Area Forecast Discussion
Issued by NWS Grand Forks, ND

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FXUS63 KFGF 101000
AFDFGF

Area Forecast Discussion
National Weather Service Grand Forks ND
400 AM CST Sun Dec 10 2017

.SHORT TERM...(Today through Monday)
Issued at 400 AM CST Sun Dec 10 2017

The train of shortwaves within upper level northerly flow
continues. A weaker wave is passing through now (10z), bringing a
weak cold front and associated weak cold air advection. This cold
air advection will continue through the morning, with warm air
advection kicking in by early afternoon as low level flow becomes
more westerly with the approach of the next upper wave. This next
wave is much stronger (confirmed on water vapor imagery). SFC low
is expected to track from the northern valley (06z) to the
Minneapolis area (12z). The main forcing mechanism will be mid-
level warm air advection along and east of this sfc low track.
This should lead to a 3-6 hour period of light to moderate
snowfall. Snow ratios expected to be lower which will help to
limit snowfall totals. Models still not in perfect agreement with
the track of the sfc low, and will continue with the general 1-2
inch snowfall forecast along and east of the valley. With that
said, potential exists for localized areas to receive 2-4 inches
of snow (depending on the track of the sfc low, and future shifts
will need to update snowfall totals once we are within the window
of the HRRR/RAP forecasts). The warm air advection snow should be
done by around 06z, and then the cold front propagates through the
region (06z to 15z from north to south). This feature looks to
bring a brief period of snow showers combined with strong winds
(potential snow squall conditions - 1-2 hour period of very low
visibility). Timing of these conditions will determine overall
impacts, with higher impacts if coincident with the Monday
morning commute. Breezy winds continue into Monday afternoon,
potentially causing drifting snow.

.LONG TERM...(Tuesday through Saturday)
Issued at 400 AM CST Sun Dec 10 2017

Active northwest flow through mid to late next week will continue to
embed multiple clippers elevating precipitation chances mainly in
the form of light snow along with periods of gusty north/northwest.

High pressure moves over the region overnight Monday allowing
temperatures to reach closer to normal lows, i.e. single digits to
teens above zero.

Varying model guidance still presents timing issues on the mid week
clipper however a quick moving clipper dropping out of Canada is
advertised around the Wednesday into Thursday timeframe. Timing
issues likely stem from handling an interaction of impulses from two
different source regions, one being the well developed cyclone
within northwest Pacific and the other embedded within the central
Pacific jet streak. These impulses have a long way to travel out of
the Pacific and over the western North American ridge before they
start to interact with each other within central Canada. Dominate
precipitation type is expected to be snow with cold temperatures
aloft expected to remain in place absent of any significant warm air
advection or swing in the general west-east oriented thermal
gradient. It still remains too early to speculate snow totals and
their locations. The chance of elevated winds associated with this
clipper is on the higher end as suggested by ensemble and
deterministic guidance along with some part of persistence
forecasting from recent clippers and climatology.

Yet another system is advertised to drop into the region from the
north/northwest late next week, however this is a result of the
flattening of the western ridge. Precipitation chances will remain
elevated late next week as well.

Temperatures are expected to remain above normal to near normal
throughout the period as coldest air remains locked in place east of
the area and a forecast shrouded in clouds and clippers.

&&

.AVIATION...(For the 06Z TAFS through 06Z Sunday night)
Issued at 1143 PM CST Sat Dec 9 2017

Changeable sky cover and flight categories thru the period. Areas
of high clouds over E ND into MN at 06z...with stratocu and MVFR
cigs lurking Winnipeg to Roseau to Bemidji. These lower clouds are
expected to work back south and southwest behind the departing
weak low during the overnight into Sunday morning. So that for
most of the daytime Sunday MVFR cigs RRV into NW MN. Light snow
developing in NE ND late in the day and spreading east brief
reducing vsbys at GFK but a longer period of snow at TVF/BJI after
00z Mon.

&&

.FGF WATCHES/WARNINGS/ADVISORIES...
ND...None.
MN...None.
&&

$$

SHORT TERM...TG
LONG TERM...CJ
AVIATION...Riddle



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