565 FXUS63 KFGF 210855 AFDFGF Area Forecast Discussion National Weather Service Grand Forks ND 355 AM CDT Sat Aug 21 2021 .SHORT TERM...(Today through Sunday) Issued at 355 AM CDT Sat Aug 21 2021 Main concerns will be windy conditions today and then severe thunderstorm chances on Sunday. Water vapor imagery indicates an upper level low just north of the forecast area across southern Manitoba. This feature will continue to propagate north/northeast through the day. Water vapor imagery also indicates another upper level low/trough across the Pacific northwest CONUS, which will propagate toward the region today and bring thunder/severe/precipitation chances to the northern plains on Sunday. Ensemble guidance in good agreement with the general pattern through Sunday and confidence is relatively high. Of course, confidence in the mesoscale environment for Sunday is still toward the lower end of the spectrum. As the first upper low propagates away from the region ridging works into the region. Much cooler airmass will be in place today. Main concern will be winds, with uncertainty regarding mixing height. Mixing potential likely dependent on cloud cover (clear sky = deeper mixing). Current satellite along with guidance indicates that strongest winds aloft will be overlaid with clouds, limiting mixing potential where winds aloft are strongest. Thus, most areas northwest winds 15-25 mph with gusts up to 35 mph. If clouds clear faster than expected there is a low chance (10-30%) for winds to approach advisory criteria. The next system on tap for Sunday appears as if there will be two upper level waves, with the strongest north of the International border and a weaker wave that would propagate through the forecast area. Confidence seems fairly high with this outcome given the current water vapor imagery. This would lead to more widespread precipitation associated with the northern wave, with scattered convection associated with the southern wave. Timing of these waves will determine exact details. 06z HRRR indicates initial widespread warm air advection showers/thunder Sunday morning/early afternoon associated with the northern wave, and then isolated/scattered thunderstorms Sunday afternoon/evening associated with the southern wave. Given the synoptic support along with strong deep layer shear, if the 06z HRRR timing of the upper waves does happen, storms Sunday afternoon should be organized and have the potential to be severe. Details would be dependent on degree of instability and mesoscale environment. With all of that in mind, the actual outcome is dependent on the interactions and timing of the two upper waves. Different timing may limit severe potential, but measurable precipitation is likely (70-90%). .LONG TERM...(Sunday night through Friday) Issued at 355 AM CDT Sat Aug 21 2021 Overview... A few periodic rain chances accompanied by cool, below normal weather will provide the main impacts across the long term. Best chances for rain will be with quick moving shortwave systems on Tuesday and Friday respectively. Sunday night through Tuesday... Lingering showers and thunderstorms will be possible across portions of northwestern Minnesota on Sunday evening as the main system moves out of the area. Otherwise, the Sunday night through Monday period will be defined by near normal temperatures and quiet weather. The next shift in the weather is progged to occur on Tuesday as a quick moving shortwave moves into the region. Ensemble guidance is in good agreement that this system will bring a showers and possibly a few thunderstorms to the area. There are some discrepancies with regards to timing, however, that would in turn limit thunderstorm potential that will need to be monitored moving forward. Overall, PWATs look rather nominal and the weak nature of this system will likely lead to generally scattered, but light rainfall accumulations. Wednesday through Friday... Moving into the latter half of the week, much cooler temperatures are anticipated following the Tuesday system and its attendant cold frontal passage. Highs in the 60s to low 70s are possible as a result. This is supported by ensemble trends indicating cool 850 hPa temperatures in the single digits to low teens for Wednesday and Thursday. The next shortwave then arrives on the scene late Thursday into Friday. Cluster analysis at this time is in rather good agreement that this wave will impact the northern Plains on Friday, although there are a few outliers indicating a weak ridge building in and suppressing this shortwave. Consensus at this time favors a chance for showers and thunderstorms across the forecast area, but trends in the eventual evolution of this system will continue to be monitored moving forward. && .AVIATION...(For the 06Z TAFS through 06Z Saturday night) Issued at 1142 PM CDT Fri Aug 20 2021 Scattered showers are still possible mainly along/north of Highway 2, with best chances over the new few hours at KDVL. Otherwise, MVFR ceilings should overspread eastern ND and northwest MN early in the TAF period as stratus fills in west to east. A few pockets of IFR ceilings will be possible mainly around KDVL. Expect an improving trend to VFR west to east during the day Saturday. Winds continue to shift from the south to southwest then to the west- northwest as low pressure transitions east, and eventually gusty west-northwest winds should persist into the afternoon Saturday. High pressure arrives late Saturday afternoon and light and variable winds would then return around sunset Saturday evening. && .FGF WATCHES/WARNINGS/ADVISORIES... ND...None. MN...None. $$ SHORT TERM...TG LONG TERM...Rick AVIATION...DJR