880 
FXUS63 KBIS 120235
AFDBIS

Area Forecast Discussion
National Weather Service Bismarck ND
835 PM CST Sat Jan 11 2020

.UPDATE...
Issued at 833 PM CST Sat Jan 11 2020

The forecast remains well on track with observations. Off-and-on
light snow showers continue across central North Dakota this
evening, as expected. Cloud cover is beginning to decrease across
the far northwest. No notable changes were needed for this update.

UPDATE Issued at 533 PM CST Sat Jan 11 2020

Updated the sky cover forecast using the 22z iteration of the NBM,
which captures current observations well. Expect at least some
clearing across the west this evening, with clouds increasing
again early Sunday morning. No other changes were needed for this
update. 

&&

.SHORT TERM...(This evening through Sunday)
Issued at 310 PM CST Sat Jan 11 2020

A shortwave trough will bring chances for light snow across western 
into central North Dakota through the evening. Weak warm air 
advection/isentropic ascent trailing the shortwave will prolong 
light snow chances across central North Dakota through tonight. 
Total accumulations should remain under one inch, with most 
locations seeing only a dusting at most. Given the cloudy skies and 
WAA, temperatures should remain fairly steady overnight. Expect lows 
ranging from around zero east to the mid teens southwest.

Some light snow may linger across northern North Dakota on Sunday as 
weak isentropic ascent continues. Otherwise, expect quiet weather 
with weak deep layer flow and a thermal ridge axis over the western 
Dakotas. It will be warmer tomorrow, especially over southwest North 
Dakota where highs may approach freezing.

.LONG TERM...(Sunday night through Saturday)
Issued at 310 PM CST Sat Jan 11 2020

Concerns for the long term period include well below normal 
temperatures, several chances for light snow, and the potential for 
dangerous wind chills. However, a significant, prolonged Arctic 
outbreak appears more uncertain now than previous forecast cycles 
suggested.

A series of shortwaves will track across the region late Sunday 
through Wednesday with general longwave troughing over central North 
America. The two most notable pieces of energy look to move through 
late Sunday through late Monday, and then late Tuesday through 
Wednesday. Each of these disturbances will bring chances for light 
snow to the area, but accumulations are expected to remain low at 
this time.

While well below normal temperatures are certainly still favored 
through the long term period, models are trending toward a warmer 
solution overall. Not only are 850 mb temperatures trending warmer, 
the synoptic pattern through Wednesday would seem to favor mostly 
cloudy skies which would limit chances for strong radiational 
cooling. The deterministic GFS, which has a known cold bias, remains 
the coldest piece of guidance. Meanwhile, the GEFS mean and ECMWF 
barely bring any sub -20 C 850 mb air into North Dakota, which would 
suggest this cold air mass will not be climatologically anomalous. 
The coldest night looks to be Wednesday night when a large surface 
high builds over the region. This night looks most favorable for 
widespread lows in the teens to 20s below zero. However, winds 
should be fairly light with the center of the high overhead. 

Another changing trend is that models are now more progressive with 
shoving the Arctic air off to the east by the weekend. There are also 
hints of a higher snowfall event crossing the area Friday into 
Saturday, but details are far from certain.

In summary, we are still expecting well below normal temperatures 
next week, and there will likely be times when wind chill headlines 
will be needed. But a long duration Arctic air mass with high impact 
wind chills looks increasingly unlikely.

&&

.AVIATION...(For the 00Z TAFS through 00Z Sunday evening)
Issued at 533 PM CST Sat Jan 11 2020

The 00z TAF period is highlighted by broken to overcast skies with
cigs mainly in the MVFR TO VFR range. Off and on light snow
showers and flurries will be possible at KBIS and KMOT this 
evening, before diminishing tonight.


&&

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

$$

UPDATE...TK
SHORT TERM...Hollan
LONG TERM...Hollan
AVIATION...TK