470
FXUS63 KMQT 230843
AFDMQT

Area Forecast Discussion
National Weather Service Marquette MI
443 AM EDT Sun Jun 23 2024

.KEY MESSAGES...

- Today`s rain will continue for central and eastern Upper Michigan,
before a lull moves in this evening. Another wave of rain expected
to move into the west this evening, then progress into the eastern
U.P. tonight.

- Additional rainfall amounts of half to one inch possible this
afternoon in the east. Tonight up to half inch of additional rain
possible west and a quarter inch east.

-A slight risk (~15%) of damaging wind and hail in the west
associated with thunderstorms Monday night into Tuesday morning.

-Tuesday will be the warmest day of the week with highs in the mid
80s, with dew points in the 60s making it a hot and muggy day.

-Next round of precipitation expected late Thursday into the weekend.

&&

.SHORT TERM /THROUGH TONIGHT/...
Issued at 131 PM EDT Sat Jun 22 2024

Current GOES 16 Water Vapor and IR imagery, coupled with current
radar data, show this morning`s precip shield spread across the
central and eastern Upper Michigan. Across western Upper Michigan,
radar returns are becoming spotty with some breakage in the cloud
cover noted in northern WI south of the Apostles. In the east, rain
showers, with some embedded moderate to heavy rain showers are
currently being observed. MRMS estimates for rainfall, so far, in
this event are estimated ~0.25 inches or less far west and Keweenaw,
widespread 0.5 to 2 inches central, and up to ~0.5 inches in the
east. As we progress through the remainder of the afternoon, expect
another 0.5 to 1 inch of rain in the east while the western lull
spreads into the interior west/central. A canopy of overcast skies
have blanketed the region today, which has limited daytime heating.
So far, highs have only climbed into the mid-upper 50s to low 60s
across the region.

Current mesoanalysis places a warm front over southern Wisconsin
eastward into lower Michigan, with a surface low over central
Wisconsin and a second low trailing over Iowa. Over western
Minnesota, a shortwave pressing eastward will force both eastward,
enabling the central Wisconsin low to deepen and press east across
Lake Michigan and to near the Straits/Lake Huron by Sunday 12z while
the Iowa low drags across southern WI along the frontal boundary.
Additional forcing between these 3 features will support another
wave of rain into the west this evening, which spreads east along
the low`s northern flank as the low transits the Great Lakes. CAMS
are a little mixed on shower coverage in this wave, but appear to
consistently suggest lighter rain then we received through the day
today so far. Recent HREF and NBM runs validates this with
probabilities of >0.5 inches at 60% or less. General consensus among
the packages suggest an additional 0.5 inches would be most likely
across the west while the east half sees up to another 0.25 inches
tonight. Expect patchy fog to develop overnight as we cool into the
low 50s to upper 40s west and mid-upper 50s east.

&&

.LONG TERM /MONDAY THROUGH SATURDAY/...
Issued at 442 AM EDT Sun Jun 23 2024

Beginning this coming week, persistent 500mb ridging over the
southwest to south-central US with longwave troughing over the
eastern coasts of North America leaves the Upper Great Lakes in the
main path of shortwaves riding above the ridge and into the larger
trough. The resulting surface features will result in multiple
distinct rounds of rainfall in this period, first Monday night
through Tuesday and then again late Thursday into the weekend. The
best chances (~15%) for strong thunderstorms will be with the
precipitation Monday night into Tuesday. Without long-duration
southerly flow, temperatures generally remain near-seasonal, with
the exception of Tuesday when temperatures look to climb to around
80 with dew points in the 60s.

Once the remaining fog burns off in the early morning hours, Monday
looks to be a mainly quiet day as the region is on the north side of
a 1015mb high pressure. CAMs resolve a lake breeze along Lake
Superior, but otherwise, southerly to southwesterly winds begin to
build in response to a deepening low pressure near 990mb transiting
central Saskatchewan and Manitoba. The warmer, moisture-rich air
will allow instability to build late, with both GEFS and Euro
ensemble CAPE probabilities of over 1k J/kg well over 50% for much
of the interior western and central UP by Monday night and 30-40%
chance of 2k J/kg. The mainly southerly surface flow contrasted with
the mainly westerly flow aloft will create a supportive shear
profile for the maintenance of storms, as surface-500mb shear values
will be near 40 kt in the west Monday night. The forcing will come
from the cold front draped from the low as it passes into far
northern Ontario. With the past 24 hours of model guidance,
confidence has increased in the cold front arriving in the western
UP around 06Z Tuesday. The current run of the HREF shows virtually
no precipitation potential prior to 00Z over the UP, however, it
does show convective initiation further upstream, and given the
present forcing and ingredients present, the SPC Slight Risk for
dual 15% risks of severe wind and hail is warranted. The biggest
source of uncertainty seems to be in storm mode, whether it will
maintain a (super)cellular structure or if a MCS will form upstream.

Southerly winds at the surface persist into the daytime hours
Tuesday, which the warm advection combined with radiational heating
will allow Tuesday to be the warmest day of the week, with the most
likely high temperatures for Tuesday being in the low to mid 80s,
though the 75th percentile shows some isolated spots of 90s. It
could also be a muggy day as forecast dew points approach 70.
Eventually, winds will veer westerly behind the front draped from
the long-away low pressure and temperatures will moderate somewhat.
Lingering thunderstorms are possible, especially if the lifting from
the front is on the stronger end of guidance, but PoPs are generally
expected to be around 30% Tuesday afternoon to evening.

Ensemble guidance has increased in certainty over the past 24 hours
in a high pressure following behind the cold front, transiting the
Upper Midwest and through the Great Lakes Wednesday through Thursday
morning. This will lead to the most prolonged dry period of the
forecast period with generally clear skies and light winds forecast.
Meanwhile, a deep 500mb trough will make landfall in the
Seattle/Vancouver region, setting up another northern Rockies low
pressure forming by Thursday evening. PoPs over the UP gradually
climb as this low will most likely eject towards and north of the
Great Lakes by Friday and the weekend. Exact timing, location, and
intensity of showers is still hard to pin down given the growing
range of possibilities, but there is a surprising amount of
certainty in the next high pressure bringing dry weather to the
region by next Sunday. Overall, nothing in the ensembles shows any
major shift in the pattern, which lines up with the CPC continuing
to outlook the UP with best chances for above average temperature
and precipitation even into the first portions of July.

&&

.AVIATION /06Z TAFS THROUGH 06Z MONDAY/...
Issued at 133 AM EDT Sun Jun 23 2024

Rain will continue overnight across primarily CMX and SAW with
IWD mostly out of the rain now. Expect LIFR to VLIFR conditions
at IWD and SAW overnight to improve at VFR shortly after sunrise
as ridging and associated drier air push in from the west. MVFR
to possibly IFR conditions at CMX overnight in a downslope NE
wind flow could improve to VFR before sunrise. Expect LLWS at
SAW overnight, and then N-NE winds gusting as high as 20 kts
during the day today.

&&

.MARINE...
Issued at 442 AM EDT Sun Jun 23 2024

A low pressure system will exit into Ontario this morning.
Today, west to northwest winds will mainly remain below 20 kts. High
pressure ridging then passes over Lake Superior tonight and Monday,
keeping light winds in the forecast until Monday night. South winds
increase to around 20 kts Monday night ahead of a passing cold
front. Southwest winds behind the front are expected around 20-25
kts, though a few gusts may be in the 25-30 kt range between Isle
Royale and the Keweenaw Peninsula Tuesday afternoon. Winds taper off
Tuesday night into Wednesday, remaining below 20 kts through the
late part of the week.

Some isolated thunderstorms are possible this afternoon and evening
across the west. Strong to severe storms are possible in the west
Monday night into Tuesday with the passing cold front. Waves will be
strongest between Isle Royale and the Keweenaw Peninsula Tuesday
afternoon and evening (4-6 feet).

&&

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

&&

$$

SHORT TERM...JTP
LONG TERM...GS
AVIATION...07
MARINE...GS