073
FXUS63 KMQT 161743
AFDMQT

Area Forecast Discussion
National Weather Service Marquette MI
143 PM EDT Sun Jun 16 2024

.KEY MESSAGES...

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

- Possible strong to severe thunderstorms Monday and possibly
  Tuesday night/Wednesday.

- Very warm early next week, with frequent chances for showers and
  thunderstorms throughout.

&&

.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 /MONDAY THROUGH SATURDAY/...
Issued at 503 AM EDT Sun Jun 16 2024

Active weather continues through the extended period as troughing
deepens over the western U.S. and ridging amplifies over the Eastern
Seaboard. This pattern will cycle very warm and moist air over us
early in the work week, in addition to many chances for showers and
thunderstorms throughout. With strong shearing and abundant CAPE in
the atmosphere, some severe weather could occur early this week.
More details follow below.

As the Great Lakes region remains situated in between the high-
amplitude ridge and digging western trough Monday through Tuesday,
southerly flow continues to pump in a warm, moist airmass with
dewpoints well into the 60s and even above 70F Monday and Tuesday.
Monday will start off with rain chances as a subtle shortwave tracks
through the area. Convection will be most likely across the western
UP, closer in proximity to the weak wave as well as the frontal
boundary that will be stalled out just to our west. Early on, shear
is rather limited, and though we will be plenty unstable given such
high dewpoints, lower to midlevel capping is apparent in soundings.
An early start to our convection may also limit destabilization.
That said, will not rule out some hail in morning/early afternoon
convection if we can realize the full potential of the ~1000j/kg of
CAPE analyzed over the area. Showers and storms will also have the
impact of limiting temperatures over the western UP to the 70s,
while the eastern half of the UP stands a better chance of reaching
the lower to mid 80s. Will note that guidance is really struggling
to come into agreement on the spatial extent of PoPs for the
daytime, with some models showing a far greater eastward expansion
than others.

Most of the UP should dry out Monday evening as the shortwave exits
northward and the eastern ridge begins to build NW-ward again. That
said, the western UP is not out of the woods as theta-e advection
increases overnight on the nose of an impressive 40-50kt LLJ that
will be directed into the Upper Midwest. Quite impressive CAPE in
excess of 1000j/kg and bulk shear in excess of 40kts indicate a
potential for strong elevated convection overnight, with the main
risks being hail and gusty winds. Will also note a potential for
heavy rain, given PWATS in excess of 1.5in and a potential for
training storms ahead of a very slowly-moving front. Very important
caveat: the front remains well off to our west, and guidance
continues to just graze the western UP and western Lake Superior
with PoPs.


Dry weather is looking likely across most of the UP through Tuesday
while the frontal boundary stalled out over MN finally begins to
slowly creep eastward. Under sunny skies, temperatures climb even
higher than on Monday, possibly peaking in the 90s in many locations
during; it`s not out of the question that we could set a heat record
or two come Tuesday as ensemble guidance shows temperatures around
the 99th percentile of modeled climatology. If there is one upside,
southerly winds will be fairly elevated given the tight pressure
gradient over the area; expect gusts around 20-25mph for much of the
UP.


The aforementioned frontal boundary crawls over the Great Lakes
Tuesday night through Wednesday, and looks to stall out just to our
south into Thursday. Expect additional rain shower and thunderstorm
chances as this moves through, with temperatures cooling close to
normal. As more zonal flow moves over us with weak high pressure
setting up shop over northern Ontario and the Northern Plains,
expect to see the rain and thunderstorm chances continue as
shortwaves continue to ride the upper-level flow across our area. A
more trough-ey pattern sets up next weekend, and though details on
track, timing, and strength of any particular features remain
uncertain, this will in general keep rain chances in through the end
of the forecast period.

&&

.AVIATION /18Z TAFS THROUGH 18Z MONDAY/...
Issued at 142 PM EDT Sun Jun 16 2024

Ample low level moisture and rain showers over the region should
improve this afternoon as weak, mid-level ridging builds west to
east across Upper Michigan. This should support an end to the rain
and ceilings lifting to VFR this afternoon/early evening. Upstream
thunderstorm development is expected in Minnesota this afternoon.
These thunderstorms will press east-southeast through Upper Michigan
this evening. These are most likely to impact KIWD and KCMX, but
KSAW may still seem some thunderstorms late this evening. These
storms could be capable of large hail, damaging winds, heavy
downpours, and frequent lightning. After the thunderstorm activity
ends, guidance is keen on fog/mist developing, which may reduce
visibilities at each terminal to MVFR or potentially IFR.

&&

.MARINE...
Issued at 503 AM EDT Sun Jun 16 2024

Winds generally out of the southeast this morning continue to gust
up to 20-25kts across the eastern and north-central portions of the
lake, but gusts increase to 25-30kts across the eastern half of the
lake this afternoon while winds turn more southerly. In addition,
some southerly gusts up to 30 knots will be possible along the south
Lake Superior nearshores throughout the day, with a few gale force
gusts up to 35 knots being possible near Grand Marais and Munising
during the afternoon hours. Winds weaken to 20 knots or less by late
Sunday afternoon/evening and remain that way until Tuesday, when
some southerly winds of 20 to 25 knots could be seen across much of
the lake. Light winds of 20 knots or less returns Tuesday night and
could remain through the rest of the week.

Several rounds of showers and storms are expected today through
Tuesday with a frontal boundary stalled out over MN eventually
moving through the area by midweek. Some severe weather is possible
over the lake, particularly over the west, Monday through Monday
night; the primary severe threat is hail, followed by winds. In
addition, while significant wave heights look to be generally 4 feet
or less over the next several days, we could see wave heights get up
to 4 to 6 feet over the eastern half Sunday given the stronger
southeast to southerly winds.

&&

.MQT WATCHES/WARNINGS/ADVISORIES...
Upper Michigan...
  Beach Hazards Statement until 10 PM EDT this evening for
     MIZ014.

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

&&

$$

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