Area Forecast Discussion
Issued by NWS Marquette, MI

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FXUS63 KMQT 211211
AFDMQT

Area Forecast Discussion
National Weather Service Marquette MI
711 AM EST Sun Jan 21 2018

.SHORT TERM...(Today and tonight)
Issued at 327 AM EST SUN JAN 21 2018

Today: Main focus will be on cold front settling southward from
Ontario and northern Lake Superior toward northern Upper Michigan in
the afternoon and evening. Expect developing east to northeast winds
in wake of the front which will result in upslope lift from the
Keweenaw to north central higher terrain. A lot of low clouds
already behind the front early this morning over northern Ontario
and expect these clouds to spread into Upper Mi late this afternoon
and evening aided by additional moisture off Lk Superior. Could even
be enough low-level moisture and lift for drizzle or freezing
drizzle so will continue slight chances for the Keweenaw into
Marquette-Baraga counties. Kept in slight chances this morning for
the far south central cwa in case weakening fgen band lingers a bit
longer to produce some light snow. Expect any patchy fog this
morning to be shallow and should lift a few hours after sunrise with
weak heating/mixing.

Both the low clouds and increasing high clouds ahead of developing
winter storm will result in cooler temps than last couple days.
Readings will be in the lower to mid 30s coolest north.

Tonight: Models continue to indicate delayed arrival of pcpn ahead
of system approaching from the Central Plains due to drier e-ne flow
off Ontario circulating around sfc high centered over the southern
tip of James Bay. Prior to the onset of system snow moving into
south central Upper Mi late tonight, easterly flow will back
northeasterly resulting in continued upslope flow across the north
central Upper Mi. Forecast soundings pick up on this upslope flow,
including deepening of shallow moisture to near 3 kft by midnight
Mon morning. Will continue mention of upslope fzdz over north
central counties (Baraga and Marquette) into Sunday evening with
snow mixing in with freezing drizzle after midnight due to seeder-
feeder mechanisms from lowering mid cloud deck.

.LONG TERM...(Monday through Saturday)
Issued at 536 AM EST SUN JAN 21 2018

...Winter storm still on track to impact Upper MI Mon into early
Tue...

Looks like the pattern over the next couple of weeks will be fairly
active with a progressive flow of energy off the Pacific and across
the CONUS. As a result, temps thru the end of this month and into
the very early part of Feb will likely be variable in response to
progressive ridges and trofs moving across the CONUS, but probably
with a tendency for more above normal than blo normal days. This
would be consistent with the signal from the current active MJO
which is now in phase 4, having shifted from the Indian Ocean to the
Maritime Continent. With the MJO over the Maritime Continent, it
favors warmth/ridging over the eastern CONUS. Farther down the line,
guidance suggests the MJO will remain active, and as it shifts to
the Western Pacific and toward the western hemisphere, it will begin
to tilt the odds toward more persistent cold weather for the Upper
Lakes heading thru early to mid Feb. As for pcpn, progressive
pattern will provide the potential for winter storms to affect the
Upper Lakes periodically for at least the next 2 weeks. With periods
of warmer weather in the offing, the pcpn will likely include mixed
ptypes. The first of these systems will impact the area Mon into
early Tue, and it will be the main feature of interest in the long
term as it provides widespread mdt to hvy snow across much of Upper
MI. The next trof will swing w to e across the CONUS Thu thru early
next week. Mixed ptypes will be an issue here late week as energy
will be initially more consolidated in the northern part of this
trof as it passes, supporting a more northerly push of warm air into
the Great Lakes. There have been some hints of additional energy
dropping into the trof as it passes across the Great Lakes,
providing the potential of a stronger storm system to spin up as the
trof moves across the area. If that occurs, it would probably be too
far e of here to have a significant impact on Upper MI, but still
something to monitor.

As mentioned, the main event for the long term occurs Mon into early
Tue. Vigorous shortwave is currently moving across the southern
Rockies with some lightning noted in AZ and southern CO during the
night. This shortwave will move out across the Central Plains Mon as
a closed mid-level low and then reach Lower MI Tue morning.
Associated sfc low will track from eastern KS tonight, to near
Milwaukee Mon evening, then out across central or northern Lake
Huron Tue morning. Track of the storm system will put a wide swath
of Upper MI under mdt to hvy snowfall, the first widespread mdt/hvy
snow event for Upper MI this cold season. Models are now in quite
good agreement on the evolution of this winter storm, but there is
still one main concern -- the degree to which snow accumulations
sharply fall off on the nw fringe of the system, which impacts the
fcst for nw Upper MI. Confidence has increased for the eastern part
of the fcst area to be impacted by hvy snowfall with very little
potential now of mixed ptypes across the s central and e. Per deep
layer q-vectors and fgen, forcing will reach peak magnitude to the
sw of Upper MI with a gradual weakening trend as it lifts across the
area. While this will lead to highest storm total pcpn to the sw of
Upper MI, vigorous forcing will still support mdt/hvy snow spreading
across the fcst area Mon/Mon night. From an isentropic standpoint,
mixing ratios of 3-4g/kg are avbl, suggesting a solid 5-8in of snow
for about 9-12hrs of main isentropic ascent. Given the vigorous deep
layer forcing and strong upper divergence as well as deformation
axis which will probably cut sw-ne across central Upper MI,
accumulations will probably end up in the 6 to locally 10in range
across the central and eastern fcst area, inline with previous
forecasts. Overall, looks like a standard type winter storm for
Upper MI, though there haven`t been any yet this cold season and
only a very few in recent years. Winter storm watch has been
expanded into the eastern counties with decent potential for 6 or
more inches of snow in a 12hr period. Deep moisture may cut out at
times after the period of heaviest snow Mon aftn/evening, so some
-fzdz could occur. Should not really pose a hazard given the prior
snow accumulation on roads in addition to sand/salt treatment during
the event. Prior to the onset of mdt/hvy snow, there may be some
-fzdz as well, especially n central. If it occurs, icy travel
conditions will be possible in the morning if there hasn`t been any
-sn.

For n central Upper MI, during the period of strongest forcing, low-
level cyclonic ne flow will be ideal to maximize orographic lift
into the high terrain of Marquette and eastern Baraga counties,
likely boosting snow totals by several inches. While 850mb temps are
borderline at best for lake enhancement, slightly colder air blo
850mb may be sufficient for a lake enhanced component. There will be
small window for n wind lake enhancement as the system snow departs
late Mon night/early Tue morning. Overall, orographic enhancement
will likely be the biggest player boosting snow amounts for the n
central. For this event, the high terrain of n central Upper MI from
just w of Marquette into the Huron Mtns, including
Negaunee/Ishpeming, will likely see the greatest snow totals from
this system, probably on the order of 12-16in.

Concerning far western Upper MI, model guidance has generally locked
in on that area being on the fringe of the synoptic snow shield with
deep layer forcing barely extending out over the lake. During this
period of synoptic forcing, low-level winds will be nearly parallel
to the shore, limiting any potential lake enhancement. As a result,
there may not be much if any lake component to the snow. Thus, with
only the western edge of the snow shield affecting the far w, snow
accumulations will likely end up blo warning criteria. At this
point, headline issuance for the Keweenaw is not warranted. Will
maintain watch headline for Gogebic/Ontonagon counties.
Interestingly, in the SREF plumes, there are quite a few members
showing snow accumulations in excess of 10in at KIWD and even
several in excess of 10in at KCMX. There`s not any support for that
in any of the 00z/06z operational models. Will be something to
monitor as the 12z model runs arrive later this morning.

In the wake of this system, there may some sct light LES off Lake
Superior into Wed. Next trof will progress eastward across the CONUS
late week. With shortwave lifting ne in the trof passing over the
Upper Lakes, associated sfc low will lift ne over or to the w of
Upper MI, resulting in a good surge of warming into Upper MI. As a
result, at some point later Fri/Fri night, there will likely be some
rain, yes just rain even though it`s late Jan. With colder air
arriving behind the system, there should be at least sct LES off
Lake Superior over the weekend.
&&

.AVIATION...(For the 12Z TAFS through 12Z Monday morning)
Issued at 635 AM EST SUN JAN 21 2018

Model

Tricky forecast for the terminals as snow melt yesterday along with
winds switching to the northeast with a frontal passage will
allow low level moisture and upslope flow to occur bringing
conditions down this forecast period with fog and/or low clouds.
Model soundings suggest stratus deck will become trapped under an
inversion leading to IFR to possibly LIFR conditions throughout
much of today into tonight. May be some freezing drizzle as well,
especially at CMX and SAW. &&

.MARINE...(For the 4 AM Lake Superior forecast issuance)
Issued at 327 AM EST SUN JAN 21 2018

Strongest winds on Lake Superior during this fcst period will occur
Monday into Tuesday as low pressure tracks from the Central Plains
across northern Lower MI into southern Quebec. NE to N gales are
expected over most of Lk Superior during that time so will continue
the posted gale watch. Heavy freezing spray will also develop late
Monday night through Tuesday.
&&

.MQT WATCHES/WARNINGS/ADVISORIES...
Upper Michigan...
  Winter Storm Watch from Monday morning through late Monday night
     for MIZ002-009>012.

  Winter Storm Watch from Monday afternoon through late Monday
     night for MIZ006-007-013-014-085.

  Winter Storm Watch from Monday afternoon through Tuesday
     afternoon for MIZ004-005-084.

Lake Superior...
  Gale Watch from Monday evening through Tuesday afternoon for
     LSZ266-267.

  Gale Watch from Monday morning through Tuesday morning for
     LSZ162-263.

  Gale Watch from Monday evening through Tuesday morning for
     LSZ264-265.

Lake Michigan...
  Gale Watch from Monday morning through Monday evening for LMZ248-
     250.

&&

$$

SHORT TERM...Voss
LONG TERM...Rolfson
AVIATION...Voss
MARINE...Voss


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