Area Forecast Discussion
Issued by NWS Marquette, MI

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306
FXUS63 KMQT 190910
AFDMQT

Area Forecast Discussion
National Weather Service Marquette MI
510 AM EDT Wed Jul 19 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...(Thursday through Tuesday)
Issued at 507 AM EDT WED JUL 19 2017

Models suggest that a brief transition to zonal flow atop a
mid/upper level ridge over the lower MS valley will give way to
some amplification this weekend as the ridge shifts westward
favoring nw flow into the Great Lakes. Temps will remain at or
above normal into the weekend and then drop below normal from Sun-
Tue.

Thursday, any lingering shra brushing mainly the srn cwa associated
with the shrtwv and area of convection sliding through WI will
depart during the morning. With plenty of afternoon sunshine, temps
will climb into the mid and upper 70s near the Great Lakes to the
lower 80s inland.

Friday, the main sfc-850 mb front remains far enough to the south so
that the next stronger shortwave and associated area of convection
should remain over WI with only lighter pcpn on the nrn fringe
possibly brushing the the srn cwa from the late afternoon into the
evening.

Sat-Sun, as the mid/upper level flow becomes more northwesterly, a
stronger shortwave trough is expected to drop from srn Manitoba into
the nrn Great Lakes. The ECMWF remained slightly faster with this
feature compared to the GFS and especially the GEM.
Although there is still some timing uncertainty, the initial band of
showers with WAA and 700-300mb qvector conv ahead of the shrtwv is
expected to move in from the west from Saturday afternoon into
Saturday evening. Shower chances will persist through most of Sunday
into Sunday night until the shrtwv slides off to the east with some
lingering light wrap-around pcpn possible into early Monday.

Mon-Tue, although the slower GFS/GEM would keep some light pcpn
going, model trends and the ECMWF suggest that mainly dry weather
will prevail. High pressure with cooler dry air will build into the
region with pleasant conditions. Highs will range from the upper 60s
north to the lower 70s south Monday with slightly warmer conditions
Tuesday.
&&

.AVIATION...(For the 06Z TAFS through 06Z Wednesday night)
Issued at 156 AM EDT WED JUL 19 2017

Rainfall yesterday may lead to shallow radiation fog at times during
the night at KIWD/KSAW. Otherwise, high pres and a dry air mass will
settle over the Upper Great Lakes today, resulting in VFR conditions
and light winds at KIWD/KCMX/KSAW.
&&

.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.
&&

.MQT WATCHES/WARNINGS/ADVISORIES...
Upper Michigan...
None.
Lake Superior...
None.
Lake Michigan...
None.
&&

$$

SHORT TERM...Ritzman
LONG TERM...JLB
AVIATION...Rolfson
MARINE...Ritzman



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