401 FXUS63 KUNR 011747 AFDUNR Area Forecast Discussion For Western SD and Northeastern WY National Weather Service Rapid City SD 1047 AM MST Tue Dec 1 2020 .UPDATE... Issued at 959 AM MST Tue Dec 1 2020 Upper trof crossing the forecast area this morning with low center dropping into the base of the trof over CO. Band of low clouds behind trof is moving into northeastern WY with some light snow showers that will continue over the Black Hills this afternoon. Morning soundings show lower levels east of the Hills are very dry, so do not expect precipitation over the plains of SD. On the surface, cold front has passed through the forecast area with strong NW winds behind it. Temperatures are starting to fall over northwestern SD and will hold steady or increase only a couple more degrees over the rest of the area. && .DISCUSSION...(Today Through Monday) Issued at 132 AM MST Tue Dec 1 2020 Brief breakdown of the persistent upper ridge ongoing as strong upper trough and associated cold front advects through the region. A period of gusty NW winds will continue early this morning, with another round of wind late morning and afternoon as the main lobe of CAA and pressure rises advect into the region. A band of light snow will push through the western FA as well today, with some light accums possible in the northern Black Hills. Have left the wind headlines as is, although the a few gusts to around 60 mph will very well be possible on the adjacent plains east of the Black Hills (esp KRAP) this afternoon. However progged soundings are not very conducive for widespread warning levels in any zones. CAA will continue into the overnight with another lobe of moisture and forcing supporting an uptick in precip chances in mainly NE WY and the northern Black Hills tonight. Retained low to moderate pops for this with some light accums possible in the northern Hills once again. Cold, dry, and breezy weather is on track for Wed as the main upper cold core passes west of the region. Some lingering morning flurries or snow showers will be possible in the SW 2/3, with clearing most areas by afternoon. After wed, the western NOAM ridge will rebuild, supporting WAA into Sat. This will allow for mild and dry weather once again. There is some indication for a potential backdoor cold front Sat night into Sun, which would offer a brief period cooler conds. However, mean ridging looks to prevail into next week, with continued dry and mild conds. Flow does become more flat toward the end of next week, with much cooler conds likely if that does materialize. && .AVIATION...(For the 18Z TAFS Through 18Z Wednesday) Issued At 1042 AM MST Tue Dec 1 2020 MVFR to IFR conditions in SHSN will continue to overspread northeast WY and the BLKHLS as a system crosses the region. Gusty northwest winds will continue, especially across the western SD plains. Gusts to 40-50 knots will be possible thru the afternoon. Winds will diminish early this evening, with conditions returning to VFR most locations from west to east later in the evening. The exception will be across the northern Black Hills where IFR ceilings and very light snow may persist into Wednesday morning. && .UNR WATCHES/WARNINGS/ADVISORIES... SD...Wind Advisory until 5 PM MST this afternoon for SDZ001-002- 012>014-025-026-030>032-043-072-073. WY...None. && $$ Update...55 DISCUSSION...JC AVIATION...15