815
FXUS63 KMQT 232356
AFDMQT

Area Forecast Discussion
National Weather Service Marquette MI
756 PM EDT Thu May 23 2024

.KEY MESSAGES...

- Another shortwave and low pressure system will bring a 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 344 PM EDT Thu May 23 2024

Current RAP analysis shows the mid level low along the southern end
of James bay with it`s associated 995 mb low pressure center still
over James bay, but just northwest of the mid level low. With weak
sfc high pressure at around 1012 mb building over the CWA, mostly
sunny skies have been the predominant sky conditions for much of the
UP this afternoon. This has allowed for temps to warm up into the
60s for much of the UP; onshore flow has kept cooler temps along
Lake Michigan between Manistique and the Mackinac Bridge as well as
near Lake Superior. The sunny skies have also helped mixing yield a
breezy day with west to northwest gusts up to 20-30 mph, strongest
in the Keweenaw. Winds will gradually diminish into this eveing as
high pressure continues to build in. Some diurnal cumulus has
developed over the southern UP and will continue to increase this
afternoon with the support of a mid level shortwave moving east
through northern WI. Afternoon highs are expected to peak in the mid
50s to mid 60s near Lake Superior, 60s along Lake Michigan east of
Manistique, and upper 60s to mid 70s elsewhere.

Some slight chances for showers return to the forecast along the
WI/MI state line with the best chances for showers in Menominee
County late this afternoon where there is better instability (5/23
12Z HREF mean MUCAPE up to 250 j/kg in south central). Accumulations
will likely be only a few hundreths at best, but showers moving
through Menominee county could bring up to 0.1" to 0.2" of rain on
the high end if the NAM Nest solution is favored.

As daytime heating ends and high pressure continues to build in
tonight, skies will mostly clear out helping temps settle slightly
cooler than normal into the upper 30s to upper 40s. While mostly
clear skies are expected with dry weather, cloud cover increases
late into Friday ahead of the next low pressure system. This
approahcing low will also turn light winds northerly then eventually
easterly by Friday morning.

&&

.LONG TERM /FRIDAY THROUGH THURSDAY/...
Issued at 344 PM EDT Thu May 23 2024

Wet, active weather continues on and off through the extended period
before we briefly dry out for the middle of next week.

By Friday, the focus will shift to the next shortwave emerging from
the western CONUS mid-upper level trough. This shortwave lifts NE
through the Plains and Upper Great Lakes, eventually swinging into
Manitoba and Ontario 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. Instability off soundings
looks pretty minimal, with just a few hundred j/kg of CAPE indicated
in HREF plots, so thunder should be fairly limited. Otherwise,
guidance continues to favor widespread rain amounts of 0.10-0.25in,
but EPS ensembles also show probabilities of 40-60% for amounts of
0.50in or more south central and southeast. Showers quickly exit
eastward during the pre-dawn hours of Saturday with clearing skies
expected as drier air works in.

Saturday should be dry with ridging/subsidence behind the exiting
shortwave. Expect 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.

There remains quite a bit of uncertainty in the Sunday-Tuesday time
frame regarding the track/strength of the next western CONUS wave
and developing cyclone. This ejects NE from the lee of the southern
Rockies into the Great Lakes region late weekend into early next
week, but many of deterministic models (particularly the GFS, UKMET
and Canadian) as well as ensembles continue to flip-flop on the
exact track with some runs taking a deep system as far north as the
Straits, and others suppressed more over the southern or central
Lower Peninsula and coming in comparatively weaker. A more southerly
route would have little if any wind and rain impacts to the UP,
while the more NW route would bring a chance for more significant
rainfall as well as gusty winds. The ECMWF, on the other hand, has
been the most consistent of the models advertising generally a more
phased and deeper system for the last several runs with a more
northern/western track through the Central Great Lakes, and thus,
greater rain and wind impacts for Upper Mi in the late Sunday into
Memorial Day time frame. Given the huge spread depicted in the
tracks of the ensemble members it`s still too soon to latch onto any
one model solution with great certainty, thus leading to poor
forecast confidence during this time frame. For now, will continue
to lean on the model blend for forecast details and wait a bit
longer for models to sort out their continuity/consistency issues
and hopefully come into better agreement over the coming days.

PoPs persist into Tuesday as the system moves into Quebec, and
associated wraparound moisture curls into the area while another
shortwave ripples through. Most of the models and ensembles do seem
to be in general agreement showing a trend toward ridging and drier
conditions for Wednesday into Thursday next week. Otherwise, expect
more or less seasonable temperatures through the forecast period.

&&

.AVIATION /00Z TAFS THROUGH 00Z SATURDAY/...
Issued at 754 PM EDT Thu May 23 2024

Dry air mass associated with sfc high pres ridge drifting across the
area tonight will allow VFR to continue at IWD/CMX/SAW. Winds will
also diminish to aob 5kt during the evening. On Fri, low pres
lifting across the Northern Plains will swing an occluded front to
the ne. That front will be approaching western Upper MI at 00z.
Although some shra well ahead of the front may push into the w half
of Upper MI mid and late aftn, the main area of shra and isold tsra
will hold off until early evening. So, for now, fcst only reflects
shra and MVFR cigs arriving at IWD around 22z. Shra/MVFR conditions
will reach CMX/SAW just beyond this fcst period. During the aftn, E
to SE winds will increase and become gusty to around 25kt at IWD/CMX
and to around 20kt at SAW. LLWS will also be possible at IWD in the
aftn.

&&

.MARINE...
Issued at 344 PM EDT Thu May 23 2024

Low pressure that impacted the area over hte past couple of days
continues to weaken over James Bay while a weak high pressure ridge
builds over the Great Lakes. Winds have been on the decrease today
in response, still gusting to 20-25 knots out of the west in the
eastern portions of the lake, but dropping below 20 knots to the
west. Winds finally fall below 20 knots to the east later this
evening. The period of light winds doesn`t last long over the
western lake, however, as northeast winds will begin to ramp up to
30 knots late tonight into Friday in advance of another low pressure
lifting from the Northern Plains towards Lake Winnipeg. Guidance
indicates around a 60-70% chance for gales Friday afternoon through
the early evening over the western quarter of Lake Superior. East to
southeast winds gradually increase over the east half of the lake on
Friday but generally stay 20 knots or less, but 25kt gusts will then
become possible for a brief period into the evening and overnight
hours. Winds over the west half becoming southwest behind the low
and the passage of its cold front late Friday night into Saturday
and generally stay in the 15 to 25 knot range. Winds decrease late
Saturday behind the exiting system, then expect light winds of 20
knots or less across Lake Superior for the rest of this weekend as a
high pressure ridge builds over the area. Looking ahead to early
next week, another system moving out of the Plains will head towards
the Great Lakes. This could present another opportunity for gusty
winds, but confidence is low given quite a bit of uncertainty on the
exact storm track.

&&

.MQT WATCHES/WARNINGS/ADVISORIES...
Upper Michigan...
None.
Lake Superior...
  Gale Warning from 11 AM EDT /10 AM CDT/ to 8 PM EDT /7 PM CDT/
     Friday for LSZ162.

Lake Michigan...
None.

&&

$$

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