281
FXUS63 KMQT 302029
AFDMQT

Area Forecast Discussion
National Weather Service Marquette MI
429 PM EDT Sun Jun 30 2024

.KEY MESSAGES...

- Rip currents and dangerous swimming conditions are possible at
  the Lake Superior beaches of Alger and Marquette counties the
  rest of the afternoon.

- Dry weather continues through Monday evening.

- There is a slight chance (<20%) for patchy frost across
  portions of the interior-western UP tonight.

- Next rounds of showers and thunderstorms arrive Monday night,
  continuing into Wednesday. Gusty southerly winds up to 25-35
  mph are also expected on Tuesday.

- Warm and wet pattern expected to continue well into July.

&&

.SHORT TERM /THROUGH TONIGHT/...
Issued at 231 PM EDT Sun Jun 30 2024

Robust upper ridging over the Plains is supporting a sprawling
1028mb surface high centered over MN this afternoon. With strong
subsidence over the UP, there is hardly a cloud in the sky. In spite
of this, temperatures remain quite cool; temperatures are only
climbing into the lower 60s across much of the UP, while shoreline
locations and the easternmost portions of our CWA are struggling
even to break out of the upper 50s under chilly NW flow off of Lake
Superior. NW winds are staying somewhat gusty across the eastern
half of the UP, but gusts should fall back heading into the
evening.

Tonight, as the aforementioned high pressure becomes centered
overhead, even stronger radiational cooling and calm winds will lead
to widespread overnight lows in the upper 30s to lower 40s. The
frost potential across the interior-western UP is still difficult to
pin down, with most of the guidance staying just warm enough to
preclude frost. Only about 10% of href ensemble members reach the
mid 30s, while the NBM 10th percentile also only flirts with the mid
30s. Will note, however, that some spots in the western half of the
UP fell farther into the 30s than expected, with the "winner" of the
night (Watton) reaching as low as 34F. Therefore, have been just
confident enough to come in a couple degrees under guidance,
particularly across Iron and southern Baraga counties, where we
may just get cool enough for patchy frost. This will continue
to be monitored/adjusted as needed.

In addition, dangerous swimming conditions for Marquette and Alger
counties are expected through this afternoon.

&&

.LONG TERM /MONDAY THROUGH SUNDAY/...
Issued at 428 PM EDT Sun Jun 30 2024

The primary focuses of the extended forecast will be for Monday
night through Tuesday night as well as a system moving through the
4th of July night, continuing into the weekend. The generally wet
pattern returns Monday night.

July starts off dry with mid level ridging centered over the UP. The
sfc high continues shifting eastward as well, resulting in southerly
flow, warmer temps, and increasing cloud cover late in the
afternoon/evening. Highs on Monday will climb into the 70s, warmer
in areas with downslope flow.

Meanwhile, the mid level trough currently over British Columbia
begins shifting east, continuing over the Canadian Prairie provinces
through Tuesday. This sends a shortwave northeast over the Upper
Mississippi Valley Monday night, lifting northeast through
northwestern Ontario on Tuesday. This set up supports cyclogenesis
in the lee side of the Rockies in southern Alberta tonight. The low
is progged to move east, just north of the international border,
through Tuesday morning. Then with the support of the northeast
lifting shortwave alongside a left exit region of a ~110 kt upper
level jet, the low deepens to ~993mb as it lifts northeast toward
Hudson Bay by Wednesday evening. This system ends the dry period
Monday night in the west as WAA/isentropic ascent touches off the
first round of showers, later supported by the northeast rotating
shortwave and increasing 900-850mb LLJ up to ~45-50 kts. Confidence
is growing in a brief lull or even break in the showers late Tuesday
morning/afternoon (better chances for a drier period in the west)
before a second round of showers and thunderstorms ahead of the low
pressure system`s trailing cold front continues PoPs into Wednesday.

With limited elevated instability (100-300 J/kg of MUCAPE) for the
first round, thunderstorms can`t be ruled out Monday night through
Tuesday morning, but no severe weather is expected. Instability
remains limited for the second round, but thunderstorm chances look
slightly better with maybe a few hundred J/kg more of MUCAPE (6/30
12Z LREF indicates up to ~750 J/kg in the 90th percentile). Also,
mid level lapse rates will be higher (approaching 6.5 C/km) and this
round has better synoptic forcing; severe weather potential still
remains low (<10%). With the LLJ overhead and a tighter pressure
gradient on Tuesday, some breezy southerly winds are expected with
gusts up to 25-35 mph. Model soundings do leave potential for mixing
to yield higher gusts up to 40-45 mph and the 6/30 12Z HREF does
show probabilities of gusts exceeding 35 mph reaching around 50-70%.
This will bear monitoring with future forecast packages. Tuesday
will be slightly cooler than Monday with highs in the mid 60s to mid
70s.

On Wednesday, the mid level trough now centered over northern
Ontario, will moves east over Quebec. The last precip should end by
the afternoon as PVA ends behind the cold front and departing
trough. The dry period looks to persist through most of the 4th of
July. Temps on Wednesday and the 4th of July will be the warmest for
the week with highs in the mid 70s to mid 80s and lows in the mid
50s to low 60s. Confidence is growing in a sfc low developing over
the lee of the central Rockies Wednesday night, lifting northeast
into the Great Lakes region for Friday afternoon into Saturday. A
mid level trough also moves through the Upper Great Lakes Friday
into Saturday morning. NBM PoPs captures this with an increase in
PoPs to around 30-50% Thursday night from the southwest, then 40-60%
PoPs for Friday into Friday evening. With uncertainty increasing
Saturday onward, 15-35% PoPs are sprinkled through the rest of the
weekend.

&&

.AVIATION /18Z TAFS THROUGH 18Z MONDAY/...
Issued at 126 PM EDT Sun Jun 30 2024

VFR conditions to prevail for duration of TAF period with high
pressure over the region. Winds generally out of the north will be
breezy at times especially at SAW this afternoon, then winds turn
light and variable tonight before shifting over to the south for
Monday.

&&

.MARINE...
Issued at 428 PM EDT Sun Jun 30 2024

High pressure continues shifting east over the Great Lakes through,
maintaining light winds below 20 kts through at least Monday.

Another system presses in from the west Monday night, bringing with
it waves of rain and maybe some thunderstorms, into Wednesday. These
rain showers may support fog developing and periods of low
visibility on the lake. A stout 900-850mb low level jet up to ~45-50
kts will also come with this system. This along with the tighter
pressure gradient will support increasing southerly winds Monday
night into Tuesday. Internal probabilistic tools suggest a low
probability (15-30%) that winds will exceed 33 kts. Given the
increasingly warm airmass and stability over the lake at the time,
the going forecast represents winds to 20-30 kts over the eastern
2/3 of the lake. That said, localized terrain driven influences
should support small pockets of mixing down low end gales,
particularly downwind of the lakeshores east of Marquette and along
the northern shores of the Keweenaw. Given the setup and the
consensus of the strength of the low level jet, this will bear
monitoring in future forecast packages. Another round of moisture
will lift through Tuesday night into Wednesday while winds settle
down. The cold front presses through west to east Tuesday night into
Wednesday morning, allowing winds to become westerly/southwesterly
for Wednesday. Another period of stronger winds up to 20-30kts,
looks possible between the Keweenaw and Isle Royale Wednesday in
this southwesterly flow. High pressure returns briefly for Thursday
with a weaker low pressure system expected to pass over the Upper
Great Lakes next weekend. Light winds below 20 kts returns Wednesday
night, continuing likely through the rest of the work week.

&&

.MQT WATCHES/WARNINGS/ADVISORIES...
Upper Michigan...
  Beach Hazards Statement until 6 PM EDT this evening for MIZ005-
     006.

Lake Superior...
None.
Lake Michigan...
None.

&&

$$

SHORT TERM...LC
LONG TERM...Jablonski
AVIATION...LC
MARINE...Jablonski