Area Forecast Discussion
Issued by NWS Marquette, MI

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FXUS63 KMQT 301955

Area Forecast Discussion
National Weather Service Marquette MI
255 PM EST Wed Nov 30 2016

.SHORT TERM...(Today and tonight)
Issued at 502 AM EST WED NOV 30 2016

Radar imagery this morning has been showing most of the radar
reflectivities over the western WI/eastern MN border as well as over
the Arrowhead of MN. Addtitonally, there have even be a couple
lightning strikes over northeatern Lower MI this morning. Surface
obs have been showing that the precip has been a mix of rain and
snow in WI with mainly snow over northern MN. WV imagery shows a
broad rotation associated with the upper level low, which is center
over the western WI/eastern MN border. There are also multiple
impulses that can be seen rotating around the upper level low. IR
satellite imagery has been showing a break in the cloud cover over
central and eastern portions of the U.P. while much of the western
U.P. remain overcast. Additionally, some fog can be seen over
portions of the eastern half of the U.P. with temperatures in the
mid to upper 20s where skies have cleared and in the low to mid 30s
where cloud cover remains or has moved back into the area.

Today: As one of the aforementioned waves wrap into the U.P. later
this morning, models have been depicting a surface low developing
over northern Lake Michigan by 12Z and then lifting to the north as
it becomes the main surface low through this afternoon. As this low
develops, initially the drier air over the eastern U.P. should limit
any sort of precipitation through the early morning hours; however,
by mid morning, increased moisture is expected to slide into the
area from the southwest, which will increase the potential for
precipitation. The best overall system forcing will likely remain
over the eastern half of the U.P. this morning; therefore, have kept
better pops in that area early in the day. At this point, it looks
like there will be a fairly significant warm layer that the
precipitation would be falling through, which would keep it in the
form of rain. The only caveat is if the rain starts before daybreak
over the far eastern areas where the skies cleared early this
morning. If the rain does start a little earlier than expected it is
not out of the question that there could be some very light freezing
rain, but indications are that it would be closer to mid morning
around 15Z before the precip starts, keeping it mainly in the form
of rain. As the low is parked over eastern Lake Superior this
afternoon, colder air will begin to filter into the western U.P.
both at the surface and aloft. This will allow the rain to mix with
and slowly change to snow over the high terrain of the west through
the late afternoon hours. 850mb temperatures are progged to fall to
around -5C this afternoon over the west half of the U.P., which
would give delta-T values in the 10C to 12C range giving increased
chances of lake effect/lake enhanced precipitation for north to
northeast wind favored locations. The eastern half will still see
mainly rain during the afternoon with no lake enhancement expected
as 850mb temps stay closer to -1C to -2C and winds stay out of the
west to southwest.

Tonight: The aforementioned surface low and upper-level 500mb low
are expected to remain over eastern Lake Superior through tonight.
At the same time, 850mb temperatures are expected to remain around -
5C over the western half of the U.P. keeping a continued lake
effect/enhanced snow in the forecast for north to northwest wind
favored locations. At this point, only expect a couple inches of
accumulation over the higher terrain with lower amounts expected
closer to the Lake Superior shoreline. The eastern U.P. will
continue to see westerly winds and 850mb temperatures only in the -
2C to -3C range, which should limit any lake effect potential over
the east. Snow will begin to mix in with the rain over the east half
as temperatures continue to slowly cool; however, only minor
accumulations are expected at this time.

.LONG TERM...(Thursday night through Wednesday)
Issued at 255 PM EST WED NOV 30 2016

During the beginning of the medium range period, a slowly weakening
cyc nw flow arnd a slowly departing closed lo in Quebec wl cause
some lk effect pcpn into Sat. Although a passing hi pres rdg wl
bring mainly dry wx for Sat into Sun, another shrtwv/lo pres trof
aprchg fm the w wl bring a return of some pcpn later on Sun. Expect
dry wx on Mon as the trailing hi pres rdg overspreads the area.
While the fcst wl include some pops much of the time during the
medium range, pcpn and any snow totals should be on the lgt side. A
more important lo pres lifting out of the wrn trof and toward the
wrn Great Lks next Tue/Wed may result in a more sngft pcpn event
then, but model differences on the fcst are too sgnft to pin down
any details attm. Overall temps into early next week wl run aoa

Thu ngt thru Fri ngt...Although the larger scale forcing to support
pcpn wl be waning as the closed lo over wrn Quebec at 00Z on Fri
weakens and drifts slowly to the e, leaving deep lyr qvector dvgc/
subsidence over the Upr Lks, a persistent albeit weakening cyc nw
flow in the presence of plentiful llvl mstr and h85 temps within a
few degrees of -6C /compared to Lk Sup water temps in the 7-8C
range/ wl support continued lk effect pcpn. This pcpn wl be in the
form of mainly snow over the interior w half, with more of a
rain/snow mix near the warming influence of the lakes. Bumped up
pops above the consensus fcst and into the likely range in the
upslope areas favored by the expected llvl flow. The incrsgly
negative larger scale dynamics...marginally chilly h85 temps...warm
ground temps and absence of a deep dgz sug snow accums wl be a few
inches at most thru this time even over the hier terrain of the w

Sat/Sat ngt...Although a sfc hi pres rdg/acyc larger scale llvl flow
extending fm Ontario into the wrn Great Lks wl drift acrs Upr MI on
Sat, many of the models depict some lgt pcpn lingering along a lk
induced lo pres trof and under some persistent llvl mstr. On Sat
ngt, the llvl flow wl shift to the s after the hi pres rdg axis
moves to the e, ending any lingering pcpn except over Lk Sup and the
ern cwa downwind of Lk MI. Any snow accums during this time wl be
under an inch.

Sun/Sun ngt...Another shrtwv/lo pres trof embedded in the more zonal
flow alf is progged to impact the area during this time. Waa/hgt
falls/uvv ahead of this disturbance wl result in some pcpn arriving
w to e on Sun. Fcst llvl thermal fields sug the pcpn wl be a rain/
snow mix, with the ptype primarily snow over the interior w half.
But since mstr inflow is progged to be marginal and the shrtwv/lo
pres trof are progged to weaken with a larger scale tendency toward
a bldg upr rdg in the Plains, expect only lgt snow accums. The sly
flow ahead of the lo pres trof off Lk MI in the presence of h85
temps still arnd -6C may result in some lk enhancement of the mixed
pcpn there. The arrival of dnva/large scale subsidence in the wake
of the passing disturbance and ahead of upr rdg/sfc hi pres in the
Plains wl cause the pcpn to diminish w-e on Sun ngt. Since h85 temps
within the trailing airmass are progged to rise toward -4C by 12Z
Mon, no lk effect pcpn is expected in the wake of the passing/
weakening trof.

Mon thru Wed...Bldg upr rdg/sfc hi pres are fcst to drift into the
wrn Great Lks on Mon, resulting in dry wx and some warmer temps as
h85 temps rebound to near 2C. Expect a return of some pops on Tue as
some waa btwn the departing sfc hi pres rdg and a shrtwv/lo pres
moving newd out of a deep wrn trof overspreads the area. The longer
range models show some sgnft differences in the evolution/track of
the sfc lo pres for next Wed that would support either rain or a
surge of colder air and some lk effect snow showers. Considering the
sgnft uncertainties, made no changes to the consensus fcst.

.AVIATION...(For the 18Z TAFS through 18Z Thursday afternoon)
Issued at 1255 PM EST WED NOV 30 2016

Conditions will begin deteriorate at IWD and CMX with increasing
rain and snow showers this afternon and evening as low pressure
moves through Upper Michigan. The more concentrated area of rain and
snow showers over the west will change over to mainly snow. VFR to
MVFR conditions will give way to MVFR to IFR conditions in the
afternoon through the overnight hours at IWD and CMX. Visibility may
also drop into the IFR range with the snow. SAW will stay VFR to MVFR
through the rest of the day and drop to MVFR tonight into Thursday
morning with minimal chances of reduced visibility as the
precipitation should remain in the form of rain into the late
afternoon hours.

.MARINE...(For the 4 AM Lake Superior forecast issuance)
Issued at 502 AM EST WED NOV 30 2016

Low pressure will linger over the western Great Lakes through
Thursday. However the pressure gradient is not expected to be as
tight today and winds should remain below 25 knots. Northerly winds
to near 30 knots are expected to develop tonight into Thursday as
the slow moving trough moves to the east of Lake Superior into
Quebec. High pressure will then build into the area into Saturday
with winds below 20 knots.

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


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