Area Forecast Discussion
Issued by NWS Marquette, MI

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FXUS63 KMQT 211121

Area Forecast Discussion
National Weather Service Marquette MI
721 AM EDT SUN AUG 21 2016

.SHORT TERM...(Today and tonight)
Issued at 424 AM EDT SUN AUG 21 2016

Wind Advisory remains in effect east of Marquette, along the Lake
Superior shoreline, through 11 am this morning and a Beach Hazard
statement remains in effect through this evening for Marquette and
Alger Counties.

Greatest weather impacts in the short term will be the continued
gusty winds over eastern Lake Superior and over the eastern U.P.
close to the shoreline of Lake Superior through mid morning. This
will also increase wave heights along the shoreline, causing a high
swim risk for Marquette and Alger counties through this evening.

Early this morning surface observations are showing the low centered
roughly over or near Whitefish Point as of 04Z/21 at right around
994mb. Winds are also gusty with Stannard Rock and Granite Island
gusting into the low 40 knot range, Copper Harbor has been gusting
to around 35 knots and the Munising buoy has been gusting to around
33 knots early this morning. Radar trends continue to show wrap
around moisture and lake enhance rain showers sliding across much of
Upper Michigan, with a diminishing trend noted on the far west end
of Lake Superior. WV imagery is indicating a shortwave trough
sliding across the Upper Great Lakes region as of 04Z/21.

Today: The aforementioned low pressure system is progged to just
north of Sault Ste. Marie by 12Z/21 as the 500mb trough axis is
positioned over the eastern half of the U.P. Plenty of moisture will
continue to be in place across the CWA in the morning to keep
scattered rain showers in the forecast, especially for the central
and eastern U.P. 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 still around 20C,
according to buoy readings, which creating 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 and mixing down of stronger winds from aloft on weak cool
advection. The addition of the aforementioned wind elements will
likely continue to give wind gusts 30 to 40 mph over Lake Superior
and along the eastern shoreline of Lake Superior; however, the trend
will be for the pressure gradient to slowly relax through the
morning hours. Between 18Z and 00Z/23, the low pressure system is
progged to shift farther northeast, to near James Bay, allowing the
pressure gradient to further 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 from the west. With the proximity of the trough axis still
fairly close by and another weak shortwave possibly sliding by just
to the north of the area, there may be a some isolated light rain
showers that pop up during the afternoon. The best chance of this
would be over the east half of the U.P. While Today will continue to
be a dreary day with some improvement in the afternoon, there will
still be a high swim risk for the beaches along Marquette and Alger
county. Therefore a beach hazard statement remains in effect through
this evening.

Tonight: As the aforementioned low pressure system slides into
northern Quebec, 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
tonight. The surface ridge in place will allow for light winds and
clear skies. This will cause good radiational cooling for inland
locations. Generally kept lows in the mid 40s inland as pwats only
drop down to around 75 percent of normal. Didn`t go with coolest
guidance as there may be some high clouds that try to work into the
area late tonight and winds become light out of the south.

.LONG TERM...(Monday through Saturday)
Issued at 503 AM EDT SUN AUG 21 2016

Models suggest that a progressive pattern will prevail with a
mid/upper level low/trough over srn BC/Alberta Monday will move to
nrn Ontario by Friday. This will bring a warmup early in the week
with waa ahead of the sfc low and increasing shra/tsra chances
Wednesday as the sfc trough/front moves into the region. Cooler and
drier weather will then move in toward the weekend as high pressure
builds from the nrn plains into the Great Lakes.

Monday into Monday night, shra/tsra associated with the initial waa
surge and 300k-305k isentropic lift along the 850 mb warm front will
remain from nrn Lake Superior northward. With 850 mb temps climbing
into the 11C-14C range, highs will rebound into the mid 70s east to
around 80 west. 850-700 mb theta-e advection and an increasing low
level jet may support shra/tsra development but coverage/strength
will be limited given the dry antecedent airmass.

Tuesday, continued waa and increasing mid level capping will will
reduce any pcpn chances and allow temps to climb into the mid 80s
with dewpoints into the lower 60s.

Wednesday and Thursday, as the sfc trough moves into the area expect
shra/tsra chances to increase by late wed into wed night as moisture
advection bring PWAT values above 1.5 inches. However, only chance
pops were included with uncertainty remaining with
the timing/position/strength of any shortwaves emerging from the
plains that will help support the pcpn. Instability/shear will be
marginal for any stronger storms. The pcpn chances will shift to
mainly the ern cwa by Thursday morning.

Friday into Saturday, Surface high pressure and upper ridging will
then bring dry and mostly clear conditions Friday into early
Saturday. A transition to a more zonal pattern during the weekend
will allow pcpn chances to increase as models suggest potential for
a shrtwv to bring another round of shra/tsra toward the area.

.AVIATION...(For the 12Z TAFS through 12Z Monday morning)
Issued at 720 AM EDT SUN AUG 21 2016

As a strong low pressure system continues to depart to the northeast
of the U.P., gusty winds and rain showers this morning will slowly
diminish throughout the day. MVFR conditions will continue at KSAW
this morning before drier air slides in through this afternoon. High
pressure will slide across each of the TAF sites late this afternoon
into tonight allowing winds to become light out of the west and
conditions to become VFR.

.MARINE...(For the 4 AM Lake Superior forecast issuance)
Issued at 424 AM EDT SUN AUG 21 2016

As the strong low pressure center over far eastern Lake Superior
slowly departs into Ontario and Quebec today, expect northwest gales
of 35-40kt to linger over eastern Lake Superior this morning. As the
low continues north and east, winds will diminish below gale force
by early this afternoon. Winds will gradually diminish further to
under 20kt from west to east this afternoon and tonight as high
pressure ridge arrives. As the high departs, winds will become south
to southwest on Monday, but should remain under 20kt. Then,
tightening pressure gradient in response to the next low pressure
trough moving out over the Plains will result in increasing winds,
with gusts possibly into the 20-25kt range at times Monday night
thru Wednesday, and even into Thursday after the trough passes.

Upper Michigan...
  Wind Advisory until 11 AM EDT this morning for MIZ006-007.

  Beach Hazards Statement through this evening for MIZ005-006.

Lake Superior...
  Gale Warning until 2 PM EDT this afternoon for LSZ251-267.

  Gale Warning until noon EDT today for LSZ250-266.

  Gale Warning until 8 AM EDT this morning for LSZ244-245-248-249-

Lake Michigan...


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