875
FXUS63 KMQT 211926
AFDMQT

Area Forecast Discussion
National Weather Service Marquette MI
326 PM EDT Sat Sep 21 2024

.KEY MESSAGES...

- The prolonged stretch of above normal temperatures ends today,
  with temperatures cooling near normal Sunday.

- A round of showers and storms accompany a cold front tonight
  through Sunday. Severe weather is not anticipated, but some
  small hail are possible with stronger storms.

&&

.SHORT TERM /THROUGH SUNDAY NIGHT/...
Issued at 321 PM EDT Sat Sep 21 2024

Latest water vapor imagery shows a well-defined shortwave trough
lifting northeast into northern Ontario and northern MN this
afternoon. This shortwave trough will move into the Upper Great
Lakes later tonight and Sunday, sending a sfc cold front across
Upper Mi tonight into Sunday morning. WAA and a 40+ kt LLJ max ahead
of the cold front have already supported showers and scattered t-
storms early this afternoon into north central WI and portions of
western Lake Superior. A few showers may have made it into far
western Upper Mi but showers have generally dissipated moving into
into ridging and the associated dry and stable air mass across Upper
Mi. While it`s been more cloudy into western Upper Mi due the
convection drifting into that area, ridging has supported more
sunshine into central and eastern areas of the U.P. this afternoon.
Afternoon temperatures have generally been in the 70s to lower 80s,
warmest inland east and coolest west under the clouds.

Heading into this evening and tonight, the vort max/shortwave will
continue to lift northeast through northern Ontario which will send
the mid-level trough axis across Upper Mi later tonight into Sunday.
As the system`s associated cold front moves across Upper Mi tonight
into Sunday morning, showers along the cold front will most likely
move into far western Upper Mi early this evening and then spread
into central Upper Mi late evening and eastern Upper Mi overnight.
Instability along the front is not particularly impressive,
generally 500 j/kg MUCAPE, with the best of that south along the WI
border. Effective shear along the front when showers will be
occurring also generally looks like it will be 30 knots or less, so
not really expecting any severe storms, but maybe a stronger storm
with some dime-sized hail could develop south central along the WI
border where marginal instability and shear appear to be maximized.
Look for min temps lowering into the 50s behind the cold front
tonight. Northwest winds behind the front could gust near 30 mph
late tonight/early Sunday along the tip of the Keweenaw.

&&

.LONG TERM /TONIGHT THROUGH FRIDAY/...
Issued at 435 AM EDT Sat Sep 21 2024

The extended forecast starts off with a ~1004mb sfc low north of the
MN arrow head tonight which lifts northeast through Sunday toward
Hudson Bay. This brings a cold front eastward across the UP and a
round of showers and storms with it. Although bulk 0-6km wind shear
will be ~35-40 kts with mid level lapse rates ~7C/km, instability is
expected to be limited; likely less than 500 j/kg of MUCAPE. So
severe weather is not anticipated, but some sub severe hail and
gusty winds could accompany stronger storms earlier on tonight. CAMs
are not in great agreement for arrival and placement of these
showers and storms over the west half this evening/early tonight,
but consistency increases early Sunday morning. At that point, there
is higher confidence in a line of showers and storms over central
Upper MI. This line gradually progresses eastward on Sunday with the
cold front; dry weather returns to the entire CWA by midnight.
Precip totals or this system look to be around a few hundreths to
0.25". Some northwest gusts up to 20-25 mph are likely on Sunday.
Otherwise, lows tonight will be in the 50s, warmer in the east.
Behind the cold front highs on Sunday will feel cooler, peaking in
the low to mid 60s.

For next week, quiet and dry weather likely returns for the first
half. Some shortwaves riding northeast from the Central Plains
through the southern half of the Great Lakes Basin Monday and
Tuesday bring a weak sfc low along a similar path. Most guidance
keeps best forcing and all precip south of our CWA save for the GFS
which just scrapes the south and eastern portions of our CWA. Also,
model soundings leave much to desire for available moisture and
ensemble guidance only shows ~10-20% chances for at least a trace of
precip, so opted for dry weather to start the work week. With
clearing skies Sunday night and mostly clear skies likely for Monday
might, some interior temps could get a bit cold, dropping into the
30s. Should these temps verify, some patchy frost could develop.
Model guidance begins to diverge for the latter part of the work
week, struggling to resolve the eastward progressing mid level
trough over the northern portions of the CONUS. What could further
complicate things are tropical systems in the Gulf of Mexico.
General consensus is for the mid level ridge in the western CONUS
Tuesday night and Wednesday to shift east, passing over the Great
Lakes region for late next week and into the weekend. This would
favor drier weather and eventually a return to above normal temps.

&&

.AVIATION /18Z TAFS THROUGH 18Z SUNDAY/...
Issued at 145 PM EDT Sat Sep 21 2024

VFR conditions should prevail at all sites through this evening,
before conditions lower to MVFR clouds late tonight in the wake
of cold frontal passage. Rain showers will also be moving in
along the front starting at IWD first this afternoon, then
reaching CMX and SAW this evening. Also, cannot rule out some
embedded thunder with the rain with the best chances of thunder
at IWD and SAW, although CMX could even see an isolated storm.
Winds will shift N-NW behind the cold front later tonight and
become gusty, gusting near 25 Kts at CMX Sunday morning.

&&

.MARINE...
Issued at 435 AM EDT Sat Sep 21 2024

Light and somewhat variable winds today remain below 20 kts through
early this evening as weak ridging briefly returns. Southerly winds
increase up to 20 kts ahead of a cold front tonight. As this cold
front passes eastward across the lake, winds winds quickly veer
northwest gusting to 25 kts tonight through much of Sunday. There is
a low chance (~30%) for gusts up to 30 kts early on tonight west of
Isle Royale. Northwest winds veer north Sunday night, falling below
20 kts across the lake from west to east by Monday morning. This
stronger period of northerly winds will result in wave heights
building up to 4 ft along the western shores of the UP tonight as
well as 4-6 ft over the east half of the lake late tonight through
Sunday evening. Thunderstorms are possible with this front, but are
not expected to be severe. Otherwise, winds are expected to remain
below 20 kts the remainder of the forecast period.

&&

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

&&

$$

SHORT TERM...Voss
LONG TERM...Jablonski
AVIATION...Voss
MARINE...Jablonski