Area Forecast Discussion
Issued by NWS Marquette, MI

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FXUS63 KMQT 021954

Area Forecast Discussion
National Weather Service Marquette MI
254 PM EST Fri Dec 2 2016

.SHORT TERM...(Today and tonight)
Issued at 444 AM EST FRI DEC 2 2016

Today and Tonight: The surface low and upper-level low that has be
slowly moving across the Upper Great Lakes over the past few days is
continues to slowly depart the area across southern Quebec today and
into the New England states tonight. As this happens, the low will
keep a surface trough extending westward across the U.P. The
presence of this trough along with 850mb temperatures in the -6C to -
10C range across much of the U.P. through this time period will give
continued chances of lake effect snow for the northwest to west
northwest wind favored locations. Overall moisture is not
particularly deep anywhere across the U.P., which will help to limit
the total snowfall accumulations. At this point, the main focus for
accumulation would be across the east through this time period as
the increased fetch helps to moisten the sounding and that area will
be closer to the pieces of energy wrapping through the area.
The western portions of the U.P., from the Keweenaw down to Ironwood
may see some scattered snow showers this morning, but the deeper
moisture slides out fairly quickly so it is possible that the precip
today may be more of a light drizzle to freezing drizzle mix with an
occasional snow shower mixed in. Again, due to the shallow moisture
out west, the probability for ice in the clouds is greatly reduced.
As the aforementioned small wave of energy works through the area
early this evening through tonight, the precipitation may transition
back to more snow over the Keweenaw as slightly deeper moisture
slides across the area. At this point the increased moisture and
energy is expected to remain over then northeast half of the U.P.,
which would keep drizzle and a few scattered snow showers southwest
of the Keweenaw, mainly in the higher terrain, with mainly snow
showers expected for areas east of Marquette and over the Keweenaw
Peninsula. In the areas where freezing drizzle does occur, roads
could become fairly slippery, especially early in the morning and at
night. This will especially be the case for untreated roads. Highs
today will be in the 30s with overnight lows mainly in the mid 20s
to low 30s.

.LONG TERM...(Saturday night through Friday)
Issued at 254 PM EST FRI DEC 2 2016

A fairly active medium/extended range period of wx is in store for
Upr MI. A disturbance passing thru the Lower Great Lks late this
weekend wl bring some mainly light sn to the area on Sun into Sun
ngt. Although relatively warm llvl temps would tend to limit snow
accums, there could be at least a period of moderate sn over
portions of the ern cwa with the sly flow off Lk MI allowing for
some lk enhancement before a trailing hi pres rdg ends this pcpn by
late Sun ngt and brings dry wx for Mon. While there are still some
differences among the longer range guidance on the interaction btwn
upr troffing drifing ewd thru the nrn Plains and a srn branch shrtwv
moving toward the mid Atlantic states on Tue into Wed, the models in
general have trended toward less phasing btwn these features and
thus a lower chc for sgnft pcpn at mid week. But once a deeper lo
pres does dvlp to the ne of Upr MI mid/late next week, the cyc nw
flow arnd this feature wl cause some les as colder air returns.
Expect above normal temps into at least Tue before the colder air
arrives for the second half of the week in the nw flow left in the
wake of the Cndn lo pres.

Sat ngt thru Sun ngt...A shrtwv over the ncentral Plains on Sat evng
embedded in a more progressive flow is fcst to move e over the wrn
Lower Great Lks by late Sun before shifting to the e on Sun ngt
ahead of a trailing shrtwv rdg axis. Although some waa pcpn in the
sly flow ahead of the associated lo pres trof may arrive over the
far w toward 12Z on Sun, lingering dry air associated with the
slowly departing sfc hi pres rdg wl bring mainly dry wx on Sat ngt
even as lo clds linger. Some of the models show the lo clds breaking
up over at least portions of the cwa on Sat ngt, allowing min temps
to fall more sharply over the interior with lgt winds. This scenario
seems most likely over the interior scentral and e as the guidance
hints more waa mid/hi clds wl arrive acrs the w later at ngt along
with a steadier s wind. Since the shrtwv/sharper dpva/deep lyr
qvector cnvgc/upr dvgc are fcst to track fairly quickly to the s of
the cwa and limit deep lyr mstr return, pcpn amnts should be modest.
The one exception may be at locations over the e, where the sly flow
off Lk MI may result in some lk enhancement with h85 temps as lo as
-7C lingering into Sun evng. Fcst sdngs indicate the bulk of the
pcpn wl fall as sn except near the warming influence of the Great
Lks, especially Lk MI. The arrival of larger scale qvector dvgc/mid
lvl drying/more acyc flow on Sun ngt in the wake of the passing
shrtwv wl diminish pcpn w-e. With an absence of llvl thermal
troffing/falling subsidence invrn/transition toward a more acyc llvl
flow, there wl be no sgnft lk effect pcpn.

Mon...Trailing shrtwv rdg alf and sfc hi pres wl bring dry wx. H85
temps fcst near 0C and partial sunshine wl allow max temps to rise
at least near 40 at some places.

Mon ngt thru Tue ngt...The fcst during this time wl depend on the
interaction or lack thereof btwn deepening upr trof migrating e thru
the nrn Plains and a srn branch shrtwv lifting newd fm the srn
Plains toward the mid Atlantic states. The 06Z GFS showed more
phasing of these features, resulting in a deeper srn branch sfc lo
pres tracking farther to the nw into the central Great Lks and a
sgnft sn storm for at least parts of Upr MI. The NCEP discussion
indicates this scenario is an outlier, and in fact the 12Z GFS has
trended toward the bulk of the other guidance showing less phasing
with a separtate nrn branch sfc lo tracking fm nrn MN into nw
Ontario dragging a sfc cold fnt with light mixed rain/snow acrs the
area on Tue well to the nw of the srn lo pres moving toward the se
Great Lks/mid Atlantic states. The wnw flow on the srn flank of the
Ontario lo wl then push colder air into the Upr Lks on Tue ngt,
bringing a return of some les as h85 temps fall toward -10C over the
w toward 12Z Wed.

Extended...Although there remain ops model differences, the extended
period wl be dominated by a sharp cyc nw flow arnd deep lo pres in
Ontario that is fcst to drift into Quebec. As h85 temps fall as lo
as at least -15C, expect a period of lk effect/enhanced snow and aob
normal temps. Bumped pops up well above the consensus fcst in areas
favored by the fcst llvl winds.

.AVIATION...(For the 18Z TAFS through 18Z Saturday afternoon)
Issued at 1252 PM EST FRI DEC 2 2016

Generally will keep with persistence forecast at the TAFs into Sat.
Expect MVFR cigs and MVFR vsby. Light snow flurries may give way to
drizzle/freezing drizzle rest of this aftn into early evening at IWD
or CMX. Will keep it snow for now as confidence in seeing drizzle as
primary ptype is low. Better chance of steadier light snow will
return later in the evening and will persist through rest of the TAF
period. As the snow moves in, vsby could drop to IFR at times late
tonight into Sat. especially at CMX, but for the most part should
stay MVFR.

.MARINE...(For the 4 AM Lake Superior forecast issuance)
Issued at 444 AM EST FRI DEC 2 2016

Surface low continues to drift east away from Lake Superior but
tighter pressure gradient continues to linger across Lake Superior,
keeping northwest winds 20 to 30 kts through today, strongest over
the east half. High pressure moving in from the Plains will diminish
the winds to 20 kts or less tonight into the weekend. An approaching
low pressure trough on Wednesday will result in southeast winds
increasing to 25 kts, strongest over eastern sections, with
northwest gales to 35 knots a possibility for Thursday across much
of Lake Superior.

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


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