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Area forecast discussion...updated 
National Weather Service Duluth Minnesota
916 PM CST Friday Dec 19 2014

issued at 915 PM CST Friday Dec 19 2014

Very slow moving upper level trough axis centered over the Red River
valley as of middle evening will move very slowly eastward through
Saturday. 00z soundings across the upper Midwest exhibit pretty
classic freezing drizzle characteristics..with little middle/upper
level ice..but the low levels are saturated below a fairly strong
inversion with weak warm advection. With weak but persistent low
level warm advection overnight and Saturday morning..we see little
reason why freezing drizzle and fog will not persist in some form
through at least midday Saturday. The drizzle will mix with/change
to light snow for short periods of time in a few places..
especially across north central Minnesota where up to a half inch
of snow can be expected.

The combination of all of this mess warrants the issuance of a
Winter Weather Advisory through midday Saturday. For now..we have
confined the advisory to areas roughly north/west of a Lake Mill
lacs to twin ports line..but we will need to closely monitor areas
farther east as well overnight. While precipitation will be
will also likely last for 12-16 hours or more..which should allow
most of the untreated roads to acquire a thin coating of ice and
result in some hazardous travel conditions overnight and Saturday

Updated grids and associated text well as the
advisory have already been sent.


Short term...(this evening through saturday)
issued at 330 PM CST Friday Dec 19 2014

Short term focus on h50 closed low over Ontario...which will
rotate a trough axis across the Northland overnight and into
Saturday morning. The cyclonic flow and middle level Omega will
support occasional snow showers/flurries...with most areas
receiving a dusting to around a half inch through Saturday afternoon.
There will be a focus for somewhat better forcing and light snow
accumulations of up to an inch overnight along the Iron Range
corridor and into the Minnesota arrowhead. The south winds from Lake
Superior may also introduce some lake enhancement and added
moisture...producing locally higher snowfall amounts up to 2
inches along the elevated terrain of the North Shore zones.

In addition to the light snow showers...there will be a continued
threat for brief light patchy freezing drizzle. There have been
reports of fzdz this afternoon over far southeast North Dakota...near the
vorticity maximum/trough axis. Based on the reports and hints of possible
periods of fzdz from the bufr soundings...will keep a mention of
fzdz through Sat morning. Due to lack of good accumulate
is expected.

Long term...(saturday night through friday)
issued at 330 PM CST Friday Dec 19 2014

There continue to be concerns that a potent winter storm system
could affect the Northland during the middle of next week...around
the peak of Holiday travel. There continue to be significant model
differences in the track of the low. The GFS track...which takes the
low to Western Lake Superior...would have a greater impact on the
Northland than the European model (ecmwf) and Gem tracks which take the low to the
central Great Lakes. This system will need to be closely monitored
in the models over the coming days.

Saturday night...there will be a weak upper level low over northwest
Ontario...and its trough will extend into the Northland. The
Northland will have weak warm air advection from south-southwest winds aloft in
the low/middle levels. The Northland could see very light snow. The
freezing drizzle threat looks pretty low considering there the low
level saturated layer is relatively shallow...and there is a
potential of ice Crystal seeding...but kept patchy freezing drizzle
in the forecast since it was in the previous forecast.

Sunday...the precipitation chances will increase over most of the Northland
Sunday as a shortwave moves across Minnesota and Wisconsin. The precipitation
type will likely be in form of light snow...but there is a very low
threat of freezing drizzle.

Sunday night through Alberta clipper will move into the
northern plains Sunday night and Monday. It will then slow down and
stall over the upper Midwest Monday night and Tuesday as it runs
into an amplifying upper level ridge over the eastern US. This low
will provide good chances of periodic light to moderate snowfall
accumulations through the period as the clipper brings more moisture
into the Northland and its inverted trough slowly moves through the

Middle of the next week...the models continue to indicate that the
stalled clipper will merge with a low over the far southern US. The
southern US low will tap into very warm and moist flow off of the
Gulf and lift and merge into the Great Lakes region by Wednesday.
This large and potent combined low will likely form over the western
or central Great Lakes region. Impacts to the Northland could be
substantial...but it will depend on its track. A more western
track...such as over Lake Superior per the GFS...would provide good
opportunity for heavy snow over the eastern forecast area. A more
eastern track...such as over Lake Huron per the European model (ecmwf) and
Gem...would not favor so much snow over the Northland. In either
case...there could be quite gusty winds on the back side of this
system Wednesday and Thursday as cold air pours into the Northland
and central US. Even with light snow...the Northland could see a
period of low visibility due to the combination of the falling snow
and gusty winds. The low level mixing layer in the GFS soundings
show the potential for winds gusts over 30 miles per hour. The cold northwest flow
could result in a prolonged period of lake effect over northwest Wisconsin
for the latter half of the week.

We will need to keep our close attention on the model projections of
this storm system due to its potentially high impact on Holiday


Aviation...(for the 00z tafs through 00z Saturday evening)
issued at 640 PM CST Friday Dec 19 2014

Generally IFR conditions expected to persist for a majority of
this 24 hour taf cycle. Weak but persistent low level warm/moist
advection will persist into Friday evening as very slow moving middle
level trough axis inches eastward across Minnesota. This should
result in persistence of low ceilings/fog and freezing drizzle
and/or very light snow/flurries. Most of the significant
visibility reductions should be resultant more from fog than from
precipitation. Some brief improvement into MVFR flight category is
possible after 18z Friday.


Preliminary point temps/pops...
dlh 22 31 27 32 / 30 30 20 40
inl 22 29 25 32 / 40 30 30 30
brd 25 31 26 32 / 20 10 20 30
hyr 22 30 27 34 / 20 20 20 30
asx 21 31 27 35 / 20 20 10 30


Dlh watches/warnings/advisories...
Minnesota...Winter Weather Advisory until noon CST Saturday for mnz010>012-



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