textproduct: Aberdeen

KEY MESSAGES

- Patchy to areas of frost is possible across portions of north central and northeastern SD early Monday morning. No freeze is anticipated.

- Slightly warmer than normal temperatures stick around through the midweek with the potential for temperatures to be 15 to 20 degrees above normal by the end of the week. - Dry conditions continue through Thursday with rain chances (30- 50%) potentially returning Friday evening into Saturday. Low confidence in exact track and timing of the system along with estimated rainfall amounts at this time.

DISCUSSION

Issued at 1252 PM CDT Sun Oct 18 2026

The cold front is currently extending over west central MN and southwestward though west central NE connected to a 982mb low over northeastern Manitoba/Hudson Bay. With the exception of east/southeast SD still ahead of the front, the rest of the CWA is in north to northeast flow with some gusty winds (20-35 mph) tracking right behind it, per weak CAA, over central SD to the James River. Downsloping winds off the Coteau will continue to diminish and finally end once the wind shifts to the northeast.

The ~1023mb high pressure will continue to slide in from the northwest, with the center over ND/MT/Canada border by 06Z. This high will remain dominant over the region Monday as we continue with dry conditions. Per this high and ongoing weak CAA, temps will be a few degrees cooler at any one location overnight than what we saw earlier this morning and around the same over the Coteau per inversion. Overall low temps are forecast to range in the upper 30s to the lower 40s. Probability of temperatures below 36 degrees (for frost formation) is 40-65% but spotty over north central and portions of northeastern SD (mainly along the ND/SD border and James Valley) per REFS/NBM. Probability of temps at 35 decrease a bit (20- 40%) for these areas with a 0% chance of temps dipping at 32 or lower. So patchy to areas of frost are in the grids for these areas with no freeze expected at this time. Highs for Monday will be the "coolest" of the week with temps ranging in the lower to mid 60s. This high will track east Monday with the CWA between this high and broad area of low pressure to our west Tuesday with ongoing dry conditions. Lack of any moisture in this dry air mass keeps the forecast dry through Thursday.

Looking at the pattern aloft by midweek, it will consist of southwest flow over the region as Clusters overall agree on a closed cutoff low developing over the Pacific and nearing the CA coast by Wednesday morning with a weaker open wave developing over the Gulf of Alaska. Due to this a broad ridge will build east of the Rockies, and really amplifying over the region Thursday, shifting eastward on Friday. Winds will be south/southeasterly at the surface and southwest at 850mb ahead of the low within the warm sector these days. This will also lead to a bit more moisture to return at lower levels as dewpoints are forecast to increase back into the 50s. Highs are forecast in the 70s, however, the 25-75th spread is 5-7 degrees as we are several days out. Clusters indicate this southern cutoff low becomes an open wave as it tracks over the western CONUS Thursday with a bit of a difference in ensembles on whether these 2 waves phase together or remain separate in split flow as the overall trough tracks east/northeast into the central and northern CONUS. With its developing surface low over the Northern Rockies Friday, models indicate the return of precip (30-50% NBM) Friday into Saturday as the low/cold front is forecast to strengthen as it tracks northeast in Canada Saturday. Models seem to have a good handle of this setup but exact placement and intensity of the surface low (and wave aloft) does vary a bit as GEFS indicates a stronger wave/sfc low with GEPS a bit weaker and ENS right in between. This results in low confidence of precip timing and QPF amounts which is why NBM pops are broadbrushed. Looking at the probability of or exceeding 0.25" per mean ensemble (GEFS/ENS/GEPS) is only about 25-35%. Again this is several day out, so probabilities for precip and QPF amounts will change.

With this incoming system/steeper pressure gradients ahead of the low will lead to winds increasing along and west River Thursday afternoon, with gusts up to 35 mph. Widespread stronger winds are forecast Friday as this low deepens with gusts potentially ranging from 35 to 45 mph Friday afternoon across the CWA with a prob of over 45 mph per NBM is 35-45% here and there for now. Relative humidity at this point looks to stay above 40% but with the lack of rain/dry air we have been dealing with and the warmup expected for the end of the week, the Grassland Fire Danger Index jumps into the High Category along and west River Thursday and High Category pretty much over the entire CWA Friday. This is still a few days away and mentioned above, depends on strength of low/pressure gradients which results in what the gusts will be, but this is something to watch for any elevated fire danger concerns.

AVIATION /18Z TAFS THROUGH 18Z MONDAY/

Issued at 1218 PM CDT Sun Oct 18 2026

Terminals KABR,KATY,KPIR,KMBG

VFR cigs prevail through the TAF period with passing high cirrus clouds at most. The cold front currently extends from west central MN and southwestward through north central NE. With the exception of KATY still in southwest flow, the rest of the TAF sites are behind the fropa with north to northeast winds. Weak CAA behind the front is leading to breezy winds with gusts of 20-35 mph across central SD. As the front tracks further away from the CWA winds will diminish this evening as a high moves in over the region. Light winds will continue out of northeast overnight, switching to more of a easterly direction through Monday morning west to east across the region.

ABR WATCHES/WARNINGS/ADVISORIES

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