-- Discussion containing changed information from previous version are highlighted. --
419
FXUS63 KMQT 270634
AFDMQT

Area Forecast Discussion
National Weather Service Marquette MI
234 AM EDT Mon May 27 2024

.KEY MESSAGES...

- Light rain increases this afternoon and evening ahead of a low
pressure system then becomes steady tonight through Monday morning.
Rainfall amounts >1 inch are possible by Monday evening, mainly east
half.

- Below normal temperatures for the first half of the week, followed
by a drying trend midweek. Areas of frost expected Thursday morning.

&&

.SHORT TERM /THROUGH THIS AFTERNOON/...
-- Changed Discussion --
Issued at 234 AM EDT Mon May 27 2024

Upper air pattern consists of a 500 mb closed low in eastern
Manitoba with a shortwave over the upper Great Lakes with another
shortwave over the northern plains. The northern plains shortwave
heads east and helps the trough amplify over the Great Lakes region
00z Tue. 850-500 mb q-vector convergence and deeper moisture remain
over the eastern half of the cwa today while the west is drier. This
will continue to be where the highest pops will be while the west
remains mostly dry. Overall, did not make too many changes to the
going forecast.
-- End Changed Discussion --

&&

.LONG TERM /TUESDAY THROUGH SUNDAY/...
Issued at 409 PM EDT Sun May 26 2024

The well-advertised low pressure system lifts northeast over Ontario
on Memorial Day then over Quebec on Monday night. Steady rain will
be ongoing across eastern and portions of central Upper Michigan
Monday morning that gradually shifts east away from the UP by
Tuesday morning. Clouds, rain, and a northerly breeze off Lake
Superior will make for an unpleasant day especially across eastern
Upper Michigan. As rain chances end with that system, a decaying
upper level low tracks southeast leading to renewed rain chances and
on Tuesday, but amounts should be light. Chilly Canadian high
pressure builds across the area Tuesday night and Wednesday leading
to a multi-day stretch of dry weather. Patchy frost is possible
across the west half Wednesday morning and across most of the area
Thursday morning. A warming trend is expected from Thursday through
the end of the week when the next system and associated rain chances
approach the area.

Starting at 12z Tuesday, the surface low will be over Quebec and
tracking away from the area as the next disturbance begins moving
across the western UP. The incoming system is weaker and has less
moisture to work with, but broad troughing extending across Ontario
and the Upper Great Lakes perpetuates cyclonic flow. The primary
disturbance digs south from western Ontario toward the base of the
trough over the Ohio Valley. Even though most of the energy passes
to our south/west, the 500 mb low tracks closer to -if not directly
over- Upper Michigan Tuesday afternoon/evening. Chilly upper level
temperatures induce weak instability and scattered rain showers,
especially when diurnal heating is maximized Tuesday afternoon. High
pressure and a dry airmass build into the region Wednesday and
should maintain mostly dry conditions through at least Friday
morning.

As the early week surface low pulls away, a cool airmass rotates
into the region. Daytime temperatures Monday through Wednesday look
to be in the 50s near Lake Superior and 60s farther south with
overnight lows in the 40s and 30s. Frost is a concern for portions
of the interior west Tuesday night and for most interior locations
Wednesday night. Confidence is highest for Wednesday night when our
internal model certainty tool indicates a 50% chance of falling
below 35F for interior portions of Upper Michigan and some bias-
corrected guidance cool temperatures to near or below freezing.
While still possible Tuesday night across the western UP, timing of
the drier air and potential for continued winds above 5 mph suggest
radiating out may be more difficult. A lower chance for frost is
also present across the eastern UP Thursday night. Dry and well-
mixed soundings, particularly Wednesday and Thursday, could also
lead to plummeting dewpoints and RH falling below 30% away from the
lakeshores. A mitigating factor for the fire weather risk, in
addition to fairly light winds, will be the widespread rain in the
preceding days.

Ridge axis builds into the region Thursday night while another
trough presses out of the Rockies. Current thinking is for the
surface high to be more stubborn than model blends give it credit
for. Ensemble means shift the ridge axis across the area on Friday
allowing for moisture return with a connection to the Gulf of Mexico
by late on Friday. Rain chances increase along/ahead of a cold front
currently scheduled for Saturday.

&&

.AVIATION /06Z TAFS THROUGH 06Z TUESDAY/...
Issued at 104 AM EDT Mon May 27 2024

Low pres over southern WI will track ene overnight, bringing shra to
mainly the e half of Upper MI. At IWD, well to the nw of the low,
VFR is likely to prevail thru this fcst period. That said, there was
some fog/stratus over portions of nw Lake Superior late yesterday.
So there is some potential for IFR cigs late tonight/Mon morning
under upslope northerly flow off of Lake Superior, but potential is
too low to include mention in fcst. At CMX, either lower clouds
wrapping back to the terminal or upsloping of fog/stratus over the
lake should result in MVFR cigs developing this morning. However,
confidence is low. VFR will return in the evening. SAW will be on
the nw edge of the pcpn shield. That should lead to IFR cigs setting
in early this morning under upslope nne winds of around 15kt. These
low clouds are likely to persist until this evening when VFR should
return. A period of LLWS is also expected early this morning.

&&

.MARINE...
Issued at 409 PM EDT Sun May 26 2024

Main item of interest is a surface low that`s tracking northeast
across Lake Michigan and northern Lower Michigan tonight into
Monday. Ahead of this system, light east-southeast winds are
occurring across eastern and central portions of the lake with
northeasterly flow across the western lake. Winds continue to back
and increase through tonight as the Colorado low approaches.

Previous model spread diminished today with the weaker and more
southerly solutions winning out. The chance for gales across eastern
Lake Superior has therefore decreased substantially for Monday.
However, northeast winds increase to 15-25 kts tonight across Lake
Superior then back northerly wind at 20 to 30 kts on Monday. The
strongest winds are expected across the east half where our local
tool indicates a 10% chance for a few gale force gusts. Stable
conditions prevent mixing of the strongest winds to the lake
surface, limiting significant wave heights to 4-7 ft.

The low tracks northeast of Lake Superior Monday night with another
disturbance prolonging northwesterly flow into Tuesday night. The
pressure gradient gradually diminishes by Tuesday night allowing
winds to fall below 20kts by Tuesday night. High pressure builds
across the lake on Wednesday supporting light and variable winds and
decreasing waves until Thursday midday, when light easterly to
southeasterly flow at 5-15 kt re-establishes itself across the
western lake, along with waves 1-3 ft.

&&

.MQT WATCHES/WARNINGS/ADVISORIES...
Upper Michigan...
  Beach Hazards Statement from 8 AM EDT this morning through
     this evening for MIZ005-006.

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

&&

$$

SHORT TERM...07
LONG TERM...EK
AVIATION...Rolfson
MARINE...EK