439
FXUS63 KMQT 092344
AFDMQT

Area Forecast Discussion
National Weather Service Marquette MI
744 PM EDT Tue Jul 9 2024

.KEY MESSAGES...

- Scattered showers and thunderstorms across the central and
eastern UP along the Lake Superior and Lake Michigan lake breezes.

- Overall, a drier pattern is upcoming compared to the last few
weeks. Though some areas of 15-35% chance of precipitation continue
into the weekend, most locations will see several days of dry
weather.

- Very warm over the weekend with high temperatures well into the
80s F. A 10-20% chance of high temperatures at or above 90F.

&&

.SHORT TERM /THROUGH THIS EVENING/...
Issued at 415 PM EDT Tue Jul 9 2024

Sunny skies across most of the area today has allowed for healthy
destabilization (1000 j/kg of CAPE analyzed over the UP), indicated
by convection firing along the Superior and Lake Michigan lake
breezes across the central and eastern UP. Given weak wind fields,
severe storms are not expected, but given fairly high reflectivity
and steeper ZDR, a quick heavy downpour is a safe bet.

Otherwise, it`s looking like a rather nice (if humid) summer
afternoon with most of the area seeing temperatures well into the
70s to lower 80s. The exception, as always, is right along Superior,
where temperatures in some spots are struggling even to get out of
the 60s. Satellite and webcams are even showing marine fog creeping
onshore from around Pictured Rocks to Whitefish Point. With onshore
flow the rest of today through tonight, fog will likely stick around
in those shoreline areas.

&&

.LONG TERM /TONIGHT THROUGH TUESDAY/...
Issued at 415 PM EDT Tue Jul 9 2024

After the diurnally-driven convection currently firing across the
central UP tapers of this evening, expect quiet conditions overnight
while high clouds continue to filter in ahead of the remnants of
Beryl (more on that later). Expect patchy radiation fog development
over the interior-western UP, with clear skies and calm winds.
Meanwhile, to the east, we may see more widespread fog/low stratus
with light NNE winds off of Superior advecting in the moist marine
layer inland while upsloping over the land. This should also be able
to advect in the marine fog/low stratus already apparent over the
open waters of eastern Lake Superior, and currently reaching the
shorelines from Pictured Rocks to Whitefish Point.

With onshore winds on Wed, low clouds/fog may end up dominating the
day from around the Marquette area to Munising, along Pictured
Rocks, to Grand Marais. Otherwise, the remnants of Beryl will be
passing through the Lower Midwest and into the Lower Great Lakes
Wednesday afternoon and evening. This will touch off our next round
of PoPs, with guidance continuing to favor the eastern UP, as an
instability gradient sets up along Lake Michigan and our southern
zones. A weaker signal for some spotty showers is apparent across
the south-central UP as well; perhaps with upsloping off of
Superior, weak showers may be able to develop and progress more
inland. With ensembles showing a few hundred j/kg of MUCAPE by the
afternoon, some rumbles of thunder will be possible. Strong
convection is not expected given a weak wind field. Otherwise,
expect a fairly mild day with temperatures generally in the upper 70s
to lower 80s away from Superior. Where we remain under persistent
marine fog/low stratus, temperatures may struggle to reach even into
the lower 70s.

Dry weather returns into Wednesday evening, but marine fog may
persist across the eastern UP while light winds and moist lower
levels allow for a potential for radiation fog development to the
west. Expect lows ranging in the 50s for most.

Ridging over the area Thursday and Friday should yield mainly dry
conditions both days. However, with lake breeze development off of
both Superior and Lake Michigan Thursday given an otherwise light
wind regime, will not rule out some spotty convection especially
across the central/south-central UP, where guidance once again shows
increasing daytime instability. Given quite a bit of uncertainty
with rather dry soundings, this forecast reflects only about a 15%
chance for any convection Thursday. There is even less confidence
for any convection Friday. By then, we will be under a southerly
flow regime on the back edge of the surface high, and less at the
mercy of any lake breeze development.

Meanwhile, a warming trend will kick off Friday and continue into
the weekend, with most of the area seeing highs well into the 80s
Friday through Sunday. The hottest day looks to be Sunday, when
ensemble guidance indicates up to a 10-20% chance of widespread highs
around 90F. Still, highs around 90F are possible each day of this
period in the southerly downsloping areas nearer to Lake Superior.
A weak passing shortwave supports a potential for some
showers/storms beginning Saturday afternoon and evening.

Late weekend/early next week, another trough eventually drops out of
Manitoba/Ontario, ushering in a cooler airmass. Ahead of that wave,
other subtle waves are indicated to progress through W/NW flow into
the Upper Great Lakes. Given the substantial instability within the
very warm/humid conditions over the Upper Mississippi Valley/Upper
Great Lakes, there will be a risk of severe storms Sunday through
Monday, but will note that the wind field remains weak. However, as
would be expected at this time range, timing of shortwaves and
resulting convection, including movement of convection that does
develop and whether Upper MI is actually affected, is highly
uncertain. Will be something to monitor over the weekend/early next
week.

&&

.AVIATION /00Z TAFS THROUGH 00Z THURSDAY/...
Issued at 743 PM EDT Tue Jul 9 2024

Periods of IFR fog are possible at CMX and SAW overnight. Overall
confidence in fog timing and development are not as high as previous
nights. Tonight`s guidance has backed down on incoming fog from the
Lake Superior marine layer, particularly at CMX, and thus only
included a period of slightly lower visibility (4 mile) before
sunrise in the TAFs. Fog development should burn off at sunrise,
however, fog could stick around at SAW through the morning with
light onshore flow.

&&

.MARINE...
Issued at 415 PM EDT Tue Jul 9 2024

A weak pressure gradient over the Great Lakes will keep winds light
for the next several days, likely coming in at 15 kts or less. By
Saturday, winds will be on the increase out of the south with
troughing to our west, but are still looking to come in generally
below 20 kts.

Fog currently plaguing portions of northern and eastern Lake
Superior will expand to the south tonight as winds become northerly.
This fog is likely to be locally dense at times. The fog may linger
on Wed across southern portions of the lake, roughly in the area
between Granite Island and Whitefish Pt.

&&

.MQT WATCHES/WARNINGS/ADVISORIES...
Upper Michigan...
None.
Lake Superior...
  Dense Fog Advisory until 11 AM EDT Wednesday for LSZ266-267.

Lake Michigan...
None.

&&

$$

SHORT TERM...LC
LONG TERM...LC
AVIATION...BW/Thompson
MARINE...LC