641
FXUS63 KMQT 171849
AFDMQT

Area Forecast Discussion
National Weather Service Marquette MI
249 PM EDT Mon Jun 17 2024

.KEY MESSAGES...

- Continued showers and thunderstorms this afternoon with some
potential for isoalted strong or severe storms.

- Multiple rounds of showers and thunderstorms expected this
week. Strong to severe storms possible Tuesday night into Wednesday.

- Hot and humid Tuesday, followed by very muggy rest of the
week.

- Potential heavy rain event this weekend.

&&

.SHORT TERM /THROUGH TONIGHT/...
Issued at 159 PM EDT Mon Jun 17 2024

A line of showers and thunderstorms moved through Upper Michigan
today along of a warm frontal boundary, with what appeared to be a
mix of strong to severe storms embedded within the complex. As of
now, some pea sized hail has been reported and a wind gust at KIMT
measured 53 mph. Ahead of the line, dewpoints surged into the upper
60s to near 70F. Behind the line, temps in the 60s were observed
ahead of another line of showers draped northeast from northwest WI
and western Upper Michigan into western Lake Superior. At the time
of this writing, no lightning was being observed with this second
line. To the south, isolated thunderstorms are developing across
northeast WI within an environment characterized by 2000-2500 j/kg
MLCAPE, per SPC mesoanalysis just south of or along the warm frontal
boundary. Effective bulk shear from the same source generally ranges
from 40-50 kts.

As we progress through the remainder of the afternoon, ongoing
thunderstorms currently across the central will continue its
eastward progression. Additional shower and thunderstorm development
will be possible as the warm front begins lifting north. Main focus
area will be across central and eastern Upper Michigan given the
mean flow and proximity to the warm front as it continues lifting
north. There is some potential for strong to severe thunderstorms
within this, but the risk is low (<25%).

&&

.LONG TERM /TUESDAY THROUGH SUNDAY/...
Issued at 248 PM EDT Mon Jun 17 2024

The overall consensus of both ensemble and deterministic guidance
packages suggests the pattern across CONUS will continue to include
a stout mid-upper level ridge over the eastern third of CONUS while
deep and broad troughing holds fast over the western third. This
places Upper Michigan in a predominate south to southwest flow
regime and open to both Gulf of Mexico moisture and a warm/hot
airmass, and on the path for any shortwave, impulse, or MCS
developing across the Plains, at least until the weekend when a more
zonal pattern begins to emerge. In terms of sensible weather, Upper
Michigan can expect at least one hot day, multiple humid days,
multiple rounds of showers and thunderstorms, and flooding and
severe weather concerns in this forecast period.

Beginning this evening into tonight, showers and thunderstorms
should be ongoing initially thanks to surface low organizing and
beginning to lift north-northeast through the Central Plains.
Initially, showers/storms should be most prevalent across the
central/east but with the warm front lifting north, coverage should
shift north through the night. There is some potential for training
thunderstorms along the boundary. Severe weather threat should be
minimal this afternoon and overnight given the thoroughly worked
over environment, but some hail, stronger winds, and frequent
lightning can`t be completely ruled out. The main hazard will be the
rain, but it should be noted that the HRRR continues to back off on
some of the training risk. At this point, the WPC slight risk for
excessive rain seems reasonable given the training potential and
PWATS upwards of 2 inches, in addition to the 0.5"-2 inches of rain
estimated from today`s event. Through the night, the warm front will
lift north into Lake Superior/Ontario, which will allow rain to end
from south to north through the night. Overnight lows should only
dip into the 60s or upper 50s and some fog may develop, particularly
after the rain lifts north.

Tuesday looks to be mostly dry with Upper Michigan positioned
squarely within the low`s warm sector as it lifts into Minnesota.
With a slightly more dry airmass in place, effective mixing under
mainly high clouds or clear skies should support a hot, humid, and
breezy day. Daytime temps climbing into the 80s to low 90s is
expected while dewpoints approach 70F. This could support heat index
values in the low to mid 90s, with perhaps near 100F in downsloping
areas in the interior. Steep low level lapse rates should also be
able to mix down strong winds aloft. Current thinking is wind gusts
near 25 mph, but potential effective mixing may support winds
exceeding 30 mph in many locations in the afternoon, particularly in
downslope areas near Lake Superior. EFI continues to highlight this
unusually high wind potential with values of 0.6-0.8 across large
portions of the forecast area.

The low will lift into Ontario by Tuesday night while it pulls its
cold front through Upper Michigan. This will bring us another round
of showers and thunderstorms into Wednesday. There is some severe
thunderstorm potential, mainly across the west half Tuesday night,
but instability should be waning as they move into the area, so the
risk appears limited. However, the risk for heavy rain will return
as PWATS look to climb above 2 inches. The front should clear the
region by Wednesday afternoon/evening, with high pressure building
in after. There may be some daytime re-invigoration of the showers
and thunderstorms across the east half and south. Thursday looks to
be mostly dry as the pattern begins to shift into something more
zonal, but there is some uncertainty in where upstream impulses
will line up and how far east they`ll extend. This, while a couple
different shortwaves embedded within the near-zonal flow beings
across the Northern Plains and exiting out of the northern Rockies.
Another warm front will lift into the Upper Great Lakes Thursday
night/Friday, potentially supporting showers/storms by Thursday
afternoon. The boundary appears to stall out Friday over the Upper
Great Lakes as a surface low deepens and lifts out of the Central
Plains. The low will press through the region Saturday night and
Sunday while the shortwave aloft takes on a negative tilt. For a few
days now, guidance has been suggesting this setup, which could lead
to a potential heavy rain/flooding event in some areas in Upper
Michigan. Of course, this will be dependent on preceding rain, but
this system warrants monitoring.

&&

.AVIATION /18Z TAFS THROUGH 18Z TUESDAY/...
Issued at 122 PM EDT Mon Jun 17 2024

Showers and thunderstorms moving through Upper Michigan will
continue pressing east, trailed by periods of light rain. Some
additional thunderstorms may develop near KSAW this afternoon, but
overall, thunderstorm activity is expected to be minimal for the
remainder of the afternoon. Another wave of showers, potentially
mixed with some thunderstorms, moves in to mainly western Upper
Michigan this evening and tonight, impacting KIWD and KCMX. By
morning, rain showers and thunderstorm activity activity is expected
to be over. With the increased moisture from rain, ceilings should
trend to MVFR this afternoon/evening at all sites and then to IFR at
KCMX/KSAW. Additionally, fog/mist should develop overnight after the
showers/storms end. Expect fog to lift in Tuesday morning, followed
by gusty winds developing.

&&

.MARINE...
Issued at 248 PM EDT Mon Jun 17 2024

Thunderstorm activity should be confined to eastern Lake Superior
this afternoon while showers will be possible mainly central and
east. In addition to this, mainly light synoptic winds will help fog
development, and its possible some that develops may be dense. Warm
front will lift north into the lake tonight and north of it by
Tuesday morning, supporting additional showers, possibly some
thunderstorms through morning. Some stronger storms should be
expected, but severe storms are not expected at this time.

South of the warm front on Tuesday, a strong low level jet will move
over Lake Superior ahead of a cold front moving eastward through
Minnesota. This low level jet will support southerly winds upwards
of 30kts across eastern Lake Superior, possibly some low end gales
for higher reporting platforms or where topography plays a local
influence on winds near the lakeshores between Marquette and
Whitefish Pt. Cold front will press through the lake Tuesday night
into Wednesday, potentially supporting another round of strong to
severe storms across western Lake Superior and thunderstorms and
showers lake-wide. High pressure appears to try to work in Thursday
but will be dependent on upstream systems. Another front moves into
the lake Friday/Saturday as a low pressure approaches from the west,
bringing with it another round of showers/storms. Current thinking
is for light winds in this system outside of thunderstorms.

&&

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

&&

$$

SHORT TERM...JTP
LONG TERM...JTP
AVIATION...JTP
MARINE...JTP