Area Forecast Discussion
Issued by NWS Marquette, MI

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FXUS63 KMQT 151006

Area Forecast Discussion
National Weather Service Marquette MI
506 AM EST Wed Nov 15 2017

.SHORT TERM...(Today and tonight)
Issued at 420 AM EST WED NOV 15 2017

Early this morning, water vapor imagery shows broad troughing
tracking across the northern and central Plains, with a few embedded
shortwave features, and the associated low pressure system moving
across the Upper Mississippi Valley. Ahead of this trough,
widespread rain has developed across the warm sector, which
continues to lift northeast across central and eastern Upper
Michigan. The main forecast concern over the next 24 hours is the
transition from rain to snow later today and tonight and the onset
of strong and gusty northerly winds, especially near the shore of
Lake Superior.

The above mentioned low pressure system will track eastward across
Upper Michigan today and slightly strengthen across eastern Upper
Michigan as the southern and northern streams phase later
today/tonight. As the surface low tracks east across the area today,
rain will eventually transition over to patchy drizzle as the deeper
moisture and better large-scale lift slowly shift eastward with the
warm sector. Across the west, wrap around precipitation will lift
across the area later today. Initially this precipitation will start
off as rain, but through the late afternoon/evening and into the
overnight hours increasing cold air advection behind the exiting
system will strengthen and allow rain to transition over to snow.

As the main 850mb low slowly traverses the region winds will become
northerly through the overnight hours, favoring lake effect snow
showers in the north wind snow belts. While accumulating snow is
expected, the cold air advection will be on the weaker end of the
spectrum, with reduced lake-induced CAPE values and inversion
heights. These factors coupled with strong winds through the
convective layer should work together to keep snowfall totals
between 1 to 3 inches. The bigger issue tonight may very well be the
reduced visibilities and blowing snow due to strong northerly winds.
Contemplated issuing a wind advisory for tonight for areas
susceptible to the northerly, onshore flow from Lake Superior.
However, there is some uncertainty in how strong the wind gusts will
get over land, so opted to issue an SPS for now. These strong
onshore winds will however lead to beach erosion and the possibility
of lakeshore flooding mainly across Alger County; therefore, have
issued a Lakeshore Flood Advisory mainly for tonight.

.LONG TERM...(Thursday through Tuesday)
Issued at 504 AM EST WED NOV 15 2017

Models suggest that a progressive pattern will prevail over the
northern CONUS/Upper Great Lakes from late this week into early
next week with a couple of mid level troughs and sfc lows
impacting the region bringing rain followed by colder air and LES.

Beginning Thursday, inversion heights quickly falling blo 3kft as
high pres builds into the area should end any lingering LES in the
morning and bring some clearing in the afternoon along with
diminishing winds.

Friday-Sunday, Still plenty of model uncertainty regarding storm
system impacting the Upper Great Lakes mainly Friday into Saturday
and this may continue to be the case until main shortwave energy
associated with the system emerges off the coast of Northern CA
late Thu night/Fri. The latest 00z GFS run shows phasing/deepening
of system perhaps a bit quicker than 18z run but showing a
similar track across central Lake Huron/Georgian Bay on Saturday.
The 00z Canadian shows the farthest south and east solution taking
a track through the Ohio Valley/Lower Great Lakes and is slowest
phasing/deepening the system. The 00z ECMWF solution offers a
compromise solution between the GFS and Canadian. The 00z ECMWF is
slightly deeper than its 12z run but indicates a similar track
across the tip of southern Lake Huron into eastern Ontario while
phasing the system farther south and east than the GFS. Given
model uncertainty will probably lean toward a model consensus
solution hedging closer to the more consistent 00z/12z ECMWF.
Following the consensus solution, expect widespread pcpn mainly as
rain to spread across Upper Michigan Friday into Friday night
with fairly strong WAA and moisture advection (PWAT above 0.75
inch) as the sfc trough moves through the Upper MS valley into the
western Great Lakes. There may be some fzra mixed with snow west
and central late Thu night into early Friday before sfc temps
climb by midday Fri. Fzra or ice potential will be limited by
initial dry 900-700 mb layer as noted on fcst soundings. Although
strong CAA and nw flow LES will develop Saturday behind the
deepening low, confidence in wind strength is still low given
models variability. A period of moderate LES with some heavier
bands will be possible on Sat as the mid-level trough axis rotates
through the area. Given the wind strength there will also likely
be considerable blowing snow. Lingering LES will diminish Sunday
as sfc and mid level ridging builds into the area.

Monday-Tuesday, model confidence in details regarding a clipper
shortwave depicted by the GFS/ECMWF/GEM is low but CAA associated
with this feature could bring LES back into the area Tue into Wed
for the nw wind snowbelts as 850 mb temps drop as low as -16c to
-18c by late Tue night/Wed morning as depicted by the ECMWF and GFS.

.AVIATION...(For the 06Z TAFS through 06Z Wednesday night)
Issued at 1111 PM EST TUE NOV 14 2017

LIFR/VLIFR conditions will continue for most of the period with slow
improvement starting Wed afternoon at all sites.

.MARINE...(For the 4 AM Lake Superior forecast issuance)
Issued at 420 AM EST WED NOV 15 2017

Winds will be less than 20 knots through much of today as a surface
low tracks across the area. However, north-northwest winds behind
the exiting surface low will ramp up across the lake later this
afternoon/evening through the overnight hours, with gale force winds
of 35 to 40 knots expected across much of the lake. Winds will
diminish to around or less than 20 knots by Thursday afternoon.
Friday through Saturday, confidence is not high in regards to how
winds will evolve across Lake Superior. Right now it looks like
southerly gales will still be possible ahead of the system on
Friday, and then northwesterly gales behind the system by late
Saturday into Sunday. In between the two possible gale events, winds
should drop down to between 15 to 25 knots as the surface pressure
gradient is relaxed along the surface trough axis.

Upper Michigan...
  Lakeshore Flood Advisory from 1 AM to 10 AM EST Thursday for

Lake Superior...
  Gale Warning from 6 PM this evening to 10 AM EST Thursday for

  Gale Warning from 4 PM this afternoon to 7 AM EST Thursday for

  Gale Warning from 4 PM this afternoon to 4 AM EST Thursday for

Lake Michigan...
  Gale Warning from 7 PM this evening to 7 AM EST Thursday for



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