Area Forecast Discussion
Issued by NWS Marquette, MI

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FXUS63 KMQT 201131

Area Forecast Discussion
National Weather Service Marquette MI
731 AM EDT Thu Oct 20 2016

.SHORT TERM...(Today and tonight)
Issued at 505 AM EDT THU OCT 20 2016

A mid-level trough extending from Northern Ontario into the Northern
Plains states will deepen as it moves east into the Upper Great
Lakes region late today into tonight. An accompanying pocket of
deeper moisture and advection of colder temps into the area under a
n-nw low-level flow should allow for increasing coverage of lake
effect showers into north central Upper Mi especially into tonight.

Radar imagery shows some scattered lake effect showers already
developing across the east half of Lake Superior early this morning
with the advection of colder temps in a nw flow. NAM model soundings
also indicate some weak instability continuing during the day today
which could sustain some isolated hybrid diurnal/lake effect showers
into mainly the east half of Upper Mi in a nw flow.

Winds begin to shift more northerly later tonight in response to a
lake-induced trough taking shape over Lake Superior. Model soundings
also indicate deepening moisture and instability especially into the
overnight hours as mid-level trough moves over the region. This
moisture/instability along with increasing low-level convergence
will help to focus lake effect showers into north central Upper Mi,
especially eastern Marquette and western Alger counties. Have bumped
up pops from low chc in the evening to likely late tonight for these
areas. Wet-bulb zero heights lowering below 1000 ft should also lead
to lake effect rain showers mixing with or changing to snow over the
higher terrain of western Marquette and Baraga counties. Given
fairly warm ground, expect only minimal snow accumulation...a
dusting at best.

As for temps look for highs today from the mid 40s west to upper
40s/lower 50s south central and east. Lows tonight will range from
the upper 20s/lower 30s western interior to mid 30s interior east
with generally upper 30s to around 40 near Great Lakes shores.

.LONG TERM...(Friday through Wednesday)
Issued at 356 AM EDT THU OCT 20 2016

While no hi impact events are likely for Upr MI in the longer term
period, the expected pattern wl feature changeable wx. Lingering lk
effect clds/showers into Fri evng wl give way to some dry wx thru at
least Sat evng as a sfc hi pres rdg lingers nearby. There could be
more showers late in the weekend depending on the track of a shrtwv/
accompanying sfc lo pres aprchg fm the wnw. Temps during this time
wl be within a few degrees of normal. There could be some lk effect
clds/showers on Sun ngt into Mon in the cooler nw flow ahead of
trailing hi pres. After a brief dry period into Tue, another
disturbance/lo pres aprchg fm the w may bring some rain mid next

Fri...Ongoing lk effect pcpn in lingering cyc nne flow/under axis of
h85 temps arnd -5C wl diminish slowly w-e on Fri as larger scale
subsidence ahead of aprchg shrtwv rdg/sfc hi pres lowers invrn base/
diminishes the llvl cyc flow. Wl retain the hier likely pops over
the ncentral cwa favored by the upslope nne flow in the mrng before
disruptive insolation/lowering subsidence invrn reduces the pops.
There could be some snow mixed with the showers in the mrng over the
interior hier terrain, but ltl if any accum is expected.

Fri ngt...While sfc hi pres shifting over central Upr MI by 12Z Sat
wl end the lk effect pcpn over the w and central, maintained some
chc pops thru the evng over the e with a more resilient cyc nnw
flow/h85 temps near -5C btwn the sfc hi pres rdg and deepening lo
pres moving into New England. Some waa clds in the llvl ssw flow
btwn the sfc hi pres rdg and a shrtwv/sfc lo pres crossing scentral
Canada may move in the w late at ngt. Expect the lowest min temps
into the 20s over the interior central where skies are moclr/winds
lgt under the hi pres rdg axis.

Sat...While some clds associated with the waa on the srn flank of
the disturbance passing thru scentral Canada may impact the cwa,
lingering llvl dry air associated with persistent h5 rdg axis/sfc hi
pres shifting slowly to the e on the wrn flank of deep lo pres in
New England and passage of the shrtwv so far to the n favors a dry
fcst for Upr MI.

Sat ngt thru Sun ngt...Most of the medium range guidance shows a
fairly strong shrtwv embedded in the fast wnw flow aloft near the
Cndn border and associated sfc lo pres moving near the Upr Lks
during this time. Despite some fairly impressive dpva ahead of this
feature, absence of any sgnft mstr return wl restrict accompanying
pops. There are some fairly sharp differences on the track/intensity
of the 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 and farther s depiction of the sfc lo 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 -5C
could bring a return of some lk effect clds/showers on Sun ngt.

Next week...Some lk effect clds/showers could linger into Mon in the
nw flow ahead of aprchg hi pres. But as this sfc hi pres builds 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, Tue mrng could be quite chilly. But many of the
models show 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, so wl
stick with the consensus fcst for now. The longer range guidance
then hints another shrtwv/sfc lo pres moving thru a more zonal flow
over the w half of NAmerica could impact the area next Wed/Thu.

.AVIATION...(For the 12Z TAFS through 12Z Friday morning)
Issued at 725 AM EDT THU OCT 20 2016

Expect mainly VFR ceilings at TAF sites today will lower to MVFR late
this evening and overnight tonight as winds veer from nw to northerly
behind a surface trough passage. There may be a few showers at IWD
and CMX, but the best chance for lake effect showers will be at SAW
late tonight with a more favorable northerly wind. &&

.MARINE...(For the 4 AM Lake Superior forecast issuance)
Issued at 505 AM EDT THU OCT 20 2016

High pressure will remain in control through much of the forecast
period with no significant low pressure systems affecting the Upper
Great Lakes. Winds will remain well blo gales through the period.

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


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