Area Forecast Discussion
Issued by NWS Marquette, MI

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FXUS63 KMQT 221958

Area Forecast Discussion
National Weather Service Marquette MI
258 PM EST Sun Jan 22 2017

.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...(Monday through Saturday)
Issued at 343 AM EST SUN JAN 22 2017

A shortwave moving through from the south late Mon into Mon night
will lead to a fairly narrow band of precip over eastern Upper MI
Mon afternoon into Mon night. Precip should start as rain then
gradually transition to snow, with a wintry mix in between. Tricky
event as exact placement of the narrow band is in question, as are
QPF amounts and ptype. Depending on these factors, could see low end
advisory level impacts, but it remains too uncertain to get that
specific at this point.

Next system to move through will be on the leading edge of a big
pattern change. A shortwave will move through the area as upper
toughing shifts from the western CONUS to the eastern CONUS. The
shortwave is currently off the Pacific Coast, so there is quite a
bit of uncertainty. As the shortwave passes, if it move farther
north like the GFS and ECMWF suggest, snow will move in from the SW
late Tue and continue into Thu before transitioning to LES with the
colder air that moves in. The NAM and GEM are farther S and leave
the CWA dry for the most part. Let the blends handle most details
with this system, which is currently forecast to bring 1-2 inches of
snow to the U.P.

More normal conditions with cooler temps and NW wind LES are then
expected through the rest of the week. Even so, 850mb temps will not
be all that cold, so LES is not expected to be heavy in most areas.
Blends handled the extended quite well, so made few changes.

.AVIATION...(For the 18Z TAFS through 18Z Monday afternoon)
Issued at 1240 PM EST SUN JAN 22 2017

Persistence is way to take this forecast. Fog and low clouds for
last couple days continues at IWD and CMX. Though vsby may come up
to 1/2sm or 1sm briefly this aftn, expect VLIFR conditions near
airport mins through end of TAF period. Meanwhile, improvement late
last night at SAW due to light mixing has continued into midday.
Expect mainly MVFR conditions at SAW to deteriorate to LIFR
this evening. Conditions may even try to fall toward airport
minimums late tonight into Mon morning. No significant improvement
is expected at any of the TAF sites even into Mon aftn as
stagnant weather pattern continues.

.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 Monday for LMZ248-250.



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