Area Forecast Discussion
Issued by NWS Marquette, MI

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FXUS63 KMQT 132000

Area Forecast Discussion
National Weather Service Marquette MI
300 PM EST Sat Jan 13 2018

.SHORT TERM...(This evening through Sunday)
Issued at 258 PM EST SAT JAN 13 2018

...Bitter temps expected for parts of Upper Michigan tonight...

Generally quiet in the short term, but that changes just beyond the
short term. Continue to see shallow lake effect with inversions no
higher than 3kft affecting northwest wind snow belts. The light lake
effect (mainly leading to brief reduction to vsby) will diminish
from west to east by the early overnight hours. Attn then turns to
min temps away from the lake effect areas. Setup is quite favorable
for temps this evening to quickly plummet with light winds, clear
skies and very dry airmass tied to high pressure ridge moving from
the Upper Mississippi River valley to the Ohio Valley. Shortwave
over northern Alberta and Saskatchewan moving toward Upper Great
Lakes on Sunday will spread high clouds over western U.P late
tonight, but don`t think it will impact low temps too much.

For min temps tonight favored blend of already cold official grids,
guidance that performed well with last couple of widespread cold
nights with similar expected lows (1 and 6 January) and the usually
superior GEM-bias corrected guidance. Overall, expect favored cold
spots over interior west to drop to at least 20 below and maybe even
near 30 below as occurred this morning over parts of Minnesota.
Favored cold spots interior east should drop to 10-20 below.
Light winds late tonight into Sunday morning should limit wind
chill issues, though as winds kick up on Sunday morning ahead of
approaching shortwave/low pressure system, could see wind chills
near criteria for a few hours over west. With the light winds
though did not do wind chill advisory attm. Soundings indicate a
lot of low level dry air to overcome initially on Sunday, but will
see thickening mid clouds through the day. Should be enough
saturation with incoming shortwave and moisture advection to allow
for some light snow to develop late day over the west. Also,
winds backing southwest ahead of the system will result in lake
effect currently affecting northern lower Michigan to quickly
expand into far eastern forecast area to east of Manistique by
sunset. This will just be the beginnings of possible moderate to
heavy snow off Lk Michigan for parts of south and east forecast
area Sunday night into Monday.

.LONG TERM...(Sunday through Friday)
Issued at 505 AM EST SAT JAN 13 2018

...Moderate to heavy lake effect/enhanced snowfall potential Sunday
night through Tuesday...

Sunday through Monday: Fairly dry air will remain in place across
much of the Upper Peninsula throughout the day Sunday limiting any
lake effect snow potential will remain over Lake Superior. By late
Sunday afternoon/Sunday evening, a shortwave and associated surface
low will approach from the west. This will allow increased moisture
to flow into the area on southerly flow. The system forcing will
allow widespread light to moderate snow to spread across much of the
U.P. Sunday night into Monday. Models are generally showing around
0.05 - 0.10 inches of QPF for much of the area, which would equate
to roughly 1 to 3 inches of snow for most locations. The locations
that would have the better chance of seeing heavier snowfall would
be over the eastern U.P. downwind of Lake Michigan. 850mb
temperatures are expected to be in the -15C to -17C range with
fairly uniform southerly flow. Inversion heights are progged to be
around 10kft Sunday night into Monday with a significant portion of
the moisture/forcing/instability in the DGZ. This will increase snow
to liquid ratios over those areas along with higher QPF totals due
to the increased fetch across Lake Michigan. Totals Sunday night
through Monday over those area will likely approach or exceed 10
inches for portions of Delta and Schoolcraft Counties. This would
likely the cause the Monday morning commute to be difficult at
times. The aforementioned counties will need a winter
headline...possibly approaching warning criteria Sunday night into

Monday night into Tuesday: The surface low will shift to the south
and east of the area as the upper level trough axis slides directly
overhead. This will allow winds to become more east to northeasterly
Monday night and then more north to northwesterly through the day
Tuesday. 850mb temperatures will cool to around -20C through this
time period, which is more than adequate for lake effect/enhanced
snow. This will allow for a period of at least moderate lake effect
snow, heaviest over the higher terrain north central and over the
Keweenaw down to near Ironwood. Additional snowfall totals during
that time period will generally be in the 5 to 10 inch range with a
few localized total near or over a foot. Exact locations will need
to be pinned down as models become more in line with wind direction
and this time period approaches. A winter headline will likely be
needed for locations downwind of Lake Superior for this time period.

Wednesday through the rest of the extended: Quieter weather is
expected for this time period with slowly warming temperatures and
mainly dry conditions expected as zonal to weak ridging builds in
aloft. There may be a system toward the end of the extended, but
models differ on solutions that far out, which is common. At this
point will stick with a blend of the models for this time period.

.AVIATION...(For the 18Z TAFS through 18Z Sunday afternoon)
Issued at 1242 PM EST SAT JAN 13 2018

Lake effect will continue at KCMX into this evening with IFR to MVFR
conditions. Late tonight conditions will become VFR as lake effect
moves north of the terminal. VFR flying conditions at KIWD and KSAW
through the period with increasing mid clouds late tonight and
Sunday morning. Conditions deteriorate late Sunday into Sunday night
at all terminals as low pressure system with snow crosses the region.

.MARINE...(For the 4 PM Lake Superior forecast issuance)
Issued at 253 PM EST SAT JAN 13 2018

Closing out the 2017 shipping season with strong winds to 30 kts
tonight through Monday. Could see a few south gale gusts to 35 kts
over eastern portions of Lk Superior late Sunday afternoon into
Sunday evening. Heavy freezing spray should be limited to early this
evening over east half, but otherwise expect only moderate freezing
spray through late Monday evening when the Sault locks close for
annual winter maintenance. Could be more heavy freezing spray
later Monday night into Tuesday and again on Wednesday. Expect
winds of 20 to 30 kts for rest of the week with potential for
west gales on Wed.

Upper Michigan...
Lake Superior...
  Heavy Freezing Spray Warning until 7 PM EST this evening for

Lake Michigan...


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