729
FXUS63 KMQT 231154
AFDMQT

Area Forecast Discussion
National Weather Service Marquette MI
654 AM EST Sun Feb 23 2025

.KEY MESSAGES...

- Widespread light wintry mix anticipated ahead of a clipper
  system tonight into Monday. A mix of rain, snow and freezing
  rain is expected with a 30-70% chance of a light glaze of ice
  from freezing rain, highest over Delta, Alger Luce and
  Schoolcraft counties prior to the Monday morning commute.
  Gusty southerly winds late tonight possibly reaching 40 mph
  for downsloping locations along Lake Superior.

- Widespread precip returns to the region Wednesday, with rain
  and snow expected.

- Further clipper lows remain possible late in the week, but
  the highest potential for more widespread precipitation comes
  late Friday into Saturday.

- Warmer than normal through the first half of next week with
  highs likely above freezing. A colder pattern shapes up into
  next weekend with single digit lows at least 40% likely over
  the weekend.

&&

.SHORT TERM /THROUGH TONIGHT/...
Issued at 421 AM EST Sun Feb 23 2025

Water vapor imagery and RAP analysis show nw mid-level flow into the
Great Lakes early this morning. A couple of shortwaves of note
upstream, one over the Dakotas and MN and a second, more prominent
shortwave moving in off the Pac NW Coast into BC and Alberta. Some
thin WAA mid-level clouds that have spread into Upper MI early this
morning ahead of the shortwave over the northern Plains have
generally kept overnight temps up into the teens to lower 20s, with
the exception of a few single digit readings over the typical cold
spots of the west and central interior.

Today, ahead of the approaching Northern Plains shortwave expect a
period of -sn to develop later this morning in response to vigorous
mid-level q-vect convergence and isentropic ascent as noted on 280K
theta sfcs along with a corresponding region of lowering
condensation pres deficits. Models qpf suggests most counties will
get some snow late morning into early afternoon with the exception
of maybe only Keweenaw and Luce counties missing out. There won`t be
much snow, probably ranging from only flurries to a few tenths at
best. Otherwise, a WAA southerly flow will result in warmer max
temps ranging from lower 30s east and southeast to upper 30s
interior west under generally mostly cloudy skies.

Tonight, the shortwave now over Alberta will be fast approaching the
Upper Great Lakes with the associated deeping sfc low near 980 mb
tracking east into northern Ontario and Hudson Bay late tonight into
Mon morning. Strong q-vect convergence and isentropic ascent noted
ahead of the system`s 850 mb warm front moving across the area will
result in an area of mixed pcpn mainly focused across the northern
and eastern tier counties as per model consensus. Model soundings
leave little confidence in p-type as profiles do show a warm nose
between 925-825mb, but the profile is also dry at these levels,
resulting in a wide range of solutions regarding p-types and timing
of them. Basically, expect a wintry mix of rain, snow and freezing
rain with the best chance of a light glaze of ice from freezing rain
occurring generally east of a line from Marquette-Iron Mountain with
the HREF indicating the highest probability (50-80%) of light ice
accumulation over Delta, Alger, Schoolcraft and Luce counties where
a few spots of .05 inch of ice is possible. This wintry mix
combination could impact the morning commute on Monday over the east
half. Will need to continue to monitor this risk as it approaches;
the afternoon forecast package may need to include an SPS for
potential slippery road conditions. A strong low-level jet of 50+
kts moving across the area combined with strong 3-hr pres falls of 7-
9 mb north of Lake Superior will likely result in gusty southerly
winds across the forecast, particularly in the downsloping areas
along Lake Superior, where gusts near 40 mph could be possible
despite the presence of an inversion 1500 ft off the surface. With
the well-mixed low-levels and clouds, expect min temps to stay up in
the upper 20s to lower 30s.

&&

.LONG TERM /MONDAY THROUGH SATURDAY/...
Issued at 502 AM EST Sun Feb 23 2025

Positive 500mb height anomalies over much of the CONUS will persist
through the first half of next week with a milder airmass over much
of that area as a result. Generally, the flow pattern over the UP
region will be primarily northwesterly with periodic quick clipper
shortwaves providing the synoptic support for precipitation and
eventually should result in temperatures cooling to more near-normal
temperatures by the end of the week. Before the return to normal
temperatures, high temperatures will climb above freezing for much
of the first half of the week. This means that what precipitation
does fall could include periods of rain as well as snow. This milder
airmass will also provide a break from lake effect precipitation
until at least Thursday.

Beginning Monday, precipitation will be rapidly departing the
eastern UP associated with near 979mb low pressure over the Hudson
Bay shores of northern Ontario. HREF hourly PoPs fall below 20%
across the UP by 14Z. With the tighter pressure gradient and
pressure rises and falls, higher winds are a possibility on Monday.
CAMs are fairly split about whether or not higher winds aloft can
mix to the surface, with the CMChr on the low end with winds around
10-15 mph UP wide and the NSSLWRF on the high end with 25-30 mph
winds UP wide with some Keweenaw spots reaching 40mph sustained.
Elected to go somewhere between those extremes, but future packages
should examine the wind potential as the (albeit usually too high)
HREF gusts show up to 40% chances of 45mph gusts for the Marquette
County high terrain and the Keweenaw Peninsula. As skies thin out,
continually increasing sun angles should lead to more efficient
diurnal heating, and this is shown in the NBM and MOS guidance
showing mid-40s expected for much of the UP and the NBM calling for
over 30% chances of reaching 50 in Menominee County!

As temperatures fall back towards freezing overnight Monday into
Tuesday, surface convergence and a weak impulse at 500mb provide
just enough lift for the LREF to call for roughly 20% chances of
drizzle/freezing drizzle/flurries in the west half overnight.
Impacts are not expected as even the 90th percentile only calls for
0.04" of QPF overnight at most. Gradual height rises are expected as
weak ridging moves over the region Tuesday, keeping the UP precip-
free, but not enough subsidence for it to be cloud-free. Still,
enough thickness is present for temperatures to climb above freezing
for all except for the extreme northern extent of the UP, with the
NBM calling for 40s for highs in the south-central.

The next potent shortwave traverses the Upper Midwest Wednesday.
Precip type will be a bit of a challenging forecast as the current
temperature forecast would support snow to begin the morning,
changing to rain as highs eclipse the freezing mark with the warm
advection associated with the shortwave, then a change back to snow
late Wednesday behind the cold front and with the diurnal heating
falling off in the evening. LREF chances of freezing rain with this
system are only about 10% as current model soundings struggle to
produce a prominent enough warm nose that straddles the 0 C
isotherm. Therefore, will only be calling for rain, snow, or a mix
of the two for this forecast package. While ensemble spread has
improved from yesterday`s "Arkansas to the Hudson" spread, the
spread in low pressure centers by 18Z Wednesday in the GEFS is still
from the boot of Missouri to Lake Superior, so there is still plenty
of wiggle room in the forecast for impactful changes to the forecast
to play out.

As the northwesterly pattern supports quite a large number of low-
amplitude shortwaves, this pattern lends itself to a rapid increase
in ensemble spread in a short period of time. Ensembles show
clusters of solutions with a clipper low over the region virtually
every day for the remainder of the forecast, but only with the best
cluster of lows Friday into Saturday do PoPs break the 50%
threshold. What does become more certain is that after Wednesday,
temperatures become more likely to be near normal for this time of
year (highs in the 20s, lows near 10) and as a result, snow becomes
the more preferred (though not guaranteed!) precipitation type by
the end of the week instead of the rain/snow alternations of the
early week. The late week could also see a return to lake effect
snow as 850mb temperatures over Lake Superior become 20-40% likely
to fall below negative 13 C by Thursday evening, and then 75% likely
next weekend.

&&

.AVIATION /12Z TAFS THROUGH 12Z MONDAY/...
Issued at 638 AM EST Sun Feb 23 2025

At IWD, VFR conditions will likely hold through much of the
period except for the potential of a brief period of MVFR
conditions late evening into the early overnight in light rain.

Expect MVFR conditions at CMX and SAW in light snow into early
afternoon with MVFR cigs holding on into the evening hours.
There could be brief period of VFR conditions at CMX before a
wintry mix of rain, snow and freezing rain moves in late evening
into the overnight, sending both CMX and SAW down into MVFR to
IFR conditions.

A low-level jet max moving across the area will also cause gusty
south to west windd tonight along with LLWS across all the
terminals.

&&

.MARINE...
Issued at 502 AM EST Sun Feb 23 2025

Benign conditions are expected over Lake Superior this morning and
for much of the day. As a strong low pressure passes through far
northern Ontario, south winds ramp up over Lake Superior through the
evening hours, increasing to 30-35 kt overnight into Monday morning
with 50% chances of brief gale conditions over the east half of the
lake Monday morning. Winds become westerly, still gusting near 30 kt
on Monday with a few isolated gale force gusts before falling below
20 kt Monday night, then remaining near or below 20 kt for much of
the week as uncertainty grows regarding the path of any potential
clipper lows through the next week. Models suggest the next
potential for a gale would be next weekend, but spread in the path
and timing of the surface low for that time period is quite high.
Waves next week are expected to be at their peak Monday as the
westerly gusts force waves of up to 10 ft.

&&

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

&&

$$

SHORT TERM...Voss
LONG TERM...GS
AVIATION...Voss
MARINE...GS