628 FXUS63 KBIS 212347 AFDBIS Area Forecast Discussion National Weather Service Bismarck ND 647 PM CDT Sat Aug 21 2021 .UPDATE... Issued at 632 PM CDT Sat Aug 21 2021 Scattered cu field over the area has gradually decreased in coverage over the past few hours and will continue to do so as the sun sets. No major changes to the forecast with this update. && .SHORT TERM...(This evening through Sunday) Issued at 201 PM CDT Sat Aug 21 2021 The main forecast issue in the short term period will be shower and thunderstorm chances late tonight and Sunday. Currently, upper level ridging is situated from eastern Montana into the western Dakotas and will keep our weather quite through this evening. Upstream a broad southwest upper flow is situated over the Northern Rockies ahead of a digging closed circulation tracking through Oregon, and another wave tracking across southern British Columbia. This progressive upper wave will track across the Northern Rockies tonight and into the northern High Plains early Sunday morning. An initially dry and stable atmosphere over the forecast area this evening will quickly moisten and destabilize as strong warm advection combined with strong mid and upper level forcing spreads west to east across the forecast area. Clouds will increase late this afternoon and this evening with precipitation holding off until after midnight. After midnight, expect a band of showers to push into western ND around 08-12 UTC, with the leading edge moving into central ND around 12 UTC. Overnight and into Sunday morning expect mainly scattered to numerous showers with some isolated embedded thunder. The instability is not that great, especially along the leading edge, but with such a dynamic system, certainly can't rule out thunder, especially along the trailing edge. The more numerous showers look to be across the north, with the highest qpf amounts over southern Saskatchewan and Manitoba. The far southwest and south central could see only trace amounts to a few hundredths of an inch, while the northwest and north central on average, will see the possibility of a tenth to quarter inch through 18 UTC. Sunday afternoon, there does look to be a short window of opportunity for a few strong to severe storms, mostly east of the Highway 83 corridor. Any rainfall in the afternoon and early evening will have more potential to occur with thunder, thus some higher qpf amounts (generally a quarter to a half inch) will be possible over the North Central into the James River Valley. The best potential for strong to severe storms at this time appears to be from around 4 to 8 PM over eastern portions of central ND. The strongest instability will be over the southern James River Valley, but there could be capping issues here. The strongest shear and steeper lapse rates will reside along the Canadian Border but overall instability will trail the strongest shear and may be behind the frontal boundary. It remains to be seen if the two can link up together over eastern portions of central ND long enough to maintain any developing updrafts. If so, the strong shear is not completely orthogonal to the the advancing frontal boundary, but enough so to potentially support a supercellular structure. The greatest threats look to be hail to half dollar size and 60 mph winds. .LONG TERM...(Sunday night through Saturday) Issued at 201 PM CDT Sat Aug 21 2021 The extended period looks to remain active with chances for showers and thunderstorms mainly east Monday night into Tuesday as a weak wave traverses the area. The again across all of western and central North Dakota Thursday into Friday and possibly lingering into the weekend as a more substantial upper level system lifts through the region late in the work week with a potential shot of cooler air late in the weekend. The warmest day of extend period will likely be on Monday with temperatures rising into the upper 80s southwest. However, the Turtle Mountains will probably remain in the upper 60s Monday. Beyond Monday, temperatures will generally be in the 70s, but with some 60 northeast and maybe some lower 80s southwest and far south central. && .AVIATION...(For the 00Z TAFS through 00Z Sunday evening) Issued at 632 PM CDT Sat Aug 21 2021 Light and variable winds will be present through the evening before picking up during the overnight hours as surface low pressure works towards the area. Showers and thunderstorms will enter the region after midnight from the west and persist off and on through the morning and into the afternoon hours Sunday. Overall, VFR ceilings and visibilities are expected. However, MVFR/IFR ceilings and visibilities are always possible while precipitation is occurring. LLWS will likely affect the western sites, as well as KMOT, tonight and into the morning hours. && .BIS WATCHES/WARNINGS/ADVISORIES... NONE. && $$ UPDATE...Telken SHORT TERM...TWH LONG TERM...TWH AVIATION...Telken