Area Forecast Discussion
Issued by NWS Marquette, MI

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FXUS63 KMQT 302118
AFDMQT

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

.SHORT TERM...(This evening through Thursday)
Issued at 417 PM EST WED NOV 30 2016

WV imagery and RAP analysis indicated a mid/upper level low over
northeast IA with troughing to the northeast through wrn Lake
Superior to James Bay. At the surface, a trough extended from wrn WI
to a developing low over se Lake Superior resulting in light winds
over most of Upper Michigan but increasing n to ne winds over west
and central Lake Superior. An area of pcpn (rain mixed with sleet)
that has lifted through n cntrl Upper Michigan into Lake Superior
and the Keweenaw was supported by 900-700 mb fgen and 285 isentropic
lift. Light lake enhanced pcpn has also slid into IWD as the low
level nrly flow edges eastward.

Tonight, expect the lake enhanced pcpn, rain changing to snow, to
expand over the wrn cwa for locations favored by nrly flow. Even
with only marginal instability (850/700 mb temps of -6C/-12C over 6C
lake surface) abundant upstream and deeper moisture along with
upslope flow will support snowfall amounts to around 2 inches. Wet-
bulb zero heights suggest that any pcpn developing over the east
half will be mainly rain.

Thursday, as the mid level low consolidates south of James Bay, the
sfc trough/low will also slide into Quebec, low level winds will
back to the southwest. Additional snowfall amounts to around 2
inches will be possible over mainly the Keweenaw and the Huron
Mountains(w of Big Bay to Herman). CAA will change the remaining
pcpn to snow over the east.
&&

.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
normal.

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
half.

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 PM Lake Superior forecast issuance)
Issued at 417 PM 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 with remaining 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.
&&

.MQT WATCHES/WARNINGS/ADVISORIES...
Upper Michigan...
None.
Lake Superior...
None.
Lake Michigan...
None.
&&

$$

SHORT TERM...JLB
LONG TERM...KC
AVIATION...JLB
MARINE...JLB



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