Area Forecast Discussion
Issued by NWS Marquette, MI

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FXUS63 KMQT 210744

Area Forecast Discussion
National Weather Service Marquette MI
244 AM EST Wed Feb 21 2018

.SHORT TERM...(This evening through Wednesday)
Issued at 309 PM EST TUE FEB 20 2018

Low pressure tracked across central and western Upper Michigan this
afternoon bringing widespread impacts to roadways as a wintry mix of
sleet, freezing rain, and snow lifted northeast across central and
eastern Upper Michigan earlier today. Across the western half of
Upper Michigan, snow transitioned to freezing rain, and eventually
freezing drizzle through the early/mid morning hours.

Tonight as the main surface low continues to lift northeast, exiting
the region, colder air behind the system will begin to filter into
the region. This will allow lingering light freezing drizzle to
transition over to light lake effect snow, mainly across the
Keweenaw Peninsula. As this colder air mass begins to track eastward
tonight, a few models show subtle hints of a narrow band of snow
developing along the weak cold front. Confidence was not high enough
to include mentions of this additional snow associated with this
front any further east than the north central, but we should start
to see any lingering fog and/or light freezing drizzle dissipate as
this colder and drier air works in from the west. As an enhanced
surface pressure gradient pushes eastward across Upper Michigan
behind the exiting system, this coupled with pressure rises, will
also allow for breezy westerly winds to develop overnight.

Lingering light lake effect snow across the west will diminish
through the early/mid morning hours as surface ridging begins to
work into the region. Cloud cover will gradually diminish away from
Lake Superior during the day on Wednesday, but expect at least some
diurnal cumulus to develop during the afternoon given the colder air
aloft and increasing insolation. The colder air progged to be in
place tomorrow will knock temperatures down about ten degrees
compared to today`s high temperatures.

.LONG TERM...(Thursday through Tuesday)
Issued at 244 AM EST WED FEB 21 2018

Nam shows a 500 mb trough in the western U.S. with a ridge in the
sern U.S. 12z Thu. A shortwave ejects out of this trough and heads
northeast towards the upper Great Lakes 12z Fri. The trough moves
moves into the Rockies and northern plains 12z Sat. Nam brings in
some deeper moisture and 850-500 mb q-vector convergence late Thu
night and both move out late Fri morning. Still looks like there
could be a wintry mix of pcpn on Fri morning with the highest pops
then. Overall, did not make too many changes to the going forecast.

In the extended, GFS and ECMWF show a 500 mb trough in the Rockies
and northern plains 12z Sat. This trough heads northeast into the
upper Great Lakes 12z Sun. 18z GFS has a 971 mb low near the U.P.
while the 00z GFS run has a 976 mb low 12z Sun. The 12z ECMWF has a
weaker low of 1004 mb 12z Sun. More upper troughing moves in for 12z
Mon. Troughing moves into the western U.S. on Tue and Wed and pushes
up a ridge into the ern U.S. Temperatures stay above normal for this
forecast period. System for Sat night into Sun continues to bear
watching with the differences in strength between models.

.AVIATION...(For the 06Z TAFS through 06Z Wednesday night)
Issued at 1238 AM EST WED FEB 21 2018

Lingering -shsn at taf sites should end by Wed afternoon as sfc high
pressure builds in strongly from the west. West-northwesterly winds
at KCMX could be gusty at times to 20 mph into Wed afternoon. By
Wednesday, low-end MVFR cigs ceilings should lift with VFR
conditions at all sites. Improvement will likely occur later in the
day at KCMX.

.MARINE...(For the 4 PM Lake Superior forecast issuance)
Issued at 309 PM EST TUE FEB 20 2018

Winds will remain between 20 and 30 knots through the day on
Wednesday, before subsiding to less than 20 knots Thursday through
the weekend. There may be a few pockets of heavy freezing spray in
areas that have more expansive open waters, mainly across the far
east late tonight through Wednesday. However, ice cover is far too
expansive to warrant any headlines at this time.

Upper Michigan...
Lake Superior...
Lake Michigan...


SHORT TERM...Ritzman
MARINE...Ritzman is the U.S. government's official web portal to all federal, state and local government web resources and services.