textproduct: Aberdeen

KEY MESSAGES

- Spotty rain showers (30-55%) return this evening through Wednesday morning across central South Dakota. Additional rain (60-90%) is expected Wednesday morning through Thursday morning. Chance of rainfall of a quarter inch or more is 40-80%, highest east of the James River through western MN.

- Occasional rain chances continue for the end of the week with the best chances (40-65%) occurring Friday through Saturday morning.

- Temperatures will remain near to slightly below seasonal average today before climbing above normal Wednesday through the week.

DISCUSSION

Issued at 141 AM CDT Tue Sep 22 2026

The mid level circulation that brought rain and clouds to the area yesterday, its center is currently circling over northeastern IA and MN/WI border with the large surface high pressure system stretched from the Great Lakes through through Ontario. Ongoing moisture, being pulled in per east/southeast flow at the lower levels, continues to spread north and westward from IA/MN and will continue through the morning. Drizzle/low viz/patchy fog has been reported at KATY occasionally through the overnight. This is backed up by your classic drizzle setup on Rap sounding. Therefore, added in this mention over far southeastern CWA through 12Z as CAMs do not show really enough deep saturation for rain. Besides the clouds expanding northwestward, RAP indicates the possibility of drizzle expanding as well through the James Valley. ABR sounding indicating this setup through the late morning before drier air moves in west to east. Not enough confidence in expanding this mention beyond the southeastern CWA yet but will watch through the morning and add in if needed. There is also mid level moisture/clouds over western SD from a very positive titled shortwave that has developed along the eastern side of a ridge that extends over the Rockies. As the low continues to track southeastward, the shortwave aloft deepens a bit and elongates northwest to southeast from northwestern SD through northeastern NE. It will slowly track northeast across SD through the afternoon and evening as the ridge tracks eastward. This setup and moisture will bring the return of clouds over central SD as the eastern half of SD will already be dealing with clouds from behind the low. However, with this drier air moving in models show a period of clearing skies west to east to the James River this afternoon and evening before clouds move back in James River overnight/Wednesday morning per shortwave.

Any precip chances from this shortwave looks to stay west and southwest of the CWA per CAMS until it starts shifting east with pops (15-30%) potentially clipping far south central SD late this afternoon. CAMs differ a bit on exact placement whether the bulk of the precip will clip this area (NAMnest/RAP) or stay more south/southwest(HRRR), so lower confidence on this and stuck with the NBM. An increasing llj (25-35kts) develops over central SD this evening through Wed AM (as it tracks/expands eastward) and really pumps in moisture per return flow. This WAA flow and shortwave energy will bring additional chances (30-55%) of showers across central SD to about the James Valley through Wednesday morning. CAMs keep the potential more spotty in nature and differences in overall coverage. Through the midday Wednesday the weak ridge will be over the CWA with the last of the exiting shortwave over eastern SD/MN.

Our next more organized shortwave (that originated over southern CA/Pacific tracking northeast) will be negative tilted over WY/MT 12Z Wednesday with southwesterly flow out ahead of it over the region (and ongoing return/southwesterly flow at low levels). It will continue to track northeast across the Dakotas and eastern ND/MN/Canada by early Thursday. With moisture, per southerly to southwesterly flow aiding in dewpoints rising into the upper 50s/60s, and a surface trough, this will interact with energy aloft will bring the return of showers and potentially weak thunderstorms. Models indicate first across north central SD Wednesday morning with precip expanding east and northeast across the CWA. High confidence in this occurring with NBM pops of 60-95%, highest James Valley and eastward by Wednesday evening through Thursday morning. Less likely to see moisture from PIR and southwestward per storm track. Precip will end west to east across the CWA through late Thursday morning. PWAT values are forecast between 1-1.25", which is about 3 standard deviations above climo per NAEFS. However, nothing anomalous for QPF expected per EC EFI as of yet. ENS/GEFS (and their AI models) agree on deterministic values between 0.1-0.4" highest over NESD into ND/MN. Probability of 24 rainfall>0.25", ending 12Z Thursday is 40 to 80%, highest along the ND/SD across central SD and through northeastern SD/MN (especially along and east of I29). Prob of a half inch is 20-55% for this location again highest over far NESD/MN. Otherwise, behind this wave dry weather is forecast Thursday afternoon through Thursday evening. Ongoing southeast to southwest flow at low levels and additional shortwaves will bring additional chances of rain through early next week with this continuing overall -PNA setup.

With the increased pressure gradient Tuesday and setup of the LLJ, winds will increase Tuesday afternoon with gusts of 25-35kts mainly along and west of the Mo River with these gusts spreading eastward with the jet across the CWA through Wednesday afternoon. Overall gusts will be between 20-35kts highest over central SD. Prob of advisory level winds are very low per NBM. Otherwise, winds diminishing through Thursday morning behind the system before increasing again across west of the Mo River Friday.

AVIATION /06Z TAFS THROUGH 06Z WEDNESDAY/

Issued at 1234 AM CDT Tue Sep 22 2026

Terminals KABR,KATY,KPIR,KMBG

Increasing low low level moisture is evident on satellite imagery early this morning with a shroud of stratus draped across eastern SD and western MN. East to southeast low level flow is advecting this layer of low clouds back toward the west and northwest into the James Valley. IFR cigs have already set in at KATY where there has been intermittent light drizzle during the late evening. Would anticipate this could become more of a trend through the pre-dawn hours at this terminal. MVFR cigs will eventually set in at KABR within the next 3-6 hours. Until then, they may experience some light fog. KPIR may also see some fog through the early morning until MVFR/IFR cigs set in there through the early morning. KMBG is currently seeing a VFR cloud deck around the terminal but they will also get into MVFR/IFR cigs closer to 12Z. The low stratus will eventually scatter out closer to late morning and midday but MVFR cigs will remain possible through the afternoon. KATY may actually see more of an improvement back to VFR this afternoon as some drier air tries to work back into the area.

ABR WATCHES/WARNINGS/ADVISORIES

SD...None. MN...None.