Area Forecast Discussion
Issued by NWS Marquette, MI

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FXUS63 KMQT 202355

Area Forecast Discussion
National Weather Service Marquette MI
755 PM EDT Sun Aug 20 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...(Monday night through Sunday)
Issued at 311 PM EDT SUN AUG 20 2017

As main upper trough moves into the Upper Great Lakes on Monday
night...a wave will develop along the frontal boundary stalled out
just south of the area. As the waves lifts east
northeastward...precipitation shield will move across central
and eastern sections of the U.P. The rain should move east of the
area by Tuesday monring. A reinforcing cold front will drop
southward across Lake Superior by late in the day Tuesday.  It`s
passage should be dry but it will usher in a stretch of cool but
tranquil weather for mid to late week.

Return flow warm advection regime returns for next weekend as will
the next chances of rain for the area.

.AVIATION...(For the 00Z TAFS through 00Z Monday evening)
Issued at 754 PM EDT SUN AUG 20 2017

VFR conditions expected through the period. Maybe an isolated shower
through late evening at KSAW as cold front moves through. Wind shift
will be the main impact from the cold front. Patchy fog possible at
SAW late tonight especially if they see some rain this evening.
Chances for showers and thunderstorms return late on Monday and into
Monday evening, especially 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...


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