Area Forecast Discussion
Issued by NWS Marquette, MI

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FXUS63 KMQT 030454

Area Forecast Discussion
National Weather Service Marquette MI
1154 PM EST Fri Dec 2 2016

.SHORT TERM...(This evening through Saturday)
Issued at 337 PM EST FRI DEC 2 2016

Though primary sfc low has made it to southern Quebec a weak trough
extends back across the lower Great Lakes. Another subtle more
mesoscale trough is also across Upper Michigan with slightly backed
winds to wnw over west half of Upper Michigan while more of a nw
wind is across Lk Superior and over east half of Upper Michigan.
Light snow showers have been in stronger convergence with the trough
all day btwn Marquette and Grand Marais. Sfc temps in the low-mid
30s and overall light intensity have resulted in minimal snow accums
in this area with rain/snow mix at times near the Lk Superior shore.
Just a few flurries elsewhere under cloudy skies. Weak shortwave is
noted upstream over southern Manitoba. As this wave moves in there
is some response with inversions rising up slightly from current 3-
4kft to 5-6kft and increasing moisture. Trouble is that initially as
this lift arrives, it may not be cold enough to introduce ice aloft
as temps in moist layer are only as low as -6c or -7c, so there
could be drizzle or freezing drizzle. Best chance of drizzle would
be over western cwa where convergent upslope nw flow will boost low-
level lift. Already seeing cigs dropping at IWD with hints of lower
vsby. Call out to Gogebic sheriff office indicates it is just cloudy
but once daylight ends, there may be better chance of lower level
saturation and some drizzle, especially as the forcing arrives toward
00z/7 pm ET.

Eventually the forcing will bring top of inversion to temps to
around -10c which should lead to better chance at introducing ice
aloft and seeing some lighter snow. Once the snow sets up best shot
for a couple inches of accumulation will be in more persistent
convergent zone over Ontonagon into Houghton county to the south of
the Portage Canal with second area of enhanced snow where the
enhanced lake effect has been set up most of today over far eastern
Marquette county into western Alger county. High pressure moving in
on Sat will gradually result in decreasing lake effect from west to
east. By late aftn expect very little in way of lake effect except
for on the Keweenaw with wsw low-level winds.

Temps will remain seasonable with lows tonight in the mid 20s to
lower 30s, warmest near Lk Superior and east. Highs on Sat will be
similar to today, low 30s west half and mid to upper 30s east half.

.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 06Z TAFS through 06Z Saturday night)
Issued at 1153 PM EST FRI DEC 2 2016

With abundant low-level moisture and light flow across Lake
Superior, fcst thru this morning will be a persistence fcst with
MVFR cigs likely to prevail at KIWD/KCMX/KSAW. Not out of the
question that IFR cigs could occur at KIWD overnight. In addition,
light downslope component to the wind may allow for some periods of
VFR at KSAW. Some -shsn are also expected at KCMX. Late this
aftn/evening, conditions may begin to break out to prevailing VFR.

.MARINE...(For the 4 PM Lake Superior forecast issuance)
Issued at 337 PM EST FRI DEC 2 2016

NW winds to 25 kts diminish to 20 kts later tonight through Sat
night as high pressure ridge crosses the region. Winds stay 25 kts
or less Sun into Mon as pressure gradient remains light. An
approaching low pressure trough crossing Tue night into Wed will
result in southeast winds increasing to 30 kts on Tue, strongest
over central and eastern sections. Winds shifting northwest on Wed
could reach 30 kts as well.

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


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