597
FXUS63 KMQT 102042
AFDMQT

Area Forecast Discussion
National Weather Service Marquette MI
442 PM EDT Fri May 10 2024

.KEY MESSAGES...

- Showers increase in coverage from west to east this evening, with
rain continuing overnight into Saturday morning for the central and
eastern UP.

- Winds could briefly gust to 30-40 mph in the WI border counties
this evening with these showers.

- Scattered thunderstorms to develop Sunday afternoon, especially
south central. There is a low chance (2%), for marginally severe
hail and/or wind.

- Dry weather returns Monday through Wednesday afternoon.

&&

.SHORT TERM /THROUGH SATURDAY/...
Issued at 338 PM EDT Fri May 10 2024

Early afternoon water vapor imagery shows a vigorous, compact, and
strengthening shortwave trough now pivoting near the Twin Ports.
DCVA forcing bands of clouds and showers from the western UP back
into NW WI/western LS. Initial band appears to be mainly
virga/sprinkles as it interacts with the antecedent dry airmass. 12
minutes of light rain was observed at IWD as this activity passed.
Successive bands of showers should allow for gradual moistening and
more widespread showers with time this afternoon and evening for the
west and central, but totals will be hydrologically insignificant
(although there could be a few brief heavier downpours). Some gusty
winds could occur due to evaporational cooling with these showers,
with a couple upstream automated observations recording 30 kt gusts.
Thunder potential is still low, but cannot be ruled out mainly over
the WI border counties this afternoon/evening.

Surface reflection of this wave will strengthen late tonight into
Saturday morning over northern Lower MI as the midlevel wave goes
negatively tilted. This will result in the eastward progression of
the showers slowing down as a mesoscale pivoting band develops along
the NW flank of the low. This will keep rain in the forecast
overnight for the eastern UP, while coverage gradually decreases in
the central. Some of these showers will likely linger into Saturday
morning for the eastern UP and possibly for the higher terrain of
the north-central due to moist upslope flow. A good soaking rain
could occur where the band pivots, as HREF 90 percentile shows a
0.75 to 1" area over Alger and Schoolcraft Counties. Otherwise,
a high pressure ridge builds in from west to east through the day
with an associated clearing trend (which may not be until in the
afternoon for the central and east). Highs expected to be in the
upper 50s/low 60s, except low/mid 50s along Lake Superior due to
onshore flow.

&&

.LONG TERM /SATURDAY NIGHT THROUGH FRIDAY/...
Issued at 442 PM EDT Fri May 10 2024

Current ridging over western N America will force a couple of
shortwaves to dive se into eastern N America over the next several
days. The first drops into the Great Lakes region tonight/Sat. The
second wave won`t drop as far s due to the upstream ridge losing
some amplitude. It will pass across northern Ontario Sun/Mon.
Thereafter, mid-level troffing developing into western
Canada/northern U.S. Rockies early next week will shift downstream
thru the week. There is and has been considerable model spread on
the evolution of this trof, amplitude of the upstream ridge forcing
the trof, and the progression of shortwaves around that ridge into
the trof. Early on in the fcst period, a couple of periods of pcpn
are expected, the first with the shortwave dropping thru the Great
Lakes region tonight/Sat and the second with the shortwave reaching
northern Ontario on Sun. A dry period will follow Mon/Tue and likely
thru Wed aftn. Approaching mid-level trof will bring shra back to
Upper MI Thu/Fri. Whether it ends up being sct or widespread pcpn
will depend on the highly uncertain evolution of the trof. As for
temps, readings most days thru the middle of next week will be
around normal, then there is more uncertainty late week depending on
rain coverage/potential sfc low developing into the Great Lakes
region. Warmest day will be on Sun. Closer to Lake Superior, it will
be on the cool side for at least Mon/Tue as high pres ridging
building southward into the Great Lakes brings a gradient onshore
wind component.

Beginning Sat night/Sun, shortwave over the NW Territories tonight
will reach northern Ontario Sun morning. In response, a 30-40kt low-
level jet develops, leading to a good push of waa/isentropic ascent
and theta-e advection into Upper MI late Sat night/Sun morning. As a
result, sct -shra should develop into roughly the w half of Upper MI
overnight Sat night, spreading eastward Sun morning. After this
initial waa/isentropic ascent pcpn moves across the area, attention
on Sun aftn turns to lake breeze aided cold front that moves across
the area. Timing of this feature will be coincident with peak
heating Sun aftn across the central, s central in particular. The
NAM/GFS have MLCAPE increasing to 500-1000j/kg, though the NAM peaks
at around 1500j/kg. The CMC RDPS and ECMWF are less than 500j/kg.
With consensus deep layer shear of 30-40kt, an isolated svr storm is
a possibility if the higher MLCAPE materializes. That will depend on
how much cloud cover and even shra from earlier in the day linger
into the aftn. Expect highs on Sun in the mid 60s to mid 70s for
much of the area, though it will turn cooler closer to Lake
Superior once winds shift off of the lake.

Shra/tsra will exit the s and e Sun evening. A secondary cold front
will pass uneventfully during the night, setting up dry days on
Mon/Tue as sfc high pres builds s into the western Great Lakes. Will
be cool near Lake Superior on Mon/Tue, especially e half, under
gradient northerly winds due to high pres ridge building s into the
area. Expect 40s F to be the rule. Temps both days will range up to
the low/mid 60s well inland w half. There is plenty of dry avbl to
mix down, especially on Tue. RH may fall blo 30pct interior w, but
winds will be lighter in that area than over the rest of the U.P.
to limit fire weather concerns.

The 12z medium range model runs not did show any trend toward
agreement with the approaching mid-level trof mid and late week.
Agreement is there for dry weather to linger thru Wed aftn.
Lingering dry air aloft is avbl to mix down, so it cloud be another
day with RH under 30pct in the interior. Thereafter, fcst will
reflect broad brush mostly 30-40pct chc shra for Thu/Fri.

&&

.AVIATION /18Z TAFS THROUGH 18Z SATURDAY/...
Issued at 130 PM EDT Fri May 10 2024

VFR conditions in place to start the TAF period. Band
of showers is approaching IWD from the west, moving in around 19Z,
then reaching CMX around 21Z and SAW around 23Z. Unlikely this
initial band will result in any flight category reductions due to
the dry air in place and quick speed of the showers. The parent
system will slow down and strengthen to the southeast of the UP
tonight, which will result in moistening at lower levels and
continued showers at times. Expect IWD to remain VFR through the TAF
period, but CMX/SAW will fall to MVFR in cigs/vsby overnight (likely
01-03Z), and IFR cigs will become likely at SAW (60% chance) roughly
between 08-13Z. Cigs will gradually improve toward the end of the
TAF period as the system drifts off to the east.

&&

.MARINE...
Issued at 442 PM EDT Fri May 10 2024

Expect winds mostly under 20kt thru Wed. However, there are a couple
of periods where winds will be a little stronger. Approaching cold
front Sat night will result in increasing southerly winds. Across
mainly the e half of Lake Superior, gusts up to around 25kt are
possible by Sun morning, but these stronger winds would be at the
high obs platforms due to the stability within the chilly marine
layer. Then on Mon, high pres ridge building s into the western
Great Lakes may support higher nw wind gusts to 25kt over far
eastern Lake Superior.

&&

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

&&

$$

SHORT TERM...Thompson
LONG TERM...Rolfson
AVIATION...Thompson
MARINE...Rolfson