758
FXUS63 KMQT 080537
AFDMQT

Area Forecast Discussion
National Weather Service Marquette MI
137 AM EDT Mon Jul 8 2024

.KEY MESSAGES...

- Through at least Tuesday, daily chances of showers and
  thunderstorms, highest chances in the afternoons.

- Drier weather expected for the last half of this week, though
  ~10% chance Beryl`s remnants complicate the forecast.

- Hot weather possible into the weekend, with ~25% chance of
  isolated high temperatures in the 90s over the weekend.

&&

.UPDATE...
Issued at 737 PM EDT Sun Jul 7 2024

As of 730 pm EDT, cluster of showers and thunderstorms straddles the
WI/MI border in eastern Gogebic County associated with a broad lower-
level confluence zone. One storm briefly perked up SW of Marenisco
earlier in an environment of 30 kt deep layer shear and 1000 J/kg
MLCAPE, showing a broad mesocyclone and likely producing around 0.5"
hail, but otherwise, activity has been fairly shallow. Still not out
of the question for a stronger core to develop and result in small
hail and gusty winds to the east and northeast of current activity
through Baraga/Iron Counties given the aforementioned
thermodynamic/kinematic environment, especially where storm mergers
occur with some downstream showers moving more northerly. Storms are
rather slow moving so locally heavy rainfall can be expected as
well. HRRR suggests this activity may persist through around 03Z as
it moves E/NE before weakening.

&&

.SHORT TERM /THROUGH TONIGHT/...
Issued at 238 PM EDT Sun Jul 7 2024

Water vapor imagery showing upper low over northern MN with several
weak shortwaves rotating around it over WI and western Lake
Superior. Given proximity to the U.P. combined with diurnal heating
have already seen scattered shras and tsras develop over the western
third of the U.P.  A couple other shras have developed along the
Lake Michigan lake breeze along the Seney stretch. While a brief
stronger storm can`t be ruled out this afternoon given marginal
shear up to 25 knots and CAPE around 1000-1250 J/kg, expect storms
to lack organization. Most activity will diminish this evening with
sunset but as weak shortwave migrates eastward will maintain
slight/low chance pops over the eastern U.P. through the night.
Areas that do see some rain over the west, especially near evening
time may then see some patchy fog develop overnight tonight.  Lows
tonight will mainly be in the upper 50s to lower 60s.

&&

.LONG TERM /MONDAY THROUGH SUNDAY/...
Issued at 337 PM EDT Sun Jul 7 2024

By Monday morning, cutoff 500mb high will be over the SW CONUS with
a ridge axis extending NNW along the Pacific coast of North America,
leading to 500mb height anomalies of up to +18 over the Vancouver
area per the 12Z GEFS. The high will remain largely stationary
throughout the week, but the ridge axis to the north will rotate
through the early portions of the week as a Gulf of Alaska trough
will kick the ridge axis to the east. For the early portions of the
week, the weak shortwaves spilling down from the peak of the ridge
and with some help from diurnal heating, will allow for daily
thundershower chances until the ridge axis progresses far enough
east for a surface high pressure to dampen precipitation chances.
The remnants of Beryl may throw a wrench in the forecast as it
passes south of the UP in the back half of the week, but regardless,
some hotter weather will return to the UP for the weekend with 90s
not out of the question (10-25%) for typical hot spots.

To begin the week, one of the aforementioned 500mb shortwave troughs
will sweep over the UP on Monday, supporting surface troughing of
around 1010mb. This will certainly help force some showers and
thunderstorms and 12Z HREF mean SBCAPE does climb to over 1000 J/kg
over the interior west and central UP. However, with only around
20kt of bulk shear, storms will likely be disorganized, so only
garden variety pulse thunderstorms are expected. This is shown in
the very scattered pattern shown in the HREF reflectivity plots.
Timing-wise, most of the HREF members show initiation around 18Z
Monday with a pretty sharp dropoff in shower coverage and intensity
after sunset.

Tuesday looks to be yet another day with a shortwave passing over
the UP with diurnal thundershowers expected, but PoPs are lower than
the previous day (20-50% instead of 40-80%) thanks to a weaker
shortwave providing less PVA and overall height rises occurring
coincident with tropa. With the 00Z LREF still showing mean CAPE
values around 500 J/kg, there are chances (~30%) of thunder, but
should be well sub-severe.

The complications come Wednesday through the end of the week as the
ridge axis moves over the Canadian Prairie and forces a 1015-1020mb
high pressure that approaches the Upper Great Lakes through the day
Wednesday. However, the remnants of Beryl will swing northeast after
making landfall in TX, with the majority of deterministic and
ensemble guidance bringing the remnants through the Lower Peninsula
of Michigan. The strength and path of both Beryl and the ridge will
have implications on the forecast through the end of the week. For
now, the current forecast reflects the solution that the high
pressure prevails over at least Lake Superior into the weekend,
though the 12Z GEFS still shows a 10-20% chance of the remnants of
Beryl passing within 200 km of the eastern UP, so the forecast is
definitely not set in stone at this point. However, confidence is
increasing that after Beryl`s remnant low passes through the Great
Lakes and flow aloft shifts from northwesterly to be more westerly,
hot temperatures could return to the UP, with the NBM showing about
a 25% chance of isolated 90 degree highs and 5-10% chance of more
widespread 90s highs.

&&

.AVIATION /06Z TAFS THROUGH 06Z TUESDAY/...
Issued at 134 AM EDT Mon Jul 8 2024

Main potential impacts in the 06Z TAF cycle are fog potential early
this morning and thunderstorm potential this afternoon and evening.
Given earlier rainfall at IWD/CMX and low dewpoint depression,
MVFR/IFR fog/mist is possible through around daybreak. VFR
conditions should return shortly after sunrise as any fog burns off.
Afternoon destabilization combined with an approaching wave should
touch off showers and thunderstorms primarily in the afternoon and
evening. Though not totally out of the question for IWD/CMX to
see a shower or storm this afternoon, only VCTS/VCSH,
respectively, was included in the TAF as more stable air looks
to arrive fairly early in the afternoon to limit potential at
both terminals. Potential for multiple rounds of showers/storms
at SAW today from early afternoon through the evening with low
confidence on timing. PROB30 was included during the most
probable timeframe for tsra. VFR should prevail outside of any
showers or storms, but brief heavy downpours could result in IFR
vsby reductions in any storms.

&&

.MARINE...
Issued at 337 PM EDT Sun Jul 7 2024

Light winds of generally 20 knots or less continue through this week
as high pressure ridging over the western US slowly drifts eastwards
throughout the forecast period. That being said, some thunderstorms
are possible across the lake this afternoon through tonight, and
then along the nearshores Monday and Tuesday. Wave heights will
remain below 2 feet through the duration of the forecast period.

&&

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

&&

$$

UPDATE...Thompson
SHORT TERM...MZ
LONG TERM...GS
AVIATION...Thompson/Rolfson
MARINE...GS/TAP