615
FXUS63 KMQT 031749
AFDMQT

Area Forecast Discussion
National Weather Service Marquette MI
149 PM EDT Mon Jun 3 2024

.KEY MESSAGES...

- Following the morning showers, another round of showers and
  occasional thunderstorm is expected for mainly the central and
  eastern UP this afternoon and evening.
- Frequent opportunities for showers and thunderstorms over the
  next 7 days, with a break on Tuesday.
- Above normal temperatures through Wednesday, then turning
  cooler for the second half of the week.

&&

.SHORT TERM /THROUGH TODAY/...
Issued at 141 PM EDT Mon Jun 3 2024

RAP analysis shows a 500mb shortwave over Minnesota generally
flattening with time this morning and early afternoon. This
correlates with the decrease in rain shower intensity with a
broad line of showers over the central UP at 15Z per KMQT radar
reflectivity and METAR obs. CAMs consistently show this
deteriorating trend continuing as forcing continues to decrease
and precipitation battles dry air. However, a break in the
showers altogether will be brief at most as a shortwave over
Iowa will progress northeast throughout the day today and force
another round of showers through central to northern Wisconsin
by 20Z today. The main source of uncertainty is the northern
extent of the showers and thunderstorms, as cloudy conditions
associated with the current shortwave are limiting the ability
of the atmosphere over Upper Michigan to destabilize. The 12Z
HREF shows some SBCAPE recovery in the west, but with forcing
being limited to the south and central UP, where even HREF max
SBCAPE struggles to reach 250 J/kg, severe weather is not
expected, and thunder chances are limited to below 33%. As far
as high temperatures go, clearing behind the showers in the west
and the persisting dry air over the east will make the west and
the east ends warm into the low 70s today while the central UP
stays in the 60s.

Overnight, as heating decreases, so too will shower coverage, with
HREF probabilities of hourly QPF > 0.01" not exceeding 40% after 03Z
tonight. Persistent cloud cover and a more moist surface airmass
will limit radiational cooling, with lows around the mid 50s and low
60s tonight. In the wake of showers, marine dense fog over Lake
Superior is 60%+ likely per the HREF, with the central UP seeing
30-60% chances to see patchy dense fog overnight. With the wide
range of probabilities, no land-based dense fog advisories are
going to be issued with this forecast package until a bit more
certainty is gained in regards to the moistening of the
atmosphere by the showers.

&&

.LONG TERM /TONIGHT THROUGH SUNDAY/...
Issued at 334 AM EDT Mon Jun 3 2024

As a cold front loses some steam over the eastern half of the U.P.
tonight, scattered shower and thunderstorm frequency lessens as they
continue to march eastward with time. With warm air advection from
the Gulf immediately moving in behind the front (one of the reasons
the cold front starts to die out), expect a saturated layer of air
up to 4 to 5 kft to bring some patchy fog and drizzle across the
U.P. behind the showers and thunderstorms of the dying front. This
will keep low temperatures tonight well above normal; temperatures
are projected to only get down into the mid 50s near Lake Michigan
to around 60.

Moving into Tuesday, expect skies to scatter out a little as the
last of the showers and storms moves out of the far eastern U.P.
into northern Ontario and the low-level clouds causing the
drizzle/patchy fog across the rest of the area scatters out during
the morning hours. CAMs have recently backed-off on precipitation
chances throughout the day Tuesday in comparison to the global
models. Therefore, while I`m thinking partly cloudy skies are still
likely (70+% chance) to occur across the area Tuesday, rainfall
chances shouldn`t enter into the U.P. again until late this
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 Porkies. In addition to the
warm temperatures, Tuesday may also feel pretty muggy, with CAMs
bringing dewpoints into the mid to upper 60s by the afternoon hours.
Therefore, if you`ve got A.C., it may be your best friend on
Tuesday.

The cold front looks to begin bringing showers and thunderstorms to
the western U.P. Tuesday evening. Severe weather is currently not
expected with the passage of the cold front Tuesday night at this
time as the showers and storms associated with it are expected to
come during the overnight hours, when CAPE will be lacking in the
atmosphere. In addition, bulk shear values generally look to remain
well below 30 knots, which should prevent the updrafts from tilting
enough for the downdrafts of the storms to kill them. However, there
are some outlier models that, should they come together just right,
may allow for some strong to severe convection to reach the far
western U.P. Tuesday evening; this would bring some marginally
severe hail and winds to the far west before the convection
diminishes overnight. However, the chance of this occurring is very
low (<5%). With ensemble guidance showing PWATs above the 90th
percentile of climatology at around 1.5 inches, heavy rainfall seems
to be the main threat Tuesday night through Wednesday. I wouldn`t be
surprised if some places received over an inch of rainfall due to
the showers and storms via the abundance of moisture ahead of the
cold front. 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.
In addition, I have a hunch that the dewpoints will be lower than
what the NBM is currently forecasting for the latter half of the
forecast period; with the cold air advection bringing dry northerly
air into our region, I wouldn`t be surprised if mixing in the
boundary layer is greater than what`s predicted by the medium range
models. Thus, there is a chance (~25-30%) that we could see min RHs
dropping down closer to 30% starting Thursday. However, my
confidence in this solution remains small at this time as there is a
bit of model divergence as to when exactly the shortwaves will
impact our area as model diffluence has increased between the
different medium range models on the shape of the upper-level
synoptic pattern. With the inclusion of rain showers increasing
dewpoints at the sfc throughout the latter half of the forecast
period from time-to-time, I decided to leave the dewpoints alone for
now. ECMWF EFI is also hinting at some windier conditions come
Thursday and Friday as the EFI values of 0.5 to 0.7 are expected
those two days. This may help to enhance drying at the surface and
increase wildfire spread (should any occur). The winds for Thursday
and Friday may need to monitored in future forecast packages given
the increased fire weather impacts they could have should the
gustier winds materialize.

&&

.AVIATION /18Z TAFS THROUGH 18Z TUESDAY/...
Issued at 141 PM EDT Mon Jun 3 2024

VFR conditions briefly prevail at all three TAF sites this
afternoon following the first passage of showers today. A
secondary wave of showers will push over Upper Michigan from the
southwest later this afternoon, though will probably miss CMX
and IWD altogether, leaving only -SHRA at SAW. With a much more
moist air mass trapped at the surface following the passage of
the second wave of showers, all three TAF sites are expected to
experience low cigs and vis tonight, though uncertainty on
timing and extent of lowered flight categories does exist. Each
site is over 50% likely to have IFR cigs and MVFR vis overnight
with around 25% chances of LIFR or lower cigs and IFR or lower
vis, so a TEMPO group was put in at each site overnight to cover
for those low-probability but high-impact scenarios.
Improvement is expected with the sunrise as skies scatter out
and fog dissipates during the morning hours of Tuesday.

&&

.MARINE...
Issued at 334 AM EDT Mon Jun 3 2024

Southeast winds increase to 20 to 25 knots over the north-central
lake and the southerly shoreline today ahead of a cold front pushing
through; I wouldn`t be surprised if we had locally higher downslope
winds near the tip of the Keweenaw, given that it`s a `hotspot` for
stronger winds when the winds come from the southerly direction.
Once the dying cold front passes through, expect the winds to
slacken back down to 20 knots or less by this evening and to remain
that way until a second, stronger cold front moves through Tuesday
night and Wednesday, when southeast to southerly wind gusts of 20 to
25 knots will again be seen over the central lake and also probably
over the southerly downslope areas along the U.P.`s shoreline
(particularly the tip of the Keweenaw). Behind the cold front, 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. However, with model divergence increasing
and cold air advection decreasing for that point in time, gusts have
trended slightly lower than what was predicted yesterday. 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 some patchy fog over
the western and north central lake today behind the cold front as
the moisture from the rainfall becomes trapped near the water`s
surface due to the strong temperature inversion caused by the cool
lake waters; the fog could be dense in some spots. 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. As for the thunderstorm chances
this week, a few thunderstorms are expected to move from the far
western lake early this morning to the far eastern lake by Tuesday
morning. 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 5 PM EDT /4 PM CDT/ this afternoon
     for LSZ162.

Lake Michigan...
None.

&&

$$

SHORT TERM...GS
LONG TERM...TAP
AVIATION...GS
MARINE...TAP