Area Forecast Discussion
Issued by NWS Marquette, MI

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FXUS63 KMQT 130549

Area Forecast Discussion
National Weather Service Marquette MI
1249 AM EST Sat Jan 13 2018

.SHORT TERM...(This evening through Saturday)
Issued at 324 PM EST FRI JAN 12 2018

Light to occasionally moderate lake effect snow will continue for
the NW/WNW wind snow belts through Saturday. Colder and drier air
combined with low inversion heights at or below 4kft have resulted
in small snowflake sizes today. Though snow amounts have been low,
the combination of the small flakes and gusts to 20kts has resulted
in visibility as low as 1/2mi in some of the snow bands. Though LES
intensity should wane into early evening, a mid-level trough
crossing the area tonight will reinvigorate LES overnight into
Saturday morning. Again, conditions are favorable for small
snowflakes sizes and resultant low visibilities from time to time.

Elsewhere, mostly clear to partly cloudy skies are expected with
unseasonably cold conditions. Wherever enough clearing and boundary
layer decoupling occurs tonight, temps should drop into the -10 to -
15F range. Wind chills across the interior west will teeter on the
-25F advisory threshold overnight into early Saturday morning.
However, any stronger winds should be associated with less
decoupling and therefore higher temperatures.

.LONG TERM...(Saturday night through Friday)
Issued at 253 PM EST FRI JAN 12 2018

...Heavy lake enhanced snow possible Sunday night through Tuesday...

Broad upper level trough and cold air remains entrenched over much
of the eastern Conus through the long term. Indications from medium
range models and GFS/ECMWF ensembles and CFS climate model point to
a warmer period trying to develop starting about a week from now but
there are mixed signals in how long that would last. Larger scale
global pattern would point to longer duration warm up for the last
portion of January though, so stay tuned.

Multiple rounds of potentially hazardous winter weather to get
through before the warm up arrives though. Light lake effect with
some visibility reduction expected into Saturday night for snow
belts east of Marquette and on Keweenaw. Sfc ridge dropping toward
the middle mississippi river valley Sat night backs winds to SW over
interior west, so it could get very cold for favored interior cold
spots away from lingering lake effect clouds. Will continue to point
min temps as low as 20 to 25 below for early Sunday morning.

Attention later Sunday and into Sunday night then turns to moderate
to heavy lake enhanced snow off Lake Michigan. Strong shortwave
trough/deep layer q-vector convergence and deep moisture and sfc
trough will bring widespread snow across Upper Great Lakes Sunday
night into Monday morning. Since the system lasts well into Monday
could see at least a few inches of snow even where there is no lake
enhancement, including along the Wisconsin state line. WPC guidance
suggests even widespread advisory amounts could occur. Not sure on
that though higher SLRs around 20:1 would help the cause. S-SE sfc
flow ahead of the sfc trough and SW flow at H85 with H85 temps
around -15c should support lake enhanced snow anywhere from Delta
county to Luce county. Heaviest snow would occur late Sunday evening
through Monday morning. Due to the system snow and lake enhancement
could be higher impact for the south central and southeast U.P. for
the morning commute on Monday morning. Cyclonic flow wrapping
around the sfc trough will also result in moderate to heavy lake
enhanced snow for north and northeast wind snow belts near Lake
Superior later Monday through Tuesday. Forecast soundings in BUFKIT
indicate areas expecting lake enhanced snow (both near Lake
Michigan and Lake Superior) will see inversions of 8-11 kft with
delta t/s pushing over 20C and a lot of DGZ in play throughout. As
previous shifts have been highlighting, there is high confidence
in many lake effect areas ending up with significant snow amounts
in the Sunday night through Tuesday morning period. Still a bit
too far out to go with any headlines but could see those going up
in the next day or two. Will continue to message this lake
enhanced snow event in Hazardous Weather Outlook and social media.

Large scale support for snow wanes later Tuesday into Tuesday
evening so heavier LES will diminish by that time. Into Wednesday,
winds continue to back to W or SW and the warm air advection ramps
up with H85 temps rising from near -20C at 00z Wednesday to warmer
than -5C by time 12z Thursday rolls around. May even be able to
sneak some sunshine in there late in the week to take advantage of
these warming temps aloft. Also some hints in latest guidance that
even as upper level flow becomes more zonal later next week a quick
moving smaller system could bring wintry mix or snow sometime
Thursday into Friday. Overall though it looks like a much quieter
and warmer end to next week compared to the beginning of the week.

.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 PM Lake Superior forecast issuance)
Issued at 324 PM EST FRI JAN 12 2018

WNW to W winds of 20 to 30 knots are expected across much of the
lake through tonight. A few gale gusts to 35 knots cannot be ruled
out over the east half of the lake in the evening as a trough
crosses the region. Also, heavy freezing spray should continue into
Saturday morning for much of the east half of Lake Superior. Winds
under 25 knots Saturday and Saturday night will give way to 20-30
knots SW winds Sunday into Sunday night. A cold will then usher in
NW winds to 30 knots with possibly some gales to 35 knots Monday
afternoon into Tuesday.

Upper Michigan...
Lake Superior...
  Heavy Freezing Spray Warning until 6 AM EST early this morning
     for LSZ244-245-248>251-264>267.

Lake Michigan...


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