806
FXUS63 KMQT 161932
AFDMQT

Area Forecast Discussion
National Weather Service Marquette MI
332 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 SUNDAY/...
Issued at 332 PM EDT Sun Jun 16 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.

Monday starts out with a band of showers and thunderstorms making
there way from west to east across the U.P. during the morning to
early afternoon hours due to a cool front kicking-off the
convection. While most of the CAMs show the convection weakening
with time, the most recent extended HRRR shows the convection
becoming quite vigorous in a couple of the cells. With 0-6 km bulk
shear being around 30 knots and MUCAPEs around 250-1000 J/kg across
the area, we could see a few strong to marginally severe
thunderstorms in this band of convection Monday morning through
early afternoon, with the primary threat being hail and the
secondary threat being winds. However, with cloud cover remaining
over the area throughout the day, the severe weather potential is
limited. Another band of showers and thunderstorms could move into
the western U.P. late in the afternoon Monday. With MUCAPE values
and shear being higher, the severe weather threat is likewise higher
with this round of showers and storms, with hail and winds being an
equal threat. In addition, these storms could train over the same
area that received the rainfall from the previous round during the
morning hours. With PWATs being about 1.50 inches (near the 90th
percentile of modeled climatology), heavy rainfall is possible. When
combined with the training aspect of these storms, we could see some
isolated ponding in the poor drainage areas. What may prevent the
severe weather, though, is if the better convection ends up further
south in Wisconsin. However, it appears that most of the CAMs bring
some strong to severe convection over us now during the late
afternoon hours over the west and central. Moving into the early
night hours Monday, the convection could keep going into the eastern
U.P. and Lake Superior (such as seen in the NAMNest). However, with
the loss of the daytime heating and weakening of the bulk shear, its
more likely that we will see the showers and storms weaken as they
move into the eastern U.P./Lake Superior Monday evening. As we
continue past midnight, expect the shower and thunderstorm chances
dwindle and move northwards as warm frontogenesis forces the
convection towards northern Ontario, bringing drier weather across
our area by Tuesday morning.

Expect sunny skies, muggy conditions, and probably the warmest
weather of the summer yet come Tuesday as we sit directly underneath
the warm sector of a low lifting through the Lake Winnipeg area.
Tuesday could also be fairly breezy, with the ECMWF EFI highlighting
unusually high southerly winds throughout the day. 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 100! Therefore, be sure to take lots of
water breaks if you are outside Tuesday, as heat exhaustion and heat
stroke are much quicker and easier to occur than normal; hopefully
the breezy southerly winds will provide a little relief from the
stifling hot and humid weather.

Moving into Tuesday night, showers and thunderstorms slowly move
back over us as the troughing pattern over the western U.S. slowly
trudges eastwards into the Plain states and weakens. We could see
some strong to severe thunderstorms yet again along the frontal
boundary as MUCAPEs could exceed 1000 J/kg and 0-6 km bulk shears
approach 40 to 50 knots. 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, some
ponding of water in poor drainage areas is certainly possible; while
the chance is low (<5%), we could also see other flash flooding
concerns such as ponding in better drainage areas and swollen creek
beds. As shortwaves continue along the frontal boundary during the
middle of this week, expect rain shower and thunderstorm chances to
continue. Weak high pressure looks to move into the Northern Plains
and northern Ontario along Lake Superior near the back-end of this
week, forcing most of the rain chances more so to the southern parts
of our area. 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.

&&

.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 332 PM EDT Sun Jun 16 2024

Southerly winds of 20 to 25 knots over the eastern lake this
afternoon decrease to 20 knots or less by this evening as a
shortwave lifts from Lake Superior into northern Ontario. The light
winds continue through Monday 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 being
possible, particularly in the nearshores from Marquette to just west
of Whitefish Point. The winds weaken back down to 20 knots or less
again by Tuesday night/Wednesday morning as the frontal boundary
just west of the area finally begins moving across the lake. The
light winds look to continue through the rest of the week as weak
high pressure ridging settles over northern Ontario.

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.

&&

.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...TAP
AVIATION...JTP
MARINE...TAP