Area Forecast Discussion
Issued by NWS Marquette, MI

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FXUS63 KMQT 210809

Area Forecast Discussion
National Weather Service Marquette MI
409 AM EDT Tue Mar 21 2017

.SHORT TERM...(This evening through Tuesday)
Issued at 409 PM EDT MON MAR 20 2017

Broad upper trough has settled across cntrl Canada. Strong upper jet
along base of trough and ribbon of mid level moisture supported mid
clouds and a patchy light rain/snow along WI border today, but
clouds have cleared out quickly this aftn leading to plenty of
sunshine for all areas except far scntrl to east cwa. After temps in
the 30s lingering til around midday, readings have risen well into
the 40s this aftn with even a 50 degree reading at fire wx site near
Kenton. Also quite dry with dwpnts in the lower teens leading to RH
as low as 20 pct over interior west. Clouds over scntrl and east cwa
will continue to diminish per satellite trends leading to clear
skies for the evening. Temps over interior west may fall off quickly
this evening given how dry it is. Lowered mins into the low teens
for those areas.

Later this evening and overnight, strong shortwave over cntrl
Manitoba this aftn will slide toward Lk Superior. This system will
be what propels sfc cold front to the northwest of Lk Superior this
aftn across the cwa after midnight. Limited moisture with the system
upstream and the dry ambient airmass overhead will result in minimal
precip chances with the front as it moves through. Have the highest
pops across Keweenaw and ncntrl for a few snow showers to develop as
the front arrives. Cold air charging in behind the front (h95 temps
falling from +5c over western Upper Michigan at midnight to near
-10c by 12z Tue) on gusty NW winds and increasing h85 moisture and
cold air advection at h85 (temps down to -18c by midday Tue) should
eventually lead to lake effect snow showers late tonight and more so
into Tue morning closer to Lk Superior. Even with extent of cold air
advection, it is still springtime and expect snow showers to spread
farther inland late Tue morning into Tue aftn. Moisture will be
provided by ongoing lake moistening/fluxes and instability will be
from daytime heating as sfc-850mb lapse rates climb above 9c/km and
forecast soundings show 30-50j/kg at inland locations like IMT and

Where the lake effect sets up Tue morning and more or less persists
through the day, increasing SLRs toward 20:1 will lead to fluffier
snow and at least isolated 2" snow amounts are not of question. Most
areas will see less than 1 inch through the day though. Will certainly
be blustery and colder for all areas. May even see some blsn near
Lk Superior where NNW winds gust over 25 mph. Temps will stay
steady in the lower 20s for northwest higher terrain areas and
will be mainly in the mid-upper 20s otherwise. Downslope areas in
scntrtl may reach well into the 30s so if there is precip that far
south, could end up being a rain/snow mix.

.LONG TERM...(Wednesday through Monday)
Issued at 409 AM EDT TUE MAR 21 2017

Nam shows a 500 mb trough on the west coast, a ridge over the plains
and a deep trough on the east coast 12z Wed. This ridge slowly moves
across the plains and into the upper Great Lakes Thu into Fri
morning while a closed 500 mb low moves into the southern Rockies.
Nam brings in some 850-500 mb q-vector convergence and deeper
moisture Thu night into the area late. Still looks like there could
be a wintry mix of pcpn for Thu night into Fri morning of snow,
sleet, rain and freezing rain switching over to all rain on Fri.
Temperatures warm aloft while the lower levels remain cold and this
is enough to keep the mix in. Overall, did not make too many changes
to the going forecast.

In the extended, GFS and ECMWF show a 500 mb closed low over western
KS 12z Fri with a ridge in the sern U.S. This closed 500 mb low and
trough moves eastward 12z Sat with upper ridging over the upper
Great Lakes. The upper low and trough move into northern IL 12z Sun
and to the lower Great Lakes 12z Mon. Another trough moves into the
central plains 12z Mon and gets ejected into the upper Great Lakes
on Tue. Temperatures look to be near normal for this forecast period
with rain/snow mix especially during the late night and morning

.AVIATION...(For the 06Z TAFS through 06Z Tuesday night)
Issued at 125 AM EDT TUE MAR 21 2017

Until a cold front sweeps across the area overnight/early this
morning, VFR conditions will prevail at KIWD/KCMX/KSAW. While isold
-shsn/-shra may accompany the front, much colder air surging into
the area combined with moisture off Lake Superior and daytime
heating should result in sct -shsn today, though the -shsn should
occur mostly during the morning hrs at KIWD/KCMX. Cigs should drop
to around 3kft this morning, but otherwise will end up in the lower
VFR range around 4kft. Vis within heavier shsn could drop to IFR at
1-2sm today, but for the most part should be MVFR to VFR. Fropa will
initiate gusty nw winds up to 25-35kt for a time, strongest at KCMX.
Otherwise, winds today should gust 20-30kt from the nw to n with the
stronger winds at KCMX/KSAW.

.MARINE...(For the 4 PM Lake Superior forecast issuance)
Issued at 409 PM EDT MON MAR 20 2017

Winds 25 kts or less into the evening then SW winds could increse to
around 30 kts before shifting NW overnight as cold front crosses Lk
Superior. May see brief gales to 35 kts immediately behind the front
over much of the lake as cold air charges in, but more persistent
gales are expected late tonight into late Tuesday aftn over the east
two thirds of the lake. There will also be freezing spray as well
late tonight through Tuesday, especially over the east half of Lk

Nnw winds as hi as 25-30kts/freezing spray over the e half of the
Lake on Tue night will diminish on Wed as a sprawling hi pres builds
over the Upper Lakes. After this hi pres shifts to the e on Wed
night, s winds up to 30 kts will be possible on Thu under the
tightening pres gradient on the western flank of the departing hi
pres. Expect winds to diminish on Thu night thru Fri as a flatter
pres gradient dominates. Stronger ne winds up to 25-30 kts may
return on Sat under the tightening pres gradient on the southern
flank of hi pres building into Ontario.

Upper Michigan...
Lake Superior...
  Gale Warning until 2 AM EDT Wednesday for LSZ249>251-266-267.

  Gale Warning until 4 PM EDT this afternoon for LSZ243>248-264-

Lake Michigan...


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