Area Forecast Discussion
Issued by NWS Marquette, MI

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FXUS63 KMQT 161825
AFDMQT

Area Forecast Discussion
National Weather Service Marquette MI
225 PM EDT Sat Mar 16 2024

.KEY MESSAGES...

- Lake effect snow tonight into Monday, especially over the
  western U.P. near Lake Superior. Highest snow amounts of 5-9
  inches possible across mainly the western counties. Elsewhere
  in the northwest wind snow belts, 2-5 inches is possible.
- A prolonged gale event on Lake Superior continues into Sunday
  night.
- Blustery northwest to north winds continue through Sunday.
- The snow, combined with blustery winds may result in some
  hazardous driving conditions.

&&

.SHORT TERM /THROUGH TONIGHT/...
Issued at 221 PM EDT Sat Mar 16 2024

With the initial cold front now having passed most of the U.P.,
blustery northwesterly winds are being seen across the area,
particularly over the Keweenaw where Houghton has already gusted up
to 43 mph as of 1 PM EDT. Meanwhile, the radar has shown scattered
snow showers developing in the western U.P., with a quick burst of
heavy snow having already occurred at the office in Negaunee
Township. As more organized precip (rain/snow) activity leaves the
far eastern U.P. this afternoon, isolated to scattered snow showers
look to take its place late this afternoon. As cold air advection
continues to cycle over us into the overnight hours, lake-effect
snowfall begins to pick up across the northwest snow belts as the
DGZ finally gets to around 13C, especially over the west. The
snowfall eventually becomes lake-enhanced late tonight as a
secondary cold front drops down from northern Ontario. With
temperatures continuing to fall the rest of today through tonight,
forcing gradually moving into the DGZ, and the moisture profile
slowly moistening with time due to the incoming secondary cold front
late tonight, I`m thinking we could see fluffy snowfall
accumulations of 3 to 5 inches across the western U.P. near Lake
Superior tonight, with some isolated spots possibly getting up to 6
or 7 inches. Meanwhile, over the rest of the northwest snow belts
tonight, it`s very likely (80 to 90% chance) that snowfall
accumulations will be around 2 inches or less, although a spot or
two could reach up to 3 inches. With the blustery conditions
continuing tonight, some patches of blowing snow will likely (70%
chance) be seen near the Lake Superior shoreline. Therefore, the
main hazards tonight will be slick road conditions, reduced
visibilities, and quickly accumulating snowfall at times. This could
increase accidents across the area if people don`t drive carefully.
Therefore, be sure to drive slower, use your low-beam headlights,
and give some extra space between the car in front of you and
yourself.

&&

.LONG TERM /TONIGHT THROUGH FRIDAY/...
Issued at 403 AM EDT Sat Mar 16 2024

The extended forecast period is largely dominated by a broad ridge
extending up the west coast and downstream troughing extending down
the east coast. The transition to this pattern will begin today
after this morning`s cold front. Both the ridge and trough will ebb
and flow as shortwaves ride down into the trough into next week, but
will help support cooler air over the region. In terms of sensible
weather, expecting this pattern to promote gusty winds and snow
chances into next week.

Tonight, deep cyclonic flow with increasing cold air aloft billowing
into the region will support lake effect snow showers developing and
pressing southeast into Upper Michigan. Model soundings show
inversion heights around 5k feet, some lift within the DGZ, and,
depending on the model, prolonged access to the DGZ. This, coupled
with the synoptic push provided by a shortwave rotating around a
closed low positioned near the Ontario/Quebec province line, will
further aid snow shower activity through the day Sunday. Given all
this, wouldn`t be surprised if this ends up becoming a decent lake
effect event for higher terrain areas of the western counties. ENS
and GEFS ensembles both highlight only isolated areas where exceeding
3 inches will be possible Sunday; these areas are only 20-40% and
located where terrain may help support additional lift. But over the
course of 24hrs, they highlight 50-90% chance of exceeding 3 inches.
This matches well with their deterministic counterparts and many
high res guidance packages. Opted to issue a Winter Weather Advisory
for Gogebic, Ontonagon, and northern Houghton for this. Snow totals
may end up climbing above 5 inches in Alger as well, but opted to
wait a forecast cycle and reevaluate if an Advisory was needed.
Elsewhere in the northwest wind snow belts, event totals appear more
closer to 2-4 inches, with isolated higher amounts in the Michigamme
Highlands in northeast Baraga and northwest Marquette counties.
Blustery winds will accompany the snow. Within the boundary layer,
model soundings suggest winds upwards of 35 mph will be possible.
These stronger winds will be most probable near Lake Superior, but
the deeper mixing from daytime heating could support winds of 25 mph
region-wide before waning Sunday night. Guidance suggests this lake
effect and period of gusty winds should only last through mid-
Monday, at which point brief ridging will help to quiet things.
Outside of the northwest lake effect snow belts, some flurries will
be possible, but Sunday should mostly be dry and with blustery
winds. Daytime highs Sunday and Monday appear mostly to be in the
upper 20s to low 30s. Overnight lows Sunday night will be in the
teens and low 20s.

Synoptically speaking on Monday, North America will be underneath
the ridge/trough pattern. This will position Upper Michigan within
northwest flow aloft and at the whim of any shortwave/clipper system
pressing southeast out of Canada. The first such system will dive
into the region Monday night and Tuesday. There`s some uncertainty
in where the surface feature will track and Upper Michigan`s
relative position to it. But this would be the next shot for snow.
Inverted surface trough may linger overhead into Wednesday thanks to
another punch of cold air aloft. This would extend the post system
lake enhanced/effect snow potential. Beyond this, a surface high
will track into the region, creating a mostly dry period on
Thursday, but another weak clipper system may move through Thursday
night/Friday.

&&

.AVIATION /18Z TAFS THROUGH 18Z SUNDAY/...
Issued at 123 PM EDT Sat Mar 16 2024

VFR conditions continue at KSAW through the rest of this afternoon
and into this evening as only isolated snow showers make it to the
terminal from time to time. Meanwhile, it looks like KIWD and KCMX
will be bouncing up and down between MVFR and VFR this afternoon as
a spurious low-level cloud deck traverses the area. Eventually, lake-
effect/enhanced snowfall begins to pick up over the western two TAF
sites this evening dropping conditions to solidly MVFR and
eventually IFR late tonight as the snowfall intensifies. Meanwhile,
KSAW is expected to stay VFR until late tonight/Sunday morning, when
more consistent snowfall finally reaches the terminal and drops vis
to IFR and cigs to probably (60-70% chance) MVFR. With moderate to
locally heavy snowfall being seen at times, we could see vis
reductions to LIFR and possibly (30% chance) airport mins from time
to time tonight through Sunday morning. Otherwise, expect the
blustery northwesterly winds to continue through the period. These
blustery winds could bring some patches of blowing snow to KIWD and
KCMX late tonight through Sunday morning.

&&

.MARINE...
Issued at 403 AM EDT Sat Mar 16 2024

Increasing cold air behind a cold front this morning will result in
increasing winds today. Guidance largely brings northwest winds up
to around 30kts, but model soundings highlight the boundary layer
winds potentially mixing down gales through the day. With this in
mind, no changes were made to the going Gale Warning for today.
Tonight, expecting winds to further increase to near 40 kts across
the east half of the lake. Internal probabilistic tools suggest near
100% chance of gales north and east of the Keweenaw tonight and into
Sunday evening. The same guidance suggests 25-50% chance of high end
gales.

Pressure gradient relaxes beginning Sunday afternoon, allowing for
the slow lightening of winds. By Monday morning, winds are mostly
expected to be less then 30 kts, with further weakening through the
day. Expecting these light winds to persist through Tuesday morning.
Another system moving through the region then will leave behind
another punch of colder air and tighter pressure gradient. Winds at
the moment appear close to 30kts with the strongest over the east
half through Wednesday evening.

With the higher winds and colder temperatures expected over the next
several days, we could see some moderate freezing spray late
Saturday night through Monday.

&&

.MQT WATCHES/WARNINGS/ADVISORIES...
Upper Michigan...
  Winter Weather Advisory from 8 PM EDT /7 PM CDT/ this evening
     to 2 AM EDT /1 AM CDT/ Monday for MIZ002-003-009.

Lake Superior...
  Gale Warning until 8 AM EDT /7 AM CDT/ Sunday for LSZ162.

  Gale Warning until 2 PM EDT /1 PM CDT/ Sunday for LSZ240>242-
     263.

  Gale Warning until 2 AM EDT Monday for LSZ243>251-264>267.

Lake Michigan...
  Small Craft Advisory until 8 AM EDT Monday for LMZ221-248-250.

&&

$$

SHORT TERM...TAP
LONG TERM...JTP
AVIATION...TAP
MARINE...JTP


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