Area Forecast Discussion
Issued by NWS Marquette, MI

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FXUS63 KMQT 182003
AFDMQT

Area Forecast Discussion
National Weather Service Marquette MI
403 PM EDT Thu May 18 2017

.SHORT TERM...(This evening through Friday)
Issued at 225 PM EDT THU MAY 18 2017

The main forecast highlights will be the diminishing cloud cover
tonight and a cold night in store across much of the area, with
low temperatures expected to drop to around or below freezing
across much of Upper Michigan. No frost/freeze headlines are planned
as climatologically it is not uncommon for temperatures of that
degree this late in the spring across Upper Michigan. However, if
you have plants that are sensitive to the cold you may want to
consider covering them, or bringing them indoors, if possible.

A cold and windy day was observed across much of the area as low
pressure continued to lift northeast across central and eastern
portions of Upper Michigan. Lingering rain showers will continue to
diminish across the eastern half of the area; however, areas
downwind of Lake Superior across central and eastern portions of the
area will likely see drizzle linger through the rest of the
afternoon and evening hours as onshore flow continues. Northerly
winds will diminish in speed from west to east as the stronger
pressure gradient gradually relaxes through the evening hours. As
dry air upstream of the area continues to filter eastward, skies
will gradually clear tonight. The key to how cold temperatures will
get tonight is dependent on how low dew point temperatures drop. The
models are in fairly good agreement with dew points dropping down in
to the mid to upper 20s; therefore, given the ample radiational
cooling overnight, expect overnight lows to drop down to around or
below freezing. Locations across the interior central will have the
best chance at seeing temperature dropping down into the mid 20s.
Locations near the Great Lakes will likely see temperatures remain
just above freezing, especially across the shores of Lake Superior
and west of Lake Michigan across south central Upper Michigan.

Friday looks dry and sunny as high pressure moves just north of the
area. Ample mixing through the afternoon hours will allow dew points
to gradually drop into the teens through the afternoon hours, as
drier air gets mixed down to the surface. This drier air mass should
be able to modify nicely back up into the 50s given the ample
diurnal heating expected. Along the shores of Lake Superior,
especially from the northwest to the northeast, temperatures will
likely stay a bit cooler, but still climb into the mid/upper 40s.
Cloud cover will be on the increase through the end of the day on
Friday, especially across the south, but no precipitation is
expected.

.LONG TERM...(Friday night through Thursday)
Issued at 402 PM EDT THU MAY 18 2017

A cool pattern is shaping up for the Upper Great Lakes heading thru
next week. Mid/upper level low currently over the central Rockies
will head out across the Plains early this weekend and into the
Upper Great Lakes early next week. As this occurs, a ridge/strong
positive height anomaly will develop along the w coast of N America
(500mb heights reach 250m above normal near the BC coast). This will
support a deepening trof downstream, becoming centered roughly in
the Great Lakes region next week. 500mb height anomalies will peak
during the middle of next week at nearly 250m blo normal for this
time of year over the Great Lakes/Ohio Valley. Needless to say, this
will set the stage for cool weather/blo normal temps next week.
Although the western ridge will weaken, positive height anomalies
bridged e across Canada toward Greenland should maintain blo normal
heights/troffing over se Canada/eastern CONUS thru the end of the
month. This should support overall blo normal temps thru the last
days of May. As for pcpn, energy ejecting from the Rockies will
support another low pres system tracking into the Upper Great Lakes
this weekend, bringing another round of wet weather, centered on Sat
aftn/night. Pcpn next week will depend on the structure of the trof
over the area and shortwaves dropping into it. Right now, it does
not look like there will be any widespread significant pcpn events,
but rather periodic light pcpn events. The midweek period will be a
period to watch for a better potential of widespread pcpn, dependent
on the track of a stronger shortwave dropping se that results in the
trof over the area reaching its peak amplitude.

Fri night...trof will move from the Rockies out over the western
Plains. Lead energy ejecting ne will help increase/thicken high/mid
clouds spreading ne into the Upper Lakes. Lingering dry air at the
lower levels will prevent any pcpn. Although temp fall will be
limited by the increasing clouds and increasing gradient easterly
flow, the lingering dry low-level air will aid temps temps falling
into the 30s for much of the area, with some locations into the
lower 30s.

Over the weekend...as trof lifts toward the western Great Lakes,
associated sfc low will track ne, probably passing across western
Lake Superior during the day Sun and driving an occluded front
across the fcst area. Strong surge of isentropic ascent/moisture
transport will likely spread a band of shra n across the fcst area
Sat aftn/evening. Not out of the question that there could be a few
rumbles of thunder. Shra will then diminish Sat night/Sun under some
dry slotting in the wake of occluded fropa. Rainfall totals for Sat
aftn/Sat night should be in the 0.25 to 0.75 inch range across the
area. Cyclonic westerly flow on Sun may lead to some isold/sct
-shra, especially w where deeper moisture will be wrapping back into
the area. Temps Sat will be held down by thick clouds/developing
shra. Sun will be a little warmer, especially e half where some
sunshine should occur in concert with departing 850mb thermal ridge.

On Mon, with broad mid-level low centered just n of Lake Superior,
some -shra may linger under cyclonic flow. More pessimisitic GFS
solution suggests a chilly day under cloud cover and more persistent
-shra for much of the day, especially across the n and e.

Tue-Thu, as previously mentioned, a stronger shortwave will drop
into the developing mean Great Lakes trof mid week. Depending on the
track of this wave and how wrapped up developing sfc low becomes,
there could be a widespread, cold rain during this time. Right now,
it appears this system will organize just far enough to the se to
keep more significant rainfall out of the fcst area. Still, expect
some potential of shra both days, but more so on Tue when shortwave
trof axis will be passing. Will be quite cool both days under
northerly winds and 850mb temps around 0C. There may be yet another
shortwave dropping into the trof on Thu, continuing at least some
risk of isold/sct -shra.
&&

.AVIATION...(For the 18Z TAFS through 18Z Friday afternoon)
Issued at 113 PM EDT THU MAY 18 2017

LIFR ceilings continue to hang out this afternoon. KCMX/KIWD will be
the first to see improving conditions into MVFR, and then eventually
clearing out through the afternoon and early evening hours. KSAW
will see the low ceilings and visibilities linger through the rest
of the afternoon and evening hours, before gradually improving
tonight into MVFR, and then eventually clearing out. The strong
and gusty northerly winds will decrease across all terminals from
west to east through the evening hours, and then eventually
becoming light and variable as high pressure begins to work into
the area from the north.
&&

.MARINE...(For the 4 PM Lake Superior forecast issuance)
Issued at 225 PM EDT THU MAY 18 2017

Gales of 35 to 40 knots are expected through the rest of the
afternoon across the east half of the lake, before gradually
diminishing to around 10 to 20 knots tonight. Across the east
half, winds have already begun to subside to around 10 to 20
knots, and will continue to further weaken through the overnight
hours. Friday winds will be around 10 to 20 knots, increasing to
20 to 30 knots through the first half of the weekend as another
storm system lifts up across the region. By Sunday afternoon winds
will subside to around 20 knots. Through the first half of next
week, winds are progged to remain around 20 knots.
&&

.MQT WATCHES/WARNINGS/ADVISORIES...
Upper Michigan...
None.
Lake Superior...
  Gale Warning until 8 PM EDT this evening for LSZ251-267.

  Gale Warning until 5 PM EDT this afternoon for LSZ244-245-
     248>250-265-266.

Lake Michigan...
  Gale Warning until 11 PM EDT this evening for LMZ221-248-250.

&&

$$

SHORT TERM...Ritzman
LONG TERM...Rolfson
AVIATION...Ritzman
MARINE...Ritzman



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