721
FXUS63 KMQT 230523
AFDMQT

Area Forecast Discussion
National Weather Service Marquette MI
123 AM EDT Thu May 23 2024

.KEY MESSAGES...

- A Wind Advisory continues into this evening over the western
  Lake Superior shore counties and in the Keweenaw due to wind
  gusts up to 45 mph.

- Waves of 6 to 8 feet along the shores of Lake Michigan yields
  a high risk 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 434 PM EDT Wed May 22 2024

Current RAP analysis shows the mid level trough now over
northwestern Ontario with the associated sfc low centered just east
of it over Lake Nipigon. As the trough pivots over the UP through
this evening, some isolated to scattered light showers already
lighting up the radar data are expected continue spreading east
through late this afternoon. Showers then will lift north and
diminish this evening as drier northwest flow works its way in and
aiding isentropic ascent ends. Median of CAMs guidance is very
minimal with only a few hundreths of QPF, so little if any
accumulation is expected.

Gusty winds continue through this evening thanks to an 800-850 mb
LLJ overhead, tighter pressure gradient, and increased mixing. Gusts
up to 35-45 mph are expected along the western counties of Gogebic,
Ontanogon, Houghton, and Keweenaw where the wind advisory continues
into this evening. Elsewhere, gusts are expected up to 30-35 mph. As
the sfc low departs north-northeast toward James Bay through tonight
and we lose daytime heating, mixing diminishes and westerly winds
weaken into tonight; the Keweenaw could still see some gusts tonight
up to 30 mph. Cloud cover gradually clears from south to north
allowing for lows to settle 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 /06Z TAFS THROUGH 06Z FRIDAY/...
Issued at 123 AM EDT Thu May 23 2024

In the wake of low pres tracking ne across northern Ontario, drier
air moving into the area will allow VFR to prevail at IWD/CMX/SAW
thru this fcst period. W to NW winds will still be elevated into
this aftn, especially at CMX/SAW. Expect w to nw winds of 15-20kt at
CMX thru late aftn. Winds at SAW will increase to 15-20kt a few hrs
after sunrise. Winds will become light, aob 5kt, at all terminals
this evening.

&&

.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...
None.
Lake Superior...
None.
Lake Michigan...
None.

&&

$$

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