FXUS63 KFSD 261958

AFDFSD



Area Forecast Discussion

National Weather Service Sioux Falls SD

258 PM CDT Thu Jun 26 2025



.KEY MESSAGES...



- Scattered showers/isolated storms will continue to diminish 

  in coverage through this afternoon. Still a low risk for an 

  isolated strong/severe storm in our far southeast counties 

  this afternoon, but greater threat will be east of Highway 71 

  corridor.



- Periodic thunderstorm chances continue Friday evening through

  the weekend. Some indication that storms could become strong

  to severe at times. Begin monitoring this time period if you 

  have outdoor plans.



- Warming temperatures and increasing humidity this weekend will

  bring a risk of heat indices above 100F in some areas Saturday

  afternoon. Otherwise seasonably warm temperatures will prevail

  much of next week.



&&



.DISCUSSION...

Issued at 258 PM CDT Thu Jun 26 2025



TONIGHT-FRIDAY: As the slow-moving wave lifts northeast through

the rest of the afternoon, our remaining showers/isolated storms

east of I-29 should continue to push east and diminish prior to

sunset. Limited mixing with broad cloud cover today, combined with

decent rainfall over the past 2-3 days will leave behind abundant

boundary layer moisture. Surface high pressure drifts in tonight,

providing light winds and a general attempt at clearing behind the

departing wave. This could set up a reasonable set-up for some fog

development overnight over a broad expanse of the forecast area,

though some question as to whether dense fog will develop or not.

This would linger just beyond sunrise Friday, but should burn off

pretty quickly.



FRIDAY NIGHT-SUNDAY NIGHT: A more unsettled quasi-zonal flow 

pattern sets up for this last weekend of June, with various waves 

triggering periodic chances for storms from Friday evening into 

Sunday. Given some dependence on the previous day's activity, the 

exact timing/location of storm chances is somewhat uncertain. 

However, we could be looking at multiple rounds of strong to 

severe storms during this period. Currently Friday evening looks 

to be round 1, though some question regarding whether storms 

coming out of central SD in the early evening will maintain 

strength as they move east of the James River. 12Z HRRR/FV3 had 

presented an alternate scenario showing limited early evening 

activity with a stronger complex diving southeast out of ND late 

evening into the overnight; however, the 18Z HRRR has backed away 

from this, instead keeping the stronger ND complex well to our 

north. Pockets of damaging wind look to be the primary threat with

storms that may impact the forecast area Friday evening.



How Friday night-early Saturday evolves could play a role in later

Saturday activity and too much uncertainty to pinpoint a preferred

solution at this point. That said, forecast soundings are much

more robust with projected instability with steeper mid-level

lapse rates supporting a greater large hail threat, and dry mid

levels and sub-cloud layers providing a risk for damaging wind.

Main question would be whether storms can maintain some semblance

of organization or be more pulsy as deep layer shear is on the

weaker side. 



Transition to a broad mid-upper level trough takes place Sunday,

which would drag a cool front southeast into the area. Could see

isolated stronger storms develop along this boundary, though its 

timing is in question with little model agreement at this range.



Compared to today, the coming days will see a return of warmer and

more humid air, with highs in the 80s most days, briefly pushing

into the 90s on Saturday. Combined with dew points in the 70s,

this could produce some areas of triple-digit heat indices by

Saturday afternoon, so may have to monitor for possible heat

headlines. 



MONDAY-THURSDAY: Early-mid week could see some modest mid-upper

level ridging build into the area, but currently not seeing any

signs that significant heat will return. Instead, temperatures

look to be near to slightly above normal as we head into July next

week. Spotty rain chances may accompany any weak waves that move

through the area, but confidence is low in pinpointing any timing

or location.





&&



.AVIATION /18Z TAFS THROUGH 18Z FRIDAY/...

Issued at 1255 PM CDT Thu Jun 26 2025



Low MVFR-IFR stratus is still rather prevalent across the 

forecast area to start this TAF period, though expect this to

slowly lift through the afternoon. Limited mixing will leave

behind plenty of boundary layer moisture, though, and with light

winds expected overnight, should see areas of fog develop later

tonight into early Friday morning. MVFR-IFR visibility seems most

likely, but cannot rule out sub-1SM LIFR visibility in some areas.

Fog should diminish pretty quickly after sunrise.



&&



.FSD WATCHES/WARNINGS/ADVISORIES...

SD...None.

MN...None.

IA...None.

NE...None.



&&



$$



DISCUSSION...JH

AVIATION...JH

