802
FXUS63 KMQT 041716
AFDMQT

Area Forecast Discussion
National Weather Service Marquette MI
116 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.

&&

.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 /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 /18Z TAFS THROUGH 18Z SATURDAY/...
Issued at 115 PM EDT Fri Jul 4 2025

VFR conditions today and tonight at all sites. Isolated to scattered
showers and thunderstorms may develop this afternoon over west-
central Upper Michigan, but these are currently expected to avoid
the TAF terminals. Otherwise, gusty winds near 20kts will be
possible. Tonight an upstream cold front will inch closer to the
region, resulting in increased sky coverage and precip spreading
into western Upper Michigan. Confidence is high on rain showers and
prob30s were introduced for thunderstorm chances.

&&

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