Area Forecast Discussion
Issued by NWS Marquette, MI

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FXUS63 KMQT 151004
AFDMQT

Area Forecast Discussion
National Weather Service Marquette MI
504 AM EST Thu Feb 15 2018

.SHORT TERM...(Today and tonight)
Issued at 503 AM EST THU FEB 15 2018

Today: A cold front stretching from west to east along Lake Superior
this morning, will shift south of the U.P. by late morning or early
afternoon. Along and directly behind the cold front 850mb
temperatures do not drop too quickly. This, along with shallow
moisture will lead to a light freezing drizzle and light snow
potential over the Keweenaw and across portions of the nw 1/3 of
Upper MI this morning, while most of the rest of the U.P. should
stay dry. While not expecting much in the way of ice accumulation,
as the potential that seeder feeder processes may keep the
precipitation in the form of snow, it doesn`t take much freezing
drizzle to make untreated roadways and elevated surfaces slippery
through at least mid morning. Confidence in the freezing drizzle
actually happening is fairly low at this point. Behind front this
afternoon, 850 mb temperatures will fall to around -8C to
-10C. This will be cold enough to transition all of the
precipitation to snow during the afternoon hours. Since the coldest
850 mb temperatures will not arrive until tonight, not expecting
much snow or ice accumulation today. Maybe a half an inch to an inch
from near Ironwood northeat through the Copper Country. Highs early
in the day will be in the upper 20s to low 30s before steadily
dropping from the north throughout the day.

Tonight: As the cold front continues south and east of the area,
north to northwest flow across Lake Superior will increase. This,
along with 850mb temperatures dropping to around -16C to -20C
overnight, will allow lake effect snow to increase for north to
northwest wind snowbelts. The best chances for lake effect snow will
be over the north central and especially the eastern U.P, downwind
of Lake Superior, due to a larger portion of the lake without ice
coverage. The west half of Lake Superior is covered with extensive
ice cover; therefore, would not expect much more than light,
intermittent lake effect snow over the western U.P. The east half of
Luce County, northern Schoolcraft and Northern Luce county could see
2 to 4 inches of snow tonight, especially in the heavier snowbands.
The increase in snowfall intensity tonight will be aided by a couple
quick moving shortwaves progged to slide across the U.P., which will
help to steepin lapse rates and overwater instability for those
locations. It seems that the Hi-Res models are having some
difficulties with ice coverage over eastern Lake Superior, so had to
adjust pops higher along with QPF manually out east.

.LONG TERM...(Friday through Wednesday)
Issued at 503 AM EST THU FEB 15 2018

Models suggest that the broad mid/upper level trough from Hudson Bay
into the n cntrl CONUS will shift into the wrn CONUS as shortwave
energy drops se from the Gulf of Alaska resulting in sw flow into
the Great Lakes through the middle of next week. This will bring the
potential for periods of snow through the region as the main sfc-850
mb frontal boundary remains just to the south. A brief period of
below normal temps Friday will rebound to readings at or above
seasonal averages through Wednesday.

Friday, high pres building into the region will result in backing
anticyclonic westerly winds with dropping inversion heights. Any
lingering LES will diminish or shift offshore.

Saturday, a weak shortwave and sfc trough will bring potential for
some light snow, with the best chance for any accumulation downwind
of lake enhancing sw flow off of Lake Michigan east of Manistique.

Sunday into Sunday night, the models were in slightly better
agreement but the ECMWF remained farther north and lighter with the
initial area of snow late Sun into Sun night with broad
WAA/isentropic lift compared to the GFS/GEFS. Snow accumulations of
a few inches may be possible.

Monday-Tuesday, The models remain in reasonabler agreement Monday as
the pattern will be favorable for stronger fgen and isentropic
ascent that could bring moderate to heavy snow accumulations.
Differences remain in handling the timing/strength of shortwaves
lifting into the Great Lakes and the impact on sfc low development
especially into Tuesday that could bring additional snow
accumulations.

Wed-Fri, Models have trended toward pushing the frontal boundary and
area with highest snow potential gradually to the east by Tue night
into Wednesday. High pressure and drier air will build into the
region. There is more uncertainty with how quickly the high will
shift to the east with warm air moving back into the region.
&&

.AVIATION...(For the 06Z TAFS through 06Z Thursday night)
Issued at 1154 PM EST WED FEB 14 2018

VFR conditions should prevail overnight at KIWD/KCMX/KSAW. However,
given the melting snow that occurred yesterday, some fog/MVFR vis
could develop, mainly at KSAW. Today, a cold front will drop se
across the area, leading to the development of low MVFR/IFR cigs and
some -fzdz/-sn that will transition to -shsn/flurries, mainly at
KIWD/KCMX. Arrival of drier air will lead to cigs lifting to high
MVFR at all terminals late aftn/evening.
&&

.MARINE...(For the 4 AM Lake Superior forecast issuance)
Issued at 503 AM EST THU FEB 15 2018

A few southwest gale force gusts are possible on Saturday and north
to northeast gale force gusts Monday and Monday night , otherwise
winds will be below gales through the forecast period.
&&

.MQT WATCHES/WARNINGS/ADVISORIES...
Upper Michigan...
None.
Lake Superior...
None.
Lake Michigan...
None.
&&

$$

SHORT TERM...KEC
LONG TERM...JLB
AVIATION...Rolfson
MARINE...KEC



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