGES...

- Seasonable temperatures persist in the Upper Peninsula for the
  work week.

- Rain showers and a few thunderstorms today, mainly across the
  west half. No severe thunderstorms are expected.

&&

.SHORT TERM /THROUGH WEDNESDAY NIGHT/...
Issued at 144 PM EDT Tue Jul 8 2025

Satellite and radar imagery shows showers from earlier this morning
continuing but dwindling over the eastern U.P. early this afternoon
as they slowly trudge eastward with time. Meanwhile, pop up showers
and storms have formed over the western U.P. recently ahead of a
cold front moving through the area tonight. While there isn`t too
much energy to work with, the partly cloudy to sunny skies over the
western half of the area this morning have allowed the atmosphere to
recover from the convection that moved through this morning. Thus,
there is enough tall but skinny sfc-based CAPE to pop up showers and
thunderstorms across the west and central this afternoon and
evening. In addition, with effective bulk shear from the SPC RAP
analysis being 30 to 35 knots over the western and central U.P. this
afternoon and evening, we could see up to marginally severe hail (up
to 1" in diameter) and marginally severe winds (up to 60 mph). While
widespread damage isn`t expected, we could see some small, dead tree
branches taken off in the stronger storms and a few isolated power
outages. In addition to sub-severe conditions, thunderstorms could
also produce heavy downpours which could lead to localized ponding
in poor drainage areas. However, given the relatively `fast` storm-
motion today and the lack of training, no flash flood concerns are
expected. The showers and storms look to continue over mainly the
west and central until sunset; the lack of sfc-based instability
will lead to the showers and storms dying over our area not long
afterwards.

Expect patchy to areas of fog to develop over the area late tonight
as weak high pressure ridging traps the moisture at the sfc. While
confidence is not high enough now being so far out in time, I
wouldn`t be surprised if the evening or mid shift put out a few
Dense Fog Advisories or SPSs late tonight/early Wednesday morning.
Expect the fog to continue until Wednesday morning just after
sunrise; expect the sun to erode away the fog at the sfc, with the
north central looking to be the last holdout due to the northerly
upslope flow from Lake Superior.

Wednesday looks to be a pretty pleasant day as cloud cover
progressively scatters out with time. Expect the Lake Superior lake
breeze to dominate as the generally northerly flow continues through
the day. Thus, we can expect cooler high temperatures closer to Lake
Superior, ranging from the 60s closer to the lake to lower 70s
further inland. As for Wednesday night, expect calm winds as the
weak ridging continues, allowing for lows to drop into 40s in the
interior areas.

&&

.LONG TERM /WEDNESDAY NIGHT THROUGH MONDAY/...
Issued at 312 AM EDT Tue Jul 8 2025

Quasi-zonal flow across the international border Wednesday breaks
down as ridging across middle North America amplifies in response to
a deep trough digging through the Rockies. As the ridge presses east
for the remainder of the week, a cutoff low off the California coast
will get pulled into the trough, resulting in split flow eventually
phasing over the Northern Plains or Great Lakes this weekend.

Lingering sfc high locks in dry weather through Thursday where
another day of widespread interior temperatures in the 70s, perhaps
low 80s interior west, and low 70s by Lake Superior, is expected.

The ridge axis presses into Upper Michigan Thursday followed by a
weak wave rolling atop the ridge Thursday night. Shower and
thunderstorm chances are co-located with diurnally driven instability
upstream in Minnesota, so any activity in western Upper Michigan or
Lake Superior overnight should be waning. Upstream Thursday into
Friday, a southern stream system, fueled by Gulf moisture, and a
robust shortwave moving through the Dakotas will begin to phase,
then lift northeast through the Midwest/Great Lakes region. Its
still unclear where the resultant surface low(s) will end up being,
but the rough approximation between the deterministic and ensemble
guidance packages suggest between Ontario north of Minnesota and
Wisconsin, before lifting north or northeast into Sunday. While
there are still differences on structure and location, fronts or
surface troughs with most options nearly all agree that precip will
lift through the forecast area Friday night into Saturday.
Instability appears to be lacking, with GEFS suggesting 20-30%
probabilities of 500-1000j/kg CAPE and similar, although slightly
higher, probabilities in the EC. While strong to severe
thunderstorms aren`t expected, thunder can`t be ruled out. Enhanced
by the Gulf`s influence, PWATs should climb to 1.5-2 inches (50-90%
chance per GEFS, GEPS, and EC ensemble systems), which alongside the
apparent modest synoptic forcing and lack of notable instability,
rainfall amounts under an inch look most likely (80-90% per LREF and
NBM). Precip will exit the region from west to east late Saturday,
perhaps returning late Sunday into Monday if a secondary shortwave
within the now-phase upper level low moves through the forecast area.

For temperatures, generally expect upper 70s to low 80s for a
majority of Upper Michigan on Friday, but more widespread cooler mid
70s for the weekend. Overnight lows also look to be mostly in the
mid 50s to low 60s.

&&

.AVIATION /18Z TAFS THROUGH 18Z WEDNESDAY/...
Issued at 1253 PM EDT Tue Jul 8 2025

A weak system moving through the Upper Great Lakes the rest of today
through tonight is expected to bring showers and storms over SAW
again sometime mid to late this afternoon. Afterwards, expect high
pressure ridging to build in, allowing FG to form at SAW and
potentially IWD (40%) and even CMX (10%). Generally, expect VFR
conditions throughout the rest of today at IWD, whereas CMX looks to
slowly improve to VFR throughout the afternoon hours. SAW looks to
be generally VFR this afternoon, but rain showers and thunderstorms
could deteriorate conditions to MVFR or lower. Any FG that forms
over the TAF sites tonight could lower conditions down to as low as
airport mins. Expect the FG to remain the longest over SAW Wednesday
morning as flow becomes northerly across the U.P.

&&

.MARINE...
Issued at 312 AM EDT Tue Jul 8 2025

Winds 20 knots or less are expected through the rest of the week as
quasi-zonal flow sets up shop aloft. That being said, a low over the
Northern Plains lifts into the Lake Superior today, bringing showers
and a few thunderstorms to the area. Expect the rainfall to end by
evening as the low slowly travels southeastward with time.
Additional showers and storms could enter the far western lake
Thursday evening, although with convection being diurnally driven
expect the showers and storms to die out with time. As low pressures
phase over the Northern Plains and lift into northern Ontario from
Friday into this weekend, expect additional showers and
thunderstorms to develop over Lake Superior for that time
period. Otherwise, expect light southerly winds <15kts turning
north tonight.

&&

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

&&

$$

SHORT TERM...TAP
LONG TERM...JTP
AVIATION...TAP
MARINE...BW/TAP