943
FXUS63 KMQT 070700
AFDMQT

Area Forecast Discussion
National Weather Service Marquette MI
300 AM EDT Sun Jul 7 2024

.KEY MESSAGES...

- Scattered showers and thunderstorms over mainly the west half
  of Upper MI this afternoon.

- Monday 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. Could
  see highs into the 90s by Friday/Saturday.

&&

.SHORT TERM /THROUGH THIS AFTERNOON/...
Issued at 258 AM EDT Sun Jul 7 2024

Water vapor imagery and RAP analysis show mid-level troffing over
central N America. Within the trof, a well-defined shortwave is over
western MN with additional shortwaves dropping se from the Canadian
Prairies thru eastern MT/western Dakotas. In association with the MN
shortwave, shra and some tsra extend from nw MN se thru eastern MN
into IA. Closer to home, it`s been a quiet overnight under clear to
partly cloudy skies and little to no wind. A few of the traditional
interior cold spots are down to 50, but current temps mostly range
from the mid 50s to lwr 60s F.

Aforementioned shortwave over western MN will drift ne today and
will be over ne MN/western Lake Superior by sunset. On this track,
best forcing will shift over western Upper MI this aftn. Models
indicate roughly 300-1000j/kg of MLCAPE will build today. Of the 00z
models, the HRRR is around and blo the low end of that range. On the
opposite end of the spectrum is the NAM which is often on the high
side. It shows widespread 1000-1500j/kg building today. With deep
layer shear on the order of 25-35kt, expect some storm organization,
and if the NAM`s greater instability materializes, there would be a
risk of an isold svr storm. Instability build up will be something
to monitor during the morning into the aftn, but with expectation of
lower instability per bulk of guidance, don`t currently anticipate
any svr storms to develop this aftn. Some brief gusty winds/small
hail is a possibility in addition to the brief hvy downpours that
will accompany some of the storms. While some of the shra to the w
and sw may brush the Ironwood vcnty mid morning, expect shra/tsra to
begin to develop toward noon or early aftn and then quickly expand
across roughly the w half of Upper MI, greatest coverage generally w
of a L`anse to Iron River line. Lake breeze will try to develop and
shift inland from Lake Superior into Alger/Luce counties. Should end
up pinned along or very close to shore. The resulting convergence
combined with building instability on the land advecting northward
across the boundary on lower level southerly winds brings the
potential of isold shra/tsra development e of Marquette toward
Whitefish Pt (including the nearshore waters of Pictured Rocks
National Lakeshore) as well during the aftn. These isold shra/tsra
may end up mostly offshore unless the lake breeze can make a bit of
inland progress. Expect high temps today to be mostly in the mid 70s
to lwr 80s F.

&&

.LONG TERM /SUNDAY THROUGH SATURDAY/...
Issued at 324 PM EDT Sat Jul 6 2024

After a very progressive pattern kicked off this summer, a more
blocky pattern has now emerged as 500mb ridging over western North
America will only very slowly progress eastward with time throughout
this forecast period. The consequence of this for the UP will be
dealing with the low-amplitude shortwaves that spill southeast from
the ridge. While none of these shortwaves on their own are going to
be strong enough to force any surface low pressures deeper than
about 1005mb per the 12Z GEFS, with the help of diurnal heating,
chances of showers and thunderstorms will increase each afternoon.
As the the northern arm of the ridging slowly moves off of the
Canadian Rockies, signal is strong for high pressure to usher in a
period of dry weather Wednesday night into the weekend for the
longest dry stretch of the summer for the UP so far.

Sunday morning, the next shortwave in line will be centered over
Minnesota and approaching the UP from the west. Without much of a
surface feature resolved in global ensembles, forcing will be fairly
broad and unfocused, but HREF does show notable destabilization
throughout the morning hours, with mean SBCAPE values climbing to
near 750 J/kg by noon. Shear will not necessarily be abundant, and
with the forcing being weaker and broad, severe thunderstorms are
not expected, though a few stronger thunderstorms could bring
frequent lightning and locally heavy rain to interrupt those
wrapping up their weekend plans. Timing-wise, the HREF shows a line
of showers approaching Ironwood perhaps as soon as 9AM Central but
more likely closer to 11AM. Showers overspread the rest of the
western half of the UP throughout the early afternoon with
Alger/Delta counties and east not seeing much rainfall until around
sunset.

Monday`s PoPs look to be a similar pattern to Sunday`s, though for
different reasons. The residual cloud cover from the previous day`s
showers will keep SBCAPE closer to 500 than the 750 of the previous
day per the 00Z LREF, but the 12Z GEFS shows a cluster of low
pressure centers around 1005 mb, which is a bit stronger of a low
pressure than the guidance of 24 hours ago. Stronger forcing but
weaker instability should lead to a similar level of impacts as a
few stronger thunderstorms are possible but should remain sub-severe.

Tuesday and Wednesday, uncertainty begins to grow as global ensemble
and deterministic models diverge in the handling of shortwave
propagation as the 500mb ridge axis finally shifts out of British
Columbia. Once showers cease Wednesday, the northern arm of the
ridge will shift towards the Great Lakes and high pressure looks
likely to keep precipitation out of the forecast Thursday into the
weekend for what would be the longest dry period UP-wide since the
beginning of the summer. One interesting thing to note will be the
progression of Beryl as it makes landfall and turns northeast. The
06Z GEFS has a 20% chance of the remnants of Beryl coming within
200km of the UP, which depending on how much strength Beryl
maintains, could introduce showers into the forecast again late in
the week. The more likely impact would be in how long the high
pressure resides over the UP and at what strength, so it will be
worth keeping an eye on Beryl as it becomes better sampled by the
upper air network.

&&

.AVIATION /06Z TAFS THROUGH 06Z MONDAY/...
Issued at 123 AM EDT Sun Jul 7 2024

VFR conditions will prevail at all TAF sites through the period.
Calm conditions are expected for the rest of the night before a weak
surface low moves into northern Minnesota today. This wave, along
with diurnal instability, should result in scattered showers and
thunderstorms developing around IWD in the early to mid-afternoon,
where a PROB30 was placed during the window when tsra are most
likely. Lower probability of tsra making it to CMX/SAW in the late
afternoon and evening, so it was not included in the TAFs.

&&

.MARINE...
Issued at 324 PM EDT Sat Jul 6 2024

Light winds of 20 knots or less will continue across Lake Superior
this weekend through next week as a cycle of weak shortwave lows
followed by weak ridging continues across the Upper Great Lakes as
high pressure continues to build over the western CONUS. That being
said, a few of the disturbances will be strong enough to produce
some thunderstorms across the lake from time-to-time over the next
several days, namely over the western portions of the lake Sunday
and over the east overnight into Monday, and in the nearshore
waters Monday afternoon and evening.

&&

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

&&

$$

SHORT TERM...Rolfson
LONG TERM...GS
AVIATION...Thompson
MARINE...GS