565
FXUS63 KMQT 040722
AFDMQT

Area Forecast Discussion
National Weather Service Marquette MI
322 AM EDT Tue Jun 4 2024

.KEY MESSAGES...

- Showers end over the east half this morning.
- Some showers and thunderstorms, a few possibly strong, could
  develop over the western U.P. late this afternoon.
- Frequent opportunities for showers and thunderstorms over the
  next 7 days.
- Above normal temperatures through Wednesday, then turning
  cooler for the second half of the week.

&&

.SHORT TERM /THROUGH THIS AFTERNOON/...
Issued at 321 AM EDT Tue Jun 4 2024

Low-level cloud cover continues across most of the U.P. the rest of
the pre-dawn hours this morning as the dying cold front continues to
bring scattered light rain showers along the front`s boundary.
Behind it, some areas could see some drizzle from time to time. With
light southerly flow continuing through the pre-dawn hours, fog is
not expected to form across the area, especially now that a low-
level stratus deck is in place. However, we could see an isolated
spot or two develop some patchy fog this morning, especially if some
clearing were to occur and the winds would locally lighten.

Nevertheless, expect the low-level stratus (and any fog) to burn off
by the mid morning hours as the sun rises. Likewise, the last of the
rain shower activity should be exiting our far east by late this
morning as a very weak ridge aloft moves overhead. With a stronger
cold front approaching from our west today, expect the pressure
gradient to tighten across our area, increasing southerly winds at
the surface. In addition, warm air advection sourced from the Gulf
will allow temps to reach the 80s over some of the interior areas
today, particularly over Ontonagon County where the downsloping
winds and warm air advection could bring high temperatures close to
90 in a few of the downslope areas. A few of the CAMs show some
scattered showers and thunderstorms developing ahead of the cold
front late this afternoon over the western U.P. While the convection
is expected to be surfaced-based, with CAPE values in the 1500-3000
J/kg range, severe weather is not expected during the late afternoon
hours as bulk shear values look to be too weak (well below 30
knots). However, given the abundant energy in the atmosphere, we
could see some strong winds and hail as the downdrafts `core dump`;
the chance of us seeing marginally severe winds and hail is around
5%.

&&

.LONG TERM /TUESDAY THROUGH MONDAY/...
Issued at 404 PM EDT Mon Jun 3 2024

Another subtle shortwave moving through the Great Lakes will keep a
potential for a few sprinkles, light rain showers, and a few rumbles
of thunder across the eastern UP into Tuesday morning. Otherwise,
with plenty of lower level moisture behind today`s rain showers and
partially clearing skies behind the front, much of the UP should
be starting off with some patchy fog. This mixes out soon after
sunrise with our high sun angles, then a brief dry period is
expected until late afternoon over the far west at the very
earliest as a second, stronger cold front approaches from the
Northern Plains. With warm air advection continuing ahead of the
cold front, expect the warmest temperatures of the week to
occur Tuesday, with highs getting into the 80s across some of
the interior areas, particularly over the west and downslope
areas near Lake Superior where the increasing southerly
downslope winds throughout the day could locally increase
temperatures by at least a few degrees; the warmest temperatures
will likely be around Ontonagon to the Porcupine Mountains. In
addition to the warm temperatures, Tuesday may also feel pretty
muggy, with much of the guidance showing dewpoints in the lower
to mid 60s across the UP.

The cold front looks to begin bringing showers and thunderstorms to
the western UP Tuesday evening, though guidance is hinting at some
earlier convection during hte late afternoon courtesy of a pre-
frontal trough rippling through. With quite an unstable airmass
(SBCAPE in excess of 1000j/kg) and an inverted-v type sounding, any
stronger cells that can get going could bring down some marginally-
severe winds or hail. That said, bulk shear remains lackluster even
as the cold front approaches, with values generally less than 30
knots likely not enough to sustain a severe threat much further
eastward into the UP. What may be more of a concern is the threat
for heavy rainfall, with ensembles generally showing PWATS around and
even in excess of 1.5in. Soundings show plenty of deep moisture and
impressive warm cloud depths, with storm motion largely parallel to
the cold front. Training could be a problem, particularly throughout
the western UP where we were able to pick up on widespread rainfall
amounts around and in excess of half an inch over the past day. For
its part, HREF ensemble mean rainfall totals show a widespread 0.5-
0.75in across the western half of the UP, but higher totals in
excess of an inch are possible with some members even as high as
1.5in.

The cold front continues through the eastern half of the U.P.
Wednesday as a secondary shortwave drops down from Canada and brings
light rain showers and maybe a thunderstorm or two back across the
western half of the U.P. Wednesday afternoon behind the front.

Behind the cold front, expect cooler temperatures to dominate the
rest of the extended forecast period as a synoptic troughing set-up
settles over Canada and rotates multiple shortwaves across our
region throughout the rest of this week and upcoming weekend. This
will bring multiple light rain shower chances across our area for
the rest of the extended period, and maybe a thunderstorm or two
during the afternoon hours when daytime heating becomes maximized.
With cooler and a somewhat drier airmass working in, it is not out
of the question that RH falls into the 30s at times throughout the
extended period...but will note that this isn`t very certain given
hit and miss rain chances, rather a cloudy period, and lackluster
mixing in soundings. Winds may be elevated at times throughout the
period, particularly Thursday and Friday with a tighter pressure
gradient over the area, which could enhance drying at the surface.
This would all point to a concern for fire weather into the extended
period, but mitigating this will be the early-week rainfall.

&&

.AVIATION /06Z TAFS THROUGH 06Z WEDNESDAY/...
Issued at 128 AM EDT Tue Jun 4 2024

Recent satellite imagery and surface observations have clarified
tonights forecast with stratus at SAW and clear skies at IWD/CMX.
Despite clear skies, light south to southeast winds have kept the
boundary layer well-mixed with ambient temps 4-6F warmer than dew
points and think this may continue all night. Upsloping SSE flow at
SAW has resulted in an IFR stratus deck and this seems unlikely to
dissipate until after sunrise on Tuesday. On the bright side, this
stratus deck is likely inhibiting fog development. If winds/mixing
subsides at CMX/IWD or clouds clear at SAW then the fog threat
becomes more likely. A TEMPO group was included around sunrise at
all TAF sites when fog is climatologically most likely, but if
current trends continue that may not be necessary. Regardless,
improvement is expected after sunrise with surface heating
dissipating fog/stratus wherever it develops/lingers. There is a
chance for a thunderstorm late in this period, mainly at IWD but
perhaps at CMX too. Otherwise, light southerly winds prevail at
SAW/IWD with southeast or easterly winds at CMX.

&&

.MARINE...
Issued at 404 PM EDT Mon Jun 3 2024

Winds generally out of the SE remain elevated across the eastern
half of the lake, gusting to around 20-25 knots for the most part.
However, especially around the Keweenaw where downsloping comes into
play, higher gusts around and even in excess of 30 knots remain
possible into the early evening hours. Winds fall back below 20
knots overnight while a high pressure ridge briefly builds into
the region. This tranquil period will be short-lived as winds
pick up again later in the day Tuesday ahead of our next
approaching frontal system. SSE winds gust to around 20 knots
across most of the lake Tuesday evening through Tuesday night,
with some higher gusts of 25- 30 knots north of the Keweenaw.
After winds briefly fall back behind the passing cold front
Wednesday morning, we could see southwest to westerly winds pick
up to around 20 knots over the west half of the lake Wednesday
afternoon as a secondary shortwave moves through. As additional
shortwaves rotate through our area the rest of this week through
this weekend, expect winds to increase from the west and
northwest at times; we could see westerly winds gust up to 20 to
30 knots Thursday and again to 20 to 25 knots from the
northwest Friday as shortwave lows impact the Upper Great Lakes.

As for other marine concerns this week, expect lingering patchy fog,
dense at times, across most of the lake tonight through Tuesday in
the wake of our rounds of rain today. This patchy fog looks to
persist until the second, stronger cold front moves through Tuesday
night and Wednesday, when the cooler air behind the front could
allow the moisture to mix out. Thunderstorms return late Tuesday
afternoon as the second cold front moves into the far western lake;
some severe weather could be seen over the far west Tuesday
afternoon and evening near Duluth, although the chance for severe
weather is still rather low (~5%); severe hail and winds are the
primary concerns. The thunderstorm activity continues across Lake
Superior from west to east Wednesday until leaving into northern
Ontario late in the day.

&&

.MQT WATCHES/WARNINGS/ADVISORIES...
Upper Michigan...
None.
Lake Superior...
  Dense Fog Advisory until 9 AM EDT /8 AM CDT/ this morning for
     LSZ162-240>243-263-266.

Lake Michigan...
None.

&&

$$

SHORT TERM...TAP
LONG TERM...LC
AVIATION...EK
MARINE...LC