Area Forecast Discussion
Issued by NWS Marquette, MI

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FXUS63 KMQT 120955

Area Forecast Discussion
National Weather Service Marquette MI
455 AM EST Sun Nov 12 2017

.SHORT TERM...(Today and tonight)
Issued at 454 AM EST SUN NOV 12 2017

The latest water vapor imagery and RUC analysis shows a well defined
shortwave trough moving e through the Upper Great Lakes. Cold
advection associated with this shortwave feature and low-level
convergence along sfc trough is supporting what looks to be isolated
-shsn over eastern Lake Superior in the past hour.  Marginally cold
airmass as noted on RAP and HRRR fcst soundings suggest it might be
cold enough to support -shsn into eastern counties today in a nw
flow although probably can`t completely rule out fzdz mixing in too.

Today and Tonight, 850mb temps drop to -7C to -8C behind the
shortwave and remain that way through today into tonight. A sfc
trough settling over eastern Lake Superior today will remain in
place into this evening and could provide a focus for isolated -shsn
into tonight. Light, isolated snow showers are possible in NW wind
snowbelts through the period, but only a light dusting of
accumulation is expected. There is a slight chance there could be
drizzle/freezing drizzle due to dryness in the DGZ, but given
dryness near the sfc on the fcst soundings fzdz/dz seems less
likely. Otherwise, expect dry conditions elsewhere across the cwa.

.LONG TERM...(Monday through Saturday)
Issued at 355 AM EST SUN NOV 12 2017

Overall the beginning of the week will start off quiet, but as we
progress through the middle to end of the week an active pattern is
expected with two systems progged to impact the region, one during
the middle of the week and the other towards the end of the week.
The first system/cold front will bring chances for breezy winds and
widespread rainfall. The second system progged to impact the region
Friday into Saturday is the stronger of the two systems and could
bring significant impacts across Upper Michigan.

Monday through Tuesday: Lingering light lake effect is possible
across the east early on Monday, but then we will see a drying trend
through the day on Monday and the first half of Tuesday as surface
high pressure tracks east across the region. A weak upper-level wave
is progged to dig across the Upper Great Lakes Monday night into
Tuesday, but do not expect any precipitation with this impulse. Late
on Tuesday, chances for precipitation will return as warm air
advection overspread Upper Michigan ahead of an approaching
shortwave trough. Given the warm air advection and low-level
temperatures climbing above freezing, expect precipitation to remain
all rain late Tuesday through the overnight hours.

Wednesday through Thursday: As the above mentioned shortwave
continue to dig across the region on Wednesday, a surface
trough/cold front will push eastward across Upper Michigan. Ongoing
precipitation will continuing, especially across the eastern half of
the area, and should remain mostly all liquid through the majority
of the day. As the front slides east across the area, winds will
become west-northwesterly and gusty through the afternoon as a brief
bout of cold air advection begins to track southward. This cold air
on the back side of the system doesn`t look terrible impressive, but
may be just cold enough to foster the development of lake effect
snow late Wednesday into Thursday across the northwest to north wind
snow belts. As these winds come onshore, expect strong and gusty
winds, especially east of Marquette where wind gusts could approach
30 to 40 mph. These strong winds off of Lake Superior will foster
the development of large waves, especially along the shoreline
across Alger county, which could lead to minor beach erosion. During
the day on Thursday, a narrow area of high pressure will track
across the area and shut down lake effect snow from west to east and
allow winds to come down as well.

Thursday night through the weekend: The attention then turns to the
potential for a significant storm to impact the Upper Great Lakes.
The medium range models continue to advertise strong longwave
troughing across the mountain west ejecting out across the Plains by
Friday. Associated with this upper-level energy coming across the
Rockies, two areas of lee cyclones are expected to develop, one
across the northern Rockies in Canada and the other developing
across the High Plains of Colorado and Wyoming. As the main upper-
level wave tracks across the Plains and towards the Midwest, the
southern and northern streams associated with the main upper-level
trough are progged to phase, allowing for cyclogenesis to occur
across the Great Lakes region. This would be especially true if the
upper-level trough takes on a negative tilt, which is advertise by a
few medium range models. Based on the main upper-level pattern, tend
to favor the GFS, GFS ensemble mean, and ECMWF solutions at this
time. This would favor a system track across southern Lake Michigan
late Friday, and then across lower Michigan and eventually Lake
Huron through the day on Saturday, keeping Upper Michigan on the
cold side of the system, with the potential for accumulating system
snow Friday into Saturday. Regardless of the track, the medium range
models are showing gusty northwest winds and lake effect snow
developing behind the system as cold air advection streams south
across the region. Overall, this time period will need to be
monitored closely as the details continue to become fine-tuned
throughout the week.

.AVIATION...(For the 06Z TAFS through 06Z Sunday night)
Issued at 223 AM EST SUN NOV 12 2017

MVFR to low VFR cigs will persist for this forecast period at all

.MARINE...(For the 4 AM Lake Superior forecast issuance)
Issued at 454 AM EST SUN NOV 12 2017

Lighter winds under a weak pressure gradient will persist into
Monday. Tuesday, southerly winds will increase to 20 to 30 knots as
the pressure gradient strengthens ahead of an approaching cold
front. This front is expected to track across Lake Superior on
Wednesday, with W-NW gales 35-40 knots still looking possible
Wednesday afternoon into Wednesday night.

Southerly gales of 35-40 knots will be possible Friday ahead of
stronger storm system developing over the Great Lakes. Higher end nw
gales seem like a good bet behind the storm system late Fri night
into Sat.

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


LONG TERM...Ritzman
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