Area Forecast Discussion
Issued by NWS Marquette, MI

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FXUS63 KMQT 150000

Area Forecast Discussion
National Weather Service Marquette MI
700 PM EST Tue Feb 14 2017

.SHORT TERM...(This evening through Wednesday)
Issued at 418 PM EST TUE FEB 14 2017

WV imagery and RAP analysis indicated an amplified pattern with a
mid/upper level ridge from the western CONUS into
Alberta/Saskatchewan and a trough from Hudson bay into the northern
Great Lakes. At the surface, a cold front extended across central
Upper Michigan from low pressure northeast of Lake Superior. A
shortwave moving into wrn Upper Michigan combined with daytime
heating supported an increase in snow showers across the area.
However, with 850 mb temps only to around -11C and Spring-like
warming over the land, the snow showers were more cellular and
disorganized resulting in little or no accumulation.

Tonight, expect that the snow showers will increase in intensity and
coverage this evening as the disruption from daytime heating
diminishes and low level conv increases across most areas of nrn
Upper Michigan favored by strong nnw flow. The LES will continue
overnight but should diminish over the west where subsidence and
850-700 mb drying is strongest behind the shrtwv. Although the
snow is later to develop than expected, 1 to 3 inch amounts are
still possible. Locations east of Marquette should still see
additional acumulations in the 2 to 4 inch range. The strongest
isallobaric component and gustiest winds are expected this evening
with some gusts to around 40 mph. The stronger winds overnight
are expected to shift into the ern cwa.

Wednesday, nnw winds will continue with 850 mb temps remaining
around -14C. This should be enough to keep light to moderate LES
going over mainly the east, downstream from the longer fetch.
Otherwise, inversion heights dropping to around 3k ft will result in
only light LES over the west.

Even with little snow this afternoon, the winter weather advisories
were retained as conditions are expected to deteriorate this
evening, especially in locations exposed to the stronger winds.

.LONG TERM...(Wednesday night through Tuesday)
Issued at 347 PM EST TUE FEB 14 2017

Generally the extended is looking quiet with well advertised warming
trend still on track starting on Fri. Should be warm enough for just
rain early next week as stronger storm system crosses Great Lakes.

Upper trough and cold enough air with h85 temps down to -17c keep
lake effect snow going Wed night for areas favored by NNW-N winds
near Lk Superior. Forecast soundings at P53 (Munising) and Grand
Marais show inversions to 4kft with most of of lake effect layer in
the dgz. Low-level flow slightly cyclonic as core of cold air works
just north of Lk Superior. Intensity will be light so nothing more
than 1-2 inches with light winds limiting impact. As high pressure
ridge moves in on Thu, inversions lower blo 3kft but sfc winds
veering more NE will still keep plenty of clouds overhead and may
keep light lake effect snow showers or flurries going ncntrl cwa.
Will stay on cooler side with max temps low 20s east cwa to near 30
over west cwa.

Upper trough heads east Thu into Fri helping to spin up stronger
storm across far eastern Canada vcnty of New Brunswick/Newfoundland
to Nova Scotia. Meanwhile upper heights will be sharply on the
rise from central Plains across Great Lakes and and as far north
as Baffin Island in northern Nunavut to the north of Hudson Bay.
No doubt will be a low level inversion in place as very warm air
spreads across Great Lakes for the weekend as temps at h85/4-5kft
rise up over +10c. Even so, forecast soundings look too moist in
lowest 1kft Fri through Sun so mixing is likely too limited.
Based on what occurred on ydy/Mon when it mixed to 875mb and
850mb with h85 temps of -2c, think even with increasing warm air
aloft we could mix to H9 and that is probably low since mostly
sunny skies are expected under the building ridge. Used 900mb
temps to gage how high max temps could be. Expect at least low 50s
for some areas Sat and Sun and, if there is full sunshine, would
not be shocked to see readings reach upper 50s to near 60F in some
areas of western Upper Michigan. Dwpnts could rise slightly above
freezing but should for most part stay blo 32F for the weekend.
Thus not expecting a lot of fog even with the very warm daytime
temps as min temps should drop just below freezing Fri night and
Sat night.

GFS, ECMWF and GEM are in really good agreement in showing
stronger shortwave trough breaking through the ridge Mon into Tue
of next week. Deepening sfc low pressure will move from the
central Plains across the upper Great Lakes. Surge of deep
moisture with sfc dwpnts pushing 40+ should bring area of showers
across Upper Michigan Mon night into Tue. With h85 dwpnts nearing
+10c and sharp theta-e ridge/strong h85-h7 moisture advection
nearby would not be out of question for some thunder Mon night.
Deep sfc low could result in windy conditions both ahead of and
behind the low and given such high sfc dwpnts advecting over snow
cover, probably will be fog too. Widespread showers likely
diminish to rain and snow showers later Tue into Tue night as
cooler air returns to the upper Great Lakes region. But, with
overall west to east upper level flow persisting beyond next Tue,
the colder air for mid to late next week does not look too

.AVIATION...(For the 00Z TAFS through 00Z Wednesday evening)
Issued at 700 PM EST TUE FEB 14 2017

Increasingly colder air moving into the Upper Great Lakes will
lead to lake effect snow showers across the area tonight under nw
to nnw winds. At KIWD, prevailing MVFR conditions should set in
this evening as some increase in coverage of -shsn occurs. At
KCMX, expect prevailing IFR conditions this evening with BLSN
adding some restriction to vis. However, as is typical for lake
effect, conditions will be quite variable with MVFR and brief LIFR
at times. As somewhat drier air arrives overnight, expect
prevailing MVFR conditions at KCMX. At KSAW, MVFR conditions
should be the rule tonight, though some periods of IFR are likely
this evening. Under an influx of drier air, -shsn will diminish
for Wed. MVFR conditions should prevail at all terminals, but KIWD
should break out to VFR in the aftn.


.MARINE...(For the 4 PM Lake Superior forecast issuance)
Issued at 418 PM EST TUE FEB 14 2017

Winds will increase to gale force late this afternoon over most of
Lake Superior as a strong upper disturbance slides into the Upper
Great Lakes and tightens the pressure gradient through tonight.
Since colder air will be arriving at the same time, heavy freezing
spray warnings were hoisted for tonight and Wednesday for most of
Lake Superior. Winds will gradually diminish from Wednesdy afternoon
into Wed evening.

Upper Michigan...
  Winter Weather Advisory until 1 AM EST Wednesday for MIZ001>004-

  Winter Weather Advisory until 7 AM EST Wednesday for MIZ006-007-

Lake Superior...
  Heavy Freezing Spray Warning until 7 PM EST Wednesday for

  Gale Warning until 1 PM EST Wednesday for LSZ266-267.

  Gale Warning until 7 AM EST Wednesday for LSZ264-265.

Lake Michigan...


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