Area Forecast Discussion
Issued by NWS Marquette, MI

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000
FXUS63 KMQT 170521
AFDMQT

Area Forecast Discussion
National Weather Service Marquette MI
121 AM EDT Sun Mar 17 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, will result in some
  hazardous driving conditions.

&&

.UPDATE...
Issued at 1054 PM EDT Sat Mar 16 2024

Water vapor imagery and RAP analysis show a mid-level low centered
btwn Lake Superior and James Bay. Upper MI is firmly under the
influence of this feature with deep cyclonic flow across the area.
Deep moisture is also present across the area, including upstream
per 00z CWPL sounding. With 850mb temps continuing to fall, lake
enhanced snowfall has been increasing into Upper MI, especially in
the area btwn Painesdale and Rockland e into Baraga County and
western Marquette County. This is an area where low-level
convergence is more focused attm.

With abundant deep moisture/deep cyclonic flow and 850mb temps
continuing to fall, bottoming out at -14 to -17C on Sun, it`s a good
setup for lake enhanced snowfall thru Sun. Fairly sharp inversion
setting up at 4-5kft on Sun as seen on 00z CWPL sounding will be a
limiter with time, keeping snow accumulations from being much
higher. Given trends this evening, opted to expand advy into
southern Houghton/Baraga counties where mdt to locally hvy snow is
currently falling. Slight veering of winds should gradually shift
best convergence/heaviest snowfall to the sw during the night. To
the e, included northern Schoolcraft into the advy and bumped up
starting time of advy for Alger/northern Schoolcraft given radar
trends.

&&

.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 /SUNDAY THROUGH SATURDAY/...
Issued at 332 PM 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. Both the ridge and trough will ebb and flow as
shortwaves ride down into the trough through the first half of the
week, but will help support cooler air over the region. We finally
see an evolution in the pattern late in the week as zonal flow sets
up over the region. In terms of sensible weather, expecting this
pattern to promote gusty winds and snow chances for much of the
coming week.

Sunday, the surface low currently analyzed just south of James Bay
will be drifting over the Ontario/Quebec border. Another shortwave
rotating around this feature will drop through the Great Lakes
during the day, with another surge of synoptic forcing and CAA.
Blustery and chilly NW flow, with 850mb temperatures falling to
around -12 to -15C, will keep lake effect snow going Sunday and at
least through Sunday night in the NW wind snow belts. Model
soundings show inversion heights around 5k feet, some lift within
the DGZ, and, depending on the model, prolonged access to the DGZ.
Thus, we could be looking at fairly decent snowfall rates at times,
with the HREF generally point to snowfall rates up to a 0.25-
0.5in/hr Sunday and through the first half of Sunday night. There
are some hints at higher embedded snowfall rates up to an inch
(around a 20% chance). Ensembles continue to favor several more
inches of snow in the NW wind belts during this time, with a 50-90%
chance of exceeding another 3 inches and ensemble means showing a
widespread 3-6 inches along the wind belts of the western UP, across
the highlands of Marquette and Baraga counties, and across Alger
county. There is a small chance (20%) that some isolated areas in
the western UP, where terrain enhancement can occur, to pick up
totals in excess of 6 inches.

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. Given a dry, fluffy snow
character with SLRs closer to 20:1 looking reasonable, blowing and
drifting snow will be possible. 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.

The heaviest of the LES tapers off through the second half of Sunday
night as soundings begin to dry out and inversion heights lower.
Weak surface ridging into Monday will see winds backing more W/SW,
and with drier air working in, LES should wrap up entirely over most
of the area. However, through the first half of the week, Upper
Michigan remains 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 apart from lingering LES potential across the
eastern UP. Friday into the weekend, we will generally be under
zonal flow aloft with a closed upper low centered over northern
Ontario. This will continue to leave us sensitive to hit and miss
snow chances as poorly-timed shortwaves rotate around this.

&&

.AVIATION /06Z TAFS THROUGH 06Z MONDAY/...
Issued at 121 AM EDT Sun Mar 17 2024

An increasingly favorable lake enhanced snow regime will be setting
up off of Lake Superior thru this aftn under nw to nnw low-level
winds. At IWD, expect varying MVFR and IFR to become prevailing IFR
overnight thru today. Some brief periods of LIFR will be possible
late in the night thru at least the morning hrs. Improvement to MVFR
may occur at IWD this evening. At CMX, expect varying MVFR and IFR
to become prevailing IFR overnight thru this aftn. Some periods of
LIFR will be possible at times late in the night thru this aftn.
Expect improvement to MVFR this evening at CMX. At SAW, expect
fluctuations btwn MVFR and VFR overnight, then prevailing MVFR for
today though some brief IFR will be possible. A slight veering of
winds this evening should bring somewhat heavier shsn to SAW,
dropping conditions to IFR. Expect gusty winds to 20-35kt at all
terminals throughout this fcst period with the stronger gusts at
CMX.

&&

.MARINE...
Issued at 332 PM EDT Sat Mar 16 2024

Colder air moving into the region is leading to blustery WNW winds
this afternoon, with gales to 35 knots mainly across the central and
eastern portions of the lake so far.  Tonight, expecting winds to
further increase to near 40 kts across the east half of the lake
while turning more to the NW. The strongest gusts will be along and
east of a line from Passage Island, to Copper Harbor, to Marquette.
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 north of the
Keweenaw.

Pressure gradient relaxes beginning Sunday afternoon, allowing for
the slow lightening of winds with gales falling off Sunday night. 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. A
few gale force gusts are not out of the question. Winds decrease
Wednesday night, coming in at or below 20 knots the rest of the
week.

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

&&

.MQT WATCHES/WARNINGS/ADVISORIES...
Upper Michigan...
  Winter Weather Advisory until 2 AM EDT /1 AM CDT/ Monday for
     MIZ002>004-006-009-084-085.

Lake Superior...
  Gale Warning until 2 PM EDT /1 PM CDT/ this afternoon for
     LSZ240>242-263.

  Small Craft Advisory from 2 PM EDT /1 PM CDT/ this afternoon
     to 11 AM EDT /10 AM CDT/ Monday for LSZ240>242.

  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.

&&

$$

UPDATE...Rolfson
SHORT TERM...TAP
LONG TERM...LC
AVIATION...Rolfson
MARINE...LC


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