Area Forecast Discussion
Issued by NWS Marquette, MI

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FXUS63 KMQT 230946

Area Forecast Discussion
National Weather Service Marquette MI
446 AM EST Mon Jan 23 2017

Issued at 1130 PM EST SUN JAN 22 2017

Although conditions remain favorable for the development of some
dense fog, many obs sites showed improving vsbys well above 1/4SM.
So canx the dense fog advy. Issued an SPS to indicate the
potential for some locally dense fog that wl persist into mid to
late mrng on Mon.

.SHORT TERM...(This evening through Monday)
Issued at 257 PM EST SUN JAN 22 2017

Sheared out shortwave over Upper Michigan and Lake Superior along
with sfc low over northern Lk Superior has brought isold light rain
showers and drizzle to a few areas of cwa today. Otherwise, the low
clouds and fog continue. The fog is not as widespread as it was this
time 24 hr ago possibly due to weak westerly flow on southern edge
of the low. Some areas do continue to see dense fog with much of
Keweenaw seeing vsby 1/4sm much of day and also over eastern U.P.
Shortwave trough weak as it is could still keep some light showers
or drizzle going tonight especially across the east cwa. Only light
precip expected but with temps falling to the lower 30s, there could
be some icy spots on untreated roads, sidewalks and parking lots. As
for the fog plan for areas of dense fog but not sure if it will be
as widespread as last night. Winds will be light but visible
satellite shows scattered to broken high clouds upstream which could
move across and disrupt radiational cooling potential at top of low
cloud deck in place. Issued a Special Weather Statement highlighting
areas of dense fog and possible black ice due to lingering moisture
and drizzle. Did not issue dense fog advy though based on concerns
of how widespread dense fog tonight will be. Later shifts can issue
if needed.

On Mon, shortwave over central Plains lifts toward the region. Rain
could become more widespread over eastern cwa as the forcing arrives
and since that area is in area of greater moisture aloft h7-h5.
Elsewhere drizzle would be the main ptype and best chance of that
would be near Lk Superior as winds become more northerly through the
day. Fog will gradually diminish but could hang on into the aftn
over the north closer to Lk Superior with onshore upslope flow (as
is occurring today over the Keweenaw Peninsula).

.LONG TERM...(Tuesday through Sunday)
Issued at 446 AM EST MON JAN 23 2017

Main stories in the long term are mid-week snow and colder air that
will bring the return of LES.

A shortwave will move south of the area Tue night and Wed, which
will bring snow to portions or all of the CWA. Exact track remains
uncertain, as a couple models are taking it farther south which
would mean parts or even much of the area would be dry (or possible
some drizzle/freezing drizzle). Current thinking is that 2-4 inches
of snow will fall 00Z Wed to 00Z Thu, with potential for higher and
lower amounts depending on track.

Major pattern change starts mid-week as the upper trough shifts E
across the country, settling over the eastern half of the CONUS by
the weekend. Colder air will promote LES in N-NW wind snowbelts
during this time, but potential for moderate to heavy LES will not
exist until the colder air (850mb temps down to -18C) move in. LES
may end on Mon as winds turn SW ahead of a potential low pressure

.AVIATION...(For the 00Z TAFS through 00Z Monday evening)
Issued at 624 PM EST SUN JAN 22 2017

With lingering llvl mstr over melting sn pack and light winds,
expect some dense fog with LIFR/VLIFR conditions to predominate
until mid/late Mon mrng. While there is likely to be improvement in
vsby on Mon into perhaps the MVFR category, lo cigs in the LIFR to
IFR range wl linger.

.MARINE...(For the 4 PM Lake Superior forecast issuance)
Issued at 257 PM EST SUN JAN 22 2017

A relatively weak pressure gradient over the Upper Great Lakes in
the absence of any strong weather systems will continue to result in
winds under 20 kts over Lake Superior most of the time into Mon and
Tue. Expect N to NW winds to 25 kts late Wed through the end of the
week as low pressure over the central Plains moves toward eastern
Canada and colder air returns to the Lk Superior region.

Upper Michigan...
Lake Superior...
Lake Michigan...
  Dense Fog Advisory until 1 PM EST this afternoon for LMZ248-250.



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