630 FXUS63 KBIS 090240 AFDBIS Area Forecast Discussion National Weather Service Bismarck ND 840 PM CST Fri Feb 8 2019 .UPDATE... Issued at 839 PM CST Fri Feb 8 2019 Little change with this update. As mid level cloud cover continues to expand across western and central North Dakota this evening temperatures should be at or near their minimums, with near steady to slowly rising temperatures through the night. No change to the Wind Chill Advisory. Expect light snow to develop late tonight and into Saturday morning, especially south of US Highway 2, with slowly strengthening low level warm air advection with a series of mid level impulses also arriving. While new snowfall amounts of generally less than an inch are expected, a zone of 1-2 inches is possible central south of US Highway 2 per the 18 UTC global suite and RAP/HRRR/NBM through their 00 UTC iterations. UPDATE Issued at 445 PM CST Fri Feb 8 2019 Update to decrease low temperatures for the evening with a quick post sunset drop off in temperatures likely, especially along and north of US Highway 2 and across the James River Valley. Lows of -25 to -30 are forecast given the very cold start to the early evening with a 23 UTC temperature of -20 at Rugby and -18 at Tioga. An upgrade of the Wind Chill Advisory to a Wind Chill Warning may be needed for these areas. With increasing clouds through the night, do expect a rising temperature trend after a quick bottoming out of temperatures late this evening. Also, increased PoPS for late tonight into Friday morning for a High PoP, Low QPF scenario with light snow associated with the baroclinic zone on the western periphery of the arctic air. && .SHORT TERM...(This evening through Saturday) Issued at 245 PM CST Fri Feb 8 2019 Widespread light snow is expected to develop late tonight along with dangerous wind chills. The 12z iterations of the NAM/GFS depict widespread light snow developing late tonight across most of western and central North Dakota as an impulse moves through the area. Q-vector convergence looks good across the area during this time, along with modest frontogenetical forcing. NAM/GFS BUFR soundings also depict a fairly deep dendritic growth zone. The latest iteration of the NAMNest was used for the probability of precipitation forecast tonight through tomorrow as this model expanded and increased probabilities accordingly. Accumulations of around 1 inch or less are expected. In addition, dangerous wind chills as low as 40 below zero are expected tonight through tomorrow morning. .LONG TERM...(Saturday night through Friday) Issued at 245 PM CST Fri Feb 8 2019 Dangerous wind chills and several chances for accumulating snowfall highlight the long term forecast. The 12z iterations of the ECMWF/GFS agree well on the timing of an upper level shortwave moving from southwest to northeast across North Dakota on Sunday. This shortwave will provide sufficient forcing for yet another round of widespread light snow across the area on Sunday. Southwest North Dakota looks to have the greatest chance for accumulating snowfall. A more significant and impactful winter storm is looking more and more likely across North Dakota Monday through Tuesday as a Colorado low develops and moves through the central Plains. The ECMWF/GFS agree well on the timing and intensity of this storm, giving much of North Dakota several inches of snow along with gusty winds. Near blizzard conditions may be possible across the James River Valley on Tuesday as the surface pressure gradient tightens and northerly winds ramp up. The latest blend of model guidance gives western North Dakota between 1 and 3 inches and 3 to 5 inches for central North Dakota. The snowfall forecast will need to be fine-tuned as we get closer to the event. In addition, it does appear heavier bands of snowfall with locally higher amounts are possible as there looks to be plenty of moisture, strong synoptic scale and mesoscale forcing, and SEPV values below 0.25 in some areas (implying the potential release of conditional symmetric instability). Yet another round of snow looks possible for Wednesday through Thursday, however there is still plenty of model disagreement. && .AVIATION...(For the 00Z TAFS through 00Z Saturday evening) Issued at 839 PM CST Fri Feb 8 2019 VFR conditions with arctic high pressure will begin the evening across western and central North Dakota. MFVR/IFR conditions in light snow and stratus will develop tonight into Saturday as the arctic high moves east. && .BIS WATCHES/WARNINGS/ADVISORIES... Wind Chill Advisory until noon CST /11 AM MST/ Sunday for NDZ001>005-009>013-017>023-025-031>037-040>048-050-051. && $$ UPDATE...PA SHORT TERM...TK LONG TERM...TK AVIATION...PA