139
FXUS63 KMQT 042352
AFDMQT

Area Forecast Discussion
National Weather Service Marquette MI
652 PM EST Wed Dec 4 2024

.KEY MESSAGES...

- Heavy lake effect snow bands will continue in the northwest
  belts this afternoon, shifting to the northerly belts late
  tonight into Thursday. The combination of heavy snow and
  blowing snow will lead to dangerous travel conditions and
  near-zero visibility in heavy snow bands. Winter Storm
  Warnings and Winter Weather Advisories are in effect.

- Blustery north-northwest winds, gusting up to 30-45 mph are
  expected this evening into Thursday morning, especially near
  Lake Superior and in the Keweenaw. During this period, wind
  chills drop to near or just below zero for much of the central
  and west.

- Storms to 50 knots develop across the entire lake this
  afternoon through Thursday morning.

&&

.SHORT TERM /THROUGH TONIGHT/...
Issued at 248 PM EST Wed Dec 4 2024

RAP Analysis shows a closed 500mb low over northwest Ontario
embedded within large-scale troughing over eastern North America,
contrasted with ridging over the Pacific Northwest. This translates
at the surface to a 992mb clipper low just northeast of Lake
Superior and a 1035mb high over Saskatchewan. This is leading to a
tight pressure gradient forming, with 995mb over Sault Ste Marie and
1007mb over Duluth and tightening. Gales are already being observed
at the West Superior Buoy and the Rock of Ages Lighthouse near Isle
Royale. These winds will continue to build throughout the evening,
with the Euro ensemble showing over 60% probabilities of 50+ kt
gusts over much of Lake Superior tonight. This in conjunction with
the snowfall will lead to blowing snow threats especially near the
Lake Superior lakeshore, but also could penetrate further inland
(20%), reducing visibility and causing drifting snow on roadways.

Northwest to southeast bands of snowfall are beginning to set up as
shown on the KMQT radar. At 19Z, the cold front from the clipper low
was draped across Luce and Schoolcraft County, with winds continuing
to veer northwesterly and eventually northerly as the low pushes
east. Snowfall rates will be quite variable with this system, with
HREF probabilities of 1"/hr rates only locally 10-30% until around
07Z Thursday, when a subtle shortwave will provide further lift and
bring over 50% probabilities of 1"/hr snowfall rates over much of
the north-facing terrain aligned near Lake Superior before coming
back to lesser rates by 12Z. 6-hourly PMM QPF is between 0.1 and
0.25 inches throughout tonight, combining with snow ratios in the
upper teens to 1 will lead to snow totals in the 2-6 inch range
except for lower in the south-central and higher in local areas of
high terrain where snow totals could (25%) eclipse 8 inches.

&&

.LONG TERM /THURSDAY THROUGH WEDNESDAY/...
Issued at 333 PM EST Wed Dec 4 2024

By Thursday morning, the upper level wave will have translated
southeast into the lower Great Lakes, continuing strong northerly
CAA over Lake Superior. 850mb temps near -16 to -13C atop Lake
Superior surface temperatures averaging ~6C will create delta-T
values upwards of 20C and lake induced ELs near 5-7k ft, possibly
upwards of 10k ft in connection with Lake Nipigon preconditioning
and convergence banding. This will continue strong LES showers as
winds veer to the north wind snowbelts late Wednesday night into
Thursday morning. Combined with gusts upwards of 45-50 mph, the
morning commute could be quite dangerous, especially near the
lakeshores where visibility will drop to near zero under the
heaviest snowbands. The current CAM suite has a solid handle on a
heavy Nipigon connection band meandering eastward from the Keweenaw
into Marquette county between 15 to 18z. Under this band, snowfall
rates could push easily 1-1.5 in/hr (per 12z HREF).

Meanwhile, 1038mb high pressure descends southward into the High
Plains, nudging into western Lake Superior late Thursday afternoon.
With this, dry air will work to lower inversion heights from west to
east through Thursday evening. Winds will begin to lessen as the
parent low pressure continues departing east, reducing the blowing
snow threat across much of the central UP. Flow over Lake Superior
backs to the northwest, refocusing heaviest snowbands over the east
half of the UP through the evening. Come Friday morning, snow
accumulations across the central north snowbelts could reach 6-10
inches with isolated areas close to a foot where dominant snowbands
have the longest residence time. Given the blustery northerly
winds, lake effect snow is likely to reach portions of the
southern UP, reaching portions of Menominee county where 1-2
inches is possible.

A weak mid-level clipper within broad northwest flow aloft
turns winds back out of the west Friday, supporting a brief
period of west/nw lake effect snow where a few inches could
accumulate in the far east and Keweenaw.

Looking ahead, there is a brief pattern shift on Saturday to
quasi- zonal flow for Sunday into Monday with WAA throughout
brings a brief warm up to the region. Highs Saturday - Monday
increase to the 30s, potentially reaching 40 inland with lows
mainly in the 20s. Ensemble spread is still significant Sunday
into next week, but the active period is progged to continue
with multiple systems quickly moving into the Great Lakes
region. A return of some rain to the central and eastern UP is
possible with the early next week system before a colder airmass
returns.

&&

.AVIATION /00Z TAFS THROUGH 00Z FRIDAY/...
Issued at 630 PM EST Wed Dec 4 2024

Expect deteriorating conditions at all 3 TAF sites tonight in
lake effect snow and considerable blowing snow from n-nw winds
gusting to 35 knots or higher at times. Prevailing IFR to LIFR
flight conditions could at times be reduced to airport minimum
visibility in snow and blowing snow at CMX and possibly at SAW
later tonight. Look for improvement to MVFR conditions at IWD
and CMX by Thursday late morning/early afternoon as ridging and
drier air from the west begin to taper off the snow and winds
weaken, slightly reducing the blowing snow. Improvement to MVFR
will be delayed until probably mid to late Thursday afternoon
at KSAW as winds weaken and back more to the nw.

&&

.MARINE...
Issued at 333 PM EST Wed Dec 4 2024

A clipper low pressure northeast of Lake Superior is marching a cold
front across the east half of the lake this afternoon. Behind the
cold front northwest gales will increase to northerly storm force
gusts 45 to 50 knots across portions of the west lake and
further into the central and east-central lake overnight into
Thursday morning. Waves continue to build up to 10-16 ft. Wave
heights over the west hold steady tonight and increase up to
15-20 ft over the east by Thursday morning. Highest waves are
expected between Stannard Rock, Marquette, and Grand Marais.
Waves then fall below 4 ft in the west Thursday evening and
Friday morning in the east. Across the lake, waves between 3-6
ft are expected on Friday. Waves then remain at or below 4 ft
the rest of the weekend. With the cold airmass surging in
tonight and increasing wave heights, some freezing spray is
expected. The main area of concern for freezing spray is the
west half of the lake this afternoon through tonight. Storm
force gusts slacken to northwest gales Thursday afternoon,
weakening below 35 knots by 18z Thursday, and further below 25
knots through the evening into early Friday.

&&

.MQT WATCHES/WARNINGS/ADVISORIES...
Upper Michigan...
  Winter Storm Warning until 1 PM EST /noon CST/ Thursday for
     MIZ001-003-010-013.

  Winter Storm Warning until 7 AM EST /6 AM CST/ Thursday for
     MIZ002-004-009-084.

  Winter Storm Warning until 7 PM EST Thursday for MIZ005>007-
     014-085.

  Lakeshore Flood Advisory from 3 AM to 1 PM EST Thursday for
     MIZ005-006.

  Winter Weather Advisory until noon CST Thursday for MIZ011.

Lake Superior...
  Gale Warning until 1 PM EST Thursday for LSZ251-267.

  Storm Warning until 4 AM EST /3 AM CST/ Thursday for LSZ162-
     241-242-263.

  Heavy Freezing Spray Warning until 7 AM EST /6 AM CST/
     Thursday for LSZ162-240>244-263-264.

  Gale Warning until 7 AM EST /6 AM CST/ Thursday for LSZ240.

  Gale Warning until 7 PM EST this evening for LSZ243>245-249-
     250-264>266.

  Storm Warning until 7 AM EST Thursday for LSZ243>245-249-250-
     264>266.

  Heavy Freezing Spray Warning until 7 AM EST Thursday for
     LSZ245>248-265-266.

  Gale Warning until noon EST Thursday for LSZ246>248.

Lake Michigan...
  Gale Warning until 1 PM EST Thursday for LMZ221-248-250.

&&

$$

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