Area Forecast Discussion
Issued by NWS Marquette, MI

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FXUS63 KMQT 182026

Area Forecast Discussion
National Weather Service Marquette MI
426 PM EDT Tue Jul 18 2017

.SHORT TERM...(This evening through Wednesday)
Issued at 219 PM EDT TUE JUL 18 2017

A weak cold front was draped across western Lake Superior and down
into central Minnesota this afternoon. Along this frontal boundary
showers and thunderstorms have developed across western Lake
Michigan and northwest Wisconsin and has slowly pushes east-
northeast early this afternoon. Ahead of the front, differential
heating across central Upper Michigan has allow a few isolated
showers to pop up as well. Dew points have increased ahead of this
boundary into the lower 70s, so conditions have become increasingly
humid this afternoon.

The main forecast concern is how convection will evolve through the
afternoon and evening hours across Upper Michigan as the cold front
pushes eastward, and the chance for strong to severe storms. As the
afternoon progresses, models are in fairly good agreement with
convection increasing in coverage across the west and central as the
warm, moist air continues to spread northeast and works with diurnal
heating to allow capping to erode. With a very moist air mass in
place and high freezing levels, expect any convection to be
efficient rainfall producers with high precipitation rates. With
storm motion only being around 10-15 knots, flooding may be possible
especially across areas that see prolonged precipitation. With
shear only progged to be around 30 knots, the main threat will be
strong downburst winds and small hail as storms may struggle to
remain organized at times. The best chances for strong to severe
storms looks to be across western and portions of central Upper
Michigan this afternoon, and then as the cold front pushes east
and storms begin to congeal into a line the threat will shift east
into the evening hours.

Tonight, the cold front will gradually push across the area and
showers and thunderstorms will diminish from west to east. Wednesday
things will dry out as high pressure moves overhead and skies clear.

.LONG TERM...(Wednesday night through Tuesday)
Issued at 426 PM EDT TUE JUL 18 2017

Wednesday night through Thursday night: A shortwave is progged to
slide through the area through this time period, especially late
Wednesday night into Thursday. There will be just enough forcing and
moisture, mainly over the southern portions of the U.P., to touch
off a few showers and thunderstorms across the area. By Thursday
evening, the shortwave will push out of the area allowing the rain
to end and skies to clear from the west. High temperatures will be
above normal through this time period with highs warming into the
80s, except cooler along the Great Lakes shorelines.

Friday through Sunday: Unsettled weather can be expected again for
the upcoming weekend as an area of low pressure and upper level
trough/shortwave are progged to slide into the Upper Great Lakes
region. Models differ on exact timing/placement and intensity of the
aforementioned features; however, it does look like there will be a
couple better chances of showers and thunderstorms over the weekend.
It doesn`t necessarily look like the entire weekend will be a
washout, but there will be some periods of heavier showers and
thunderstorms. The timing will have to be pinned down as better
sampling occurs and models converge on a final solution. At this
point, will stick with a consensus of the models for this time
period. Temperatures will be above normal for Friday, with highs in
the 80s; however, with more unsettle weather over the weekend,
expect high to cool off a bit to more seasonable readings, in the

Rest of the extended: High pressure is expected to move into the
area through the rest of the extended allowing for mainly dry
conditions for Monday into Tuesday. Again, temperatures should
remain near to slightly below normal through the remaining extended

.AVIATION...(For the 18Z TAFS through 18Z Wednesday afternoon)
Issued at 140 PM EDT TUE JUL 18 2017

Challenging aviation forecast with the arrival of a cold front and
expected showers and thunderstorms. These storms will impact
KIWD/KCMX this afternoon and then KSAW later this afternoon/evening.
There is some uncertainty in regards to the exact location of where
the stronger convection will move; therefore, amendments may be
needed to fine tune as the afternoon/evening progresses. The main
threats will be locally heavy rain, which will likely lead to
reduced visibilities, and gusty winds. Later tonight as the cold
front pushes south of the area, showers and storms will vacate the
area. There is the potential for some fog in areas that see heavier
rainfall this afternoon, but with a drier air mass progged to move
into the region wasn`t confident enough to include mentions at this

.MARINE...(For the 4 PM Lake Superior forecast issuance)
Issued at 219 PM EDT TUE JUL 18 2017

Winds will remain around 20 knots just ahead of the cold front
currently pushing east across Lake Superior as an enhanced pressure
gradient remains in place. As the front moves across the lake, there
will be a transient area of lighter winds, before 15 to 20 knot winds
fill in behind the front tonight into Wednesday. High pressure
quickly moving across the region on Wednesday and allow winds to
remain around 10 to 15 knots. Through the rest of the week into the
first half of the weekend, winds will remain less than 15 knots
across the lake. Towards the later half of the weekend, depending on
the track of another storm system moving across the region winds
could increase to around 20 knots across the lake.

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


SHORT TERM...Ritzman
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