textproduct: Aberdeen

KEY MESSAGES

- Patchy early morning fog.

- Two waves Saturday. First brings light moisture to northeastern SD and western MN early (up to 80% chance Glacial lakes region) but just a few hundredths. 2nd wave 20-30% chance for moisture Saturday night, isolated to scattered coverage of showers.

- Well above normal temperatures Sunday, highs in the 70s to low 80s (15 to 25 above normal). West winds 25 to 35 mph. Rangeland Fire Danger increases to High/Very High category.

DISCUSSION

Issued at 1255 AM CDT Fri Apr 10 2026

Fog has developed over the recently acquired snowpack, with only 1-3 degree dewpoint depressions during the late evening and fog already picking up on webcams and GOES nighttime microphysics. Its pretty localized to mainly Highway 12 in Brown/Edmunds counties, and even here through the last 2 hours has come and gone. Southwest low level winds may provide enough mixing to counter cooling. No headlines at current.

Today: Upper trough coming into the western CONUS, with a departing wave to the east putting us into northwest flow initially, with a broad ridge building in upstream and then overhead tonight. At the surface we start with high pressure across the east of the state, moving into the Western Lakes region later today. On the backside of the high we see a developing pressure gradient, with the strongest gradient west river through the afternoon (21Z) spreading east overnight. The gradient tops out at 12-16 mb by Saturday morning (09Z-12Z) and by then is more universally spread across the state. For the day, with the surface high over the east, low level flow is south southwesterly and not very strong. 850mb warm advection is pretty weak as well. Lingering fog, and snow cover may make an initial dent in holding back warming today, but not very confident it will have a strong impact in comparison the the current NBM which has highs in the 50s. We're pretty close to the 50th percentile, and its only about 3-4F between the 25th/75th so no good evidence to shift one way or the other. Mixing overnight to keep us quite mild. NBM deterministic is 2-4F warmer over the mean, also with a 3-4 degree spread between the 25th/75th percentiles. Lows in the 30s to near 40 degrees represent 5 to 10 degrees above climo.

Saturday: Start the day with that pressure gradient and 1/2km winds between 30 and 40kts. NAM BUFKIT mixed winds are around 20 to 30kts. NAM/GFS and RRFS profiles also highlight a fairly stable boundary layer. Aloft, a broad upper ridge has set up across the eastern CONUS, putting us into a southwest flow regime. There is a very subtle wave in the NAM moving across the CWA early in the day, with a slightly stronger wave late in the day/early overnight. For most of the day, the NAM BUFKIT profiles indicate the moisture associated with the first feature is mostly above 10kft or trapped at 4kft below the inversion. Even in the mid level deck, we're only seeing a few microbars of lift. There is an hour or two in there with full saturation of the profile before mid levels dry back out again. Deterministic models all show some output across eastern South Dakota/western Minnesota. Going through the CAMS also indicates some fairly light, sporadic moisture. NBM probability for moisture are around 25% James valley and 50/60% for the Glacial Lakes region from this setup. Output is only a hundredth or two and looking at the profiles woudn't be surprised if this is just scattered sprinkles. May better refine the time range however, with CAMS pretty limited before 09Z, peaking around 15Z and everything east by 21Z. Second wave is only depicted as mid level moisture with in NAM BUFKIT profiles with a deep dry and very warm subcloud layer. Deterministic models also have much less precipitation output, with a dry GFS/NAM. GEFS plumes are limited to 2 members, though these have greater than 0.1" with one member for Mobridge coming in with 0.65" suggesting that we cant rule out some form of convection. NAM BUFKIT profiles do show some weak, elevated CAPE to support this theory. For temperatures Saturday, deterministic NBM is 4-5F below the 50th percentile, with a 5-8 degree range in the 25th/75th percentiles.

Sunday: For the upper levels, there will be a subtle ridge coming in from the intermountain west as a broad upper trough evolves over the western CONUS. We also have the departing shortwave early Sunday into east central North Dakota. A surface low associated with this wave is located over western North Dakota to start the day, and moves east. That results in westerly low level flow with a gradient. Additionally, there is a plume of some very mild air aloft. Sunday 06-12Z, GEFS 850mb thermal anomaly peaks at 2 standard deviations above climo and as such NBM temperatures are running 18 to 25 degrees above climo. Here's the kicker! Deterministic NBM is in the 70s, tops out around 80, which is only about the 10th percentile. But if we look at both NAM/GFS profiles, we see a very strong inversion/warm airmass just off the surface, but that weakens through the morning, countered by daytime heating later. The reason ends up being the departing wave also takes the core warmest air east. Westerly flow and weak cold advection would end up enhancing mixing though, countering the loss of warmer air aloft. Not sure if we'll be making changes during this timeframe, but current NBM is getting close to red-flag.

This is also the second day here with an deterministic NBM low bias though one doesn't exist for Today (Friday). As such, not sure where to go with adjusting NBM.

Monday: Brief period of dry weather late Sunday into the first half of Monday. Pattern appears to be split flow, with waves moving east out of the 4 Corners region and a second in WY/MT moving through ND/northern SD. NBM POPs increase to about 40% with this WY/MT southwest flow shortwave, though we're starting to see at this range differences in placement/strength of the wave and associated surface low locations. This timeframe is when we are SPC outlooked in the east, but its too far out to start in on any details with confidence. With the surface low potentially overhead or to the south, outside the southeast CWA were into more stable and slightly cooler northeast flow, with a thermal gradient from north to south.

Mid-Week: Its an active pattern with the 4 Corners wave lifting northeast. Another wave coming into the Pacific Northwest starts taking shape into the next upstream trough. 850mb temperatures and anomalies point to seasonal, possible slightly milder in comparison to climo.

AVIATION /06Z TAFS THROUGH 06Z SATURDAY/

Issued at 1255 AM CDT Fri Apr 10 2026

Terminals KABR,KATY,KPIR,KMBG

Freezing fog continues to be a concern at ABR since around 03Z. This is over the area that has received 2+ or more inches of rain. MVFR ceilings farther east (at ATY) has acted to limit the fog, but fog development may be possible closer to 12Z Friday. Looking at area webcams, and with limited low level moisture present, fog is not expected at MBG/PIR. Wind gusts will increase to 20-25kts Friday night at PIR/MBG, but remain around 10kts or less at ABR/ATY through the TAF period.

ABR WATCHES/WARNINGS/ADVISORIES

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