528
FXUS63 KMQT 041145
AFDMQT

Area Forecast Discussion
National Weather Service Marquette MI
745 AM EDT Fri Jul 4 2025

.KEY MESSAGES...

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

- A warm front may bring scattered showers and storms this
  morning and afternoon across the western half of Upper
  Michigan.

- 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.

&&

.SHORT TERM /THROUGH SATURDAY/...
Issued at 437 AM EDT Fri Jul 4 2025

Early morning GOES satellite imagery and RAP analysis reveal a stout
ridge axis extending through much of the central CONUS into the
Upper Great Lakes. To the west, troughing occuring on the backside
of the eastward moving ridge aided by shortwaves present in central
Canada and the PNW is supporting sfc cyclogenesis across the far
northern Plains. A warm front extends from west-central WI
northwestward into far western Ontario, aiding in thunderstorm
development in WI into far eastern MN. Closer to home, mostly clear
skies have been observed across the UP save for some anvil cirrus
rounding the upper ridge. Temps have cooled to the 50s and low 60s,
however, better warm air advection is beginning to take shape in the
west where IWD has already achieved 70 at the time of writing this
discussion.

Heading into daybreak, the aforementioned warm front will begin to
lift through the UP with associated convection ahead/along the
boundary spreading into the west and central. CAMs this morning have
a poor handle on the evolution of these elevated showers/storms
though the general consensus is a diminishing line approaching the
west half by 8-10am EDT, further depleting with eastward extend into
the afternoon.

The main concern today will be the increased heat and humidity
behind the frontal boundary as we look to warm into the mid to upper
80s, perhaps breaking 90F in the downslope prone areas of Ontonagon
and southern Houghton counties. Given the dewpoints climbing into
the upper 60s to low 70s, heat index values climb into the 90s,
potentially mid to upper 90s. The western U.P. is in the Orange and
Red category (or 2 and 3 of 4 category) for being at risk of heat
related impacts. Those planning to be outside today should plan on
limiting their time outside, especially if they are prone to heat
related illness or are without adequate cooling systems. The east
should be cooler, peaking in the low 80s away from the lake, given
overlake flow moderating the airmass a little. Warm and humid
conditions continue this evening and overnight, with widespread near
mid to upper 60s to near 70 degree lows expected across the forecast
area.

Additionally, with the increased pressure gradient overhead and
moderate southerly flow aloft, gusty southerly winds upwards of 20-
25 kts should be expected along the lakeshores, which may pose a
hazard to recreational boating on the hot summer holiday. Wind gusts
may be further accelerated along the typical downsloping locations
of the central and east-central UP. A few model soundings along the
Marquette county shoreline even suggests mixing down winds closer to
30 kts in the late afternoon and early evening hours.

Looking into Saturday, the ridge axis presses eastward while
troughing in the northern Plains and far northern Ontario move into
the Upper Great Lakes region, dragging a cold front across the
region that will be the focal point for showers and thunderstorms,
which may become strong to severe. Expect the day to start off dry,
with warm and humid conditions still in place prior to the incoming
cold frontal passage. Southwest flow ahead of the front will enable
MUCAPE to climb upwards of 2000 j/kg and marginal bulk shear,
supporting an SPC Marginal Risk (1/5) for severe storms capable of
producing damaging winds and 1" hail. Whats more concerning is PWATs
approaching to exceeding 2", near the 99th percentile to max of
climatology. Latest 00z HREF suggests PMM 3-hourly QPF values
approaching 1-2" across the west and central UP Saturday evening,
pointing to potential flash flood concerns where training
thunderstorms occur.

Right now WPC suggests only a marginal risk of flash flooding (at
least 5%), but will be something to monitor. 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 /SATURDAY NIGHT THROUGH THURSDAY/...
Issued at 437 AM EDT Fri Jul 4 2025

Near zonal flow stretching across the Northern Tier Sunday and
Monday will be interrupted by a couple weak shortwaves. The first
will move through Upper Michigan Sunday night/Monday and the second
follows Monday night while high pressure at the surface keeps the
region mostly dry. The third wave, potentially Tuesday/Tuesday
night, may overlap with a slowly moving frontal boundary, which may
support precipitation. Another wave may dip down into the region
Wednesday in the lee of upper level ridging across the Northern
Plains and central Canada. Overall, this provides for showers and
thunderstorms Saturday, notably with a Marginal risk for severe
weather Saturday. Humid with warm to hot temperatures look possible
on Saturday, but afterwards the pattern favors mostly widespread 70s
for daytime highs and 50s interior/ near 60 for overnight lows.
Surface high over the area looks to keep the region mostly dry
through Tuesday despite a few different upper level waves moving
through. Tuesday, a wave diving southeast in the lee of mid-upper
level ridge atop a slow moving surface boundary may be enough to
support the next round of precipitation.

&&

.AVIATION /12Z TAFS THROUGH 12Z SATURDAY/...
Issued at 744 AM EDT Fri Jul 4 2025

VFR conditions are expected at all sites throughout this TAF period.
Have included prob30 groups for low chance (sub 25%) of TSRA at each
site. The greatest chance may be at IWD this morning where current
radar depicts a clusters of storms approaching the Bayfield.
Guidance struggles on the eastward progression of convection today,
thus very low confidence on anything even occuring at all.
Otherwise, the main hazard will be strong S to SE winds. Expect
light winds to strengthen out of the south with gusts to 25 kt
possible at all sites.

&&

.MARINE...
Issued at 437 AM EDT Fri Jul 4 2025

Mostly calm winds this morning will be on the rise through the day
as a warm front pushes through the Upper Great Lakes, developing
gusty southerly winds this afternoon and evening. Gusts 15-20 kts
will be common with localized gusts upwards of 25 kts are possible
along Lake Superior shorelines where southerly downsloping
accelerations occur. Elevated S to SE 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.

&&

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

&&

$$

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