872 FXUS63 KUNR 290945 AFDUNR Area Forecast Discussion For Western SD and Northeastern WY National Weather Service Rapid City SD 245 AM MST Wed Nov 29 2017 .DISCUSSION...(Today Through Tuesday) Issued at 230 AM MST Wed Nov 29 2017 Potent fast moving shortwave trough continuing to support staunch WAA and an associated amplifying southerly LLJ across the region. Pressure gradient deepening across the Black Hills, with downslope flow impacting portions of the northern and eastern foothills as wells as parts of the adjacent plains. Downsloping will continue into the morning ahead of the system trough with ridge tops and favored downslope areas expected to see wind adv winds. Will cancel the high wind warning for the Black Hills as any potential high wind warning wind will be very isolated and confined to mainly ridge tops. Another area that will experience gusty SW winds will be scentral SD where adv winds can be expected this morning into the afternoon. The strongest winds are expected into the early afternoon there with winds likely dropping below adv levels as the trough passes through the area and winds veer NW. However, gusty NW winds could reach adv levels there this afternoon for a bit. Hence, will issue a wind adv this morning through the afternoon to cover both situations. Otherwise, the strongest winds will occur across NW SD where warning winds are expected late this morning into afternoon. Strong linked flow, CAA, and isallobaric forcing will align to produce warning level sustained winds and gusts there, with gusts of 60-65 mph expected there. Otherwise, adv level winds can be expected for most of the rest of the SD plains. Thermal ridge will time over the eastern FA supporting highs in the upper 50s and lower 60s there, with the rest of the area likely to see highs this morning or early afternoon. Winds will quickly wane this evening with much cooler conds tonight. WNW flow will continue through the end of the week, supporting mild and dry weather through the weekend. A couple subtle impulse look to pass through the area Friday and Sat. However forecast models keep things dry with these systems. Forecast models still support an amplifying western NOAM ridge by the end of the weekend as a deep trough drops into the western CONUS and splits. A strong cold front looks likely early next week as the western NOAM ridge amplifies and a longwave trough develops to the east. This would support the coldest air of the season locally. However, forecast models are keeping the core of the coldest air well east of the FA, with a CP/arctic front potentially setting up over the FA mid next week. Longitudinal placement of the expected NOAM ridge will highly dictate the amount and duration of cold air into the region, which still remains uncertain attm. && .AVIATION...(For the 06Z TAFS Through 06Z Wednesday Night) Issued At 928 PM MST Tue Nov 28 2017 VFR conditions are expected through Wednesday morning. South to southwest winds will increase tonight across NE WY and much of western SD, ahead of an approaching cold front. Gusts of 35 to 40 kts can be expected at KGCC overnight. Along the northern and northeastern foothills of the Black Hills...windy conditions are also expected tonight with gusts over 50 mph possible. LLWS is expected on the SD plains including KRAP. These winds will decrease shortly after sunrise. Winds will then become gusty out of the northwest tomorrow behind the cold front, with gusts to 60 mph possible across NW SD. Some light rain or snow showers are possible tomorrow afternoon across NE WY and far western SD behind the cold front, but mainly VFR conditions expected. && .UNR WATCHES/WARNINGS/ADVISORIES... SD...Wind Advisory from 8 AM this morning to 6 PM CST this evening for SDZ046-047-049. Wind Advisory from 10 AM this morning to 6 PM MST this evening for SDZ014-027-031-032-041-043-073. High Wind Warning from 9 AM this morning to 6 PM MST this evening for SDZ001-002-012-013. Wind Advisory until 6 PM MST this evening for SDZ025-026-072. WY...None. && $$ DISCUSSION...JC AVIATION...Johnson