Area Forecast Discussion
Issued by NWS Marquette, MI

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FXUS63 KMQT 242007

Area Forecast Discussion
National Weather Service Marquette MI
407 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 through Sunday)
Issued at 358 AM EDT MON OCT 24 2016

Mean upper level troughing remains in place into this weekend.
Daytime temperatures should stay at or slightly blo normal mainly in
the 40s while nighttime temperatures in the upper 20s to upper 30s
are pretty typical for this time of year. Confluent northwest flow
on Tue will result in high pressure ridge building across Great
Lakes. Could see light lake effect hang on early in the day over
north central cwa as blyr winds veer northerly as the ridge builds
in. Probably will see good deal of cloud cover persist even after
lake effect ends as higher rh remains in the 925-850mb layer beneath
a subsidence inversion. Clouds should eventually try to clear out
later in the day with mixing, though there are indications at least
scattered clouds could linger into Tue evening.

Attn later Tue night into Wed will be on shortwave trough sliding
across the Central Plains. Sfc-h85 low tied to the wave should be
crossing vcnty of IA to southern MN by 12z Wed. Deep layer q-vector
forcing and lift within right entrance region of of jet streak from
northern Ontario to mid Atlantic will support rain moving in through
the day on Wed. Despite temps in the 30s on Tue night, soundings
look too warm in the lowest levels /wbzero heights aoa 1000 ft agl/
to support any snow as precip moves in so have took out any mention
in the wx grids. As long as circulation in low-levels remains south
of Upper Michigan, suspect heavier rain will remain there as well
closer to where better moisture influx 925-700mb is located and on
northern edge of elevated instability. Even if precip stays light,
likely pops still appear on track for Wed into Wed night. Lack of
phasing btwn lead system moving through Wed and additional shortwave
dropping across in northwest flow late Wed night into Thu continues
to lead to lower potential for much in way of accumulating snow late
Wed night into Thu, but there will be enough low-level cooling in
wake of the sfc low to keep a mix of rain/snow especiallly for the
interior as has been in forecast for a while now.

Well for at least this model cycle, there is okay agreement among
the GFS, ECMWF and GEM for Fri-Sun. Model consistency during this
time frame has been low so we`ll see if the agreement continues in
the coming days. For now though, another shortwave working through
in the nw flow will keep troughing across the region into the
weekend. Best chance for precip would be on Fri-Fri night as
associated sfc low crosses the Upper Great Lakes while deepening.
Exact track of the low still a bigger question though. If the
pressure pattern holds up as forecast, then would be chilly and
windy on Sat behind this system. High pressure/dry low-levels
building in quickly would limit lake effect precip on Sat though
probably cannot rule it out. Weaker system(s) that would produce
light precip as deep moisture is lacking crosss the region on Sun
and maybe Mon as well.

.AVIATION...(For the 12Z TAFS through 12Z Tuesday morning)
Issued at 712 AM EDT MON OCT 24 2016

Lake clouds will linger today bringing MVFR to VFR ceilings across
the area today. Drier air moves in this afternoon and should
decrease the cloud cover. Lake clouds could roll back into SAW late
tonight as winds shift from NW to N-NE over Lake Superior.

.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...


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