Area Forecast Discussion
Issued by NWS Marquette, MI

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FXUS63 KMQT 241025

Area Forecast Discussion
National Weather Service Marquette MI
525 AM EST Thu Jan 24 2019

.SHORT TERM...(Today and tonight)
Issued at 525 AM EST THU JAN 24 2019

Quite busy early this morning, so will hit the highlights. Specifics
are available in the winter weather statement.

High impact system still on track to hit the area today and tonight.
Synoptic snow is currently moving into the western U.P. and will
continue to move E across the area. Snowfall will be enhanced near
Lake Superior where upslope and lake enhancement will occur. In
addition, a meso-low is expected to form over S-central Lake
Superior along the trough, further enhancing snow over the N-central
U.P. Through 0Z tonight, have 3-6" forecast for the enhanced areas
(highest over the higher terrain), with 2" or less elsewhere. Snow
will transitions to just NW wind snowbelts late this evening into
tonight. The most snow during the 12 hour overnight period will fall
over far eastern Marquette and much of Alger counties, where 3-6" is
forecast. Elsewhere near Lake Superior, expect 2-4" of additional

Models have slowed with the timing of the stronger winds by 3-6
hours, but strong winds are still expected near Lake Superior. Winds
will gust to 30-40mph along the lake this afternoon into tonight,
leading to widespread blowing snow and near-zero visibilities at
times in exposed areas. The greatest concern will be over the open
areas of the Keweenaw and near and east of Marquette.

Wind chills tonight will drop to -40F over far western Upper MI
tonight, with other areas of the central and western U.P. seeing -
25F to -35F. Wind chill headlines have been issued to cover the gaps
in winter storm warnings or winter weather advisories.

.LONG TERM...(Thursday night through Wednesday)
Issued at 320 PM EST WED JAN 23 2019

...Very cold with bouts of severe cold expected over the next week
along with dangerous travel conditions in the lake effect snow

Cold will lock in for the Upper Lakes for the next 7 to 10 days
under a highly amplified pattern. Strong positive height
anomalies/ridging developing over far western N America and another
strong height anomaly over the N Atlantic will force a deep mean
trough centered from Hudson Bay to the Great Lakes, a classic
pattern for cold/below normal temps, and at times, severe cold for
the Upper Lakes. Models advertise several surges of reinforcing
bitter cold air into the Upper Lakes as the mean trough sets up from
Hudson Bay to the Great Lakes. The most significant surge of cold
air will likely occur Sat night into Sunday with another one due in
next Tuesday. Once the Upper Great Lakes gets deep into the bitter
cold Arctic air mass starting Thu night, lake effect snow
accumulations will likely be limited from Fri heading into next week
as the DGZ will either be eliminated or squashed near the sfc of
Lake Superior. This will result in fine/powdery lake effect snow
that is extremely effective at reducing vsby, but does not add up to
significant accumulation (generally 1-4 inches/12 hours). Expect
near constant white-out conditions in the lake effect snow belts.
The combination of extreme cold and white-out conditions in the Lake
Superior snow belts will lead to dangerous winter weather from Thu
into much of next week. Anyone with travel plans Thu through at
least the middle of next week should be aware that travel in the
Lake Superior snow belts will be dangerous anytime winds have an
onshore component. It will be dangerously cold at times (either wind
chills or actual temperature) across all of the fcst area.

Beginning Thu night, As air mass gets increasingly colder in a NW
flow snowflake size in lake effect bands will become small and
highly effective at reducing visibility, and the snow will be easily
blown about. So even though winds will diminish later Thu night,
expect white-out/near white-out conditions to continue in the nw
flow LES bands. Conditions will be especially difficult across the
Keweenaw and between Marquette and Munising. The bitter cold will
also be a significant impact. Temps by Fri morning will be zero to
20F below with wind chills 20 below to 35 below zero. Counties not
impacted by the lake effect snow and blowing snow Thu into Thu night
will still be impacted by dangerous cold wind chills late Thu night
into Fri morning. As a result have issued an SPS for Baraga, Iron,
Dickinson, Menominee and Delta counties for late Thu into Fri to
highlight dangerously cold wind chills.

Winds will begin to back slowly Fri, aided by land breeze
components, but more so Fri night/Sat in response to next
shortwave/Arctic surge heading sse toward the Upper Lakes. As is
typical, expect a dominant w-e LES band to form on the leading edge
of the backing winds as convergence becomes focused. This band may
end up hanging up on the Keweenaw on Sat prior to the arrival of the
next shortwave/Arctic surge Sat night. LES will probably end for a
time over the eastern fcst area on Sat as winds back sufficiently to
the wsw/sw. Another blast of heavy lake enhanced snow/strong
winds/blsn will then accompany this next Arctic front off Lake
Superior Sat night. This surge of Arctic air could be the coldest
yet as the 12Z GFS and 00Z ECMWF indicate -30 to -35C 850mb temps
which would likely yield subzero highs across much of the fcst area
on Sun.

May see a fairly decent clipper shortwave round the western ridge
and track thru the mid Mississippi Valley/Great Lakes region on Mon
but this wave may be too far s of the area to have much impact other
than swinging around winds to east and confine LES to the Keweenaw.
Another Arctic shortwave may drop into the Upper Lakes Tue/Wed,
bringing another surge of bitter cold air and shifting winds back
around to the NW. This will allow fine-flaked LES to move back
onshore for much of the area and create more white-out concerns for
the NW wind snowbelts.

.AVIATION...(For the 06Z TAFS through 06Z Thursday night)
Issued at 1214 AM EST THU JAN 24 2019

Although VFR conditions are currently prevailing at KSAW,
conditions are expected to rapidly deteriorate as lake-effect
blowing snow intensifies after sunrise this morning. KCMX and KIWD
may briefly continue to bounce in and out of VFR, but overall
through the remainder of the overnight hours, expect at least MVFR
to dominate, with the occasional lake-effect snow shower
potentially dropping visbys into IFR. Similarly to KSAW,
conditions are expected to deteriorate rapidly as lake-effect
blowing snow takes hold of the northern portions of Upper
Michigan. Toward the latter portion of this TAF period, winds
should start to slacken enough to slightly improve conditions.

.MARINE...(For the 4 AM Lake Superior forecast issuance)
Issued at 525 AM EST THU JAN 24 2019

In the wake of a passing Arctic cold front, northwest to north gales
35 to 45 knots will overspread the late this afternoon into tonight.
NW gales to 35 knots are possible Sat night into Sun and again Tue
night. A bitterly cold air mass will allow for a prolonged period of
freezing spray.

Upper Michigan...
  Winter Storm Warning until 7 AM EST /6 AM CST/ Friday for MIZ002-

  Winter Storm Warning from 2 PM this afternoon to 7 PM EST Friday
     for MIZ006-007-085.

  Winter Storm Warning until 7 AM EST Friday for MIZ001-003.

  Winter Weather Advisory from 10 AM this morning to 1 AM EST
     Friday for MIZ004.

  Wind Chill Advisory from midnight EST /11 PM CST/ tonight to 1
     PM EST /noon CST/ Friday for MIZ004-010>012.

  Winter Storm Warning from 1 PM this afternoon to 7 AM EST Friday
     for MIZ005.

  Winter Weather Advisory from 2 PM this afternoon to 4 AM EST
     Friday for MIZ013-014.

Lake Superior...
  Heavy Freezing Spray Warning from 10 AM this morning to 7 PM EST
     Monday for LSZ245>251-265>267.

  Gale Warning from 10 AM this morning to 7 AM EST Friday for

  Heavy Freezing Spray Warning until 7 PM EST Monday for LSZ243-

  Heavy Freezing Spray Warning until 7 PM EST /6 PM CST/ Monday
     for LSZ162-240>242-263.

  Gale Warning until 10 PM EST /9 PM CST/ this evening for LSZ162-

Lake Michigan...
  Heavy Freezing Spray Warning from 4 PM this afternoon to 7 AM
     EST Saturday for LMZ248-250.



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