-- Discussion containing changed information from previous version are highlighted. --
816
FXUS63 KMQT 251747
AFDMQT

Area Forecast Discussion
National Weather Service Marquette MI
147 PM EDT Sat May 25 2024

.KEY MESSAGES...

- Showers, with some thunder possible far west this evening.

- Low pressure system brings steady rain chances late Sunday
  into early Monday, mainly to the central and eastern UP.
  Rainfall amounts >1 inch are forecast by Monday evening.

- Below normal temperatures for the first half of the week,
  followed by a drying trend into the weekend. Patchy frost
  possible Thursday morning.

&&

.SHORT TERM /THROUGH THIS AFTERNOON/...
Issued at 240 AM EDT Sat May 25 2024

Upper air pattern consists of a 500 mb closed low near Lake Winnipeg
this morning which meanders slowly northwest into western Ontario by
00z Sun. There is some 850-500 mb q-vector convergence and some
moisture that comes into the west late in the day while earlier
moisture and q-vector convergence moves out across the cwa this
morning. Showers will continue to move out this morning and then the
next wave comes into the far west by late this afternoon. Appears
like this next wave would be in the southern part of a deformation
zone from the closed low that gives the far west a glancing blow.
Could be some thunder with this elevated convection. Overall, did
not make too many changes to the going forecast.

&&

.LONG TERM /TONIGHT THROUGH FRIDAY/...
Issued at 521 AM EDT Sat May 25 2024

Active pattern for Upper Michigan continues in this forecasting
period. The long term pattern for Upper Michigan will start off with
an anomalous surface low and shortwave lifting northeast into the
Great Lakes Sunday and Monday. From there, broad mid-level troughing
establishes itself across the eastern half of North America before
ridging gradually builds into the region for the latter half of the
week and into the weekend. Together, these will yield early week
rain, a few cooler days, and then warmer and dry to take us into
the weekend.

Forecast period starts off tonight, with the main focus being a
deepening surface low and shortwave lifting northeast into the Great
Lakes. With the system being over the Central Plains tonight, a weak
associated frontal boundary will stall out over western Lake
Superior, allowing warm air advection to ride a low level jet into
the region. This may support some rain showers and modest weak
elevated CAPE may support some thunderstorms across the west half of
Upper Michigan and central/western Lake Superior. Otherwise, a mild
night is expected with lows near 50F.

The aforementioned surface low/shortwave will build into the region
through the day Sunday and stick around Monday. PWATS building to 1-
1.5 across the region coupled with increasingly strong dynamics
should yield widespread rain for Upper Michigan by Sunday afternoon,
persisting until the system pulls away Monday. QPF varies per model,
but the general thinking is widespread 0.5-1.5 inches of rain, with
those most likely to see the higher amounts being the central and
eastern portions of Upper Michigan. Precip should end west to east
through the day Monday, but another shortwave pressing eastward
across Minnesota/Wisconsin, followed by a more broad shortwave
dropping southeast out of Ontario/Manitoba Monday night may support
shower activity into Tuesday night. High pressure and a dry airmass
builds into the region Wednesday and should maintain mostly dry
conditions for the forecast area to finish off the week.

As the early week surface low pulls away, a cool airmass will rotate
into the region. Daytime temperatures on Tuesday/Wednesday look to
be in the 50s and 60s with overnight lows in the 40s and 30s. Recent
NBM run suggests around 20% of temps falling below 35F in the
interior by Thursday morning. I suspect this probability to be a
little low given deterministic solutions suggesting PWATS could be
below 0.2 inches, coupled with the light winds and cooler airmass.

Ridge axis builds into the region Thursday night while another
trough presses out of the Rockies. Current thinking is for surface
high to maintain its spot over the region until the eastward
progressing trough shifts into the region. Earliest potential
for this appears to be late Friday in the west.

&&

.AVIATION /18Z TAFS THROUGH 18Z SUNDAY/...
-- Changed Discussion --
Issued at 146 PM EDT Sat May 25 2024

VFR cigs/vsby are expected to prevail at each terminal through this
TAF period, but showers and embedded thunderstorms are expected to
impact IWD/CMX this evening. Gusty southwest winds up to 25 kts
continue at IWD and up to 35 kts at CMX until wind profiles weaken
and surface heating subsides late this afternoon. Confidence in
thunder occuring is in the 50-75% range, justifying inclusion in
TAFs even though storms may not track directly over each terminal.
TAFs reflect the most likely outcome, which is a brief ~2-3 hour
period of shra/-tsra followed by a 12-15 hour dry period toward the
end of the TAF period. However, a weak frontal boundary lingering
nearby may be sufficient to trigger light rain showers throughout
Sunday morning at CMX/IWD. Showers are increasingly likely late in
the TAF period as a low pressure system lifts north toward Upper
Michigan with a period of light to moderate rain expected at all
terminals late on Sunday. SAW stays dry with VFR cigs/vsby
through tonight, but deteriorating cigs/vsbys are expected near
or shortly after the end of this TAF period.
-- End Changed Discussion --

&&

.MARINE...
Issued at 521 AM EDT Sat May 25 2024

As the low pressure system currently in southern Ontario lifts north
and weakens, converging southerly flow will back throughout the day
Saturday and weaken. In eastern Lake Superior, winds decrease from
20 kt, gusting 25-30 kt, early this morning to 5-10 kt by mid-
morning, to less than 5 kt by early Saturday afternoon. Winds in
western Lake Superior remain higher for somewhat longer, diminishing
from 20 kt, gusting 25-30 kt, early this morning to 5-10 kt by
Saturday evening. Waves throughout this time will diminish from 6-9
ft across Lake Superior to 3-5 ft by Saturday evening. A slight
chance of thunderstorms exists on and off throughout Saturday night
in the southern part of western Lake Superior, including the
Keweenaw, and lingering mid-lake into Sunday morning.

By early Sunday morning, weak high pressure building into the region
results in light southerly flow of less than 5-15 kt, veering
slightly until Sunday morning. Waves continue to decrease to 1-3 ft
by Sunday midnight. Ahead of the low currently in the lower Plains,
winds throughout Sunday will back and strengthen beginning mid-
morning. By early Sunday evening, winds are forecasted to be
easterly across Lake Superior at 10-15 kt. Winds continue to back
and build throughout Sunday night as the Colorado low approaches,
reaching northerly by Monday morning at 15-20 kt and waves building
to 3-5 ft. A slight chance of thunderstorms exists on eastern Lake
Superior very early Monday morning.

Backing continues until Monday night, when steady northwesterly flow
becomes established at 10-20 kt, being higher in eastern Lake
Superior. This northwesterly flow and wave heights of 3-5 ft are
expected to remain steady until Wednesday midday when high pressure
begins to build into the area. At this time, expect light and
variable winds and decreasing waves until Thursday midday, when
light southerly flow at 5-10 kt re-establishes itself, along with
waves 1-3 ft, for the remainder of the forecast period.

&&

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

&&

$$

SHORT TERM...07
LONG TERM...JTP
AVIATION...EK
MARINE...RE