528
FXUS63 KMQT 042343
AFDMQT

Area Forecast Discussion
National Weather Service Marquette MI
743 PM EDT Fri Jul 4 2025

.KEY MESSAGES...

- Hot and humid conditions this afternoon and Saturday. Please practice
  necessary heat safety measures if you plan on participating
  in outdoor holiday weekend festivities.

- Isolated and scattered showers and storms possible across
  central half of Upper Michigan this afternoon.

- Showers and thunderstorms are expected Saturday afternoon into Sunday
  morning. Heavy downpours and lightning should be expected in
  these storms. Some storms could be strong to severe Saturday
  afternoon and evening.

- Stronger winds on the Great Lakes may result dangerous
  swimming conditions in Schoolcraft County late Saturday and
  Sunday in Alger and Luce counties.

&&

.SHORT TERM /THROUGH SATURDAY NIGHT/...
Issued at 1259 PM EDT Fri Jul 4 2025

Early convection associated with a warm front lifting into the
region petered out this morning. In its wake, cloud cover streamed
through the forecast area and the western UP began heating without
much interference. As of this publishing, widespread upper 70s to
mid 80s are currently being observed, with the highest temperatures
over Ontonagon, western Gogebic, southern Houghton counties behind
the front. Dewpoints have climbed through the 60s and inched into
the 70s far west this morning, which is helping to support higher
heat index values. Currently feels like near 90F so far today in the
hottest locations

CAMS suggest a majority of the forecast area will be mostly dry for
the rest of the afternoon and evening. However, outlier solutions of
the 12z NAMnest, FV3, and ARW, and the occasional hourly RAP/HRRR
run aren`t ruling out isolated to scattered storms late afternoon
and evening. With this in mind, isolated showers have just started
building along the Spine of the Keweenaw. Main area of potential
additional develop appears to be in the middle third of Upper
Michigan from the Spine and Munising. In this area, MUCAPE values
are currently between 1000 and 1500j/kg with deep layer shear of 25-
30kts, and isentropic ascent tied to the transiting warm front. If
we`re able to erode the CAP, coverage may become more widespread
this afternoon as instability grows. Will continue to hold onto low
pops (<25%) this afternoon into the early evening though given this
low chance.

Looking into Saturday and Saturday night, guidance continues to
suggest a cold front will be pulled through the region from west to
east. Ahead of the boundary, increasing heat with a very moist
airmass still over the area will enable MUCAPE to climb upwards of
2000 j/k with a 30-35kt 925-850mb LLJ. This environment should be
enough to support showers and thunderstorms, which may become strong
to severe by afternoon and evening. SPC continues to place the
region in a Marginal Risk (1 of 5) for severe storms capable of
producing damaging winds. CAMS suggest varying degrees of timing,
but mostly suggest scattered showers and storms developing across
the western third of Upper Michigan before noon. Convection then is
expected to become more widespread by mid-afternoon into the central
third, with the possibility of upscale development into a couple
linear thunderstorm segments as a synoptic surface low develops over
Wisconsin. Should this occur, these would mostly impact the central
and eastern Upper Michigan late afternoon and evening. With PWATS
potentially exceeding 2", alongside corfidi vectors of 5-15kts, the
conceptual model roughly matches potential training thunderstorms
capable of producing high rainfall amounts, fast rainfall rates, and
or flash flooding. While the risk for the later is low, it is
currently non-zero. Latest HREF continues to suggest widespread QPF
values of 1-2 inches being possible.

Those with outdoor plans Saturday afternoon and evening should stay
weather aware just in case precipitation or severe weather impacts
their plans. The system slowly inches through the region overnight,
with lingering precip across the east half Sunday morning.

&&

.LONG TERM /SUNDAY THROUGH THURSDAY/...
Issued at 229 PM EDT Fri Jul 4 2025

Beginning Sunday, near zonal flow stretching across the Northern
Tier will be interrupted by a couple shortwaves. The first will move
through Upper Michigan Monday while high pressure at the surface
keeps the region mostly dry. The second follows Monday night into
Tuesday evening, potentially overlapping with a slowly moving frontal
boundary, which may support precipitation. Some deterministic
solutions suggest another wave may dip down into the region
Wednesday in the lee of upper level ridging across the Northern
Plains and central Canada. Afterwards, notable differences in
deterministic guidance packages in regards to the timing of the
eastward progression of the upstream ridge. This impacts the timing
and position of a closed upper level low dipping through Ontario,
perhaps into the Upper Great Lakes Thursday and the next system
dropping southeast out of the Canadian Rockies. Overall, this
provides for shower and thunderstorm potential, to some degree, most
days in this forecast period, with the best chances on Tuesday (20-
50%). At the moment, notable severe weather signals are not present,
or at least there isn`t a consensus on any of these signals. Daytime
temperatures look to peak in the upper 60s to upper 70s on Sunday,
then the upper 70s to low 80s away from Lake Superior and upper 60s
to low 70s by Lake Superior each day thereafter. Overnight lows look
to fall into the 50s most days, except low 60s in southern Menominee
County and perhaps, some high 40s Sunday night in the interior.

&&

.AVIATION /00Z TAFS THROUGH 00Z SUNDAY/...
Issued at 743 PM EDT Fri Jul 4 2025

VFR conditions prevail for the remainder of Independence Day at all
sites. These conditions continue overnight until showers arrive at
all sites in the morning to early afternoon hours of Saturday, with
TSRA chances ramping up at all sites in the afternoon. With the
precip will come lowered ceilings and thus lowered flight
categories. IWD falls to MVFR by 15Z and up to 25% chances of IFR or
lower in the afternoon. CMX is expected to fall to MVFR around 19Z
but could as soon as 15Z if the terminal experiences a heavier
thundershower, with IFR expected around 21Z. SAW will see MVFR
ceilings around 21Z with around 20 percent chances of IFR late.
Expect gust winds out of the southwest until a cold front pushes
through around 00Z, veering winds to be out of the northwest.

&&

.MARINE...
Issued at 229 PM EDT Fri Jul 4 2025

Winds turning over to the south are on the increase this afternoon
with gusts up to 15-20 kts becoming common. However, higher
localized gusts upwards of 25 kts are possible along Lake Superior
shorelines where southerly downsloping accelerations occur. Elevated
S to SW winds are expected to persist through Saturday before
veering NW late along a cold front. Additionally, this frontal
boundary may produce strong thunderstorms which may bring erratic
winds, lightning, and small hail. Strong N to NW winds will follow
the front late Saturday into Sunday, with gusts generally up to 20-
25kts. Winds fall back into early next week.

&&

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

&&

$$

SHORT TERM...JTP
LONG TERM...JTP
AVIATION...GS
MARINE...BW/LC