Area Forecast Discussion
Issued by NWS Marquette, MI

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FXUS63 KMQT 242315

Area Forecast Discussion
National Weather Service Marquette MI
715 PM EDT Mon Oct 24 2016

.SHORT TERM...(This evening through Tuesday)
Issued at 404 PM EDT MON OCT 24 2016

WV imagery and RAP analysis indicated nw mid/upper level flow
through the nrn Great Lakes between a trough from ern Canada into
New England and a ridge from the srn plains into Saskatchewan. At
the surface, a ridge extended from Manitoba into the Upper MS valley
resulting in anticyclonic nw flow into Upper Michigan. Although 850
mb temps around -6C (water temps near 11C) provided enough
instability for isolated lake effect rain showers over the east,
with daytime warming and an influx of drier air, the pcpn has
diminished this afternoon.

Tonight: As high pressure continued to build into the region,
veering winds to the nne and 850 mb temps remaining near -6C will
push the lake effect westward toward n cntrl Upper Michigan.
Inversion heights near 4k-5k ft and continue acyc flow will limit
intensity. Wet-bulb zero heights suggest pcpn will remain mainly as
rain. Otherwise, mostly clear skies inland west will allow temps to
fall into the upper 20s. Temperatures in the lower 30s are expected
over the rest of the cwa.

Tuesday: Confluent mid upper level flow, high pressure building over
the region with low level dry air, and inversion heights lower to
near 3k ft will bring an end to the lake effect pcpn by afternoon.
However, the 925-850 mb thermal trough will remain close enough to
support extensive stratocu development keeping highs in the mid 40s
north and upper 40s south.

.LONG TERM...(Tuesday night through Monday)
Issued at 432 PM EDT MON OCT 24 2016

Surface ridge will slowly lift northeast away from the Great Lakes,
allowing flow to turn easterly by late Tue night. Guidance continues
to prog a shallow channel of moisture lingering overhead Tue ngt
into Wed, but feel this is likely overdone and could end up with
less shallow cloud cover Tue ngt. Upstream weak diffluent flow
across the upper midwest will slow the arrival of a mid-lvl
shortwave from pushing into the Dakotas until early Wed.

This should all point towards precip not arriving over the Western
Upper Pensinula until after midnight, and that too could be slower
due to a weak downstream mid-lvl ridge over eastern Quebec. Wed
morning the diffluent flow will begin to weaken, allowing the
surface wave to strengthen across Iowa and produce a much tighter
pressure gradient along the lee-side lifting north from Wisconsin
towards Upper Peninsula. But the challenge will be on timing of
cloud cover which could dampen the mixing of higher winds to the
surface Wed. Profile will be moistening more Wed morning, with
thermal profiles showing considerable cool air within the column and
could support light snow mixing with rain. Accumulations should be
difficult given the warm surface conditions; however, could see some
minor slushy mix on grassy surfaces along the eastern forecast area
with temps struggling to warm from the mid/upr 30s to lower 40s.

The shortwave will be slow to push through the forecast area Wed
ngt, and with a downstream weak ridge in place, this could result in
a longer duration of a rain/snow mixture early Thur before the
profile should warm enough to push it over to all liquid p-type.
Current thinking is that temps will be cooler for Thur highs, and
could see the lower 40s trending into the upper 30s away from the
marine environment.

The trough axis will then push east Thur ngt/Fri, with ridging
returning to the upper midwest and eventually the Northern Great
Lakes Fri. This may only be short-lived as operational guidance is
indicating the Pac-NW system will be lifting north through the
Canadian Rockies and arriving over the Upper Midwest/Great Lakes
late Fri/early Sat. In between the mid-week system and weekend
system, temps could rebound into the lower 50s before turning colder
and into the low/mid 40s. Confidence in the extended periods for
Sat/Sun is low at this time, given the spread amongst ensemble

.AVIATION...(For the 00Z TAFS through 00Z Tuesday evening)
Issued at 715 PM EDT MON OCT 24 2016

Lake clouds will move back into SAW late tonight as winds shift from
NW to N-NE over Lake Superior and cause conditions to drop to MVFR
there. VFR conditions are expected elsewhere.

.MARINE...(For the 4 PM Lake Superior forecast issuance)
Issued at 406 PM EDT MON OCT 24 2016

Winds will remain below gales through the period. A tightening
gradient between a deep low pressure system moving through Quebec
and a high pressure ridge building into the Plains will lead to NW
winds gusting to 30 knots over eastern Lake Superior into this
evening. High pressure will then build across the area overnight
into Tuesday, keeping winds generally light across Lake Superior.
Southeast winds will increase again to 20 to 30 knots Wednesday into
Wednesday evening as a low pressure system passing just south of the
area. There will be a trough passage on Thursday but winds should
still remain fairly light. Friday will see south winds increase to
20 to 30 knots again over the east half of Lake Superior as another
low pressure system approaches from the Northern Plains.

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


LONG TERM...Beachler
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