374 FXUS63 KUNR 280452 AFDUNR Area Forecast Discussion For Western SD and Northeastern WY National Weather Service Rapid City SD 1052 PM MDT Mon Mar 27 2023 .UPDATE... Issued at 234 PM MDT Mon Mar 27 2023 With the location of the convective heavy snow showers across the central/southern hills now apparent, have issued a Winter Weather Advisory. && .DISCUSSION...(This Evening Through Monday) Issued at 1255 PM MDT Mon Mar 27 2023 Water vapors shows trof axis over the central CONUS, with main upper low over northeast CO and compact short wave over southwest SD. Rather flat upper ridge covers the western CONUS with next upper low offshore the Pac NW. At the surface, inverted trof extends northward from eastern CO to along the western SD border. Light snow continues to fall over much of western SD and parts of northeast WY, with enhanced snowfall moving east across northern Oglala Lakota and southeast Pennington counties, associated with the compact short wave. For this rest of this afternoon in tonight...snowfall associated with the compact short wave will move east this afternoon into south central SD, then should dissipate this evening, with most accumulations an inch or less. Another area of enhanced snowfall will fall over the southern Black Hills where the best low level convergence resides. Could see a quick few inches in that area given the steep lapse rates in place. Most snow will gradually end this evening with dry conditions overnight. Flat upper ridge will build in for Tuesday and Wednesday, bringing slightly warmer weather. A speed max associated with the northern stream could bring a few flurries or very light snow showers Tuesday night from the Black Hills eastward. Otherwise, dry weather expected. Upper trof over the intermountain west on Thursday will build eastward into the Rockies Thursday night, with a closed low developing across the Central Plains Friday. After a much warmer day Thursday in the warm sector, where some readings near 60 south and east of the Black Hills may occur, widespread snow will develop and shift east across our area Thursday night into Friday, especially our southern two-thirds of zones. This will be a very progressive upper low which will help limit impacts. NBM probs for 6+ inches are generally in the 20-30% range and mainly for areas south of I-90 across western SD. At this time, it looks more likely to be an advisory type storm unless winds become more significant. Still some time to work out the details the next few days. After this storm departs, drier and warmer weather for at least the first half of the weekend before more unsettled weather arrives early next week. && .AVIATION...(For the 06Z TAFS Through 06Z Tuesday Night) Issued At 1046 PM MDT Mon Mar 27 2023 VFR conditions are expected through most of the TAF period. Late Tuesday night a backdoor front swings down, bringing MVFR/IFR cigs into the region. && .UNR WATCHES/WARNINGS/ADVISORIES... SD...None. WY...None. && $$ Update...Johnson DISCUSSION...Johnson AVIATION...Dye