Area Forecast Discussion
Issued by NWS Marquette, MI

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FXUS63 KMQT 151948
AFDMQT

Area Forecast Discussion
National Weather Service Marquette MI
348 PM EDT Fri Sep 15 2017

.SHORT TERM...(Today and tonight)
Issued at 455 AM EDT FRI SEP 15 2017

An inverted surface trough/warm front is currently draped southwest
to northeast across Lake Superior, with much of the area under a
warm and humid airmass early this morning. Showers and
thunderstorms that developed last night across the Arrowhead of
Minnesota have tracked across western portions of Lake Superior.
The main forecast concern today and tonight will be the showers
and thunderstorms moving across western portions of Upper Michigan
through the morning hours, unseasonable warm temperatures, a
moderate swim risk for the beaches along northern Lake Michigan in
southern Schoolcraft County, and then the arrival of additional
showers and thunderstorm later this evening across the west.

Today: With the main axis of warm, moist air advection associated
with the ongoing early morning convection taking aim towards north
central portions of Lake Superior, expect these showers and storms
to continue to lift northeast across the west and north central
portions of Upper Michigan through the rest of the morning. With an
outflow boundary trailing into southwest portions of the area,
cannot rule out some additional development across the south as
moisture continues to stream overhead. However, the more
widespread convection is expected to stay across the west and
north central. By the mid/late morning hours, lingering showers
and storms should vacate the area and push out across the open
waters of Lake Superior. Cloudy skies will begin to break up a
bit, and possible even clear out in some locations through the
afternoon hours. We`re looking at another unseasonable warm
summer-like with temperatures around 10 to 15 degrees above normal
with breezy south winds. The breezy southwest winds will create a
moderate swim risk at Lake Michigan beaches in southern
Schoolcraft County.

This evening/tonight: Showers and thunderstorms will be possible
late in the day across the far west as the inverted surface
trough/warm front is progged to anchor across Upper Michigan. This
baroclinic zone should be further enhanced by the cooler air pushing
inland and increasing low-level moisture. Later tonight, the main
axis of better moisture is progged to lift north of the area as mid-
level flow transitions from westerly to southwesterly in response to
shortwave energy lifting north across the northern Plains. This will
keep the better instability west of the area for the most part, but
we should still see enough instability to warrant mentions of
thunder in the forecast. As the better, deeper moisture lifts north
into the Arrowhead of Minnesota over night, expect showers and
thunderstorms to come to an end across the west as we progress into
the overnight hours.

.LONG TERM...(Saturday night through Friday)
Issued at 348 PM EDT FRI SEP 15 2017

Guidance continues to hold onto the dominant upper level ridge
across the eastern CONUS through the weekend; however, there
continues to be some nudging to the east which could bring the
upstream trough further east towards the Upper Peninsula. Will
continue to bring steady increases of precip and possibly thunder.
With a low pressure system lifting north of the forecast area Sun,
guidance indicates a frontal boundary will precede a surface ridge
of high pressure late in the weekend into early next week. This will
then allow dry weather to return.

The pattern does start to become more active with a quasi-zonal
orientation from Tue-Thur of next week. This will bring periodic
chances for showers and possibly thunder, but also with more
seasonal temps.
&&

.AVIATION...(For the 18Z TAFS through 18Z Saturday afternoon)
Issued at 246 PM EDT FRI SEP 15 2017

LLWS at all sites tonight and a fairly straightforward forecast at
KIWD.

A little more complicated at KCMX and KSAW. KCMX is still stuck in
low CIGS with eastern flow off the lake and plenty of upstream low
level moisture. Expect fog to develop tonight at KCMX, but there is
uncertainty in the timing and extent of that. Conditions should
improve at KCMX Sat morning as winds become southerly.

At KSAW, models continue to indicate northern low level winds
bringing moisture off Lake Superior, which may result in fog this
evening. South to southwest winds tonight should improve that
situation. Plenty of uncertainty with that scenario though.
&&

.MARINE...(For the 4 AM Lake Superior forecast issuance)
Issued at 455 AM EDT FRI SEP 15 2017

An inverted surface trough currently anchored across Lake Superior
will strengthen later today and tonight, expect winds between 20 to
30 knots in response. Saturday through Sunday, winds will be around
or less than 20 knots. Next week, winds look like they will remain
less than 15 knots through the first half of the week.
&&

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

$$

SHORT TERM...Ritzman
LONG TERM...Beachler
AVIATION...Titus
MARINE...Ritzman



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