Area Forecast Discussion
Issued by NWS Marquette, MI

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171
FXUS63 KMQT 030802
AFDMQT

Area Forecast Discussion
National Weather Service Marquette MI
302 AM EST Sat Dec 3 2016

.SHORT TERM...(This evening through Saturday)
Issued at 337 PM EST FRI DEC 2 2016

Though primary sfc low has made it to southern Quebec a weak trough
extends back across the lower Great Lakes. Another subtle more
mesoscale trough is also across Upper Michigan with slightly backed
winds to wnw over west half of Upper Michigan while more of a nw
wind is across Lk Superior and over east half of Upper Michigan.
Light snow showers have been in stronger convergence with the trough
all day btwn Marquette and Grand Marais. Sfc temps in the low-mid
30s and overall light intensity have resulted in minimal snow accums
in this area with rain/snow mix at times near the Lk Superior shore.
Just a few flurries elsewhere under cloudy skies. Weak shortwave is
noted upstream over southern Manitoba. As this wave moves in there
is some response with inversions rising up slightly from current 3-
4kft to 5-6kft and increasing moisture. Trouble is that initially as
this lift arrives, it may not be cold enough to introduce ice aloft
as temps in moist layer are only as low as -6c or -7c, so there
could be drizzle or freezing drizzle. Best chance of drizzle would
be over western cwa where convergent upslope nw flow will boost low-
level lift. Already seeing cigs dropping at IWD with hints of lower
vsby. Call out to Gogebic sheriff office indicates it is just cloudy
but once daylight ends, there may be better chance of lower level
saturation and some drizzle, especially as the forcing arrives toward
00z/7 pm ET.

Eventually the forcing will bring top of inversion to temps to
around -10c which should lead to better chance at introducing ice
aloft and seeing some lighter snow. Once the snow sets up best shot
for a couple inches of accumulation will be in more persistent
convergent zone over Ontonagon into Houghton county to the south of
the Portage Canal with second area of enhanced snow where the
enhanced lake effect has been set up most of today over far eastern
Marquette county into western Alger county. High pressure moving in
on Sat will gradually result in decreasing lake effect from west to
east. By late aftn expect very little in way of lake effect except
for on the Keweenaw with wsw low-level winds.

Temps will remain seasonable with lows tonight in the mid 20s to
lower 30s, warmest near Lk Superior and east. Highs on Sat will be
similar to today, low 30s west half and mid to upper 30s east half.

.LONG TERM...(Sunday through Friday)
Issued at 301 AM EST SAT DEC 3 2016

Upper pattern consists of a closed 500 mb low over Mexico 12z Sun
with a shortwave over the northern plains. There is also a shortwave
over the Canadian Rockies. This shortwave will move into the
Canadian Prairies 12z Mon and the shortwave will then dig into the
northern plains 12z Tue. Nam brings in some deeper moisture and 850-
500 mb q-vector convergence Sun and both move out Sun night. Could
see up to 2 inches of snow out of this event for Sun and Sun night.
Overall, did not make too many changes to the going forecast.

In the extended, GFS and ECMWF show a broad and deep 500 mb trough
across most of the U.S. with a strong shortwave over the northern
plains 12z Tue. Behind this shortwave is very cold air in the
northern Rockies. A closed 500 mb low forms with this shortwave and
moves slowly east in western Ontario 12z Wed. This closed low makes
it east into the upper Great Lakes 12z Thu and the associated trough
makes it into the ern U.S. 12z Fri. Interesting thing is airmass
does not look as cold now as it did for the 00z Fri run yesterday as
all the models now break off a piece of the colder air while keeping
it mostly over Canada which was a change from yesterday.
Temperatures will go below normal and stay there this forecast
period. There will also be some lake effect snow and this is covered
well in the forecast.
&&

.AVIATION...(For the 06Z TAFS through 06Z Saturday night)
Issued at 1153 PM EST FRI DEC 2 2016

With abundant low-level moisture and light flow across Lake
Superior, fcst thru this morning will be a persistence fcst with
MVFR cigs likely to prevail at KIWD/KCMX/KSAW. Not out of the
question that IFR cigs could occur at KIWD overnight. In addition,
light downslope component to the wind may allow for some periods of
VFR at KSAW. Some -shsn are also expected at KCMX. Late this
aftn/evening, conditions may begin to break out to prevailing VFR.
&&

.MARINE...(For the 4 PM Lake Superior forecast issuance)
Issued at 337 PM EST FRI DEC 2 2016

NW winds to 25 kts diminish to 20 kts later tonight through Sat
night as high pressure ridge crosses the region. Winds stay 25 kts
or less Sun into Mon as pressure gradient remains light. An
approaching low pressure trough crossing Tue night into Wed will
result in southeast winds increasing to 30 kts on Tue, strongest
over central and eastern sections. Winds shifting northwest on Wed
could reach 30 kts as well.
&&

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

$$

SHORT TERM...JLA
LONG TERM...07
AVIATION...Rolfson
MARINE...JLA



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