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