FXUS63 KABR 210531 AFDABR Area Forecast Discussion National Weather Service Aberdeen SD 1231 AM CDT Sun Jun 21 2026 .KEY MESSAGES... - Widespread rainfall through the day Sunday with the bulk of the rain falling over central South Dakota. Probability of exceeding 1" of rainfall is 75-90% along and south of a line from Eagle Butte to Highmore with a 40-60% chance of exceeding 2" for this area. Potential rainfall amounts drop off dramatically with little if any expected east of a line from Aberdeen to Watertown. - A faster moving system will bring additional moisture to the region Monday evening through Tuesday evening. Probability of rainfall amounts exceeding 0.25" is 50-80% over portions of north central through northeastern SD into west central MN. Severe weather is not anticipated. - Temperatures remain near to slightly below normal through next week. Coolest day being Sunday at 5 to 20 degrees below normal. && .UPDATE... Issued at 840 PM CDT Sat Jun 20 2026 Scattered light rain showers/sprinkles across the western CWA this evening. Adjustments to PoPs were made earlier this evening to account for a bit further north and eastward development than previously forecast. Otherwise, not much activity in our CWA now, but more coming in from southwest SD. Models still suggesting an uptick in coverage of showers/storms later tonight into Sunday morning as shortwave energy from WY approaches. && .DISCUSSION... Issued at 143 PM CDT Sat Jun 20 2026 Looking at the synoptic setup, west to slight northwest flow continues aloft as the axis of the ridge is along the MT/WY and Dakotas border. Interesting pattern sets up tonight through Sunday with two closed lows ongoing to our northeast and northwest over Canada with the slight ridging pattern continuing over the Northern Conus/Canadian border in between these two lows. The ridge breaks down with more of a zonal flow over SD. Within this pattern a shortwave, with several embedded pulses, will move from the Intermountain west and track eastward across the region through late Sunday night with the CWA on the backside of this wave by Monday morning. The start of the rain is forecast to move in from the west over south central SD with CAMs indicating this either late this afternoon or early evening and spreading over north central SD through tonight with the bulk of the widespread rain continuing over much of central SD through Sunday. A slight shift eastward with the wave on Sunday may bring some light rain over portion of the James Valley and east central SD. Model soundings at KPIR indicate a completely saturated profile by 06Z and KMBG by 12Z. Elevated skinny CAPE (500 j/kg or less) may lead to a few weak thunderstorms here and there, mainly over south central SD. With the synoptic pattern mentioned above, models indicate this large area of rain will be very slow moving/near stationary at times over central SD as storm motion of only 10-15kts is forecast, per HREF. Precip looks to taper off northwest to southeast Sunday night as dry air moves in aloft behind it with a high. With this ongoing high to our northeast and easterly winds, this will bring in drier air with a sharp cutoff on where rain is falling and where it's just sprinkles or dry over NESD. As of now, this lies along and east of a line from Hecla to Milbank where pops will be under 20% or less with pops increasing to near 100% further southwest you go in the CWA. EC ABR/ATY model soundings shows this drier air below 700mb leading to higher confidence on less rainfall amounts here. Any shift in this high or shift in the wave aloft will greatly influence where this sharp cutoff in pops and QPF lie, so lower confidence on this, with high confidence on the highest pops/QPF over south central SD and lowest over western MN. QPF ranges from nothing to a few hundredths over far northeastern SD/MN with the potential of 1 to 2+" over south central SD per both HREF and NBM. Deterministic models are more bullish on this higher precip potential over south central SD ranging from 3-4" per GFS/Canadian as well as ARV/FV3. EC/NAM are on the lower end of 1- 2". 90th percentile of both HREF/NBM does show this higher end potential. Especially if the system ends up slowing down or really stalling over the area. So therefore as of now, the probability of exceeding 1" of rainfall or more is 75-90% along and south of a line from Eagle Butte to Highmore with a 40-60% chance of 2" or more of rainfall for this area. Potential rainfall amounts drop off dramatically with little if any expected east of a line from Aberdeen to Watertown. NBM 25-75th QPF spread is still on the order of an inch or more over central SD due to uncertainty (and lower confidence) in exact amounts with less of a spread further northeast in the CWA due to less overall rain potential. The WPC has put a Slight Risk (15%) of exceeding flash flood criteria over central SD due to the slow storm motion combining with PWATs of 1 to 1.4", west of James River and highest west of the Mo River (above 90th percentile). No flood headlines issued due to dry soils out here but will watch for the potential of areal flooding if we do see this occurring or we get this higher end rainfall. Behind this system, a clipper will track northwest to southeast over the Northern Plains Monday afternoon through Tuesday afternoon bringing the return of showers (and weak thunderstorms) ahead and along the front as it tracks across the CWA with additional wrap around moisture continuing over NESD/MN Tuesday afternoon. Probability of rainfall>0.25" is 50 to 80% over north central through NESD/MN with the highest chances over Roberts through Traverse Counties. Again, weak instability of lack of shear will keep storms from reaching severe criteria. A ridge that will be over the western CONUS will track eastward and over the central CONUS for the end of the week. Weak embedded shortwave energy may bring additional chances of showers and thunderstorms Thursday over far south central SD and more widespread Friday. Low confidence this far out on exact setup with general pops of 20-40%. Additional chances of precip continue through next weekend as -PNA pattern sets up synoptically and southwest flow aloft over the CWA. Ongoing cooler air aloft will result in temps being 5-10 degrees below average Monday through Thursday of next week and near to a bit below average Friday. && .AVIATION /06Z TAFS THROUGH 06Z MONDAY/... Issued at 1230 AM CDT Sun Jun 21 2026 Terminals KABR,KATY,KPIR,KMBG VFR conditions are expected for a majority of the time period. The highest chance of steady rain/showers will be over PIR, where MVFR to IFR ceilings will be possible from 08Z this morning through the remainder of the daytime hours. Farther north and east, expect VFR conditions to continue. While thunderstorms will be possible, the coverage/confidence is less than 30% at this point at PIR. Little to no precipitation is expected at ABR/ATY, with more off and on showers at MBG through the daytime hours today. && .ABR WATCHES/WARNINGS/ADVISORIES... SD...None. MN...None. && $$ UPDATE...TMT DISCUSSION...MMM AVIATION...06