Area Forecast Discussion
Issued by NWS Marquette, MI

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FXUS63 KMQT 011000

Area Forecast Discussion
National Weather Service Marquette MI
500 AM EST Thu Dec 1 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...(Friday through Wednesday)
Issued at 458 AM EST THU DEC 1 2016

Fri into Fri night: Models indicate the closed low over sw Quebec
will weaken and lift east toward New England late Fri. Behind the
low, cold air will linger over the Upper Great Lakes under a
cyclonic nnw flow. However 850 mb temperatures progged to be in the
-5C to -6C range will only be marginally cold enough to support lake
effect pcpn with Lake Superior sfc temps of 6-7C. Snow will be the
primary precip type although a mix of rain is possible along the
shoreline and east during the daytime hours on Fri. Given the
general absence of enhancement and a fairly elevated dgz expect any
snow accums to be inch or less.

Sat into Sat night: Light lake effect precipitation supported by low-
level convergence should be dwindling or ending over the east half
by afternoon or evening as the high pressure ridge axis moves across
Upper Michigan and winds back more west to southwest.

Sun into Sun night: Models indicate that the next shortwave trough
in zonal flow aloft will move in from the Northern Plains late Sun
into Sun night. Deep layer q-vector convergence ahead of this
shortwave will result in pcpn spreading w to e across the cwa on
Sun. Pcpn will be mostly in the form of snow over the west half but
will be more a mix of rain and snow east half due to moderation from
Lake Mi in southerly flow ahead of shortwave. 850 mb temps
-6 to -7c should be sufficiently cold enough given Lake Mi sfc temps
of 9C for some lake enhancement of pcpn into Schoolcraft and Luce
counties Sun into Sun evening which could produce some accumulating
snow well inland from Lake Mi. Given limited moisture inflow with the
system expect most system snow amounts to be generally less than an

Monday into Thursday: Models trending toward more amplified pattern
for next week as a 120+ kt 300-250 mb jet max and assoc shortwave
energy digging in from the eastern Pacific will carve out a broad
mid-upper level trough over the Western CONUS by early next week.
Model consensus of downstream ridging into the Great Lakes region in
response to the developing western CONUS trough will keep Upper Mi
mostly dry Mon into Mon night with a slight warming trend. Model
uncertainty increases from Tue into late week with the 00Z GFS being
much more progressive than 00Z ECMWF and Canadian with stronger
shortwave energy ejecting out of base of western CONUS trough. Given
uncertainty will use model consensus for pops which tend to keep
area dry from Mon into most of Tue but then brings in pcpn for Tue
night into Wed. Evolution/track of developing strong sfc low is very
much in question so initial pcpn for Tue night into Wed may end up
being more of a mix of rain/snow and then transition to more lake
enhanced/lake effect snow for late next week. Once cold advection
ensues behind the system, there will also likely be a period of
stronger winds accompanying lake effect snow later in the week. &&

.AVIATION...(For the 06Z TAFS through 06Z Thursday night)
Issued at 1154 PM EST WED NOV 30 2016

Cyclonic flow on the backside of low pres over eastern Lake Superior
will result in mostly prevailing IFR conditions with -shsn at
KIWD/KCMX/KSAW overnight into the morning hrs. With a more direct
upslope flow, IFR conditions will be most persistent at KIWD with
even some LIFR at times overnight. -Shsn will continue today,
especially at KIWD/KCMX. Conditions should also improve to low MVFR,
though IFR may tend to hang on at KIWD.

.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.

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


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