Area Forecast Discussion
Issued by NWS Marquette, MI

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FXUS63 KMQT 192342

Area Forecast Discussion
National Weather Service Marquette MI
742 PM EDT Sat Aug 19 2017

.SHORT TERM...(This evening through Sunday)
Issued at 349 PM EDT SAT AUG 19 2017

Main concerns in the short term forecast will be the potential for
very warm high temperatures Sunday, along with showers and
thunderstorms moving in from the west during the mid to late
afternoon hours.

Tonight: Evening showers and thunderstorms will diminish across the
south-central and eastern U.P. as daytime heating diminshes and lake
breeze boundaries fade. Some stronger storms are still possible
through late this afternoon into the early evening hours. This would
be mainly along the boundaries in the greater shear areas. Small
hail and gusty winds would be the main threat, again, this would be
early in the evening. Added support early in the evening would come
from a very subtle/weak shortwave brushing past the east half of the
area. Otherwise, the rest of the night should remain fairly quiet as
weak upper-level ridging builds in across the area from the west.
Winds will be fairly light as the pressure gradient remains fairly
light. This will allow radiation cooling to occur, causing at least
patchy fog to develop over the west half of the U.P. and especially
in areas where rainfall occurred this afternoon and evening.
Overnight lows will be in the 50s across most area; however, areas
along Lake Superior may stay in the 60s as downsloping winds develop

Sunday: The first half of the day will continue to be fairly quiet
across the U.P. as the upper-level ridge and surface ridge begin to
shift eastward. This will allow an upper-level trough and associated
cold front to shift slowly eastward into the west half of the U.P.
during the afternoon hours. Showers and thunderstorms are expected
to develop along and ahead of the cold front as both forcing and
instability increase. Instability values ahead of the front are
progged to be in the 1000-1500 J/kg range as dewpoint jump into the
low 60s. A couple strong to isolated severe thunderstorms are
possible ahead of the cold front as shear values are progged to 25
to 35 knot range orthogonal to the front, lending support to storm
organization. At this point, it looks like the main threat would be
small hail and gusty winds in the strongest thunderstorms. The east
half of the area should remain dry through much of the afternoon as
a CAP remains in place. This capping, along with mostly sunny skies
and downsloping winds, will allow temperatures to warm into the 80s
for most locations. The exception will be along Lake Michigan where
south winds will help to cool temperatures due to the marine
influence. The warmest tempertures will likely occur along Lake
Superior due to downsloping southerly winds. Temperatures in those
areas may warm as high as the upper 80s and a 90 degree reading
would not be totally out of the question.

.LONG TERM...(Sunday night through Saturday)
Issued at 315 PM EDT SAT AUG 19 2017

A band of showers and thunderstorms will develop over west central
Upper Michigan along an advancing cold front and upper trough Sunday
afternoon. These showers and thunderstorms will progress east
southeastward across the remainder of the U.P. Sunday evening.

Trends continue to suggest Monday will now be drier with a more
optimistic cloud cover forecast now expected through the early
afternoon hours during the eclipse. Another shortwave trough will
move out of the northern Plains by late in the day Monday producing
a surface wave along the frontal boundary south of the area over
Wisconsin. Precipitation shield from this feature will remain mainly
south of the U.P. but may graze southern sections Monday night into
early Tuesday.

A reinforcing push of cooler air will push into the Upper Lakes by
late in the day Tuesday with an extended period of cool but pleasant
weather expected through the remainder of the week into next
weekend. It could even be cool enough Wednesday night into Thursday
for some patchy frost across the interior west. Temperatures will
slowly modify to near normal by next weekend.

.AVIATION...(For the 00Z TAFS through 00Z Sunday evening)
Issued at 738 PM EDT SAT AUG 19 2017

VFR conditions expected at each TAF site through late Sun afternoon.
S winds may gust over 20 kts on Sun afternoon at SAW and there could
be scattered showers or thunderstorms at all the TAF sites late in
the aftn as a cold front approaches from the west.

.MARINE...(For the 4 PM Lake Superior forecast issuance)
Issued at 349 PM EDT SAT AUG 19 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. South winds may gust close to 25 knots Sunday afternoon as
a cold front slides through, but it should be for a short duration.
The next chance for gusty winds will be Wedensday 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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