Area Forecast Discussion
Issued by NWS Bismarck, ND

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FXUS63 KBIS 171455
AFDBIS

Area Forecast Discussion
National Weather Service Bismarck ND
855 AM CST Sun Dec 17 2017

.UPDATE...
Issued at 852 AM CST Sun Dec 17 2017

Considerable sunshine is expected today in the presence of
westerly downsloping flow extending through North Dakota. Current
forecast looks ok.

UPDATE Issued at 617 AM CST Sun Dec 17 2017

Weak high pressure remains over the area this morning. With clear
skies and light winds, have updated low temperatures based on
latest observations. Otherwise quiet weather expected today.

&&

.SHORT TERM...(Today and tonight)
Issued at 146 AM CST Sun Dec 17 2017

Quiet short term period today.

A weak upper level trough tracking across the southern Prairie
Provinces of Canada this morning will give way to upper level
ridging this afternoon. Partly to mostly sunny skies and a
generally light southwest winds should allow temperatures to reach
into the 30s across the forecast area, with some lower 40s
possible.

Clouds increase tonight with nearly zonal flow and pacific
moisture streaming across the northern rockies pushes into the
region. Surface low pressure well to our north will drag a cold
front across southern Canada and into northwest North Dakota by
late tonight. Generally mild conditions tonight ahead of the cold
front with overnight lows in the 20s. A blend of models bring some
slight chance pops to the northern tier counties after midnight.

.LONG TERM...(Monday through Saturday)
Issued at 146 AM CST Sun Dec 17 2017

Brisk Monday, Snow on Wednesday, followed by the coldest air of
the winter season so far highlight the extended forecast.

The aforementioned cold front drops south across the state on
Monday. Breezy to windy Monday, especially southwest and far south
central, ahead of the cold front. GFS indicates strongest winds
aloft ahead of the cold front, coinciding with steep lapse rates.
Winds aloft diminish with the passage of the cold front but there
may be a brief period when the strong winds aloft align with the
strong cold advection and isallobaric component, and possibly
aided by convective rain/snow showers. Will monitor but at this
time probably sub-advisory. NAM is also weaker with the winds
during this period.

Snow behind the cold front will be mainly limited to the northern
tier counties with amounts very light. But we could see some
rain/snow showers track along with the cold front as it drops
south through the forecast area. We should still warm into the 30s
north to 40s south on Monday ahead of the cold front.

Noticeably colder air spills into the state Monday night and
Tuesday. Highs will range from the 20s north to 30s south on
Tuesday, but it will be dry as surface high pressure tracks across
the forecast area.

Late Tuesday night through Thursday will be a transition period
as an upper level trough moves onto the West Coast and then drop
into the Desert southwest. The strongest synoptic scale forcing
will track to the south of our area, with the upper low, but
modest synoptic scale forcing will still exist over the area ahead
of a northern stream trough. This will combine with a period of
decent warm advection associated with a strong baroclinic zone
that moves across the northern plains Tuesday night and Wednesday.
Models continue to wobble around regarding the placement of
precipitation with the system. Latest runs keep higher amounts
across the northern tier counties, with little or possibly even
no precipitation across the far south. For now will continue to
stick with a model blend.

No matter where the snow ends up, at this time it looks like we
can be assured of a blast of Arctic air late in the forecast
period and lingering at least through Christmas.

&&

.AVIATION...(For the 12Z TAFS through 12Z Monday morning)
Issued at 617 AM CST Sun Dec 17 2017

VFR conditions are forecast across western and central North Dakota
for the 12z TAF cycle. High cirrus clouds across south central ND
early this morning should give way to mostly clear skies through
much of this evening, then mid level clouds increasing later tonight
across the north. Southwest winds should prevail through the TAF
period, with increasing southwest winds aloft this afternoon and
night.


&&

.BIS WATCHES/WARNINGS/ADVISORIES...
NONE.
&&

$$

UPDATE...WAA
SHORT TERM...TWH
LONG TERM...TWH
AVIATION...JV



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