Area Forecast Discussion
Issued by NWS Marquette, MI

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FXUS63 KMQT 130955

Area Forecast Discussion
National Weather Service Marquette MI
455 AM EST Wed Nov 13 2019

.SHORT TERM...(Today and tonight)
Issued at 359 AM EST WED NOV 13 2019

The overall story of the short term will be light snow overspreading
the region forced by modest low to mid level theta-e advection ahead
of a low level trough currently over the eastern Dakotas early this
morning. High-level clouds can already be seen streaming in from the
NW this morning on IR satellite. As the clouds continue to work in,
and as a SW LLJ lifts overhead, this morning`s very chilly temps (-5
to -10 at a few RAWS sites) should warm back to at least the mid
single digits by sunrise. In the downslope areas around IWD,
Ontonagon, MQT, Munising, and Grand Marais, localized gusty winds of
20-25 mph may warm the air slightly because of this downsloping
in southerly flow but also make it feel colder. These gusts will
cover all of Upper Michigan by mid-morning once some low level
mixing develops, and will be strongest out east today where the
passage of the LLJ coincides with deeper diurnal mixing (though
all things considered the mixing is still quite shallow) as well
as along the immediate Lake Michigan shoreline from the Garden
Peninsula to Manistique and Port Inland where a few 30 mph gusts
will be possible. Overall snowfall amounts look pretty modest with
this wave. They should be around 1-2" roughly along and south of
M-28, with 2-3" expected from Iron Mountain east to Escanaba and
south to around Menominee.

However, there`s a big exception here, and one that`s been talked
about for at least a few days now. SSW flow off of Lake Michigan and
the Bay of Green Bay is expected to significantly enhance snowfall
over parts of the eastern U.P. today. 850 mb temps around -13 C atop
Lake Michigan`s surface temps about 48 F gives a delta T of 23 C,
give or take, and lake-based equilibrium levels of around 8 kft,
which is plenty of lake-based instability for a robust snow band to
point somewhere int the eastern U.P. Confidence is high in
significant snows falling somewhere east of M-94 in Schoolcraft
County, but low in exactly where. The NAM continues to be the west
outlier, bringing the convergence band right into Manistique, while
most other models drive it just east of there, up through Blaney
Park, Germfask, McMillan, Newberry, and then into northeastern Luce
County. The CONSShort, NBM, and WPC QPF are all in pretty good
alignment, so feel that the QPF grids are justified. Looks like
there should be deep enough snow growth per model soundings for at
least 15:1 SLRs (and maybe higher) though stronger winds and some
shear in the low levels could fracture the dendrites and drop them
somewhat. Overall though stayed in the mid to upper teens for SLR,
which ends up giving amounts of 8-12" in these areas.

Even though confidence isn`t high in exactly who will see the
highest totals, the combination of these amounts, this being a
slightly wetter snow, and gusty winds leading to patchy blowing
snow justifies upgrading Luce County and southern Schoolcraft
County to a Winter Storm Warning. Even outside of the main band,
secondary bands or at least enhancement from lake moisture and
land breeze convergence should lead to amounts of 3-6" east of
Nahma Junction, across the Garden Peninsula, and into Manistique.
Therefore, will end up including Delta County in a Winter Weather
Advisory along with northern Schoolcraft. For much of Delta
County, accumulations are right on the advisory criteria
threshold, but there are a few nudgers which make the advisory
defensible: the roads are cold allowing for immediate
accumulation, it will again be breezy leading to some blowing
snow, and the snow will fall during the day into the afternoon,
leading to slick roads for the afternoon commute.

For tonight, once that band of precip moves out attention turns to
the west and the Keweenaw where there should be enough convergence
along the actual trough combined with lake-based instability for a
brief burst of snow showers this evening. Not expecting much if any
accumulation from these, however. In-house tools continue to
highlight the possibility of freezing drizzle, but all NAM and GFS
soundings I could find still showed saturation to at least -10 C.
Therefore, stuck with just snow showers as the ptype. Regardless of
any precip, lake-effect clouds will certainly stick around through
the night, except far from Lake Superior in the south-central U.P.

.LONG TERM...(Thursday through Tuesday)
Issued at 413 AM EST WED NOV 13 2019

Although at the start of Thursday, NW LES will be ongoing, it
should be short-lived as it tapers off by about midday for most.
However, by Thursday evening, as a frontal boundary works its way
down into the U.P., some light snow showers and/or freezing
drizzle will be possible. Despite this boundary, the overall
airmass aloft will be rather dry, hence not much vertical depth to
being able to produce much more than said drizzle and/or light
snow. Little to no impacts are currently anticipated.

This light stuff will continue into Friday, primarily for the
east, coming to an end Friday night as high pressure builds in.
Enjoy this brief reprieve because by late Saturday, the next round
of precip arrives as a shortwave marches through. Mixed precip may
be possible during the day on Sunday given the temps expected
(more on temps just below here) with the precip largely gone
overnight Sunday. But, the pattern remains unsettled into early
next week as more showers grace the area with its presence, with
those mixed precip chances persisting.

Now for temps: near normal temps are anticipated to return. On
Thursday, the below normal temps continue, with a reinforcing shot
of colder air on Friday before an overall warming trend commences.
Highs are looking to warm into the upper 30s to around 40 degrees
on Monday and Tuesday, with lows of course responding accordingly.
Expect the coldest night Friday night into Saturday morning, with
single digits (the last time for this forecast period) and teens.

.AVIATION...(For the 06Z TAFS through 06Z Wednesday night)
Issued at 1208 AM EST WED NOV 13 2019

Expect VFR conditions for the TAF sites into Wed morning under
ridging and generally clear skies.

For late Wed morning into the afternoon, it is possible some
light snow could work into the terminals towards the 15-18Z time
frame along with MVFR cigs. Still quite a bit of uncertainty on
timing right now, so mid shift can fine-tune the arrival of this
snow tomorrow on 12z TAF package.

.MARINE...(For the 4 AM Lake Superior forecast issuance)
Issued at 454 AM EST WED NOV 13 2019

Expect a few gale force gusts out of the south today over eastern
Lake Superior with 25-30 kt winds elsewhere. The strongest winds
will likely be this afternoon near Whitefish Point. However since it
is a short duration and gusts should stay in the mid 30s kts, did
not feel a Gale Warning was needed. Winds veer to NW tonight behind
a cold front and weaken slightly to 20-25 kts. The next strong wind
event will be on Thursday with WSW gales expected by Thursday
afternoon over the western lake, becoming W gales across the lake in
the evening. A few 40 kt gusts are expected where winds channel
between Isle Royale and the Keweenaw. Therefore, have issued a Gale
Watch for the entire lake for Thursday afternoon through late
Thursday night/early Friday morning. Winds veer to NW on Friday and
diminish to 15-20 kts by Friday afternoon, then quickly back to S on
Saturday and increase back to near 30 kts by Saturday evening,
especially over the eastern lake. Southerly winds continue into
Sunday but relax back to around 20 kts.

Some freezing spray is expected to continue this morning, mainly near
the Michigan shore but probably intersecting the shipping lanes near
the tip of the Keweenaw Peninsula. That should abate by this
afternoon. More freezing spray (but still not warning-criteria) is
likely over the north-central lake Friday morning.

Upper Michigan...
  Winter Weather Advisory from 9 AM this morning to 10 PM EST this
     evening for MIZ013-085.

  Winter Storm Warning from 9 AM this morning to 10 PM EST this
     evening for MIZ007-014.

  Lakeshore Flood Advisory from 11 AM this morning to 9 PM EST
     this evening for MIZ014.

Lake Superior...
  Gale Watch from Thursday afternoon through late Thursday night
     for LSZ265>267.

  Gale Watch from Thursday afternoon through Thursday evening for

Lake Michigan...


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