Area Forecast Discussion
Issued by NWS Marquette, MI

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FXUS63 KMQT 011220
AFDMQT

Area Forecast Discussion
National Weather Service Marquette MI
720 AM EST Thu Dec 1 2016

.SHORT TERM...(Today and tonight)
Issued at 506 AM EST THU DEC 1 2016

Cloud cover continues to cover much of the Upper Great Lakes region
as shown by IR satellite imagery. WV imagery shows the upper-level
low between eastern Lake Superior and southwest Quebec with muliple
waves rotating around the main low. Radar imagery continues to show
precipitation across much of the U.P. this morning with the bulk of
the precip close to the surface low over eastern Lake Superior.
Surface observations, where available, continue to show a mix of
rain and snow across the area, with mainly snow over the high
terrain and a mix or all rain elsewhere. Upstream RAOBS are showing
more shallow moisture working out of the area with colder air
through the profile.

Today: The surface low and 500mb low, centered over eastern Lake
Superior this morning, will shift eastward into southwest Quebec by
this afternoon; however, a surface trough is expected to continue to
stretch across the CWA throughout the day. Colder air is expected to
continue to filter into the U.P. from the west and northwest
throughout the day, which will help to continue the transitioning of
rain to snow across the area. 850mb temperatures around 12Z are
progged to be around -6C to -7C across the western U.P. while the
eastern half of the U.P. maintains 850mb temperatures around -2C to -
3C. Throughout the day, the western U.P. will see 850mb temps fall
to around -8C to -9C while the east see 850mb temps drop to around -
5C to -6C. This gives the setup for continue lake effect/enhanced
snow showers over the west half throughout the day with a continue
transition to mainly snow showers over the east through the
afternoon hours as the system slowly departs the area. The main area
of focus for accumulations will be along the Huron Mountains and
west along the high terrain of the Keweenaw southwest to near
Ironwood. At this point, expect to see around 1 to 3 inches of
snowfall accumulation through the day with locally higher amounts
close to 4 inches. The east half, east of Marquette will only see
light accumulations. There may still be a bit of a rain mixture
along the Great Lakes shoreline, but the colder air moving in may
help to limit that as well. The lake effect/enhanced locations that
will see the heaviest precip will be in the favored north to north-
northwest wind favored snow belts. Snow ratios should remain fairly
low through this time period as there is not much forcing in the DGZ
and the DGZ looks as if it will remain above the lake effect
convective layer.

Tonight: As the surface low and upper-level 500mb low continue to
slowly slide to the east, the surface trough will linger across the
area. Temperatures aloft will continue to cool through this time
period with much of the U.P. dropping into the -6C to -9C range at
850mb. This again will keep lake effect snow chances in the forecast
through the overnight hours. One limiting factor for Lake effect is
the deeper system moisture will be exiting the area as the surface
low slips farther off to the east. This will help to reduce the
amount of lake effect snow over the western U.P. and actually,
soundings suggest that the lake effect snow may transitions over to
an occasional mix of snow and drizzle/freezing drizzle over the far
western U.P. by late evening as the potential for ice in the cloud
decreases. Areas from the Keweenaw Peninsula eastward along Lake
Superior (northwest wind favored areas) will continue to have a good
chance of lake effect snow as that area will remain a bit close to
the departing deeper system moisture. Additionally, an increased
fetch on the northwest flow will help to keep the sounding more
moisture through tonight over the eastern U.P. In addition, another
shortwave rotating around the main upper-level low is progged to
slide into the area this evening through the overnight hours, which
will help to steep lapse rates a bit and keep the lake effect snow
cover fairly extensive over the eastern portion of the U.P.;
therefore, have increased the chance of snow for those areas.
Overall QPF does not appear to be too heavy with the lake effect
with the west only seeing and additional inch or so tonight while
the east sees and additional 1 to 2 inches of snow through the
overnight hours. Snow ratios should continue to be fairly low
through this time period as there continues to be little forcing in
the DGZ; however, the colder air aloft and the hint of the shortwave
sliding through tonight may bump the snow to liquid ratios up a bit.

.LONG TERM...(Friday through Wednesday)
Issued at 458 AM EST THU DEC 1 2016

Fri into Fri night: Models indicate the closed low over sw Quebec
will weaken and lift east toward New England late Fri. Behind the
low, cold air will linger over the Upper Great Lakes under a
cyclonic nnw flow. However 850 mb temperatures progged to be in the
-5C to -6C range will only be marginally cold enough to support lake
effect pcpn with Lake Superior sfc temps of 6-7C. Snow will be the
primary precip type although a mix of rain is possible along the
shoreline and east during the daytime hours on Fri. Given the
general absence of enhancement and a fairly elevated dgz expect any
snow accums to be inch or less.

Sat into Sat night: Light lake effect precipitation supported by low-
level convergence should be dwindling or ending over the east half
by afternoon or evening as the high pressure ridge axis moves across
Upper Michigan and winds back more west to southwest.

Sun into Sun night: Models indicate that the next shortwave trough
in zonal flow aloft will move in from the Northern Plains late Sun
into Sun night. Deep layer q-vector convergence ahead of this
shortwave will result in pcpn spreading w to e across the cwa on
Sun. Pcpn will be mostly in the form of snow over the west half but
will be more a mix of rain and snow east half due to moderation from
Lake Mi in southerly flow ahead of shortwave. 850 mb temps
-6 to -7c should be sufficiently cold enough given Lake Mi sfc temps
of 9C for some lake enhancement of pcpn into Schoolcraft and Luce
counties Sun into Sun evening which could produce some accumulating
snow well inland from Lake Mi. Given limited moisture inflow with the
system expect most system snow amounts to be generally less than an
inch.

Monday into Thursday: Models trending toward more amplified pattern
for next week as a 120+ kt 300-250 mb jet max and assoc shortwave
energy digging in from the eastern Pacific will carve out a broad
mid-upper level trough over the Western CONUS by early next week.
Model consensus of downstream ridging into the Great Lakes region in
response to the developing western CONUS trough will keep Upper Mi
mostly dry Mon into Mon night with a slight warming trend. Model
uncertainty increases from Tue into late week with the 00Z GFS being
much more progressive than 00Z ECMWF and Canadian with stronger
shortwave energy ejecting out of base of western CONUS trough. Given
uncertainty will use model consensus for pops which tend to keep
area dry from Mon into most of Tue but then brings in pcpn for Tue
night into Wed. Evolution/track of developing strong sfc low is very
much in question so initial pcpn for Tue night into Wed may end up
being more of a mix of rain/snow and then transition to more lake
enhanced/lake effect snow for late next week. Once cold advection
ensues behind the system, there will also likely be a period of
stronger winds accompanying lake effect snow later in the week.
&&

.AVIATION...(For the 12Z TAFS through 12Z Friday morning)
Issued at 720 AM EST THU DEC 1 2016

Cyclonic flow on the backside of low pressure over eastern Lake
Superior will result in mostly prevailing IFR conditions with -shsn
at KIWD/KCMX/KSAW through this afternoon. The snow may mix with rain
at times at KSAW. With a more direct upslope flow, IFR conditions
will be most persistent at KIWD with even some LIFR at times. -Shsn
will continue today through Friday morning at KIWD and KCMX with NW
flow off Lake Superior, which will keep ceilings lower and visiblity
reduced in the heavier snow bands. KSAW will see visibility improve
late this afternoon through tonight as winds turn northwesterly,
which should keep most of the precip north and east of the site. Low-
level moisture will linger though, keeping ceiling at MVFR to IFR at
times at KSAW.
&&

.MARINE...(For the 4 AM Lake Superior forecast issuance)
Issued at 506 AM EST THU DEC 1 2016

A surface low over eastern Lake Superior this morning will slowly
drift eastward through into Quebec by this afternoon. On the back
side of the low pressure center, the pressure gradient will be tight
enough to support winds of 20 to 30 knots over eastern Lake Superior
this morning with a few gale force gusts to 35 knots possible. A low
pressure through will then linger over the western Great Lakes
tonight through Friday; however the pressure gradient is not
expected to be as tight with winds remaining 25 knots or less. High
pressure will then build into the area Saturday and Sunday with
winds expected to be below 20 knots.
&&

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

$$

SHORT TERM...KEC
LONG TERM...Voss
AVIATION...KEC
MARINE...KEC



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