Area Forecast Discussion
Issued by NWS Marquette, MI

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FXUS63 KMQT 210859

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

.SHORT TERM...(Today and tonight)
Issued at 457 AM EDT MON AUG 21 2017

WV imagery and RAP analysis indicated zonal flow across the nrn
CONUS with a couple of upstream shortwave troughs over the cntrl
Dakotas. At the surface, a cold front extended from James Bay
through ern Upper Michigan to cntrl WI. IR loop indicated mostly
clear skies from nw WI through wrn Upper Michigan with patchy
clouds lingering over the cntrl and east.

Today, expect mid clouds to gradually increase as WAA strengthens
ahead of a trough developing from Nebrasaka into WI. The clouds,
around 600 mb, may thin or broken enough for some viewing of the
partial eclipse early this afternoon. Rain chances will increase
over the west by mid to late afternoon as the effects of the Dakotas
shortwave also arrive. Although MUCAPE values only to around 1k
J/Kg are expected, highest over the south, effective deep shear
values into the 30-40 knot range may support some stronger storms
with small hail.

Tonight, as the mid level trough deepens into the n cntrl CONUS the
models have trended toward a stronger sfc wave of low pressure
lifting into se Upper Michigan late tonight. The combination of
moderate to strong deep layer qvector conv and upper level div
with the right entrance of a 250-300 jet over nrn Ontario along
with strong moisture transport and mid level fgen will support a
large area of showers over the cwa. High res models suggest PWAT
values to around 1.75 inches may also support some narrow bands of
heavy rain of a few inches, especially over the cntrl cwa. With
mainly elevated convection, the main severe risk may again be for
hail over the south half, where the instability is highest.

.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 AM Lake Superior forecast issuance)
Issued at 457 AM EDT MON AUG 21 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. The next chance for gusty winds will be Tuesday night into
Wednesday as low pressure slides to the east 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
MARINE...JLB is the U.S. government's official web portal to all federal, state and local government web resources and services.