968
FXUS63 KMQT 062324
AFDMQT

Area Forecast Discussion
National Weather Service Marquette MI
724 PM EDT Sat Jul 6 2024

.KEY MESSAGES...

- Slight chance (~20%) for late afternoon showers and thunderstorms
across interior western Upper MI late afternoon/early evening.

-Sunday through Wednesday, daily chances of showers and
thunderstorms, highest chances in the afternoons.

-Dry period begins Thursday, could be dry into next weekend.

&&

.SHORT TERM /THROUGH TONIGHT/...
Issued at 300 PM EDT Sat Jul 6 2024

Not much to talk about in the short term through tonight. Surface
ridge axis extends from the Upper Midwest up into the Upper Great
Lakes. Diurnally driven cu field has developed across the interior
of the U.P. with light onshore flow along the Lakes shorelines. Fog
per visible imagery over eastern Lake Superior has been shifting
slowly eastward with time with the Luce county shorelines over to
Whitefish point the only remaining areas experiencing fog/stratus.

12Z models have been consistent with previous runs showing enough
destabilization by late afternoon/early evening for isolated
shra/tsra activity mainly in the WI bordering counties.  Will
maintain slight chance pops until about 2-3Z there but most
everybody will remain dry this evening.

By late in the night, convection initiating this evening over MN
along next shortwave moving into the Upper Mississippi Valley will
be approaching northwest WI and far western Lake Superior.  The U.P.
will remain dry through 12Z with just an increase in mid/upper level
clouds towards morning.

Expect seasonable overnight lows mainly in the 50s.

&&

.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 /00Z TAFS THROUGH 00Z MONDAY/...
Issued at 724 PM EDT Sat Jul 6 2024

VFR conditions will prevail at all TAF sites through the period.
Spotty showers and thunderstorms are starting to develop along the
far MI/WI border near IWD, but will be rather short lived and taper
off with the setting sun. Calm conditions are expected overnight
before a weak surface low moves into northern Minnesota on Sunday,
sending a wave of light showers across the west half of the U.P. in
the early afternoon. More convective showers and thunderstorms look
to develop across the west towards the end of the period, however,
there is low confidence in the coverage and timing and have
therefore been left out of the TAFs at CMX and SAW.

&&

.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...MZ
LONG TERM...GS
AVIATION...BW/Thompson
MARINE...GS