330
FXUS63 KMQT 292039
AFDMQT

Area Forecast Discussion
National Weather Service Marquette MI
439 PM EDT Sat Jun 29 2024

.KEY MESSAGES...

- Thunderstorms continue across the far eastern UP through the
  early evening; some storms may be strong to severe with large
  hail and gusty, damaging winds.

- Rip currents and dangerous swimming conditions will be
  possible at Lake Superior beaches of Alger and Marquette
  counties through this evening.

- Dry weather Sunday morning through Monday evening under high
  pressure.

- Next rounds of showers and thunderstorms arrive Monday night,
  continuing into Wednesday.

- Warm and wet pattern expected to continue well into July.

&&

.SHORT TERM /THROUGH SUNDAY NIGHT/...
Issued at 418 PM EDT Sat Jun 29 2024

Thunderstorms continue across the far eastern UP this afternoon,
with a cold front not far behind in the central UP. These storms
have a history of producing large hail, and with MUCAPE still up to
2000 j/kg and sufficient shear to sustain updrafts, will not rule out
additional strong convection from eastern Luce county southwest
through Green Bay. Meanwhile, outflow from earlier storms in
northern Marquette and Alger counties is quite apparent on radar,
and has touched off additional weak showers. That said, most
convection apart from clusters currently working through Luce,
southern Schoolcraft, and Mackinac counties have struggled to climb
high enough even to produce lightning - not surprising, given modest
capping indicated in model soundings and the afternoon NUCAPs
profiles.

Upstream, additional spotty shower activity has become apparent.
Given cooler post-frontal flow as winds turn over to the NNW, moist
lower levels, and another shortwave dropping from northern MN
through the UP tonight, expect spotty shower activity to continue at
least through the first half of the night. This would be most likely
across portions of the UP where NNW flow is upsloping (so, much of
the higher terrain of the western UP, portions of the north-central
UP, and across Alger and northern Luce counties). Skies gradually
clear out the rest of the night, with temperatures largely bottoming
out in the lower to mid 40s. However, some cooler spots in the
western and north-central UP may fall even further into the upper
30s.

Strong post frontal northwesterly winds are expected to create
dangerous swimming conditions for Marquette and Alger counties
through this evening. A Beach Hazards statement is in effect.

&&

.LONG TERM /SUNDAY THROUGH SATURDAY/...
Issued at 438 PM EDT Sat Jun 29 2024

Dry weather and clear skies will have returned to all Sunday morning
as a 1027 mb high pressure shifts west from MN into the Great Lakes;
mid level ridging over the Plains follows the westward movement into
the region as well. That said, most of the day will be influenced by
northerly flow resulting in a cooler day in the upper 50s to
possibly low 70s, cooler by the eastern Lake Superior shores. This
will gradually taper winds off throughout the day, however some
northerly gusts up to 20 mph are expected during the day over the
east half of the UP. The high pressure brings a drier airmass more
directly overhead Sunday night, subsidence increases, and winds
become near calm, setting Upper MI up for a good radiative cooling
night. Lows are expected in the 40s, however a few low lying spots
in the interior west may dip into the upper 30s. Mid level ridging
becomes centered over the UP on Monday as the sfc high continues
eastward, yielding increased southerly flow and warmer temps. Highs
on Monday will climb into the 70s, warmer in areas with downslope
flow.

Meanwhile, the mid level trough over British Columbia and Alberta
Sunday night begins shifting east. The trough continues east over
the Canadian Prairie provinces through Tuesday, sending a shortwave
northeast over the Upper Mississippi Valley Monday night. The
shortwave continues lifting northeast through northwestern Ontario
on Tuesday. This set up supports cyclogenesis in the lee side of the
Rockies in southern Alberta Sunday night. There still is a bit of
wiggle room in the low pressure track, but low is progged to move
east, just north of the international border, through Monday night.
Then with the support of the northeast lifting shortwave alongside a
left exit region of a ~100 kt upper level jet, the low deepens as it
lifts northeast toward Hudson Bay. The GFS in the last 24 hours has
trended closer to the ECMWF solution with a slightly deeper sfc low
reaching around 994 mb over Hudson bay by Wednesday evening. This
system ends the dry period Monday night in the west as
WAA/isentropic ascent touches off the first round of showers, later
supported by the northeast rotating shortwave and increasing LLJ up
to 40-45 kts. With little to no instability, some thunder is
possible through Tuesday morning, but no severe weather is expected.
A brief lull in precip is likely late Tuesday morning/afternoon
before a second round of showers and thunderstorms ahead of the low
pressure system`s trailing cold front continues PoPs into Wednesday.
While instability looks better with the second round (especially if
there is an actual break or good clearing on Tuesday) and mid level
lapse rates do approach 7C/km, the LREF mean is only around 200-500
J/kg. Thus, the second round has better chances for some
thunderstorms (20-40% chance), but confidence in any severe weather
remains low. With the LLJ overhead on Tuesday, some breezy southerly
winds are expected with gusts up to 20-30 mph. Tuesday will be
slightly cooler than Monday with highs in the mid 60s to mid 70s.

There still is some uncertainty with the pattern following this
system, but the 4th of July looks to remain mostly dry through the
early afternoon. Temps on Wednesday and the 4th of July will be the
warmest for the week with highs in the mid 70s to mid 80s and lows
in the mid 50s to low 60s. Confidence is growing in a sfc low
developing over the lee of the central Rockies Wednesday night,
lifting northeast into the Great Lakes region for Friday afternoon
into Saturday. A mid level trough also moves through the Upper Great
Lakes Thursday night and Friday. NBM PoPs captures this with an
increase in PoPs to around 30-50% Thursday night from the southwest,
continuing through Friday evening. With uncertainty rapidly
increasing Saturday onward, slight chance PoPs are sprinkled through
the rest of the weekend.

&&

.AVIATION /18Z TAFS THROUGH 18Z SUNDAY/...
Issued at 129 PM EDT Sat Jun 29 2024

IFR ceilings prevail at CMX this afternoon, while IWD and SAW
continue to come in at VFR so far with just some thickening lower to
midlevel cumulus. Meanwhile, cold front is moving through the region
this afternoon, which should drop ceilings to MVFR at IWD over the
next couple of hours, the SAW follows by the early evening. Showers
and thunderstorms are already developing near SAW, and vcts will be
possible the rest of the afternoon before the front finally clears
the area. Post frontal upslope flow should enable additional showers
at KCMX and KIWD this evening before all terminals improve to MVFR
and finally VFR overnight.

&&

.MARINE...
Issued at 438 PM EDT Sat Jun 29 2024

With increased mixing and a tighter pressure gradient, northwest
winds this afternoon into early tonight are expected up to 20-30
kts; strongest winds are expected over the east half of the lake.
Some higher observing platforms may see some isolated gusts up to 35
kts through around midnight (chance of gusts exceeding 34 kts is
around 15-25%, mainly in LSZ266 and the nearshore areas between
Marquette and Grand Marais). Winds gradually fall back below 20 kts
Sunday morning as high pressure builds in from the west. Winds are
then expected to remain below 20 kts through most of the day Monday
as this high pressure moves east over the lake. With the next
passing system early next week, southeast winds increase Monday
night to 20-25 kts, veering south on Tuesday as the low pressure
system passes well to the north of Lake Superior. Besides a brief
period Wednesday of southwesterlies to 20-25 kts, winds Tuesday
night onward look to remain below 20 kts through the remainder of
the forecast period.

Stronger northwest winds behind the cold front this evening will
result in waves building up to 6-8 ft waves over the eastern half of
the lake tonight, falling below 4 feet Sunday morning. Sustained
southerly winds Tuesday will allow waves to grow to 4-6 feet along
the US/Canada border on Lake Superior Tuesday afternoon into Tuesday
night.

&&

.MQT WATCHES/WARNINGS/ADVISORIES...
Upper Michigan...
  Beach Hazards Statement until 10 PM EDT this evening for
     MIZ005-006.

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

&&

$$

SHORT TERM...LC
LONG TERM...Jablonski
AVIATION...LC
MARINE...Jablonski