244
FXUS63 KMQT 290614
AFDMQT

Area Forecast Discussion
National Weather Service Marquette MI
214 AM EDT Sat Jun 29 2024

.KEY MESSAGES...

- Strong to potentially severe storms, capable of large hail and damaging
  winds, could develop today across the east half of Upper
  Michigan.

- Rounds of showers are expected into Saturday and then Monday
  night into Tuesday night with quiet weather following each
  round.

&&

.SHORT TERM /THROUGH TONIGHT/...
Issued at 214 AM EDT Sat Jun 29 2024

A rich theta-e airmass across the eastern half of the forecast area
has resulted in a few waves of rain showers with some observed
lighting here and there. This, while the west has been under the
influence of a weak surface low positioned over western Lake
Superior per MSAS analysis. Further upstream, mid-level trough
moving through western Minnesota has supported convection across
central Minnesota ahead of a surface cold front pressing eastward.
Mild and moist conditions, in addition to some pockets of fog, have
also been observed under mostly cloudy skies.

The mid-level shortwave in Minnesota will force the surface low in
western Lake Superior through the region and into Ontario while it
pulls behind the trailing cold front. Showers with some
thunderstorms should develop ahead of the boundary as it shifts east
through the region. Deterministic packages suggest instability could
grow to 500-1000j/kg MLCAPE under 50+kts of deep layer shear.
Primary spots for this environment will be central, south, and
eastern portions of the forecast area by early/mid afternoon. This
environment could support some strong to severe storms. Primary
hazards would be large hail and damaging winds if they do develop.
Behind the front in the west, winds become onshore and, with the
additional upslope component and a continued saturated near surface
layer, light rain and/or drizzle is expected to develop. Ahead of
the front in the south and east, expect temps to climb into the mid-
upper 70s to low 80s while frontal passage should limit heating to
the low 70s in the west and 60s Keweenaw.

&&

.LONG TERM /SATURDAY THROUGH FRIDAY/...
Issued at 510 PM EDT Fri Jun 28 2024

Starting Saturday morning, the broad trough will be centered over
northern MN with two embedded shortwaves to focus on through the day
as the trough shifts east through northern Ontario and the Upper
Great Lakes. The first shortwave on the forefront of the trough is
situated over western Lake Superior, lifting northeast toward James
Bay. The second shortwave trough over the ND/MN state line pivots
over the Upper Great Lakes into Saturday night. The associated sfc
low around 1004 mb follows the first shortwave northeast into
Quebec, dragging a cold front from eastward across the UP through
the later part of the day. PVA ahead of the passing cold front
supports isolated showers and possibly some rumbles of thunder
through the morning, but better chances for thunderstorms hold on
until the afternoon with the passing cold front. The NAM and HRRR
are the stronger solutions, kicking off storms in the east and south
central along Lake Michigan with the higher instability (SBCAPE up
to 2000-2500 J/kg). However lingering clouds from previous showers
will be a limiting factor for instability, the 6/28 12Z mean SBCAPE
only builds up to around 750-1000 J/kg in the afternoon with bulk
shear to 45-50 kts. Another limiting factor will be the timing and
location of the cold front. While an isolated strong storm bringing
some gusty winds and some small hail is possible, severe weather
seems unlikely. Forecasted highs were bumped up from the previous
forecast into the 70s, warmest south central where MOS guidance
points to highs reaching near 80. The exception to this is in the
Keweenaw where temps may struggle to reach low 60s under the
stronger northwest flow off Lake Michigan. With northwest winds
increasing through the day, a high swim risk is expected for the
Alger county beaches starting in the afternoon.

Moving into Saturday night, high pressure begins building in from
the west at the sfc, but one last shortwave digs south across the
UP. With the north-northwest upslope flow and low level moisture
noted in model soundings, this may support some light showers in
areas nearer to Lake Superior. Dry weather is expected to return
from west to east overnight as a drier airmass works its way into
the area. Stronger mixing is also expected Saturday night, resulting
in some gusts up to 20-30 mph over the east. Lows are expected in
the 40s, however with clearing and radiative cooling in the west,
some interior spots may dip into the upper 30s.

The dry period continues through Monday with high pressure overhead
and mid level ridging building in from the west. Highs on Sunday are
expected to be cooler under northerly flow, generally in the 60s. An
And with another night of mostly clear skies and radiative cooling,
lows Sunday night dip into the 40s. Mid level ridging becomes
centered over the UP on Monday with southerly flow at the lower
levels bringing temps near or just below normal with highs in the
70s.

Dry dry period ends Monday night in the west ahead of a deepening
low moving northeast off the northern Rockies. Confidence is growing
in the sfc low track, bringing it through far northern Ontario on
Tuesday, reaching Hudson Bay by around Wednesday morning as it
deepens to around 995mb. While the details with this system are
still a bit murky, general consensus is that it brings two rounds of
showers and thunderstorms. The first round touches off Monday night
with WAA and isentropic ascent in the west, later supported by a
shortwave traversing east over the Upper Great Lakes, then dries out
around mid day Tuesday. The second round is driven by the low
pressure system`s trailing cold front Tuesday afternoon into
Wednesday. After this system, model guidance really begins to
diverge. A dry period is expected to follow, but how long that
period lasts is still uncertain. Generally a wetter pattern
continues into through the first half of July.

&&

.AVIATION /06Z TAFS THROUGH 06Z SUNDAY/...
Issued at 122 AM EDT Sat Jun 29 2024

Flight restrictions to persist for duration of TAF period as showers
and isolated thunderstorms form to the south along a cold front
early this morning. A brief period of VFR at IWD should deteriorate
to MVFR over the next few hours, and the MVFR conditions currently
at CMX will fall to IFR/LIFR. Elsewhere, the most persistent LIFR
conditions through the early morning will be at SAW due to upsloping
southerly winds. Improvement is expected, though, later this morning
with frontal passage. For now, will only carry VCSH mention at IWD
and CMX, but confidence in an uptick in convective activity is
higher at SAW in the Sat 08-11Z time.  So, will carry VCTS mention
there.  Otherwise, southerly wind gusts have tapered off over the
last few hours and the only other wind impact will be a wind shift
to the northwest in wake of cold front later today.

&&

.MARINE...
Issued at 510 PM EDT Fri Jun 28 2024

Southeast winds up to 20-30 kts, strongest over the east, are
expected to diminish this evening from west to east with winds
falling below 20 kts by around midnight. Behind the cold front,
winds veer northwest on Saturday with increased mixing and a tighter
pressure gradient allowing for gusts up to 25-30 kts over the
eastern half of the lake. North to northeast winds Saturday night
gradually fall back below 20 kts late Saturday night as high
pressure builds in from the west. Winds are then expected to remain
below 20 kts through much 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 to southeast on Tuesday as the low pressure system passes well
to the north of Lake Superior. Winds Tuesday night onward look to
remain below 20 kts through the remainder of the forecast period.

Stronger northwest winds behind the cold front on Saturday will
result in waves building up to 5-8 ft waves over the eastern half of
the lake Saturday night.

&&

.MQT WATCHES/WARNINGS/ADVISORIES...
Upper Michigan...
None.
Lake Superior...
None.
Lake Michigan...
None.

&&

$$

SHORT TERM...JTP
LONG TERM...Jablonski
AVIATION...TDUD
MARINE...Jablonski