Area Forecast Discussion
Issued by NWS Marquette, MI

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FXUS63 KMQT 181744

Area Forecast Discussion
National Weather Service Marquette MI
144 PM EDT Tue Oct 18 2016

.SHORT TERM...(Today and tonight)
Issued at 446 AM EDT TUE OCT 18 2016

00Z raobs/latest wv imagery and RAP analysis show the shrtwv
responsible for the heavy ra/svr storms yday evng exiting to the ne
along the most sgnft showers/TS. The associated cold fnt on the sw
flank of deepening lo pres moving into se Ontario has sank to the s
of all but the far scentral cwa. Despite some deep lyr qvector dvgc
in the wake of this disturbance, some showers/a few TS linger along
a line fm scentrl MN acrs nw WI into central Upr MI ahead of another
shrtwv aprchg fm the wsw and under axis of h85-7 fgen behind the
cold fnt and where mucapes up to 500j/kg and steeper mid lvl lapse
rates up to 7C/km linger per spc mesoanalysis/00Z MPX raob.
Farther to the nw, the 00Z INL raob shows a much drier sfc-h5 lyr,
but a good deal of hier clds linger in the mstr aoa h5 shown on that
raob and on the cyc side of the shrtwv supporting the lingering

Main fcst concerns in the short term wl be on pops today and then
cld/temp trends as the drier llvl air shown on the 00Z INL raob
grdly slides into the area.

Today...Incrsg deep lyr h85-3 qvector dvgc in the wake of stronger
shrtwv exiting to the ne with deeper convection is fcst to dominate
Upr MI, so expect the line of showers stretching fm scentral MN into
wcentrl Upr MI to diminish with time and probably by mid mrng as
they shift to the ese under axis of h85-7 fgen in the wake of the
departing sfc cold fnt. Plan to carry some sct showers thru mid mrng
mainly over the scentral. There wl be some gusty nw winds mainly
this mrng over the ne cwa in the wake of the departing/deepening sfc
lo pres, but these winds should diminish during the aftn as the pres
gradient weakens with the closer aprch of sfc hi pres toward the Upr
MS River Valley. The arrival of the drier llvl air depicted on the
00Z INL roab/larger scale subsidence/more acyc llvl flow should
result in clrg thru the day. Since h85 temps wl fall to only 6-8C by
00Z Wed, expect another relatively warm day with max temps in the
50s to as hi as the mid 60s over the se with the downslope NW flow.

Tngt...While there are hints some clds wl move into at least the wrn
cwa late as a weak shrtwv/lo pres trof aprch fm the w, lingering
llvl dry air/acyc flow most of the ngt wl maintain dry wx thru 12Z

.LONG TERM...(Wednesday through Monday)
Issued at 443 AM EDT TUE OCT 18 2016

Nam shows a 500 mb shortwave over WY and another over the Canadian
prairies 12z Wed. Both of these shortwaves move east and help dig a
deep trough over the central U.S. on Thu and Thu night. Looks pretty
quiet for this forecast period, but could still see some lake effect
pcpn starting on Thu as colder air comes into the area and across
Lake Superior. 850 mb temperatures fall to -3C to -5C on Thu and
with lake temperatures from 9C to 12C, this is enough lake-850 mb
delta-t for lake effect pcpn. Did add in some pops for this with low
chance pops in northwest and north lake effect pxpn belts for thu
and thu night. Did not make too many changes to the going forecast.

In the extended, GFS and ECMWF show a 500 mb ridge over the desert
sw with a deep trough over the central U.S. 12z Fri. This trough is
very deep with the GFS and broader with the ECMWF with 850 mb
temperatures down to -4C to -7C 12z Fri and this cold air remains
over Lake Superior through 12z Sat. A shortwave moves through Sat
night into Sun morning. A broad 500 mb ridge moves into the Rockies
with a trough over the ern U.S. 12z Mon. Temperatures look to be
below normal for the start of this forecast and then get to near
normal by the end of the forecast period.

.AVIATION...(For the 18Z TAFS through 18Z Wednesday afternoon)
Issued at 144 PM EDT TUE OCT 18 2016

Drier air has been slower to reach KCMX than expected today. Back
edge of lower clouds is currently near the western shoreline of the
Keweenaw, but is being held up by the upslope westerly flow. Should
see low MVFR conditions break out to VFR there around 20z. May see a
period of MVFR cigs at KSAW over the next hr or two before shallow
moisture is pushed/mixed out. Other than these initial lower
conditions, drier air mass settling into the area will lead to VFR
conditions being the rule at KIWD/KCMX/KSAW.

.MARINE...(For the 4 AM Lake Superior forecast issuance)
Issued at 446 AM EDT TUE OCT 18 2016

Cancelled previous gale warning in effect for the e half of Lake
Superior as lo pres exiting to the ne is not intensifying as quickly
as anticipated, resulting in weaker nw winds up to only 30 kts in
this area. Then expect winds to diminish to under 25 kts by this
aftn and remain at 20-25 kts or less through the rest of the week as
a relatively weak pressure gradient dominates.

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


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