792
FXUS63 KMQT 111957
AFDMQT

Area Forecast Discussion
National Weather Service Marquette MI
357 PM EDT Thu Jul 11 2024

.KEY MESSAGES...

- Quiet weather persists into Friday.

- Isolated (~20%) showers with a few rumbles of thunder in the
interior Friday.

- Hot and muggy conditions this weekend with the potential for a few
strong to severe thunderstorms Saturday through Monday.

- Cooling and drying trend into the midweek portion of next week
with the arrival of high pressure.

&&

.SHORT TERM /THROUGH TONIGHT/...
Issued at 151 PM EDT Thu Jul 11 2024

Surface high pressure is sprawled out over the Great Lakes, and
water vapor imagery reveals dry midlevel air overhead. Visible
satellite shows plenty of fair weather cumulus over the central and
interior-eastern UP, though lake breezes off of Superior and Lake
Michigan are also evident. This diurnal cumulus shouldn`t be
considered a harbinger of showers/storms later in the day given dry,
well-capped soundings. Otherwise, temperatures are already well into
the 70s across most of the area, on track to peak in the upper 70s
to lower 80s in the interior UP. The exception, of course, is along
the lakeshores of the Great Lakes. Look for highs in the mid 70s
along Lake Michigan, and in the 60s to lower 70s along Superior.

Skies remain clear overnight, and with light winds, temperatures
should easily be able to fall back to the dewpoint. Expect lows in
the  mid 50s across most of the area, and closer to 60F along the
Superior shorelines of the western and north-central UP.

&&

.LONG TERM /FRIDAY THROUGH THURSDAY/...
Issued at 357 PM EDT Thu Jul 11 2024

Aloft, the path of most prominent troughs and ridges is well to the
north over Canada, leaving the Upper Great Lakes in a primarily
zonal pattern aloft. This will lead to the primary driver of
sensible weather to be weak shortwave impulses in the zonal flow.
While the forcing may be weak and ambiguous, hot and muggy
conditions this weekend will allow for instability to grow, allowing
for the potential for strong to severe thunderstorms over the
weekend and to begin next week. High pressure then settles over the
region by next Wednesday, allowing for a cooler dry period towards
the middle and late week period next week.

As sunny skies kick off the day on Friday, diurnal heating will
allow temperatures to climb to around 80. The main question of the
forecast is whether any diurnal convection might develop. Mid-level
height rises during the day will provide enough subsidence to keep
widespread showers from develop, but enough of the CAMs do resolve
shower formation to keep slight chances (15-25%) in the forecast. As
SBCAPE values do climb to 750-1000 J/kg, any isolated showers that
do form will have potential for some thunder.

Over the weekend, warming under low-level meridional flow will send
high temps into the mid and upper 80s. The two zones where the NBM
highlights probabilities of exceeding 90F are over the south-central
on Sunday at 20-40 percent and in downslope areas near Lake Superior
on Saturday and Sunday as high as 60-90 percent. Moisture values
increase as well, with the 12Z GEFS showing coin-flip odds of PWATs
exceeding 1.5 inches by late Saturday and higher chances by Sunday.
Dew points are forecast to be in the mid-upper 60s Saturday with
Sunday`s dew points touching 70 for at least some period of time for
much of the UP, creating quite muggy conditions.

These hot summertime conditions will be accompanied with westerly to
west-northwesterly flow at 500mb, which will allow for some minor
shortwaves to progress through the region. The combination of a
summertime airmass and the flow pattern aloft combine for a
climatologically favorable setup for convection over the UP. As the
hot and humid temperatures set up, CAPE values climb to over 1000
J/kg on Saturday and Monday and over 2000 J/kg on Sunday (with the
90th percentile showing worst-case values of over 3000). With the
southwesterly surface flow contrasting the west-northwest flow
aloft, directional shear will be present, though speed shear will be
somewhat lacking. Regardless, shear will be present enough to help
maintain whatever thunderstorms do initiate, so if forcing is
present enough to realize the plentiful instability, severe weather
is a possibility for Saturday through Monday. However, without great
consensus on forcing, exact probabilities or timings are unknown at
this time.

There might (20%) be one more day of afternoon rain showers, but as
broad troughing aloft shifts from northern Ontario towards the East
Coast, ridging fills in behind and high pressure to around 1020mb
will keep weather quiet Wednesday and Thursday. A cooling trend is
also expected to accompany the arriving ridging as north and
northwest flow will bring highs only in the upper 60s and low 70s
Tuesday through Thursday.

&&

.AVIATION /18Z TAFS THROUGH 18Z FRIDAY/...
Issued at 129 PM EDT Thu Jul 11 2024

Mostly clear skies dominate the TAF period with light winds
throughout.

&&

.MARINE...
Issued at 357 PM EDT Thu Jul 11 2024

Light pressure gradient will keep wind gusts below 20 knots and wave
heights below 3 feet for the next week. The greatest hazards will
come in the form of thunderstorms which will threaten the lake
Saturday through Monday, with a few storms being potentially strong
to severe in the nearshore waters. Patchy dense fog is also a
possibility in the wake of precipitation.

&&

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

&&

$$

SHORT TERM...LC
LONG TERM...GS
AVIATION...LC
MARINE...GS