515 FXUS63 KBIS 210901 AFDBIS Area Forecast Discussion National Weather Service Bismarck ND 401 AM CDT Sat Aug 21 2021 .SHORT TERM...(Today through Sunday) Issued at 401 AM CDT Sat Aug 21 2021 Skies becoming mostly sunny today with highs mostly in the 70s. Chances for precipitation return late tonight, with the conditional potential for a few severe thunderstorms in the south central through southeast Sunday afternoon and evening. Aloft, the mean flow pattern over the CONUS features ridging over the south, with two troughs evident on water vapor imagery within the stronger flow across the north. The first trough was exiting the Northern Plains to the east, having delivered widespread precipitation to the region on Friday. A shortwave ridge will move from the Northern Rockies to the Northern Plains today, ahead of the upstream trough currently located over Washington and Oregon. With the brief ridging pattern expected today, mostly sunny skies will be expected after the comma head cloud region of the previous low exits eastward. Highs today will be mostly in the 70s, with some upper 60s scattered across the north. The next shortwave trough is expected to impact the region late tonight, with showers moving from west to east through Sunday. By Sunday afternoon the associated surface trough should be into central to eastern North Dakota, where a potential for stronger convection in the James River Valley is possible depending on how instability develops. Given the progressive nature of the wave which should push the stronger instability eastward through the afternoon, as well as the lingering cloud cover and showers impacting possible instability, the window for stronger convection Sunday afternoon and evening remains uncertain. HREF/SREF severe guidance does highlight a modest severe potential in this region with 35-40 kts of effective shear providing the kinematics necessary for discrete rotating storms. With uncertain instability but adequate shear and vectors oriented orthogonally to the initiating boundary for a discrete cell potential, we will advertise half- dollar size hail and 60 mph wind gusts possible in the HWO. Though locally heavy rainfall with any storm will be possible, it should remain brief with the progressive nature of the upper level wave. More widespread precipitation during the day Sunday will be favored on the nose of the 850mb jet, which should be near or north of the International Border. .LONG TERM...(Sunday night through Friday) Issued at 401 AM CDT Sat Aug 21 2021 The upper level pattern over the northern CONUS remains active with another shortwave set to impact the region Monday night and Tuesday. Shortwave riding ahead of this wave again keeps Monday sunny and mild before precipitation chances increase Monday night. Moderate upper level flow with an injection of steep mid-level lapse rates may create a potential for stronger convection, though the various deterministic solutions have major differences on location and timing with this potential. The end of the week features good agreement in another trough impacting the region, this one more broad with precipitation chances becoming widespread Thursday and Friday. WPC cluster analysis shows some differences in wave amplitude and QPF, but with all clusters showing some sort of precipitation at the end of the period. NBM's blend of guidance produces chance to likely PoPs which lines up with deterministic/ensemble signals. && .AVIATION...(For the 06Z TAFS through 06Z Saturday night) Issued at 1240 AM CDT Sat Aug 21 2021 Conditions gradually improve from west to east this morning. KMOT-KJMS will remain with MVFR cigs longest, with periods of IFR possible. After the low pressure system exits to the east later this morning, VFR conditions expected at all terminals for the remainder of the 06Z TAF period. && .BIS WATCHES/WARNINGS/ADVISORIES... NONE. && $$ SHORT TERM...AE LONG TERM...AE AVIATION...AE