782
FXUS63 KMQT 170818
AFDMQT

Area Forecast Discussion
National Weather Service Marquette MI
418 AM EDT Mon Jun 17 2024

.KEY MESSAGES...

-Possible strong to severe thunderstorms this evening and tonight.
Large hail, damaging winds, frequent lightning, and heavy downpours
will be possible.


- Strong to severe storms possible Tuesday night into Wednesday.

- Very warm to start the work week, then temperatures trend towards
normal from midweek onward.

- Frequent chances for rainfall continue the rest of the week.

&&

.SHORT TERM /THROUGH TONIGHT/...
Issued at 142 PM EDT Sun Jun 16 2024

Rain showers continue to lift through the forecast area
atop a very moist surface layer. As of publishing this AFD,
rain showers were spread across the eastern and central UP with
dewpoints in the mid 50s to low 60s across the region.
Destabilization ahead of mid-level ridging building into the
west may support additional shower development, or some
thunderstorms in this afternoon across the east half before they
exit into Ontario. Severe weather is not expected in this wave.

The atmosphere will further destabilize ahead of a cold front/low
pressing eastward through Minnesota this afternoon. Guidance
continues to suggest this will result in shower and thunderstorm
development with quick upscale growth into an MCS, which will
progress east-southeast into Wisconsin and Upper Michigan this
evening. The strong destabilization in the pre-frontal space
stretching from Wisconsin into the U.P. is characterized by 2000-
3000 j/kg of elevated CAPE. While the region where this will develop
is expecting much stronger deep layer shear, guidance over Lake
Superior generally suggests around 30-40kts of 0-6km bulk shear
oriented off the boundary, suggesting the linear complex may survive
the transit and move into Upper Michigan. With DCAPE 500-1000j/kg
and increasing mid-level lapse rates to around 8C/km, strong to
severe thunderstorms will be possible if so. Main hazards will be
large hail up to 1 inch in diameter, strong or damaging winds
upwards of 60mph, frequent lightning, and heavy rain upwards of 1+
inches this evening. Primary risk areas will be across the
west/central, but some guidance packages, namely the RAP, ARW and
FV3, suggests the thunderstorms could hold together as they move
into the east half around midnight.

A warm and muggy night is projected after the convection ends. As
temps begin to cool, patchy dense fog may develop overnight.
Overnight lows and dewpoints are likely to remain in low to mid 60s
for most of the forecast area.

&&

.LONG TERM /TUESDAY THROUGH SUNDAY/...
Issued at 418 AM EDT Mon Jun 17 2024

The active weather pattern doesn`t look like it will relent over the
rest of this week as troughing deepens over the western U.S. and
ridging amplifies over the Eastern Seaboard early this week. This
keeps us on tap for very warm and moist conditions Monday through
Tuesday, before the troughing pattern moves east and brings cooler
temperatures across our area Wednesday into Thursday; be careful if
working outside Tuesday, as the hot and humid weather could cause
heat exhaustion and heat stroke! Meanwhile, expect showers and
thunderstorms chances to continue across Upper Michigan throughout
the rest of this week into next weekend, with a few strong to severe
storms being possible Monday and Tuesday night/Wednesday. The severe
weather threat, should any occur, would be hail, winds, and repeated
heavy rainfall causing ponding. Additional details follow below.


The frontal boundary lifts north of the area Tuesday, and should
stall out across northern Lake Superior and northern MN. Skies turn
sunny, then expect muggy and even warmer weather Tuesday as we sit
directly underneath the warm sector of a low lifting through the
Lake Winnipeg area. A tight pressure gradient and a 30-40kt LLJ over
the area all point to a potential for a breezy day (will also note
the EFI continuing to highlighting unusually strong winds for Tuesday).
However, with a low-level cap in place, it may be difficult to get
the winds to gust much more than 30 mph, save for the downslope
areas near Lake Superior where mixing could be locally enhanced.
Expect temperatures to get into the high 80s to low 90s during the
afternoon hours, with dewpoints reaching up into the low 70s. This
will cause the heat index to get into the 90s across much of the
area, with a spot or two possibly flirting with the 100 degree mark.
Breezy conditions may help to keep things from feeling so
oppressive, but be mindful of the heat and take precautions
regardless. Stay hydrated!

Moving into Tuesday night, the aforementioned low near Lake Winnipeg
will continue to move through Ontario while weakening, then the cold
front off to our west slowly swings through overnight into
Wednesday. Showers and storms begin to move back into the western UP
as early as Tuesday evening along the front, which would be
favorable timing for strong to severe convection. MUCAPE across the
western UP could exceed 1000 J/kg and 0-6 km bulk shears approach 40
to 50 knots. Our main threat would be hail, with damaging wind a
secondary concern. In addition, expect heavy rainfall, with
ensembles showing PWATs near the max of climatology/around 2 inches!
With storms possibly training ahead of the frontal boundary, ponding
of water in poor drainage would be a concern. However, as episodes
of rain in the preceding days have chipped away at hourly flash
flood guidance, some flash flooding is not out of the question
(around 5% chance) in smaller streams and even in somewhat better-
draining areas. The central and eastern UP may miss out on severe
convection Tuesday night as we`ll have long since run out of
daylight by the time the front moves in.

Meanwhile, nighttime won`t do much to alleviate heat concerns as
temperatures only fall back as far as the mid/upper 60s for a large
portion of the area.

Wednesday, the front finally begins to settle just to our south.
Weak waves rippling through will provide some additional lift to
keep chances for convection to fire along the boundary Wednesday
through Friday. Will note that PoPs are concentrated mainly across
the southern half of the UP given the potential for weak high
pressure over Ontario to further suppress the frontal boundary
southward. Going into next weekend, a low pressure lifting off of
the Colorado Rockies and an upper level Clipper low look to phase
with each other over the Upper Midwest. This will bring additional
showers and thunderstorms across our area via warm frontogenesis
through at least the first half of next weekend, then the cold front
moves through late in the weekend with lingering PoPs. Ensembles
continue to favor PWATs as high as 2in, well above normal,
highlighting another couple of days worth monitoring for the heavy
rainfall potential.

&&

.AVIATION /06Z TAFS THROUGH 06Z TUESDAY/...
Issued at 122 AM EDT Mon Jun 17 2024

Expect maybe some isolated showers across the area tonight with
showers affecting mainly IWD and CMX. The moist conditions could
still lead to MVFR conditions overnight in patchy fog or stratus.
Around round of convection is expected to move in from the west
after sunrise as ceilings will likely go to MVFR during the day on
Monday. Showers will be most prevalent at IWD and SAW with SAW
having the best chance of getting a thunderstorm. A break in the
showers in the afternoon could be followed by more scattered showers
Monday evening. Look for MVFR ceilings to lower to IFR Mon evening
and fog formation possible again.

&&

.MARINE...
Issued at 418 AM EDT Mon Jun 17 2024

Light winds around 5-10kts start off mainly from the west this
morning, but shift over to the east this afternoon. The light winds
continue through tonight before increasing from the south to 20 to
25 knots over the eastern half of the lake Tuesday. In addition,
expect some downsloping winds near the southern shoreline to gust up
to 20 to 30 knots, with a few gale force gusts up to 35 knots
possible (10% chance or lower), particularly in the nearshores from
Marquette to just west of Whitefish Point. The winds fall back down
to 20 knots or less again by early Wednesday morning as the frontal
boundary just west of the area finally begins moving across the
lake. Winds stay light through the rest of the week as weak high
pressure ridging settles over northern Ontario.

Several rounds of showers and storms are expected across the lake
from this afternoon through Wednesday. Some strong to severe storms
are possible during this time, with hail and wind being the main
threats. Areas of fog, dense at times, are possible following rounds
of rainfall.

&&

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

&&

$$

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