393
FXUS63 KMQT 231742
AFDMQT

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

.KEY MESSAGES...

- 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 318 AM EDT Thu May 23 2024

RAP analysis shows a stacked closed low north of Lake Superior
with central surface pressure near 994 mb. While a tight
pressure gradient and tapping into a LLJ caused windy conditions
earlier, the weakening low departing the region is allowing
winds to come down somewhat, though some gusts to 25 mph may
linger throughout the morning.

Despite weakening surface flow, diurnal heating will support cu
development with a few CAMs suggesting some shower development in
the south and interior west. Instability has trended lower with the
last 24 hours of model runs, so confidence in showers of any
strength is low, but left some 15-24% PoPs from 18Z to 02Z. Expect
highs mainly in the mid 60s, close to the climatological normal for
this time of year. The exceptions will be locations downwind of
Lake Superior that will have highs near 60 and the south, which
bias- corrected guidance suggests mid- to upper-70s may be
observed between Menominee and Iron Mountain.

Overnight, winds turn easterly and northeasterly in response to a
00Z GEFS-mean 997 mb low approaching Minnesota. Previous forecasts
had rain arriving in Ironwood by 12Z Friday, but virtually all of
the most recent model runs at varying resolutions have backed
off on the initial line of precipitation, so PoPs have been
largely removed from the overnight time period. Low temperatures
will be in the 40s, near normal for this time of year.

&&

.LONG TERM /FRIDAY THROUGH WEDNESDAY/...
Issued at 354 AM EDT Thu May 23 2024

Several models and ensembles showing signs the pattern could remain
fairly active and wet from late this week into early next with
probably a period of drying for the middle of next week (Wed-Thu).

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 for thunder so probably only isolated t-storm
coverage at best. Otherwise, guidance continues to favor amounts
widespread amounts of 0.10-0.30 inch, but EPS ensembles also
show probabilities of 40-60% for amounts of 0.50 inch or more
south central and southeast before the showers lift east of the
area with the exiting shortwave/front by late Saturday morning.

Saturday for the most part should be dry with ridging/subsidence
behind the exiting shortwave. 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.

Bigly model uncertainty rears its ugly head in the Sunday-Tuesday
time frame regarding the track/strength of the next western
CONUS wave and developing cyclone ejecting NE from the lee of
the southern Rockies into the Great Lakes region late weekend
into early next week as many of deterministic models
(particularly the GFS, UKMET and Canadian) have been flip-
flopping over solutions more in the past few days of runs than a
politician in an election cycle. One model run will show a
weaker, suppressed system tracking well south with no impacts
for the UP, with the next run showing a deeper system tracking
north through Lower Mi indicating greater rain and wind impacts
for the UP late Sunday into at least Monday. 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.
That said, the latest 00Z Thu and 12Z Wed ECMWF runs did back
off a bit from its much deeper, northward 00Z Wed solution
through the Mackinac Straits and now instead has a slightly more
suppressed track through central Lower Mi on Monday, more in
line with the fcst EPS and GEFS mean tracks. However, 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 go with 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.

Most of the models and ensembles (with the exception of the latest
00Z GFS run) do seem to be in general agreement showing a trend
toward ridging and drier conditions for Wednesday into Thursday
next week.

&&

.AVIATION /18Z TAFS THROUGH 18Z FRIDAY/...
Issued at 142 PM EDT Thu May 23 2024

VFR flight conditions are expected to prevail throughout the
duration of the 18Z TAF period. While some lingering gusts in the
20-30 kt range are expected at CMX yet this afternoon, west winds
are expected to taper off into tonight as they become northerly.
This afternoon should see some scattered diurnal cumulus, but no
precip is expected at any of the TAF sites. LLWS is possible at IWD
Friday morning, however confidence was too low to include in this
TAF issuance. Precip and lower cigs with the next low pressure
system look to hold off until after this TAF period ends.

&&

.MARINE...
Issued at 354 AM EDT Thu May 23 2024

Fairly deep low pressure centered over northern Ontario early this
morning will gradually shift ene to near James Bay later this
morning and remain nearly stationary into this evening before
shifting e into Quebec later tonight. As the low shifts east with
time, it will be replaced by a weak high pressure ridge over Lake
Superior today. Winds have diminished significantly across the lake
this morning and should drop below 20 knots across the lake this
afternoon into 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 30-40% chance for gale force gusts
Friday into Friday 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
could briefly gust near 25 knots over northern portions of the lake
Friday night as winds veer more southerly in advance of associated
cold front from the Plains system. 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. Behind this system, 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.

&&

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

&&

$$

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