Area Forecast Discussion
Issued by NWS Marquette, MI

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FXUS63 KMQT 131007

Area Forecast Discussion
National Weather Service Marquette MI
507 AM EST Sat Jan 13 2018

.SHORT TERM...(Today and tonight)
Issued at 505 AM EST SAT JAN 13 2018

Light lake effect snow and low temps/wind chills are the focus in
the short term.

Light NW wind lake effect will continue today. Even though the
intensity will be light for the most part, low snow to liquid ratios
will promote visibility reductions to a half mile or less at times,
mainly E of Marquette. Could see 1-4 inches over the eastern U.P.
snowbelts and up to 2 inches over the western U.P. snowbelts.

For tonight, a ridge will move in, promoting lake effect to shift N
through the night. This will mainly focus snow into the Keweenaw and
NE. Expect generally 1-3 inches in these areas. Overnight lows will
be in the -15F to -25F range over the interior W half. Winds will be
light, but could still see some wind chills to -30 if even a light
breeze is observed. Will let the day shift determine if any
headlines are needed.

.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 06Z TAFS through 06Z Saturday night)
Issued at 1247 AM EST SAT JAN 13 2018

Light to sometimes moderate lake effect snow in a northwest flow
will continue through the period at KCMX and through Sat morning at
KIWD. Backing flow should allow for clearing skies and VFR
conditions at KIWD by Sat afternoon. At KSAW, northwest flow could
result in periods of MVFR to low VFR clouds but generally expect
little to no snow. Though the LES will not be heavy, small snowflake
sizes should be effective at reducing visibility with IFR conditions
at KCMX and KIWD into Saturday morning.

.MARINE...(For the 4 AM Lake Superior forecast issuance)
Issued at 505 AM EST SAT JAN 13 2018

Heavy freezing spray will continue today over portions of the east
half of Lake Superior. Could see some gales to 35 knots for portions
of the lake late Sun into Sun night, late Mon into Mon night, and
again in the middle of next week. Otherwise, no gales are expected.

Upper Michigan...
Lake Superior...
  Heavy Freezing Spray Warning until 10 AM EST this morning for

  Heavy Freezing Spray Warning until 7 PM EST this evening for

Lake Michigan...


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