Area Forecast Discussion
Issued by NWS Marquette, MI

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FXUS63 KMQT 160838

Area Forecast Discussion
National Weather Service Marquette MI
438 AM EDT Wed Aug 16 2017

.SHORT TERM...(Today and tonight)
Issued at 432 AM EDT WED AUG 16 2017

High pressure remains in place over the Great Lakes this morning.
Light onshore flow off Lk Superior and nighttime cooling has
resulted in fog central and east, most dense inland. Otherwise high
clouds are spilling in from the west out ahead of pair of shortwave
troughs over the mid Conus. Lead shortwave with moisture advection
is leading to rain over ND and northwest MN while stronger shortwave
trough and sfc low pressure system is resulting in widespread shra
and tsra over KS and Neb. After fog diminishes this morning, winds
turning SE ahead of approaching low pressure system could lead to
intervals of more low clouds across central at times. Initial push
of moisture advection aloft may lead to a few showers this aftn over
the west. Highs low to mid 70s, warmest east where there could be
more sunshine.

Decent agreeement that most forecast area stays dry in the evening
except far west, then widespread showers move in after midnight
from the west and southwest as main shortwave trough/deep layer
q-vector convergence and sfc low move toward western and northern
WI. Have pops ramping up quickly after midnight but far north
will stay with just chancy pops all night as main forcing does not
arrive there til Thu morning. Strong h925-h7 moisture tranport
with pwats 1.5-2.0 inches and warm cloud depth of at least 12kft
will lead to efficient warm rain processes with moderate to heavy
rain expected after midnight. Some areas over southwest and scntrl
could see rain amounts by daybreak Thu near an inch. Elevated
instability (1-6km MUCAPE over 500j/kg) moves in very late
tonight so there could be embedded thunder which will only further
enhance rainfall rates. E-SE winds will be strong enough late
tonight for small craft conditions to develop on both Lk Superior
and Bay of Green Bay/Lk Michigan and these conditions will carry
on into first part of the long term Thu into Fri.

.LONG TERM...(Wednesday night through Tuesday)
Issued at 312 PM EDT TUE AUG 15 2017

The arrival of the strengthening low pressure system that has been
advertised for days still looks to move across Upper Michigan late
Wednesday night through Friday. The models have remains consistent
with the track of this low across portions of Upper Michigan and
Lake Superior during the day on Thursday. As the warm front pushes
north and moisture transport ramps up, as the ridge of higher theta-
e noses into the region, expect a fairly widespread area of rain to
move across much of the area. With PWATs approaching 1.5-2.0 inches
and warm cloud layer depths approaching 11,000-13,000 feet, rain may
fall heavy at times. Right now the timing of this rainfall across
the west  looks to be early Thursday morning through early afternoon
hours. The highest amounts are expected to reach the 1.5-2.0 inch
range primarily over the western half of Upper Michigan, where not
only the leading edge of the better moisture will take aim, but also
where wrap around precipitation within the deformation zone will
linger into the evening hours on Thursday. Through the morning and
afternoon hours, as the low pressure system tracks across the area
and the warm front lifts north the area of fairly widespread rain
showers will lift into central and eastern portion of the area.
Through the afternoon hours, models try to bring in a dry slot
across central portions of Upper Michigan. This will allow for a
break in the rainfall in some locations; however, as the cold front
pushes through later in the afternoon and evening hours, depending
on how much instability can get into south central portions of Upper
Michigan, there may be a round of afternoon/evening thunderstorms
near the triple point and south along the cold front. While mid-
level lapse rates do not look terribly impressive, resulting in
skinny CAPE profiles, models are forecasting upwards of 1500-2000
J/kg with around 30-40 knots of bulk shear. Therefore, it isn`t out
of the question that if we can get additional development, a few
storms could be on the stronger side across the south central on
Thursday afternoon/evening. This remains conditional as it will all
depend on how cloud cover evolves during the afternoon hours and how
far north the better moisture can get.

Lingering wrap around showers are possible across the central and
east Thursday night into Friday morning as the area of low pressure
moves over eastern Lake Superior and eventually tracks eastward into
Canada. Low-level wind fields are fairly consistent with northwest
winds behind the exiting low across much of the area, albeit not as
conducive in some locations to upslope flow as northerly flow would
be, still expect low clouds and perhaps some drizzle across northern
and eastern portions of the area on Friday. Due to the lingering
cloud cover and cold air advection behind the system, temperatures
will be about 10 degrees below normal.

The first part of the weekend looks like we could see a few showers
and perhaps a few rumbles of thunder as another shortwave trough
swings through the region. As this shortwave digs into the eastern
Great Lakes region, high pressure will take over on Sunday and allow
for temperatures to climb a few degrees above normal with drier
weather. A few locations may even see temperatures climb into the
lower 80s by the end of the weekend.

Early next week upper-level flow looks to become more zonal with
broad longwave troughing spanning much of central Canada. This will
push a trailing cold front eastward across the Upper Great Lakes
region and return chances for showers and thunderstorms.
Unfortunately, right now it looks like cloud cover may hinder our
ability to see the partial solar eclipse on Monday. However, given
the transition from a quasi-amplified upper-level pattern to more
zonal, there certainly is time for things to change!

.AVIATION...(For the 06Z TAFS through 06Z Wednesday night)
Issued at 143 AM EDT WED AUG 16 2017

VFR conditions will continue at IWD through the forecast period. CMX
has seen some LIFR cigs early this morning and that may continue
through daybreak though may not be prevailing condition. May even
see vsby reduction as fog forms toward sunrise. VFR after that at
CMX through rest of forecast period. LIFR/VLIFR stratus and fog
will continue overnight at KSAW with upslope northeast winds.
Stratus and fog will burn off to MVFR conditions later this

.MARINE...(For the 4 AM Lake Superior forecast issuance)
Issued at 432 AM EDT WED AUG 16 2017

Easterly winds will increase into Thu as low pres moves from the
Central Plains to the Upper Great Lakes. Wind gusts on Thu will be
as high as 30kt as the low reaches the area. Could be some gale
force gusts over eastern Lk Superior if the low pres is deeper.
Stronger winds will linger into Fri over eastern Lake Superior as
the low departs. Lighter winds, mostly under 15kt, are expected over
the weekend with high pres over the region.

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


LONG TERM...Ritzman
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