469
FXUS63 KMQT 250809
AFDMQT

Area Forecast Discussion
National Weather Service Marquette MI
409 AM EDT Tue Jun 25 2024

.KEY MESSAGES...

- Tuesday will be the warmest day of the week with highs in the mid
  70s to mid 80s. Gusty winds to 30 mph are also expected, especially
  over the Keweenaw.

- Pattern remains active, especially from late week into early next week,
  with yet more rounds of showers and storms

&&

.SHORT TERM /THROUGH TONIGHT/...
Issued at 143 PM EDT Mon Jun 24 2024

Current mesoanalysis across the region places an upstream shortwave
moving through northern Minnesota and a cold front tied to a surface
low moving through Lake Winnipeg not far behind. Precip associated
with this is trending down per DLH radar and GOES IR. To the south,
mid-level ridging extends across the Plains with subtle shortwaves
perturbations embedded atop. At the surface, a surface low was
observed moving across eastern South Dakota along with a
southeastward draped warm front and several surface troughs tied to
the mid-level perturbations. Across our forecast area, surface high
has allowed for clear skies to largely dominate; at the time of this
publishing though, high clouds streaming eastward into the region
associated with the shortwave pressing through Minnesota was
observed on GOES Vis imagery. With these mostly clear skies and
predominately southerly flow, daytime temps have warmed into the 70s
while dewpoints in the 50s have been observed.

As we progress through the remainder of the afternoon and overnight
tonight, upstream weakening showers in Minnesota will continue to
weaken as it presses into Lake Superior/western Upper Michigan. HRRR
and other CAMS suggest it may hold together enough to support some
showers in our forecast area late this afternoon/early evening.
Otherwise, expect temps to continue climbing into the upper 70s to
low 80s and increasing cloud cover.

Impressive instability will continue building on the south side of
the decaying shower activity over Minnesota. As this area of
instability grows and southwesterly low level winds strengthen this
evening, a line of thunderstorms will develop over central
Minnesota. These will grow upscale and evolve into a bowing MCS as
they stream southeast along the instability gradient. CAMS appear to
be coming into better agreement that the strongest storms will stay
south of our forecast area, but storms capable of mostly damaging
winds can`t be ruled out early in the event. Some large hail will
also be possible. The main risk area will be in the counties
bordering Wisconsin. North of this bowing segment, the HRRR and to
some degree, the FV3 and NAMNEST resolve a secondary line of showers
and thunderstorms across the Arrowhead into Ontario, then press
these into Lake Superior and Upper Michigan. Some large hail and
maybe strong winds will be possible with these storms if the
materialize, but confidence in these developing is low to medium (25-
50%) given their proximity to the main bowing segment and the lack
of a consensus among the various CAMS solutions. If this develop,
these and the northern fringes of the MCS pressing southeast, will
press eastward through Upper Michigan, likely clearing the east just
after sunrise. While confidence in the evolution is lacking
somewhat, consistent temporal signatures in the various CAMS suggest
the main period of thunderstorms to be between 5z and 11z with the
most likely period for strong to severe being early in the event.

&&

.LONG TERM /WEDNESDAY THROUGH MONDAY/...
Issued at 408 AM EDT Tue Jun 25 2024

Starting Wednesday, a northwest flow shortwave and associated cold
front moves from the Northern Plains across the Upper Great Lakes.
Most of the models show an inverted sfc trough inflection associated
with the shortwave from northern WI along the U.P. border.
Instability is limited at 200 j/kg or less so expect isolated to
scattered showers Wednesday, probably focused mainly west and along
the WI border where the inverted sfc trough axis is situated. Expect
drying and clearing skies from the west and north behind the
shortwave trough and cold front in the afternoon into early evening
as highs peak mainly in the 60s. However, those near the eastern
Lake Superior shores may stay in the 50s throughout the day.

Weak high pressure ridging persists across the region from Wed night
into at least Thu evening, dry weather prevails. Under clear skies
and near calm winds, radiative cooling will drop Wed night lows into
the 40s, coolest over the interior. Expect highs Thu generally
in the lower to mid 70s.

Meanwhile, a trough just east of the Pacific northwest will move
onshore Wednesday night. This trough progresses east along the
international border toward the Upper Great Lakes by Saturday
morning with at least a couple of shortwaves embedded in it. This
will support cyclogenesis in the northern Rockies Thursday night
with the low ejecting east into northern Ontario Friday
night/Saturday. WAA/isentropic ascent and theta-e advection ahead of
the low will support showers and thunderstorms spreading into Upper
Mi on Friday. The first of the shortwaves within the mid-level
trough moves through Sat which pushes a cold front through the area
Fri night into Sat. Increased instability noted along the cold front
should increase chances for thunder as it moves through the area at
this time. The second shortwave in the trough will send a secondary
cold front and another round of showers across the area late Sat
into early Sun along with a burst of gustier nw-n winds and colder
temps.

High pressure building in quickly behind the front will result in
drier, albeit cooler conditions Sunday afternoon into Monday. Models
advertise another shortwave and associated sfc low lifting off the
Northern Rockies and tracking e across the Northern Plains and
Canadian Prairies into the Upper Great Lakes for early next week.
This feature will bring another round of showers/t-storms into the
area for next Mon night into Tuesday.

&&

.AVIATION /06Z TAFS THROUGH 06Z WEDNESDAY/...
Issued at 129 AM EDT Tue Jun 25 2024

VFR conditions will prevail early this period, followed by a rapid
deterioration as a line of thunderstorms moves into Upper Michigan.
Expecting most activity between 06Z and 11Z, with the greatest
potential for severe winds, maybe some large hail, at KIWD early on
in the event. Expect ceilings to fall to MVFR/IFR after the line
moves through with some brief fog/mist developing before the
sunrise. Tuesday, gusty winds are expected to develop as ceilings
improve. Initial thoughts are KCMX could gust near 30kts from the
west. LLWS will occur overnight at IWD and SAW.

&&

.MARINE...
Issued at 408 AM EDT Tue Jun 25 2024

Thunderstorms tracking across eastern Lake Superior along a cold
frontal passage will bring somewhat gusty winds and lightning to
mariners over the eastern lake early this morning. Winds will shift
from southerly to westerly winds behind the cold front later this
morning while gusting as high as 30 kts. Strongest winds are
expected over the central portion of the lake as fcst soundings and
model guidance suggest a (20-30%) potential for west gale gusts to
35 knots, especially at higher platform locations like Stannard
Rock. This period of longer fetch and stronger winds will help waves
build up to 4-6 feet this afternoon and evening north of the
Keweenaw. Winds around 20-25 kts veer north tonight behind an
additional cold front that drops south across the lake before
tapering off below 20 kts Wednesday morning. With high pressure over
the lake through Thursday, winds are expected to mainly remain below
20 kts. A weakening low pressure tracking through the Upper Great
Lakes early this weekend will allow for s-se gusts near 20 kt Friday
and 20-25 kt nw gusts behind a cold frontal passage Saturday before
building high pressure returns Sunday and ushers in lighter winds.

&&

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

&&

$$

SHORT TERM...JTP
LONG TERM...Voss
AVIATION...07
MARINE...Voss