Area Forecast Discussion
Issued by NWS Marquette, MI

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FXUS63 KMQT 251741

Area Forecast Discussion
National Weather Service Marquette MI
141 PM EDT Mon Sep 25 2017

.SHORT TERM...(Today and tonight)
Issued at 506 AM EDT MON SEP 25 2017

WV imagery and RAP analysis indicated a mid/upper level over Wyoming
embedded in a trough over the wrn CONUS and a ridge over the ne
CONUS resulting sw flow from the cntrl plains to the upper MS Valley
and wrn Lake Superior. At the surface, a cold front extended through
wrn Lake Superior through nw WI into se MN from low pressure over
nrn Ontario. Radars indicated an area of showers and a few tsra from
nw WI through e cntrl MN into nw IA supported by 850-600 mb fgen
behind the front.

Today and tonight, short range higher res models suggest that the
pcpn will remain mainly over wrn Lake Superior and far wrn Upper
Michigan this morning. However, from late this afternoon into this
evening expect the pcpn coverage to increase as a shortwave
trough lifts toward the area from the plains. With PWAT values to
around 1.5 inch, and the possibility for convection lifting
northeast along with an area of fgen behind the front, some
locally heavy rain may be possible over the west half of Upper
Michigan. However, confidence in the position of any heavier rain
band is still low. MUCAPE values mainly aob 1k J/Kg along with
modest shear values may support some small hail with any stronger
storms. By later tonight, the focus for the heavier pcpn is
expected to shift again to the nw of the cwa with the strongest
qvector conv and upper level div ahead of the shrtwv lifting out
of the nrn plains.

Temperatures will climb again to around 80 or the lower 80s cntrl
and east before falling off this afternoon with the front moving in.

.LONG TERM...(Tuesday through Sunday)
Issued at 411 AM EDT MON SEP 25 2017

Tuesday into Tuesday night: A surface low will lift through the
Upper Great Lakes region and slide into Ontario through this time
period. An associated north-south oriented cold front will begin to
quick shift east through Upper Michigan through the day Tuesday
ahead of the approaching deep trough from the west. A continued very
moist environment ahead of the cold front will allow for at least
some heavy downpours at times; however, rainfall totals are not
expected to be too impressive across the area as the cold front is
expected to shift east fairly quickly. Temperatures will continue to
be above normal through Tuesday; however, the trend will be more
toward normal temperatures by late Tuesday afternoon, coolest for
western portions of the Upper Peninsula as the front passes.

Wednesday through Friday: A bit drier air will push into the area
for Wednesday, which should lead to mainly dry conditions across
much of the area under near normal temperatures in the upper 50s to
around 60. Wednesday night through Friday, models have solutions
that differ slightly on how strong/quick the next wave of energy
will be as it rotates into the Upper Great Lakes. The GFS is not as
strong and much quicker with moving the wave through the area, while
the EC is much stronger and more persistent in keeping deep
troughing across a good portion of the eastern CONUS into Friday.
The Canadian model shows a very similar trend to the EC, which have
both been showing a similar setup over the past few model runs. This
lends more credibility to keeping cooler temperatures along with
rain showers and increased cloud cover across much of the area. The
system forcing will initially be the cause for rain showers;
however, cooler air aloft, associated with the trough, will allow
850mb temperatures to potentially drop to or slightly below zero by
late Friday morning potentially resulting in a lake effect rain
shower component through Friday afternoon. Outside of the rain
shower potential, temperatures will cool off significantly from
where they`ve been over the past couple days. In fact most places
will be near to below normal by the end of the work week. High
temperature will fall into the low to mid 50s by the ind of the work

Rest of the extended: The trough will begin to progresses eastward
through Sunday, allowing for warming temperatures aloft along with
drier air to filter into the area. This should lead to a diminishing
trend in the rain shower potential along with a steady warming trend
toward the end of next weekend. Generally stuck with a consensus of
the models for this time period.

.AVIATION...(For the 18Z TAFS through 18Z Tuesday afternoon)
Issued at 141 PM EDT MON SEP 25 2017

A cold front slowly moving across Upper MI combined with a wave of
low pres moving nne along the front will bring lowering cigs. with
front already passed KIWD/KCMX, lower cigs have already developed.
At KIWD, expect low MVFR cigs to fall to IFR later this aftn, then
to LIFR tonight as -shra coverage increases. At KCMX, MVFR cigs
should prevail into the evening before falling to IFR late tonight
as -shra coverage increases in nw Upper MI as well. At KSAW, VFR
conditions initially will likely fall to low MVFR or IFR this
evening under upslope nne winds. Further reduction to LIFR will
occur overnight thru mid morning. There could be some -shra around
KSAW beginning late this aftn. Not out of the question that there
could be a tsra at any of the terminals, though KSAW is more favored
due to build up of instability this aftn. As a result, mention of
thunder was only included at KSAW for the late aftn/early evening.

.MARINE...(For the 4 AM Lake Superior forecast issuance)
Issued at 506 AM EDT MON SEP 25 2017

A developing low pressure behind a cold front will bring increasing
ne winds to 25 knots over wrn Lake Superior tonight.
As the cold front moves across Lake Superior Tue night into Wed with
colder air moving in, wind gusts will increase to 20 to 30 knots.
Winds should also increase to 30 knots by Friday with some gales
possible over the east as another disturbance moves through the area
with additional cold air.

Low to mid 60s dewpoints sliding across Lake Superior are expected
to linger into Tue bringing patchy to areas of fog across the lake.
Some of the fog could be locally dense at times.

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


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