Watertown, SD 57201 Weather

Key Messages

- Temperatures continue to be about 10 to 20 degrees above normal through Wednesday, with highs in the upper 60s to mid 70s. By the end of the week temperatures are forecast to be 15 to 25 degrees above normal, ranging in the 70s to potentially the lower 80s.

- Dry conditions continue through Thursday with rain chances (30- 50%) returning Friday into Saturday. Percent chance of rainfall amounts of a tenth of an inch or more is 40 to 60% along and east of the Sisseton Hills with less than a 50% chance for a quarter of an inch or more at this time.

- Warm, dry, and breezy conditions lead to elevated fire weather concerns across central South Dakota Thursday with more widespread concerns Friday.

Update

Issued at 849 PM CDT Tue Oct 20 2026

Not much in the way of changes for the overnight period. Skies will remain mostly clear as a weak cold front drops southeast through the CWA later tonight into Wednesday morning, switching winds to a north-northeast direction. Wouldn't be surprised if some areas dropped into the 30s within the surface trough axis where winds will be light and variable for a few hours before winds switch to the north. But having said that, forecast lows remain in the low 40s for most areas.

Discussion

Issued at 1250 PM CDT Tue Oct 20 2026

The region continues to be under a broad upper level ridge, in southwest flow, as the cutoff closed low continues to spin off the CA coast. At the surface, the region sits between a high to our east and frontal boundary to our west. This results in ongoing sfc winds to 850mb out of the south/southwest continuing to usher in warmer air resulting in warmer than average temps. The ridge flattens a bit as a weak shortwave tracks east across Canada with its cold front tracking east/southeast across the CWA this evening and a secondary weak low developing along the front over western SD and over SD/NE by 12Z. By this time the front will be extending from northeastern SD through northern NE with the CWA behind the fropa by the late morning. With ongoing drier air over the region, no precip is expected with the only noticeable feature is winds will be switching to the north then northeast behind it as high pressure moves in.

Behind the shortwave, the ridge amplifies over the region Wednesday afternoon and continues over the area through Thursday before tracking eastward Friday. Our attention then turns our next system as this cutoff low moves onshore over southern CA with split flow as a shortwave moves in over western Canada. This low becomes a negatively tilted open wave and will track northeastward (and northern wave eastward) and somewhat phase together over the northern Rockies Friday. This leads to the formation and deepening of its surface low with models indicating the center of the low over MT Friday morning. However, there is still a bit of a difference in exact position and intensity of the low with ENS indicating a ~1004mb low slightly southward of where GEFS has the low with GEFS indicating a bit stronger around ~1000mb. Through Friday evening, this low will track eastward then northeastward across ND into Canada with ENS still a bit more southeast with the track and GEFS more northwest and stronger. By Saturday morning, ENS actually accelerates the speed of the low and wave (given weaker setup) as GEFS is slower/stronger (and now more southwest of ENS) as its positioned either over southwestern or central Manitoba by 12Z Thursday where it will continue its track northeast and occluding. So still ongoing low confidence in exact position, track, and intensity of the low.

As of now these models show the possibility of showers per warm front over NESD/ND/MN Friday as the front lifts northward with NBM pops of 25-40% east of the James River. As its cold front tracks west to east across the CWA Friday evening through Saturday, precip is again possible ahead and along the front. NBM and models not really agreeing of QPF coverage just yet, as mentioned, with broadbrush pops of 20-35% over central SD. It seems like both NBM and models indicate the best chances and better forcing will be Friday afternoon/evening (help from diurnal heating) but all depends on where the cold front will be. As of now, pops of 20-40% lie east of the James Valley Saturday morning/midday and eastern SD into MN by afternoon/evening. However amounts overall still look to be light with a probability of QPF at or exceeding 0.10" at 15-60% with the probability increasing further east in the CWA, highest along and east of the Sisseton Hills per mean grand ensemble (GEFS/ENS/GEPS) with NBM pretty close to this. At or over a 0.25" is 20-30% from south central through eastern SD grand ensemble and up to 40% NBM. Don't be surprised if we get a couple thunderstorms associated with a strengthening LLJ, WAA, and CAPE within the warm sector Friday! CSU ML guidance does indicate a 5% chance of severe over north central and into ND and portions of southern SD Friday afternoon.

With pressure gradients steepening ahead of the low and the 850mb LLJ ahead of it strengthening to 20-30kts Thursday and 30-50kts Friday. Shallow diurnal mixing will lead to gusty surface winds with gusts of 20-35mph, highest along and west of the Mo River Thursday afternoon with widespread wind gusts by Friday afternoon 30-45mph. Probability of wind gusts>45 mph is 30-50% over the southern James Valley and far south central SD Friday afternoon. With ongoing WAA continued the trend of blending NBM90th for temps through Thursday. With Collab kept temps near NBM per low confidence and dealing with more clouds with the system. This results in highs overall in the upper 60s and 70s for Wednesday and 70s to potentially 80s degrees for the end of the week. Probability of temps at 80 or above is 40- 80% Thursday afternoon and 40-90% over central SD highest confidence across south central SD. EC EFI values of 0.8 to 0.99 with a shift of tails of zero is highlighted for Friday meaning a significant amount of EC members have shifted away from the reforecast climatology meaning higher confidence on this occurring. NDFD records does indicate we could be flirting with record min max temps Friday and Saturday morning. With gusts winds and warmer temps this leads to elevated fire danger concerns with GFDI index in the High Category along and west river Thursday afternoon and widespread across most the region Friday afternoon.

Aviation

Issued at 626 PM CDT Tue Oct 20 2026

Terminals KABR,KATY,KPIR,KMBG

VFR conditions are forecast through the TAF period. Southeast surface winds this evening will eventually switch to the north or northeast later tonight into Wednesday morning as a frontal boundary passes through.