Area Forecast Discussion
Issued by NWS Marquette, MI

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FXUS63 KMQT 200813

Area Forecast Discussion
National Weather Service Marquette MI
413 AM EDT SAT AUG 20 2016

.SHORT TERM...(This evening through Saturday)
Issued at 355 PM EDT FRI AUG 19 2016

Today`s weather has been driven by a group of MCV centers
originating from multiple convective complexes last night. As of
1930Z, the first is lifting NE near Manistique, while the second is
centered over SW Baraga County. A third center has formed with a
self-maintaining heavy rain/storm complex now over Whitefish Bay.

With some clearing between the first and second MCV, the boundary
layer has recovered to some extent as temps across the south-central
have risen into the mid to upper 70s. This will be a focus for
further convective initiation ahead of the second MCV. In fact,
recent radar trends show activity already increasing. Meanwhile, the
main cold front is draped across the western Upper MI counties.

Expect showers and some storms to track eastward through the early
evening across the south-central. Isolated to scattered showers will
also occur along the cold front as it drifts SE across the CWA
through the evening. With decreasing upper-level support late this
evening into the overnight, most of the CWA will experience a dry

Focus then turns to widespread rain for Saturday. The
aforementioned cold front will stall across northern Lake MI to
central WI overnight as a sharp trough over ND shifts across the
Upper MS Valley. A rapidly strengthening sfc low is expected to
develop along the front late tonight through Saturday. Model
guidance continues to waver on the location of the sfc low, but
solutions are converging on a track from SW WI late Saturday morning
to around the bay of Green Bay at 00Z Sunday. Signs point to the
potential for a band of heavy rain across central Upper MI in
response to decent isentropic lift and deformation under a passing
right entrance to an upper jet axis. At this time, rainfall amounts
of 1.5-2 inches late tonight into Saturday evening will be possible
across a swath of the central U.P.

.LONG TERM...(Sunday through Friday)
Issued at 411 AM EDT SAT AUG 20 2016

Greatest weather impacts during the extended will be Sunday morning
with continued very strong and gusty winds expected over the east
half of Lake Superior and along the east half of Upper Michigan
along the Lake Superior shoreline.

Sunday: The low pressure system is progged to be over far eastern
Lake Superior by 12Z Sunday as the 500mb trough axis is positioned
over the eastern half of the U.P. Plenty of moisture will be in
place across the CWA in the morning to keep scattered rain showers
in the forecast. This will be a result of the proximity to the low,
wrap around moisture as well as 850mb temperatures dropping to
around 5C to 6C. Lake surface temperatures are around 20C, according
to buoy readings, which would create delta T values around 14-15C.
This would result in lake enhanced rain showers with the north to
northwest winds across the area. Winds will continue to be very
gusty over the eastern half of Lake Superior and over the eastern
half of the U.P. between 12Z/22-18Z/22 due to the tight pressure
gradient, mixing down of stronger winds from aloft on cool advection
and enhancement due to the isallobaric wind component. The pressure
change associated with the isallobaric component is progged to be
around 6-8mb between roughly 12Z and 15Z Sunday. The addition of all
the aforementioned wind elements will likely continue to give wind
gusts 35 to 45 mph over Lake Superior and along the eastern
shoreline of Lake Superior, with some of the models showing as high
as 50 mph wind gusts. Between 18Z and 00Z/23, the low pressure
system is progged to shift east of the U.P. allowing the pressure
gradient to relax across the area. This will allow winds to decrease
below 15 to 25 mph by mid to late Sunday afternoon. The rain showers
will also be on a diminishing trend in the afternoon as the low
continues to slide east and winds begin to shift out of the west.
While Sunday will continue to be a dreary day, there will be a high
swim risk for the beaches along Marquette and Alger county, likely
requiring a headline.

Sunday night through Tuesday: As the aforementioned low pressure
system slides into Quebec Sunday night, a surface high pressure
ridge and upper level height rises will slide into the CWA. This
will put the U.P. on the inflection point between ridging aloft and
the trough to the east. Drier air will also be in place allowing for
dry conditions for Sunday night. The surface ridge in place will
allow for light winds and clear skies. This will cause pretty good
radiational cooling for inland locations. Generally kept lows in the
low to mid 40s inland as pwats only drop down to around 75 percent
of normal Sunday night. Overall moisture will continue to be limited
for the remainder of this time period; however, a shortwave is
progged to slide through the area Monday, which may bring additional
cloud cover. Otherwise, the only chance of precipitation will be
Monday night as WAA pushes into the region along and ahead of an
approaching warm front from the southwest. Again, moisture will be
limited so kept the coverage to isolated at this point.

Tuesday night through Wednesday night: Models are depicting a low
pressure system and 500mb trough sliding across central Canada to
northern Ontario during this time period. This would also allow a
cold front to slide through the area. Ahead of the front, southerly
flow will kick in, allowing temperatures to continue to be above
normal for Wednesday. Showers and thunderstorms are expected to
develop along and ahead of the front, with the best chances expected
Wednesday afternoon through late Wednesday night, before the cold
front passes to the east of the U.P. by late Wednesday night into
Thursday morning.

Thursday through the extended: The cold front will continue east of
the area Thursday morning with perhaps some lingering showers and
thunderstorms early in the morning over the far east.
Otherwise,abroad surface ridge will be in place across the Upper
Great Lakes Region with nearly zonal flow expected aloft. This will
keep temperatures near normal for this time period with fairly quiet

.AVIATION...(For the 06Z TAFS through 06Z Saturday night)
Issued at 123 AM EDT SAT AUG 20 2016

Showers will move back into the area before daybreak this morning.
Periods of rain will then continue into the evening as a strong
low pressure system lifts across Upper Michigan. Have backed off
of low clouds at SAW for rest of tonight. VFR conditions at all the
terminals will quickly trend to MVFR late tonight then IFR on Sat
due to the rain and some fog at times, especially at SAW with moist
upslope flow off Lk Superior. As the low moves over eastern Lk
Superior later tonight, expect north winds to increase sharply at
SAW with gusts to 25 kts or higher.

.MARINE...(For the 4 AM Lake Superior forecast issuance)
Issued at 411 AM EDT SAT AUG 20 2016

A low pressure system, rapidly developing along the cold front
stretching across the central U.P. into Wisconsin, will track from SW
WI this morning, to near Green Bay this evening. The low will the
shift east of Sault Ste. Marie by Sunday morning. In response, NE
winds will increase to 25 knots through this afternoon. After the low
passes this evening, N to NNW gales to 40 knots are expected to
develop across the east half of Lake Superior. There could also be
some storm force gusts as high as 50 knots over south central and
eastern Lake Superior late tonight into early Sunday morning. As high
pressure then slowly builds in from the west through Monday, NW winds
will gradually diminish from around 30 knots Sunday morning to less
than 15 knots by Monday morning. A period of southerly winds of 10 to
20 knots is then expected Tuesday into Wednesday as the high pressure
drifts to the SE and low pressure develops over south-central Canada.

Upper Michigan...
Lake Superior...
  Gale Warning from 5 AM to 2 PM EDT Sunday for LSZ251-267.

  Gale Warning from 8 PM this evening to 2 PM EDT Sunday for

  Gale Warning from 8 PM this evening to 11 AM EDT Sunday for

  Gale Warning from 2 AM to noon EDT Sunday for LSZ250.

Lake Michigan...
  Gale Warning from 11 PM this evening to 11 AM EDT Sunday for



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