Area Forecast Discussion
Issued by NWS Marquette, MI

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FXUS63 KMQT 121158

Area Forecast Discussion
National Weather Service Marquette MI
658 AM EST Mon Feb 12 2018

.SHORT TERM...(Today and tonight)
Issued at 502 AM EST MON FEB 12 2018

WV imagery and RAP analysis indicated a trough from ne Canada and
Hudson Bay into the nrn Great Lakes resulting wrly mid/upper level
flow through the region. At the surface, a ridge of arctic high
pressure extended from Saskatchewan and Manitoba into the nrn plains
and Mississippi valley. Despite the extensive ice cover on Lake
Superior, there were enough gaps so that low level wnw flow with 850
mb temps to around -22C has produced several stronger LES bands into
the ern cwa, especially around Munising where web cams showed
several inches of accumulation. The shorter fetch over wrn Lake
Superior and more solid ice cover has limited the LES to mainly
flurries into the west half of the cwa.

Today, as the sfc ridge builds into the area with backing winds and
falling inversion heights, the remaining LES should steadily
diminish. Another inch or two may be possible early today from P53
eastward before the bands shift position/offshore and weaken.
Otherwise, even with another day with plenty of sunshine, temps will
remain below normal with highs to around 10 west and 15, central and

Tonight, favorable radiational cooling conditions this evening will
allow temps to drop to around -10 inland, toward the lower end of
guidance, before increasing clouds and weak WAA result in rising
temps late.

.LONG TERM...(Tuesday through Sunday)
Issued at 417 AM EST MON FEB 12 2018

No major weather impacts expected through the extended with
occasional light snow chances and generally near to below normal
temperatures expected. There will be a couple a brief periods of
near to above normal as well for the middle of the week and toward
the end of next weekend.

Tuesday night through Wednesday night: The upper level trough will
continue to flatten through this time period as southerly flow kicks
up ahead of a cold front approaching from Ontario. This will allow
850mb temperatures to warm to around +4C to +6C by Wednesday
afternoon. This, along with partly cloudy skies, will allow daytime
highs to warm above average briefly, with many locations expected to
reach the the upper 30s to low 40s. There is a shortwave progged to
slide through the area Wednesday, but soundings are very dry,
keeping a precip chance to a minimum. Late Wednesday night, the cold
front will approach the U.P. from the northwest. Most locations will
remain dry through this time period with the only noticeable changes
being a shift in winds to the north and increasing cloud cover.

Thursday and Friday: Increasingly colder air to near -20C is
expected to move across the Upper Great Lakes by Thursday night in
the wake of Wednesday night/Thursday morning`s frontal passage. This
will for better chances for nw flow lake effect snow especially late
Thursday into Thursday night. However, extensive ice cover on Lake
Superior and large scale anticyclonic flow should keep snow
accumulation light. The eastern U.P. would have the better chances
as it looks like there is still an decent area of open water. Flow
backing west by Friday afternoon will confine any additional lake
effect accumulation to the Keweenaw.

The rest of the extended: At this point, will stick with a consensus
of the models through this time period, which shows fairly steady
troughing over the eastern CONUS into the first part of the weekend.
This will bring occasional waves through the area, giving
intermittent light snow showers. This would also support continued
below normal temperatures for that time period. Models diverge on
the track of an approaching system for the last half of next weekend
into early next week; however, they do have a trend of keeping the
system just west of the U.P. If that does occur this would lend
support to warmer southerly flow into the area, with temperatures
possibly warming to above normal again late in the weekend into the
next week.

.AVIATION...(For the 12Z TAFS through 12Z Tuesday morning)
Issued at 657 AM EST MON FEB 12 2018

Lake effect cloud MVFR cigs and a few snow showers at KIWD and
KCMX will give way to clearing this morning with VFR conditions by
mid to late morning. Otherwise, VFR conditions will prevail
through the rest of the forecast period.

.MARINE...(For the 4 AM Lake Superior forecast issuance)
Issued at 502 AM EST MON FEB 12 2018

A period of wnw to nw gales to 350 knots is expected early today t
over the eastern lake. Southwest gales are possible Tuesday
afternoon into Tuesday night across central and eastern Lake
Superior. These will be the strongest winds for this forecast period.

Upper Michigan...
Lake Superior...
  Heavy Freezing Spray Warning until 7 AM EST this morning for

  Gale Warning until 7 AM EST this morning for LSZ266-267.

Lake Michigan...


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