Area Forecast Discussion
Issued by NWS Marquette, MI

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FXUS63 KMQT 210831

Area Forecast Discussion
National Weather Service Marquette MI
431 AM EDT Fri Oct 21 2016

.SHORT TERM...(Today and tonight)
Issued at 426 AM EDT FRI OCT 21 2016

A mid-upper level trough over the area this morning will move east
of Upper Mi later this afternoon as it is replaced by a mid-upper
level ridge from the west. A northerly flow of colder air (h85 temps
to -5C) ahead of a sfc ridge centered over western Lake Superior has
generated isolated to scattered lake effect rain showers over nw and
n central Upper Mi early this morning.  Not out of the question
that some light snow could briefly mix in over higher terrain areas
west of Marquette this morning.

Today, weakly cyclonic northerly flow and fairly deep moisture to
around 750 mb as noted on NAM and RAP fcst soundings will continue
to support isolated to scattered lake effect showers into this
afternoon over mainly central Upper Mi. Weakening northerly flow
with the eastward advance of the sfc ridge into central Upper Mi
along with a slightly lowering subsidence inversion should diminish
showers later this afternoon and end showers by the evening hours.
Expect highs in the 40s.

Tonight, Expect dry conditions with ridging aloft and at the sfc. A
shortwave now over the Northern Rockies is expected to ride across
the Canadian/northern CONUS border today and then weaken/shear out
as it moves through the mid-level ridge over the western Great Lakes
later tonight. Models fairly consistent showing best moisture and q-
vector convergence associated with incoming shortwave will be shunted
nw into Ontario. As a result, expect just some increase in mid clouds
over the west with dry conditions prevailing. Min temps will range
from the mid 20s over the central interior under cloud free skies of
the sfc ridge to the mid to upper 30s far west where increasing
clouds and onset of downsloping southerly winds on backside of
ridge will keep temps warmer.

.LONG TERM...(Saturday through Thursday)
Issued at 342 AM EDT FRI OCT 21 2016

A relatively benign wx pattern is expected to dominate in the
medium/extended range. The period into early Sun should be dry with
lingering sfc pres dominating. Some showers could impact Upr MI on
Sun ahead of an aprchg disturbance, with some lk effect showers psbl
on Sun ngt into Mon in its wake. But any pcpn should be lgt during
this period. Then sfc hi pres near the upr confluence on the wrn
flank of a deep, slow moving upr trof in Quebec is likely to bring a
period of dry wx later Mon thru at least Tue and perhaps Wed if the
next shrtwv moving toward the wrn Great Lks is shunted far enuf to
the sw by the slow moving hi pres. More showers are psbl at the end
of next week as another shrtwv aprchs fm the nw.

Sat...Some waa in the ssw flow btwn a sfc hi pres rdg over ern Upr
MI and a shrtwv/lo pres tracking thru far nw Ontario wl bring some
clds to the cwa. Some of the models even generate some lgt pcpn, but
lingering near sfc dry air associated with persistent h5 rdg axis/
the sfc hi pres rdg held in place on the wrn flank of deep lo pres
in New England and passage of the shrtwv/sharper forcing so far to
the n favor a dry fcst for Upr MI. H85 temps recovering to arnd 5C
over the wrn U.P. wl allow for a warmer aftn despite the clds.

Sat ngt thru Sun ngt...Most of the medium range guidance show a
fairly strong shrtwv embedded in the fast wnw flow aloft near the
Cndn border on the nrn flank of upr rdg in the Plains and associated
sfc lo pres moving near the Upr Lks during this time. Clds in
advance of this disturbance wl roll into the area on Sat ngt.
Despite some fairly impressive dpva/deep lyr cnvgc/band of h85-7
fgen ahead of this feature, absence of any sgnft mstr return wl
restrict accompanying pops/qpf. There are some fairly sharp
differences on the track/intensity of the shrtwv and sfc lo pres.
With a more confluent nw flow aloft just to the e on the wrn flank
of the deep lo pres track tracking slowly n thru Quebec, suspect the
weaker/quicker/farther s depiction of the sfc lo shown by the 00Z
GFS/12Z ECMWF is on the right track. This scenario would further
reduce pops. But considering the uncertainty in the fcst, maintained
consensus fcst for now. A colder nw flow in the wake of the
departing disturbance and in advance of trailing hi pres that wl
drop h85 temps toward -5 to -6C could bring a return of some lk
effect clds/showers on Sun ngt. Lowering invrn base under 5k ft agl
in the overall subsidence left in the wake of the departing shrtwv
wl restrict the intensity of any lk effect pcpn. But upped consensus
fcst pops into the lo chc category to reflect this potential in the
areas favored by the nw flow to the e of Marquette, where a longer
fetch acrs Lk Sup wl allow more moistening of the incoming airmass.
Shorter fetch into the w as well as a more acyc/diffluent llvl flow
closer to the incoming hi pres rdg should maintain dry wx there even
if there are some sc near the invrn base.

Next week...Some lk effect clds/showers could linger over the e into
Mon in the nw flow ahead of aprchg hi pres. But as this sfc hi pres
shifs into the Great Lks on Mon ngt into Tue under a bldg upr rdg
left in the wake of slowly departing upr trof/sfc lo pres in ern
Canada, expect a period of dry wx. If the hi pres rdg/axis of pwat
under 0.50 inch is ovhd on Mon ngt with lgt winds/moclr skies, Tue
mrng could be quite chilly. Many of the previous medium range models
showed waa clds invading the area by then on the wrn flank of a
faster exiting sfc hi pres along with some lgt pcpn on Tue, but
model trends appear to be for a slower moving sfc hi pres and dry wx
persisting thru Tue. Considering the deep lo pres near the Cndn
Maritimes/deep upr trof in Quebec, suspect the slower moving sfc hi
pres/longer dry period is the way to go. So lowered fcst min temps
at most places over the interior blo the consensus fcst. Although
another shrtwv is fcst to drift e thru the ncentral Plains toward
the Upr Midwest on Wed, the persistence of the slower moving sfc hi
pres/dry airmass may shunt the accompanying sfc lo pres/deeper mstr
far enuf to the s-sw to maintain dry wx over much of the cwa thru
Wed. Another shrtwv dropping into the Great Lks next Thu/Fri could
bring some showers then. Expect no sgnft temp departures fm normal
next week except for the potential for some chilly mrngs on Tue and
perhaps Wed if the sfc hi pres is more resilient.

.AVIATION...(For the 06Z TAFS through 06Z Friday night)
Issued at 205 AM EDT FRI OCT 21 2016

Cold air moving through the area will generate lake effect clouds
and pcpn with variable CIGs and isolated showers. CIGs will lower
late tonight into Fri as a trough moves through the area, leading to
increased lake effect rain. Dry air will only slowly move in Friday
afternoon with a returned to sct clouds and VFR conditions from
west to east.

.MARINE...(For the 4 AM Lake Superior forecast issuance)
Issued at 426 AM EDT FRI OCT 21 2016

No significant low pressure systems are expected to move through the
Upper Great Lakes in the next several days. Winds will remain below
gales through the period. A tightening gradient between a deep low
pressure system moving through Quebec and a high pressure ridge
building into the Plains could lead to a period of nw winds to 30
knots over north central and eastern Lake Superior late Sunday into

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


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