Area Forecast Discussion
Issued by NWS Marquette, MI

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FXUS63 KMQT 191032

Area Forecast Discussion
National Weather Service Marquette MI
632 AM EDT Thu Oct 19 2017

.SHORT TERM...(Today and tonight)
Issued at 401 AM EDT THU OCT 19 2017

...Dry and breezy conditions will lead to elevated fire weather
conditions today...

Early this morning, a cold front continued to push eastward across
Upper Michigan. Behind this front, much drier air began to advect
across the region. In fact, dew points this morning dropped down
into the upper teens and 20s across much of the west and central.

The main weather story today is the elevated fire weather conditions
due to the very dry airmass and breezy westerly winds. Behind the
front a brief stint of cold air advection has begun moving across
Upper Michigan, and will continue through much of the day today.
This cooler air aloft will allow low-level lapse rates to steepen as
diurnal heating picks up later this morning and afternoon. As a
result, expect the boundary layer to mix quite a bit deeper than
yesterday. BUFKIT momentum transport values suggest wind gusts could
approach 30 to 40 mph at times later today. Along with the high
momentum mixing down, much drier is will also mix down to the
surface and drop dew points down into the 20s. This will result in
relative humidity values plummeting into the 20-30% range across
much of Upper Michigan. There is some uncertainty in how low
relative humidities will get, in fact we could see a few values drop
into the teens briefly this afternoon. Temperature wise, we will see
a cool down compared to yesterday; however, given how dry the
airmass will be temperatures should modify nicely into the low to
upper 60s. Locations locations in prime downslope flow due to
westerly winds will likely see the warmest temperatures today.

Tonight, return flow will develop across the area as surface high
pressure tracks eastwards towards the Mid-Atlantic states and a
developing surface low in the lee of the northern Rockies in Canada
becomes established. This return flow will push the drier are out
the region overnight, so dew points should be on the rise. Winds
could get a little breezy, especially across the west where the
pressure gradient will be a bit stronger. The combination of breezy
winds and increasing low-level moisture will allow overnight lows to
remain fairly mild and drop into the 40s, with 50s closer to the
Great Lakes.

.LONG TERM...(Friday through Wednesday)
Issued at 259 AM EDT THU OCT 19 2017

Troughing in the west and a ridge over the ern U.S. will be found
12z Fri. The ridge moves to the eastern seaboard 12z Sun while the
trough moves into the plains. Dry weather looks to hold into Sat
before chance pops move into the west late and then they gradually
move to the east. Did not make too many changes to the going
forecast. Above normal temperatures continue this period.

In the extended, GFS and ECMWF show a 500 mb trough over the central
U.S. Sun with a sfc cold front moving through the area. More
troughing remains over the area for Mon and then cold air with a
digging trough comes in for Tue. This 500 mb trough digs further for
Wed with 850 mb temperatures dropping to -5C to -6C. With Lake
Superior being around 10C to 12C, this would be enough for lake
effect pcpn. The trough moves into the ern U.S. on Thu. Above normal
temperatures continue into Mon and then cooler and near normal
temperatures come in for Tue and beyond.

.AVIATION...(For the 12Z TAFS through 12Z Friday morning)
Issued at 631 AM EDT THU OCT 19 2017

VFR conditions are expected to prevail over the next 24 hours. The
main aviation concerns will be the continuation of strong and gusty
westerly winds at KCMX, and then the transition back to gusty  winds
at KIWD and KSAW later this morning through the afternoon. Tonight,
winds at all terminals will subside, but low-level wind shear
will ramp up.

.MARINE...(For the 4 AM Lake Superior forecast issuance)
Issued at 312 AM EDT THU OCT 19 2017

Today, expect gales of 35 to 40 knots across the northern and
eastern portions of the lake as colder air continues foster better
mixing of higher winds down to the lake waters. Given the westerly
flow, locations especially north of the Keweenaw Peninsula may see
additional funnel of the wind, and therefore further enhanced wind
speeds. Expect these gales to hold on through a good portion of the
day today, but they will start to diminish from west to east across
the lake later this evening. Tonight winds will subside to around or
less than 25 knots. Friday through Monday, winds will remain mostly
between 20 and 25 knots.

Upper Michigan...
Lake Superior...
  Gale Warning until 5 PM EDT this afternoon for LSZ243>245-264-

  Gale Warning until 2 PM EDT this afternoon for LSZ263.

Lake Michigan...


SHORT TERM...Ritzman
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