624
FXUS63 KMQT 222002
AFDMQT

Area Forecast Discussion
National Weather Service Marquette MI
402 PM EDT Wed May 22 2024

.KEY MESSAGES...

- A Wind Advisory continues into the evening over the west due to
wind gusts up to 45 mph along the western Lake Superior shores of
the UP with up to 50 mph possible in the Keweenaw.

- Waves of 6 to 8 feet along the shores of Lake Michigan to cause
high risks of rip currents through sunset.

- Another shortwave and low pressure system will bring another round
of showers and a slight chance (around 20% chance) for some thunder
to Upper Mi late Friday into early Saturday.

- There will be more opportunities for rain next week although model
uncertainty leads to low forecast confidence on timing/extent.

&&

.SHORT TERM /THROUGH TONIGHT/...
Issued at 351 AM EDT Wed May 22 2024

GOES-16 Water Vapor imagery and radar returns show that behind a
line of showers over the eastern UP, only isolated showers remain in
an otherwise dry slot. RAP Analysis shows a 989mb low over the
northwestern shores of Lake Superior progressing to the NNE. As the
low and parent trough move into northwest Ontario today, an 850mb
LLJ will be source of the most impactful weather over the UP today.
By 20Z, the 00Z HREF shows 50 kts at 850mb over the Keweenaw with 35-
45 kt over the remainder of the west half of the UP. Mixing will
allow for some of those winds to be transported to the surface in
the form of wind gusts over the Keweenaw up to 50 mph and gusts
across the rest of the west half of the UP to 35-45 mph. HREF and
EPS guidance suggests only around 10% probability of wind gusts
exceeding 58 mph over the Keweenaw, so the High Wind Watch is
cancelled. The HREF does indicate some 30% probabilities along the
western shores of the Keweenaw of 58 mph gusts, so coastal
communities such as Freda, Eagle River, and Eagle Harbor could see a
peak gust of that strength, but as far as widespread, sustained
gusts are concerned, gusts up to 45 mph are the main concern. The
Wind Advisory will continue for Gogebic and Ontonagon and will
expand to cover northern Houghton County and Keweenaw County. For
the remainder of the UP, gusts to 35 mph are expected today, which
is still pretty gusty, but no products are expected to be issued,
given the HREF has trended towards a more compact area of higher
winds over the west.

As the dry slot will continue to reside over the UP today, shower
chances will be low, however, the HREF does show isolated to
scattered showers supported by diurnal heating this afternoon, so
some low-end (15-30 percent) PoPs are left in, but impacts from this
should be minimal. For those willing to brave 55 degree water
temperatures over Lake Michigan, waves of 6-8 feet over the
nearshore waters of Schoolcraft County are leading to high chances
of rip currents, prompting a Beach Hazard Statement. Tonight, as
mixing becomes less efficient and the low pressure continues to lift
north and away from the UP, winds fall off and the weather is mainly
benign, with lows falling into the 40s.

&&

.LONG TERM /THURSDAY THROUGH WEDNESDAY/...
Issued at 401 PM EDT Wed May 22 2024

By Thursday morning, the deep surface low just north of Lake
Superior this afternoon will have moved over James Bay while slowly
weakening. A mid-level ridge building over the Northern Plains
should lead to weak ridging/subsidence and mostly dry conditions
across the area on Thursday. That said, will still hang on to some
chance PoPs during the afternoon with a few of the models hinting at
a subtle shortwave rotating thru the area in the afternoon from the
storm system over James Bay. Any shower development from this weak
wave should be sparse given dry low-levels depicted in fcst
soundings. With some CAPE present in soundings, a few rumbles of
thunder will not be ruled out - but there is some capping to
overcome. Otherwise, expect sunny skies for the most part while
temperatures climb into the 70s across most of the UP, and in the
60s near Lake Superior. Though winds will come in much lighter than
today with a weakening pressure gradient, shallow daytime mixing
could still bring down some 20mph gusts across much of the UP,
potentially higher across the Keweenaw.

By Friday, the focus shifts to the next shortwave emerging from the
western CONUS mid-level trough . This shortwave lifts NE through the
Plains and Upper Great Lakes, eventually swinging into Manitoba and
phasing once more with the broader troughing over the western
CONUS/Canadian Prairies. Increasing isentropic ascent, 850 mb theta
advection and moderate q-vector convergence out ahead of the
shortwave will lead to another quick round of showers across the
area beginning late Friday afternoon in the western UP and spreading
eastward during the evening. If showers can hold off until later in
the afternoon, then we`ll stand a better chance at eroding a
building cap which would allow for some rumbles of thunder.
Otherwise, guidance continues to favor amounts largely around a 0.10-
0.25in, but ensembles are also showing around a 40% chance for more
isolated amounts around and in excess of 0.50in. Rain showers move
eastward out of the UP late Friday night, then for the most part,
Saturday should be dry with ridging behind the exiting shortwave
with much drier air working in. However, with another subtle wave
emanating out from the parent low over Manitoba, a few additional
sprinkles/light showers will not be ruled out; little to no rain
accumulations are expected. Expect otherwise partly cloudy skies and
seasonable temperatures for the rest of the day with highs mostly in
the 60s with a few cooler mid 50s readings near Lake Superior.

While models indicate weak ridging should hold on long enough to
keep Sunday dry, there is plenty of model uncertainty with what will
happen after that. Latest deterministic Canadian guidance continues
to maintain mostly dry conditions through the first half of next
week, suppressing a southern stream trough over the Lower Great
Lakes/Ohio Valley and keeping the Upper Great Lakes mostly dry. This
increasingly looks to be the outlier among the global models. The
Euro, UKMET, and now the GFS are trending toward a phased, deeper
and farther north system tracking somewhere between the central
Lower Peninsula and the Straits of Mackinac. If a more northwestward
solution verifies it will potentially be a much more impactful
system for the Upper Great Lakes into early next week with much of
the UP receiving significant soaking rainfall, and the eastern UP
potentially seeing heavy rainfall Sunday night through Monday.
Wraparound moisture in the deformation zone, comma head of the
deepening system will lead to the potentially heavy rainfall Tuesday
as well. The deep system would also lead to more wind impacts with
gales likely over Lake Superior and windy conditions across much of
the U.P. Needless to say, model trends will be watched closely in
the coming so stay tuned to possible forecast changes into early
next week. As of right now, given the uncertainty, this forecast
reflects the latest NBM solution which does bring in an increase in
wind speeds as well as better chances for rainfall early next week.

&&

.AVIATION /18Z TAFS THROUGH 18Z THURSDAY/...
Issued at 152 PM EDT Wed May 22 2024

As the low pressure system just north of Lake Superior continues
north-northeast today, all sites will see improvement to VFR by the
0Z TAF. Gusty west winds are expected this afternoon to 25-30 kts at
SAW and IWD with up to 40 kts at CMX. Winds lighten up tonight,
however some gusts near 20 kts remain at SAW and IWD; gusts at CMX
hold in the 20-30 kt range through Wednesday. Some isolated showers
are possible this afternoon and evening at all TAF sites. Skies
gradually scatter out from south to north as drier air works its way
in from the west. A few showers and maybe some thunder is possible
Thursday afternoon at IWD and SAW.

&&

.MARINE...
Issued at 401 PM EDT Wed May 22 2024

Deep low pressure is centered just north of Lake Superior this
afternoon, with a tight pressure gradient over the lake. SW gales of
35 knots are common across the western half of Lake Superior, but
higher gusts to 40 knots are still possible through the evening
especially closer to the shoreline of the Keweenaw. Winds are coming
in comparatively lighter to the east, mainly up to 20-25 knots. As
the low gradually lifts north through Ontario and weakens this
evening, winds should fall below gale force by midnight. Internal
probabilistic guidance indicates only around a 20% chance for gales
the rest of the night. The winds continue to diminish through
Thursday morning and afternoon, with light winds of 20 knots or less
returning to the area by evening. The period of light winds doesn`t
last long over the western lake as northeast winds will begin to
ramp up to 30 knots late Thu night into Friday in advance of another
low pressure lifting from the Northern Plains towards Lake Winnipeg.
Guidance indicates around a 30-40% chance for gale force gusts
Friday afternoon in far western Lake Superior. Winds diminish to 15
to 25 knots over the west half of the lake and becoming southwest
behind the low and the passage of its cold front late Friday night
into Saturday. Behind this system, expect light winds of 20 knots or
less across Lake Superior for the rest of this weekend as high
pressure ridging moves over the area. &&

.MQT WATCHES/WARNINGS/ADVISORIES...
Upper Michigan...
  High Wind Watch from 6 AM EDT Wednesday through Wednesday
     evening for MIZ001-003.

  Wind Advisory from 9 AM EDT /8 AM CDT/ to 10 PM EDT /9 PM CDT/
     Wednesday for MIZ002-009.

Lake Superior...
  Gale Warning until 8 PM EDT /7 PM CDT/ Wednesday for LSZ162.

  Gale Warning from 7 AM EDT /6 AM CDT/ to 8 PM EDT /7 PM CDT/
     Wednesday for LSZ240-241.

  Gale Warning from 10 PM this evening to 11 PM EDT Wednesday
     for LSZ242>244-263-264.

  Gale Warning from 2 AM to 11 AM EDT Wednesday for LSZ245>251-
     265>267.

Lake Michigan...
None.

&&

.MQT WATCHES/WARNINGS/ADVISORIES...
Upper Michigan...
  Wind Advisory until 10 PM EDT /9 PM CDT/ this evening for
     MIZ001>003-009.

  Beach Hazards Statement until 10 PM EDT this evening for
     MIZ014.

Lake Superior...
  Gale Warning until 8 PM EDT /7 PM CDT/ this evening for LSZ162-
     240-241.

  Gale Warning until 11 PM EDT this evening for LSZ242>244-263-
     264.

Lake Michigan...
None.

&&

$$

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