Area Forecast Discussion
Issued by NWS Marquette, MI

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FXUS63 KMQT 171749

Area Forecast Discussion
National Weather Service Marquette MI
149 PM EDT Tue Apr 17 2018

.SHORT TERM...(Today and tonight)
Issued at 504 AM EDT TUE APR 17 2018

Water vapor imagery and RAP analysis show a broad, deep mid-level
low extending from the Great Lakes to the Mid-Atlantic States. Small
embedded mid-level low developed over eastern Lake Superior last
evening, supporting the increase in lake enhanced snow that
occurred. That low is now moving se across eastern Upper MI at a
quickening pace. Ongoing lake enhanced snow under 850mb temps of -10
to -13C began to diminish slightly several hrs ago, but recently it
has picked up again as another shortwave is swinging across
central/eastern Lake Superior in the circulation around the mid-
level low. Radar trends show this increase in snow nicely as
reflectivities have increased and expanded in areal coverage. Snow
has been the much fluffier lake effect variety with snow-to-water
ratios up around 25 to 1 here at the office during the night.

Expect a few more hrs of mdt to ocnl hvy shsn from the Keweenaw into
n cntrl Upper MI, n central in particular, until aforementioned
shortwave over Lake Superior passes. With a few more hrs of snowfall
upwards of 1 in/hr at times, extended ongoing advy to 8 AM.
Thereafter, expect a rapid decrease in snow intensity as forcing
departs and 850mb temps begin to rise. Ocnl lighter snow across the
rest of west and central Upper MI will also diminish. With the
departure of deeper moisture this aftn, any lingering -shsn should
become confined to the higher terrain and may actually end
altogether. Expect high temps in the low/mid 30s.

Tonight, majority of models show some light pcpn over the higher
terrain near Lake Superior as northerly low-level winds gradually
veer ne and increase as sfc high pres ridging noses s over northern
Ontario. Skeptical that any pcpn would occur since obs don`t show
much in the way of IFR or lower cigs n of Lake Superior early this
morning. However, given the signal in most model guidance, opted to
include a mention of pcpn over the high terrain n central and far w
where upsloping would be maximized. Any pcpn that occurs would
transition from -shsn/flurries to -fzdz as temps in the low-level
moist layer rise above -10C. Low temps tonight will be in the 20s.

.LONG TERM...(Wednesday through Monday)
Issued at 422 AM EDT TUE APR 17 2018

Quiet in the long term. Precip-wise, could see some very light
drizzle or snow in the higher terrain of the W and N-central Wed
into Wed night, but chances of seeing anything significant from that
are low. Clipper system with greater precip stays far enough S to
keep any widespread precip out of the CWA.

Dry for the most part otherwise, with temperatures gradually
increasing each day to near normal values. Should see a couple highs
in the 50s on Fri, then for Sat and Sun highs will range from the
mid 40s to mid 50s. Could even see some highs around 60 Sun and

.AVIATION...(For the 18Z TAFS through 18Z Wednesday afternoon)
Issued at 148 PM EDT TUE APR 17 2018

MVFR ceilings have lingered through the morning and will continue
to do so through the rest of the afternoon and into the evening
hours at all terminals, except KIWD/KCMX should see a brief break
this evening as they`re right along the leading edge of the drier
air. Light wintry precipitation continues to impact KCMX/KIWD, but
sharply reduced visibilities haven`t been reported. Tonight
through mid-day on Wednesday north to northeast flow will provide
additional lift and support for lowering ceilings through the
latter half of this TAF period. Models are fairly consistent with
ceilings dropping down into the IFR category, especially at KSAW.
However, confidence was not high enough that cloud depths will be
deep enough to support the development of freezing drizzle after
these lower ceilings fill in, so opted to only include mentions of
vicinity showers for now to hint towards the potential for some
light precipitation.

.MARINE...(For the 4 AM Lake Superior forecast issuance)
Issued at 504 AM EDT TUE APR 17 2018

Under a tight pressure gradient between high pres to the n and w and
low pres over southern Ontario, northerly winds of 20-30kt will
continue this morning across Lake Superior along with some patchy
freezing spray. Not out of the question that there could be a few
gale force gusts to 35kt over the central part of the lake. Winds
will diminish dramatically over the far w part of Lake Superior this
aftn while winds of 20-30kt continue over the e. As high pres
remains to the n and w and low pres tracks from KS this evening to
New England Thu morning, expect n to ne winds mostly in the 20-30kt
range across Lake Superior tonight thru Wed night. Winds will then
diminish to under 15kt w to e Thu/Thu night as high pres settles
over the Upper Lakes. With high pres holding over the area Fri/Sat,
winds will remain under 15kt.

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


SHORT TERM...Rolfson
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