Area Forecast Discussion
Issued by NWS Marquette, MI

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FXUS63 KMQT 261132

Area Forecast Discussion
National Weather Service Marquette MI
732 AM EDT Wed Jul 26 2017

.SHORT TERM...(Today and tonight)
Issued at 254 AM EDT WED JUL 26 2017

Lingering showers and thunderstorms have bisected Upper Michigan
this morning. One wave moving across the eastern half
associated with 700mb moisture transport, and a second wave
moving into the western half associated with deeper moisture
transport just ahead of a cold front that continues to push east
across the Arrowhead of Minnesota and towards Upper Michigan. Over
the last hour or so, additional convection has developed across west
and central portions of the area as the previously mentioned deeper
moisture arrives and the main shortwave begins to dig over
northern portions of Lake Superior.

The main forecast concern is the development of widely scattered
showers and thunderstorms this morning, that will produce moderate
to heavy rain at times, and a high swim risk for the northern
shores of Lake Michigan. Ahead of the the above mentioned cold
front, south-southwest winds of 20 to 30 knots across Lake
Michigan will allow dangerous currents to be in place throughout
the day today. Deep moisture pooling ahead of the cold front has
also allowed PWATs to approach the 2.0 inch mark, this moisture
should work well with the favorable entrance region of a 100 knot
upper- level jet tracking across Lake Superior to produce a fairly
widespread area of showers and embedded thunderstorms this
morning. With plenty of elevated instability over the area as
MUCAPES remain around 1000-2000 J/kg, a few embedded thunderstorms
could get pulsey through the morning hours; however, effective
shear is 30 knots at best, which does not bode well for
maintaining a persistently organized updraft. As we progress into
the mid- morning to afternoon hours, the surface cold front will
continue to push eastward across the area and allow precipitation
chances to diminish from west to east. The best chance for seeing
lingering showers and thunderstorms throughout the afternoon hours
will be across the eastern and south central portions of the area
as the front will be slowest to vacate those areas. A few of the
high- res models are a bit slower with the fronts progression this
afternoon and regenerate another round of showers and storms
along the cold front in the south central portions of the area,
which is possible as the speed of the front will slow this
afternoon as it becomes more west to east oriented. Confidence is
not high that these storms will develop, but if they can get going
later this afternoon they would be strong at best as the better
instability will be push well south of the area.

As the front continues to push south of the area overnight, we
will begin to dry out across the area and cloud cover will thin
from west to east.

.LONG TERM...(Thursday through Tuesday)
Issued at 343 AM EDT WED JUL 26 2017

Looks quiet through the first part of the extended as main sfc
feature is high pressure over the region late Thu through most of
the weekend. Cold front may move in close enough late this weekend
to produce a chance of rain, though there are still questions on
that. High temps should mainly be upper 70s to low 80s through Sat,
though it will be cooler Thu and Fri near Lk Superior with gradient
onshore NE flow on leading edge of the high. Nighttime lows will be
seasonably cool in the 40s/50s as the high allows for radiational
cooling to develop. Even warmer temps are possible Sun with daytime
highs mainly in the 80s as long as there is sufficient insolation.

One exception to the overall dry forecast into the weekend could be
on Thu. Strong shortwave that currently shows up on wv loop over
southern Alberta drops through in NW flow aloft. This compact
shortwave and associated steeper h7-h5 lapse rates near 7c/km may
arrive just in time at end of peak heating to produce a few showers
along WI state line late Thu aftn into early Thu evening. GEM is
quicker and would support better chance of rain. Negatives are
limited deep moisture meager instability so not looking at anything
significant in terms of convection, just a buildup of cu and some
light showers.

Then, concerning the cold front for late this weekend, the GFS is by
far most aggressive/southward with front with boundary east to west
over Upper Michigan by late aftn. That solution would also support
scattered thunderstorms as the front would be arriving during peak
heating of Sun aftn and running into sfc based CAPES over 1000j/kg.
GEM and ECMWF not near as aggressive as they hold main front to the
northwest of Lk Superior through Sun aftn as high pressure remains
entrenched over the Great Lakes. Main shortwave should stay well to
the north over far northern Ontario but it is unclear if there could
be weaker shortwave farther south which could help support the GFS
idea. Blends yielded slight chances and will probably just let that
go for now as cannot completely rule out more aggressive/southward
front off the GFS.

Still some small rain chances early next week at the end of the long
term. Daytime temps should end up at or slightly above normal in the
upper 70s to mid 80s. Nighttime lows will remain seasonable in the

.AVIATION...(For the 12Z TAFS through 12Z Thursday morning)
Issued at 731 AM EDT WED JUL 26 2017

Ceilings have improved this morning ahead of schedule at all
terminals, with VFR conditions prevailing. Expect the VFR ceilings
and visibilities to continue over the next 24 hours. With a cold
front pushing east across the area today, wind will veer from the
southwest to northwest. Precipitation chances will remain confined to
KSAW terminal wise as the front has yet to pass through central
Upper Michigan this morning. As the afternoon progresses and the
front pushes off to the east of KSAW, precipitation chances will wane
and skies will gradually clear into the evening hours.

.MARINE...(For the 4 AM Lake Superior forecast issuance)
Issued at 254 AM EDT WED JUL 26 2017

A cold front will push east across the lake today with the
strongest winds expected to be ahead of this front generally
across the eastern half of the lake, with speeds of 25 to 30 knots
at times through the mid-morning hours. Across the west half of
the lake this morning winds will be around 10 to 15 knots as the
pressure gradient is a bit more relaxed in the vicinity of the
front. Throughout the day winds across the east half will relax
and increase across the west half, overall winds of 15 to 20 knots
are expected this afternoon into the overnight hours. By Thursday
morning, winds will relax further to around 10 to 15 knots. As
high pressure settles into the region for the end of the week and
weekend, expect the winds to remain around 10 to 15 knots through
the weekend and even linger into early next week.

Upper Michigan...
  Beach Hazards Statement through this evening for MIZ014.

Lake Superior...
Lake Michigan...


SHORT TERM...Ritzman
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