textproduct: Aberdeen

KEY MESSAGES

- Highs in the 60s and 70s Saturday through Monday will be 15 to as much as 30 degrees above normal for this time of year.

- Winds will shift to southerly Saturday, with gusts of 35 to 45 mph. Higher winds are favored for the Sisseton hills downslope areas and could exceed 60 mph. Mild and dry air, with dry fuels and strong winds will result in widespread high/very high Grassland Fire Danger Index values.

DISCUSSION

Issued at 143 AM CDT Fri Mar 27 2026

Complex scenario regarding fire weather conditions with surface high pressure moving over central/north central South Dakota this morning, and into the east this evening. This leaves us with a cold airmass but initially efficient mixing. As we move through the afternoon winds should weaken despite daytime driven mixing. NAM BUFKIT winds for Summit area peak around 25-30kts 2-3 pm with unidirectional flow aloft. Thereafter mixed winds begin to slowly drop. This is the most mixy part of the east though. Despite the cold temperatures (highs in the 30s/40s)...dewpoints in the single digits/teens means afternoon humidity drops to 20% across central/western South Dakota and 40% up across the far northeast.

As that high pressure continues east, during the evening and overnight, the gradient increases to about 14mb across the state. 1/2km winds increase, with the NAM peaking around 50 to 55kts across central/north central South Dakota at 09Z, transitioning east into the James valley and increasing to 55+kts by 12Z, and topping out at 65kts over the Sisseton hills with a downslope component. Those winds mix out by 15Z as the core of the gradient shifts into far eastern/southeastern South Dakota. There is uncertainty as to how long that lingers in the far southeast CWA (Watertown south and east) where we currently have the Fire Weather Watch with the NAM lingering longest and the GFS suppressing the gradient a little more rapidly southwards. Thats mainly a question of end timing for any fire weather headlines moving forwards we will need to address. For the daytime conditions however, warm advection will somewhat impeded a full mixing of these winds save for the downslope region, but that still leaves us with a fairly sizable fraction and NAM BUFKIT mixed down winds for Watertown are 40+kts. HREF mean is up around 60mph and NSSL WRF is up around 70mph.

In regards to dewpoints, the GFS is more mixy typically and should be fairly representative of the lower bounds, with initially dewpoints around -10C (low teens) to start the day, but all the models show a bit of a advection of some 'higher' dewpoint airmass, closer to the mid 20s. NBM has a good representation of this transition, though probably not with as tight a gradient as some the CAMS suggest.

And of course its dry during all this. Upper flow is mostly zonal with broad shallow ridge across the central CONUS. A weak shortwave crosses the northern tier of the CONUS for late Monday/Tuesday. The surface low associated with this feature develops overhead. NBM probabilities of moisture is around 25% for 0.01 and only about 10% for a tenth of an inch. The system that follows for later in the week is a broader, deeper trough for the northwestern CONUS, which would support a low to the north and one possibly for the Southern Plains. NBM has higher probabilities for moisture of appreciation (about 40% for 1/4 inch).

As for temperatures for next week, there is a frontal passage associated with the Tuesday system. Until the frontal passage, Sat/Sun and Monday 850mb temperatures are about a standard deviation above climo. That means, according to NBM highs, Saturday will be 15 to 25F above climo, closer to 15 to 20 for Sunday and 20 to 30 above for Monday. The cooler airmass Tuesday/Wednesday/Thursday puts us closer to average.

AVIATION /06Z TAFS THROUGH 06Z SATURDAY/

Issued at 143 AM CDT Fri Mar 27 2026

Terminals KABR,KATY,KPIR,KMBG

VFR conditions will prevail at all terminals through this forecast cycle. A BKN/OVC low end VFR cig will be possible through the pre- dawn hours this morning at KABR/KATY. Increasing northwest breezes will move into central SD and across the KPIR/KMBG terminals before sunrise and then translate east into KABR/KATY terminals later this morning into the afternoon. Winds will become southeast again tonight and turn gusty at KPIR/KMBG by the end of this forecast period.

ABR WATCHES/WARNINGS/ADVISORIES

SD...Fire Weather Watch from Saturday morning through Saturday evening for SDZ019>023.

MN...None.