FXUS63 KABR 191948

AFDABR



Area Forecast Discussion

National Weather Service Aberdeen SD

248 PM CDT Tue Aug 19 2025



.KEY MESSAGES...



- Isolated thunderstorms possible (10-20%) around the Watertown

  area this afternoon. Severe weather is unlikely. 



- Heat index values will top out in the upper 90s to around 100 

  degrees Wednesday and Thursday across central South Dakota.



- The passage of a low pressure system and cold front late

  Thursday afternoon through Thursday night will bring a 40 to 

  70 percent chance of precipitation, with a marginal risk (1/5) 

  of severe storms.



&&



.DISCUSSION...

Issued at 230 PM CDT Tue Aug 19 2025



Weak wave overtopping a strengthening ridge that was responsible for 

early morning central ND convection may support additional 

redevelopment in eastern South Dakota this afternoon as we are 

already seeing cumulus development along the Buffalo Ridge/eastern 

Sisseton hills. Despite increasing heights on a whole, BUFKIT 

profiles point to a high CAPE (2500+ j/kg) but very low shear 

environment.



Will once again need to contend with fog in the morning. HREF and

several of its members all hint at fog development along and/or 

east of the James by morning. Not a great consensus thus far, will

leave in inherited grids which have more coverage in comparison 

to blends at this time.



For the upper level flow: A Four corners high, or more precisely a 

ridge extending from it is the dominant feature Wednesday and 

Thursday. That breaks down with an upper trough moving from central 

into eastern Canada late in the week. This will shift the upper 

level flow into more of a NW flow regime.



At the surface, the heat and humidity will not go anywhere in the 

short term. The core of the warmest air aloft remains just to our 

west until Thursday, folding over with the mid-level ridge. 700 and 

850 millibar Temperatures will run at a standard deviation above 

climatology by Thursday. That'll be in stark contrast to the 

standard deviation below climatology that can be expected Friday and 

through the weekend. NBM heat index values top out at around 100 in 

central South Dakota for a for both Wednesday and Thursday. 



An inverted trough will extend northeast off a low that looks to hug 

the South Dakota/Nebraska state line. This may provide the focus for 

surface based convection Thursday, however will need to contend with 

the warm temperatures aloft. A positively tilted shortwave will 

provide ascent aloft as well. If convection remains wholly aloft, it 

will be in a unidirectional sheer environment with stronger mid 

level flow along the North Dakota/South Dakota state line with 

weakening shear as we proceed south. There will also be a low level 

jet that develops early Friday ahead of the boundary as the boundary 

migrates southeast.



Regarding smoke aloft, RAP/HRRR models both bring in smoke late on 

the 20th and persist through the remainder of the model runs. If 

this lingers into Thursday, it could also negatively impact daytime 

heating and thus the potential for surface based convection to break 

the cap.



The rest of the forecast will deal with cooler temperatures, with 

the NBM running 5-10 degrees below climo  and a significant drop in 

humidity.



&&



.AVIATION /18Z TAFS THROUGH 18Z WEDNESDAY/...

Issued at 1125 AM CDT Tue Aug 19 2025



Terminals KABR,KATY,KPIR,KMBG



VFR conditions for all terminals. Fog redevelopment looks probable

for a number of hours again Wednesday morning, with the most

likely terminal impacted being KATY. 





&&



.ABR WATCHES/WARNINGS/ADVISORIES...

SD...None.

MN...None.

&&



$$



DISCUSSION...07

AVIATION...07