706
FXUS63 KMQT 310902
AFDMQT

Area Forecast Discussion
National Weather Service Marquette MI
502 AM EDT Fri May 31 2024

.KEY MESSAGES...

- Scattered showers and isolated thunderstorms possible today
  for western Upper Michigan, then frequent opportunities for
  showers and thunderstorms over the next 7 days.

- Above normal temperatures through the first half of next
  week, then turning cooler, potentially much cooler.

&&

.SHORT TERM /THROUGH TODAY/...
Issued at 355 AM EDT Fri May 31 2024

Southerly flow with increasing moisture, in addition to high clouds
building into western Upper Michigan has produced a mild night
across the forecast area, except interior portions of the east where
dry air and light winds have supported effective radiational cooling.
So far interior temps have fallen into the upper 30s while the
lakeshores have remain in the 40s or 50s. Across the west, min temps
in the 50s and even some low 60s have been observed so far.
Upstream, a line of showers with some preceding isolated showers has
been observed moving through northern Minnesota, pressing northeast
as a weakening cold front advances. Some lighting has been observed,
but activity has waned in the past couple of hours.

As we move through the remainder of the morning hours and into
today, showers and storms across central Minnesota will lift
northeast as the boundary presses eastward into the Arrowhead and
western Lake Superior. Some rumbles of thunder can`t be ruled out.
The weak boundary will continue pressing east while upper level
support shifts northeast, bringing with it increasing pops for the
west. Onset is a little tricky given the anticipated dwindling line
as it approaches, but the overall consensus is for light rain to
move into the west by late morning. While the boundary inches across
the Arrowhead, continued convergence with growing weak instability
out in front will result in continued shower chances through the
afternoon for the west half. Thunderstorms can`t be ruled out, but
severe weather is not expected. In the east, dry air will win out,
likely resulting in clear to partly cloudy skies. This, coupled with
dinural heating, will support mixing and enable drier air aloft to
mix down to the surface. Model soundings suggest mixing only to
around 2k feet, which would support RH percentages dipping down into
the mid 20s. If we are able to warm more and mix higher then
expected though, lower RH near 20% will be possible. Daytime highs
across the region should climb into the 70s, except remain in the
60s by Lake Michigan.

&&

.LONG TERM /TONIGHT THROUGH THURSDAY/...
Issued at 500 AM EDT Fri May 31 2024

A progressive flow regime will prevail thru about the middle of next
week as a series of shortwaves track off of the N Pacific, then
eastward roughly along the vcnty of the U.S./Canada border. As a
result, frequent opportunities of pcpn are in the offing for Upper
MI with the first already arriving over western Upper MI
today/tonight. That pcpn will slowly spread eastward thru the first
half of the weekend. The second wave and pcpn chc will be centered
on late Sun night/Mon, and the third during Tue night/Wed, but this
third round of pcpn may end up lingering for a few days due to
potential mid-level low development over the Great Lakes region,
resulting from a significant pattern change over and around N
America late next week thru much of the week of June 9. Medium range
ensembles are depicting development of a positive height anomaly
across the Arctic Ocean, amplified ridge development across western
N America, extending to the Arctic Ocean, and positive height
anomalies/ridge development in the Labrador Sea area. If it was Jan,
this type of pattern that would support a harsh arctic outbreak into
the Great Lakes region. However, it`s June, so we`ll be looking at a
mostly seasonably cool stretch of weather beginning late next week
and continuing thru the week of June 9. Given the pattern though, a
couple of unseasonably cool days (max temps upwards of 20 degrees
blo normal) would not be unexpected during that time. It is noted
that the EPS has been and continues to be more amplified with the
pattern than the GEFS/GEPS. Its max ensemble mean 500mb height
anomaly now reaches 195m over the Great Lakes region on June 7,
suggesting coolest weather in the June 7-9 period. Prior to the cool
down beginning late next week, temps will likely run above normal.

Beginning tonight/Sat, an anomalously deep mid-level low will be
centered over northern Saskatchewan/northern Manitoba. Main
shortwave associated with this feature will swing thru northern
Ontario to Hudson Bay today. A weakening cold front tied to this
wave will stall out over western Lake Superior or western Upper MI
tonight, but it does become quite difficult to track the sfc front
with time. This boundary combined with the development of upper
diffluence from right entrance of a sw-ne oriented 110kt upper jet
streak across northern Ontario will support shra over about the
western third to half of Upper MI tonight. CAPE up to 200-300j/kg
may be avbl for parcels lifted from around top of sfc based stable
layer. So, some rumbles of thunder are possible. Around the mid-
level low, a shortwave will swing along the International Border
tonight and then ene into northern Ontario Sat. This will give the
subtle boundary and associated shra/tsra an eastward push into
central Upper MI during Sat. Then, diminishing shra/tsra should
spread across the eastern fcst area Sat evening. HREF shows
probability of rainfall exceeding 1 inch up to 30-40pct over western
Upper MI as that area will be affected by frequent sw-ne moving shra
thru Sat morning before the weak sfc boundary shifts e.

Should be able to slip in a dry day on Sun with sfc high pres ridge
moving across the western Great Lakes. Expect highs in the 70s F.
Temps will be in the 60s lakeside of the Great Lakes or will fall
back to the 60s in the aftn as lake breezes develop.

The next shortwave moving onshore over the Pacific NW on Sat will
reach the Upper Mississippi Valley late Sun night and the western
Great Lakes by Mon aftn. Along/ahead of the associated cold front,
developing/organizing shra/tsra across the Dakotas into MN Sun
aftn/evening will move e Sun night thru Mon. For now, it appears
that the arrival of these shra/tsra late Sun night into western
Upper MI will work against a svr storm risk as instability
diminishes with time and eastward extent, but with a 40-45kt low-
level jet translating over western Upper MI by 12z Mon, it will be
worth monitoring in the coming days. Coverage/persistence of
shra/tsra moving across the area Mon morning and whether any
clearing occurs before cold front clears the area will determine if
any stronger storms then develop along the cold front Mon aftn. That
won`t be known until we get closer to Mon.

In the wake of the cold front, passing sfc high pres ridge on Tue
should support a dry day. A vigorous wave will then move out across
the Northern Plains on Tue. The fate of this wave is tied to the
aforementioned late week pattern amplification over and around N
America. As would be expected at this time range and with the start
of significant pattern amplification, there is considerable
uncertainty in the evolution and progression of this vigorous wave.
For now, it appears that shra will enter the picture at some point
Tue night/Wed with shra chc probably continuing Thu/Fri and maybe
into or thru the weekend if a large mid-level low sets up over the
Great Lakes region. Cool conditions will set in during this time as
well.

&&

.AVIATION /06Z TAFS THROUGH 06Z SATURDAY/...
Issued at 123 AM EDT Fri May 31 2024

VFR conditions are likely to continue through the TAF period.
Moisture will increase from the southwest late tonight into
Friday at IWD and CMX with cigs lowering to 4-5kft under
isolated showers by late Friday morning into early afternoon. A
period of low-level wind shear is expected between roughly
07-14Z at IWD as southwesterly winds increase to around 40kt
between 1-1.5kft AGL.

&&

.MARINE...
Issued at 500 AM EDT Fri May 31 2024

Under a relatively weak pres gradient and stable conditions over the
lake, expect winds mostly under 20kt today thru Sun. An approaching
cold front Sun night will bring an increase in southerly winds,
especially across the e half of Lake Superior which is typically
favored for stronger winds this type of situation. By sunrise Mon, s
to se winds up to 25kt are expected, though given the stability over
the cold lake waters, these winds up to around 25kt will mostly be
observed at high obs platforms. That said, 25kt winds may observed
locally in the nearshore waters where flow off of the terrain
affects the wind. Cold front will pass later Mon/Mon night with
winds under 20kt following on Tue.

&&

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

&&

$$

SHORT TERM...JTP
LONG TERM...Rolfson
AVIATION...Voss
MARINE...Rolfson