textproduct: Aberdeen

KEY MESSAGES

- Red Flag warnings today for much of central, north central and northeast SD/western MN.

- Temperatures again in the upper 70s/low 80s, west winds of 25 to 40 mph, strongest along the ND/SD state line, afternoon humidity down to around 15 to 20%.

- Dry again for Saturday.

- Storm chances increase Saturday night, continue through Sunday, followed by rain Monday.

- Slight Risk (2 of 5) mostly focused across central and northeast South Dakota Sunday afternoon.

DISCUSSION

Issued at 242 AM CDT Fri May 15 2026

Temperatures have dropped along with the winds under clear skies early this morning.

The forecasted upper level pattern is initially mainly zonal, but with a trough developing over the northern Rockies for the weekend. It makes a slow transition east while deepening, ejecting 3-4 waves before moving east around mid-week. The upper level pattern that follows is weak and disorganized.

Today: Zonal flow aloft, with a northeast-southwest gradient in 850/700mb temperatures. There is a plume of slightly warmer mid level air overhead in the morning, followed by slightly subtle cooling through the afternoon. This may slightly enhance winds given deep mixing, dry conditions and ample sunshine. There is no gradient across the state however, so winds are primarily due to this degree of mixing. Will go with NBM winds, which have trended slightly downwards. Even going 90th percentile only yields the minimum wind required for a Red Flag in Jones/Lyman/Buffalo counties. As such, will remove Buffalo, Lyman and Jones counties from the Red Flag. Farther north, the 75th percentile meets/exceeds criteria and as such its much harder to articulate a need for cancellation or changes.

Up along the ND/SD state line, where westerly flow mixed winds are close to 30kts, we could see some localized blowing dust, and the dust model is picking up on this, however at these wind speeds and lacking an organizing feature/boundary, should not see widespread issues. Temperatures today about the same as Thursday sighting only slight changes in airmass/mid level temperatures.

Friday night: A weak wave crosses through mainly North Dakota. CAMS are hinting at some light precipitation coming in from the west. RRFS hints at the mid level deck above 12kft associated with warm advection. Shouldn't really do anything.

Saturday: An upper level ridge strengthens overhead, with southwest flow aloft later in the day. Mid-level warm advection develops across the area late in the day, and BUFKIT profiles show some mid- level moisture, albeit up around 8-10kft, is limited in thickness, and is above a deep dry subcloud layer. Again, aside from some cloud cover, little change in low/mid level temperatures means another day with highs around 80F and afternoon humidity down around 20%. Winds have shifted to easterly around weak high pressure moving overhead and east. Return flow on its backside, with an increasing gradient ahead of a lee low, around 12mb across the state. Mixed winds only yield upper teens (kts) however NBM deterministic values are showing some spots west river up around 30kts.

Saturday night/Sunday: This warm advection continues to strengthen overnight into Sunday morning, with elevated convection out ahead of a surface low/inverted trough that evolves across the western Dakotas, with a secondary low developing over southeast South Dakota. Additional support aloft provided by a southwest flow shortwave early in morning and then a second later in the afternoon/evening at which point we are looking at mainly saturated profiles and elevated instability as the surface low moves up along the SD/MN state line. How much moisture is expected with this round? Given the convective nature, NBM probabilities should be taken with a grain of salt, and in fact the 25th-75th range reflects these uncertainties, with the lower bounds of just a tenth or two (maybe up to 1/3) with a higher range closer to 1 inch to inch and 1/4. Now, I'll point out the first round of moisture is under weak mid level low, meaning slow moving storms. This is countered by the elevated nature of convection with less instability or ascent. The afternoon/evening round occurs under stronger mid level flow limiting storm duration.

As for severe weather potential, as mentioned before there is strong mid level shear. Surface low moving up across the far eastern CWA provides the best location for surface based instability, though this is late into the evening/overnight. 75th percentile surface based instability is around 1000j/kg CAPE, however profiles are more suggestive of elevated convection with straight line hodographs, supporting fast moving storms with supercell structure. Still lots of time and any shift or adjustments to timing will likewise impact the severe weather threats.

Monday/Monday night: Surface low traverses northeast across Minnesota. Some wrap around moisture evident in deterministic models, dry elsewhere before another shortwave lifts up across the area. Profiles are less convective in nature, suggesting a more stratiform nature of precipitation. NBM 24 hour moisture probabilities still show a lot of range, with the lower 25th down around a tenth or two, with the higher 75th over 1".

Tuesday/Wednesday: On the back side of the upper trough, much cooler mid level temperatures move into the region. 850mb temperatures are on the order of -1 to -2C Tuesday morning with some moderation for Wednesday morning. That said, this is on the backside of a low and not associated with a strong high pressure system. As such, much depends on timing of cloud cover and daytime heating driven strato- cumulus. Still NBM temperatures are in the low to mid 30s raising the specter of possible frost.

AVIATION /12Z TAFS THROUGH 12Z SATURDAY/

Issued at 626 AM CDT Fri May 15 2026

Terminals KABR,KATY,KPIR,KMBG

VFR conditions are expected to continue through the period, with winds gusting out of a westerly direction 20-30kts 16Z today-00Z Saturday.

ABR WATCHES/WARNINGS/ADVISORIES

SD...Red Flag Warning until 9 PM CDT /8 PM MDT/ this evening for SDZ003>011-015>017-021. Red Flag Warning until 7 PM CDT /6 PM MDT/ this evening for SDZ018>020-022-023-033>037. MN...Red Flag Warning until 9 PM CDT this evening for MNZ039-046.