Area Forecast Discussion
Issued by NWS Marquette, MI

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FXUS63 KMQT 210655

Area Forecast Discussion
National Weather Service Marquette MI
255 AM EDT Mon Aug 21 2017

.SHORT TERM...(This evening through Monday)
Issued at 354 PM EDT SUN AUG 20 2017

Tonight: The main focus for tonight will be the potential for
isolated to scattered showers and thunderstorms along and ahead of a
cold front sliding through the U.P. Capping has generally been
strong enough over the area to keep the overall coverage at a
minimum; however, a few pop up showers and thunderstorms remain
possible. Again, this will be right along the front and the best
chances will be through the early evening hours. Overnight,
temperatures will cool, allowing the atmoshpere to become even more
stable across the area. This, along with diminishing cloud cover
will allow some patchy fog to form for inland locations and
especially in any location that manages to see some precipiation.
Overnight lows will be mainly in the 50s over the west half, while
the east half will stay in the upper 50s to low 60s.

Monday:  The cold front will stall out to the south of the U.P. by
Monday morning, keeping most of the showers and thunderstorms to the
south of the U.P. through most of the morning hours. Cloud cover
will be reduced through most of the morning into the early
afternoon; however, low pressure sliding across the Upper
Mississippi Valley will cause the stationary front to lift back
northward as a warm front in the afternoon. This will cause cloud
cover to steadily increase across the area from the south, with the
east half of the area expected to see the most cloud cover during
the early to mid afternoon. In addition, model guidance is depicting
an increase in shower and thunderstorm activity during the afternoon
as the frontal boundary lifts northward through the area an
forcing/instability increases. Instability values are expected to be
around 1000 J/kg range, of course, this will largely depend on how
far north the warm front lifts. Deep layer shear values are progged
to be around 35 to 45 knots across the area; however, the shear
vectors are expected to be parallel to the forcing late in the
afternoon. At this point, any severe potentail looks to be limited
to the south central portions of the U.P. where the warm front lift
north of the area. This will keep the better instability across that
area. Locations north and west of that area should see much lower
instability values at or around 500 J/kg or possibly even lower. The
main threats from any strong to isolated severe thunderstorm would
be hail and gusty winds. Temperatures will be a bit cooler as cloud
cover increases during the afternoon hours; however most locations
will still warm into the upper 70s to around 80.

.LONG TERM...(Tuesday through Sunday)
Issued at 253 AM EDT MON AUG 21 2017

Overall, the weather looks to quiet down later this week with brief
sample of fall-like temperatures. On Tuesday, we could see some
lingering showers across the east as a cold front continues to
push across Upper Michigan. Behind this system, high pressure
will slide down from Canada and linger across the area on the
western side of longwave troughing. This cooler Canadian airmass
will ushering in fall-like temperatures by Wednesday, as some
areas may struggle to climb into the lower 60s. By the end of the
week seasonable temperatures will return. For the most part, the
weather looks to remain dry later this week with only a slight
chance for diurnal showers on Wednesday afternoon as a shortwave
digs quickly across the area. Early Thursday morning will be
chilly as clear skies will give way to ample radiational cooling.
Given the very dry airmass progged to be in place, it isn`t out of
the question that we may see a few areas of patchy frost across
the interior west, closer to the Wisconsin border.

The first half of this weekend looks to remain dry; however, as we
progress through the end of the weekend and into the early part of
next week precipitation chances will return as another system tracks
across the region.

.AVIATION...(For the 06Z TAFS through 06Z Monday night)
Issued at 129 AM EDT MON AUG 21 2017

VFR conditions expected through early Mon evening. Patchy shallow
dense fog is expected at IWD and possibly at SAW with lingering
humid airmass in place. Chances for showers and thunderstorms
return late on Monday and into Monday evening, especially at SAW.
May see MVFR conditions develop late Monday evening at SAW.

.MARINE...(For the 4 PM Lake Superior forecast issuance)
Issued at 354 PM EDT SUN AUG 20 2017

Winds will remain at or below 20 knots through the first half of the
work week as the pressure gradient remains fairly weak across Lake
Superior. Southwest winds may gust close to 25 knots through this
evening ahead of a cold front moving through, but it should be for a
short duration. The next chance for gusty winds will be Wednesday as
low pressure slides to the northeast of Lake Superior. Northwest
winds may gust as high as 30 knots during that time period.

Upper Michigan...
Lake Superior...
Lake Michigan...


LONG TERM...Ritzman
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