431
FXUS63 KMQT 061036
AFDMQT

Area Forecast Discussion
National Weather Service Marquette MI
636 AM EDT Sun Apr 6 2025

.KEY MESSAGES...

- After some snow showers begin this afternoon, lake effect snow
showers return through Monday night over the north wind snow belts.
Widespread 1-3 inches of snow is expected with 4-6 inches possible
(60+%) north of US-41 in Marquette and Baraga Counties.

- High pressure dominates the forecast Tuesday into the weekend,
though 15-30% chances of precip linger for a system passing south of
the region late Wednesday/Thursday.

&&

.SHORT TERM /THROUGH THIS AFTERNOON/...
Issued at 239 AM EDT Sun Apr 6 2025

Upper air pattern consists of a split 500 mb pattern with a southern
trough over the southern plains and a northern trough over the upper
Great Lakes. The northern trough leaves, but a shortwave plunges
back down into the upper Great Lakes by 00z Mon and brings with it
some deeper moisture along with some 850-500 mb q-vector
convergence. Looks quite dry for this morning and removed most pops
that were in there with the exception of eastern Lake Superior where
the ADJLAV model actually picked up on a snowband north of Grand
Marais that is hitting near Whitefish Point. Have kept some pops in
for that as this band has been persistent. As the next shortwave
moves in this afternoon, chance pops are in the forecast. Overall,
did not make too many changes to the going forecast except took pops
out this morning.

&&

.LONG TERM /TONIGHT THROUGH SATURDAY/...
Issued at 422 AM EDT Sun Apr 6 2025

General pattern aloft is highly meridional as deeply anomalous
troughs over Hudson Bay/northern Ontario and the Gulf of Alaska are
separated by a tall ridge that extends from California to the Canada
Arctic coast. Despite a low number of waves, the pattern does
progress with the trough over eastern Canada delivering one
shortwave over the Upper Great Lakes by this evening before shifting
to the east coast Tuesday with central North America ridging moving
into the Plains. A shortwave then pushes through into the Midwest
around Thursday before ridging builds back over the western CONUS to
end the week. Ridging looks to dominate the central CONUS next
weekend, but agreement is good for this time range on the Gulf of
Alaska trough making landfall late next Saturday into next Sunday
and progressing into the Northern Plains by midweek. Generally
speaking, this type of pattern looks to be dominated by high
pressure over the central CONUS with brief interruptions by
shortwave lows (think Clippers, etc), though the pattern could
change for mid-April depending on how that trough progresses when it
makes landfall and passes through the Rockies.

In the wake of a quickly-departing 1005-1010mb low to the south and
east, winds are expected to become straight northerly, and with cold
advection at 850mb dropping 850mb temperatures well into the
negative teens, lake effect snow is back! Low level RHs are
maximized tonight through Monday morning and approaching high
pressure upstream of the central North America ridge will gradually
whittle down PoPs through the day Monday and the showers will end
altogether by th afternoon hours of Tuesday. The HREF shows LPMM 6-
hourly QPF rates of 0.15 to 0.25 inches per 6 hours by 12Z Monday
along the terrain of Marquette and Baraga counties. With saturated
DGZ depths of near 3kft, snow ratios will climb above 15:1, but with
this being so late in the season, it`s uncertain whether 20:1 can be
realized. Expecting widespread 1-3 inches with this system, but
with the orographic boost for Marquette and Baraga counties
seeing 0.5 to 1 inch/hour rates around the Monday morning
commute, hoisted a Winter Weather Advisory for those counties.
In addition to the snow, it could also get a bit breezy Monday,
with Euro ensemble probabilities of gusts to near 40 mph along
the Lake Superior shores ramping up to near 50%, though the HREF
mean gusts are closer to 25 mph despite good mixing into a 30+
kt layer expected.

1020s mb high pressure then keeps the weather quiet for Tuesday into
Wednesday. Clearer skies and light winds under the high pressure
will allow for an efficient radiational cooling night Tuesday night,
with NBM lows Wednesday morning in the single digits for portions of
the interior west. A clipper low passing from the Plains to the
Great Lakes in the midweek has trended further south with the last
24 hours of model guidance, yet NBM PoPs of 15%-30% remain for the
UP. Expecting this event to be primarily rain, though being in the
cooler sector of this low could result in some light snow. Expansive
high pressure returns to give pleasant weather Friday into the
weekend, with NBM highs in the 60s in the interior west 40-60%
likely Friday and Saturday. Spread then remains high on the surface
features into the following week, but there`s some signal beginning
in a low pressure coming off of the High Plains in the early- to mid-
week associated with the landfalling Gulf of Alaska trough. Such a
surface low would arrive in the Tuesday-Thursday range, but a
sufficiently deep low could also miss the UP entirely, so this is
only a triviality to watch for now.

&&

.AVIATION /12Z TAFS THROUGH 12Z MONDAY/...
Issued at 636 AM EDT Sun Apr 6 2025

VFR conditions will persist at IWD and CMX through today. SAW will
go from VFR to MVFR later this afternoon. Snow will develop with a
shortwave moving through the area tonight with MVFR conditions at
IWD and CMX and conditions dropping down to IFR by evening at SAW
which lasts all night.

&&

.MARINE...
Issued at 422 AM EDT Sun Apr 6 2025

Winds will remain below 20 kt today before northerly gusts surge to
near 30 kt tonight into Monday. Models are still uncertain on
whether or not gales will occur, with around half of guidance s
suggesting gales likely (up to 70% chance) but others
suggesting gusts to only around 25 kt. For this package, the
forecast will split the difference and not include straight
gales, but will reflect winds of 30-33 kt. Waves will increase
to 4-9 feet on Monday, highest between Stannard Rock and
Marquette. Light to moderate freezing spray is expected, with
some heavy freezing spray possible (around 50%) in the vicinity
of Isle Royale Monday morning. As winds back to the northwest,
gusts fall below 20 kt from west to east throughout Monday night
with waves falling below 4 ft by Tuesday afternoon. Under
primarily high pressure, winds will remain light and variable
throughout much of next week.

&&

.MQT WATCHES/WARNINGS/ADVISORIES...
Upper Michigan...
  Winter Weather Advisory from 2 PM this afternoon to 2 PM EDT
     Monday for MIZ004-005.

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

&&

$$

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