947
FXUS63 KMQT 030020
AFDMQT

Area Forecast Discussion
National Weather Service Marquette MI
820 PM EDT Sun Jun 2 2024

.KEY MESSAGES...

- Isolated afternoon showers possible interior eastern Upper MI
  due to converging lake breezes.
- A round of showers and storms moves into the far western UP by early
  Monday morning.
- Frequent rain chances this week including thunderstorm
  potential through Wednesday. A few strong storms are possible
  Tuesday evening and overnight.
- Above normal temperatures through Wednesday, then turning
  cooler for the second half of the week.

&&

.SHORT TERM /THROUGH TONIGHT/...
Issued at 302 PM EDT Sun Jun 2 2024

Skies remain sunny across the area with weak ridging sliding over
the Great Lakes and plenty of dry midlevel air in place. Still, some
agitated cu is firing across the eastern UP, with converging lake
breezes off of Superior and Lake Michigan. Cloud tops remain fairly
low so far, and latest model and NUCAPS profiles still show some
thermal capping aloft. If this can be overcome, though, a few
showers out east cannot be ruled out.

Otherwise, temperatures across most of the UP are climbing well into
the 70s, but are a little cooler (mainly 60s) along the shorelines
of the Great Lakes. Dewpoints are dropping into the lower 40s and
even upper 30s in the interior-western UP, but light winds continue
to limit our fire weather concerns.

Meanwhile, RAP analysis shows midlevel troughing digging into the
Plains, with tightening 850mb flow and WAA over MN already touching
off some convection. This feature will continue to swing NE towards
the Great Lakes into tonight while phasing with another wave
currently moving across southern Saskatchewan. Showers finally reach
the far western UP by the early hours of Monday, while a LLJ core
becoming directed over the area potentially lending some divergence.
Some thunder will not be ruled out, but given an unfavorable onset
timing during the pre-dawn hours, would not expect any severe
convection.

Expect an otherwise mild night under increasing clouds. Temperatures
likely won`t fall below the 50 degree mark over most of the UP, save
the far east, where clear skies hold out the longest. There, we may
dip into the upper 40s.

&&

.LONG TERM /MONDAY THROUGH SUNDAY/...
Issued at 416 PM EDT Sun Jun 2 2024

Warm and moist southwest flow ahead of an upper level trough lingers
through Wednesday resulting in almost daily chances for showers and
embedded thunderstorms. There should be a general lull on Tuesday,
but rain chances linger into Tuesday morning across the east and the
next disturbance arrives Tuesday afternoon/evening across the west.
Tuesday looks to be the warmest day this week with highs warming to
near or above 80F except for 70s downwind of Lake MI. A chance for
strong thunderstorms and locally heavy rainfall accompanies a cold
front passage Tuesday night. A cooler but still humid air mass
follows the front as an upper level low establishes a broader trough
across the Great Lakes region late this week. As a result, rain
chances late this week appear much lighter with limited thunder
potential and primarily diurnal in timing.

Starting with Monday morning, the UP will be positioned between
surface ridging to the east and a surface low to the west. A fairly
tight pressure gradient is accompanied by a ~45-50 kt low level
jet that translates east and weakens to 35-40 kts during the
day. This suggests some potential for stronger winds/gusts, but
considerable cloud cover and rain showers inhibit mixing so kept
forecast winds close to NBM. I considered removing thunder
chances on Monday due to meager CAPE values around or less than
100 J/kg, but any breaks in cloud cover could allow for greater
destabilization. Rain showers gradually diminish while tracking
across the eastern UP Monday evening and clearing skies expected
shortly after the front passes. Conceptually, this scenario
suggests potential for terrestrial radiation fog and maritime
advection fog by Tuesday morning.

Terrestrial fog should dissipate Tuesday morning allowing for mostly
sunny skies and temperatures warming to around 80F across most of
the UP. Dew points around 60F indicate potential for unseasonable
destabilization during the day (perhaps in the 2000-3000 J/kg
range), consistent with EFI value of 0.5-0.7. Soundings suggest the
area stays capped on Tuesday until the cold front moves in Tuesday
night, but will need to monitor potential for a pop-up storm along
any lake breeze boundaries that develop. Bulk shear also increases
as the front approaches indicating an increasingly favorable
environment for strong to perhaps severe thunderstorms. Diurnal
timing is more favorable for severe storms to our west, but the warm
sector of a ~990 mb surface low in early June seems more threatening
than the marginal risk currently outlooked by the SPC suggests.
NAEFS guidance also indicates pwats increasing above the 90th
percentile Tuesday evening implying a heavy rain threat.

Model spread increases by Wednesday morning, presumably due to
differences in convective development late on Tuesday. Most
operational 12z models indicate the cold front will still be
overhead or at least nearby Wednesday afternoon implying potential
for afternoon redevelopment, mainly east. Modest mid-level cold air
advection may dynamically destabilize the area on Wednesday leading
to a round of diurnal showers/storms. However, I decided to pull
thunder chances for Wednesday night onward as dew points fall below
50F and cool/dry air advection continues. The upper level low tracks
southeast across the UP Wednesday thru Thursday night resulting in
an extended period of unsettled and showery weather. Total rain
amounts are expected to be light due to lack of quality moisture
while temperatures trend below normal, especially daytime highs.

&&

.AVIATION /00Z TAFS THROUGH 00Z TUESDAY/...
Issued at 819 PM EDT Sun Jun 2 2024

VFR conditions will prevail until an approaching disturbance
spreads showers across IWD/CMX after Mon 12Z, followed by SAW
on Monday afternoon. During rain chances, expect MVFR cigs to
prevail. IWD could see a return to VFR by the end of this TAF
period when the disturbance begins exiting the area, but CMX and
SAW should remain at MVFR. In addition, there will be a LLWS
threat at IWD and CMX early Monday morning with the low-level
jet ahead of aforementioned disturbance. Southerly surface winds
will also exceed the 12 kt threshold with some gusts up to 21
kts Monday morning and afternoon.

&&

.MARINE...
Issued at 416 PM EDT Sun Jun 2 2024

Light winds of 20 knots or less continue today into tonight as weak
surface high pressure continues over Lake Superior. However, as a
cold front moves through late tonight into Monday, southerly winds
gust up to 20 to 25 knots Monday, particularly over the north-
central lake and near tip of the Keweenaw. By Monday evening, winds
diminish to 20 knots or less and stay light until a cold front
approaches the lake Tuesday afternoon with southeast winds gusting
to around 20 kts. The front cross the lake late Tuesday night and
Wednesday with southwest winds to gusting up to 20 to 25 knots over
the western half of the lake behind the front. A low pressure stalls
over northern Ontario for the latter half of the week, resulting in
a prolonged period of unsettled weather including west or southwest
winds gusting to 15-25 kts through Friday evening. A few stronger
gusts up to 30 kts are possible on Thursday.

As for other marine hazards, patches of dense marine fog are
occurring across northeastern Lake Superior this evening. Dew point
temperatures well above lake water temperatures and several periods
of rain indicate potential for fog redevelopment on Monday through
Tuesday night. A few thunderstorms are possible across the western
lake tonight before spreading across the remainder of the lake
Monday and Monday evening. Another cold front Tuesday night brings
scattered thunderstorms across the lake from west to east from
Tuesday afternoon through Wednesday. While severe thunderstorms are
not expected at this time, a few stronger storms capable of hail,
gusty winds, and frequent lightning are possible Tuesday night into
Wednesday

&&

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

&&

$$

SHORT TERM...LC
LONG TERM...EK
AVIATION...TDUD
MARINE...EK