Brandon, South Dakota 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

491
FXUS63 KFSD 291115
AFDFSD

Area Forecast Discussion
National Weather Service Sioux Falls SD
615 AM CDT Thu May 29 2025

.KEY MESSAGES...

- Areas of valley fog early this morning should diminish by 8-9
  AM. Widespread dense fog is not expected.

- Isolated to scattered light showers are possible again today,
  mainly near/east of I-29 corridor. Potential for weak funnels
  is lower than previous couple of days, but showers may produce
  gusty winds.

- Will see increase in smoke aloft tonight into Friday from
  Canadian wildfires. Surface impacts from smoke are not expected.

- Warmer with highs in the 80s to perhaps some lower 90s this
  weekend into Monday, then moderate (40-60%) chances for showers
  and storms Monday night through Wednesday. Some potential for
  strong-severe storms, though details are far from certain.

&&

.DISCUSSION...
Issued at 355 AM CDT Thu May 29 2025

TODAY: Main mid-upper level low as moved east into the Upper
Mississippi Valley, but an elongated trough axis extends westward
into SD. More expansive cloud cover associated with this trough
will slide south across our forecast area this morning, though
some thinning is possible with weak subsidence behind the trough
as it shifts into Nebraska/Iowa. Cannot rule out spotty sprinkles
with this feature this morning, but not expecting any measurable
rainfall. As far as early morning fog, surface observations show
patchy reduced visibility, but area web cams are not showing much
of concern, perhaps some localized lower visibility near the lower
Missouri/Vermillion River Valley area (Gayville-Vermillion-Irene).
At this time do not anticipate any headlines, but will highlight
potential for patchy low visibility in the HWO.

By this afternoon, daytime heating aided by a trailing weak wave
will again produce diurnal cumulus and the potential for isolated
to scattered light showers. Overall, though, the air mass is drier
than recent days and instability is weaker, so anticipate lesser
coverage of showers and minimal thunder threat (<10%). The weaker
instability and slightly stronger winds within the cloud layer
contribute to a much lower enhanced stretching potential (ESP)
today, so currently do not expect to see the weak funnels as we
have seen the past couple of days when the upper low was parked
overhead. However, a dry sub-cloud layer could still result in
erratic wind gusts with the spotty showers/virga that may develop.

TONIGHT-FRIDAY: Mid-upper level flow which has been predominantly
east-northeast the past few days will take on a more northerly
trajectory as the upper trough continues to swing off to the east
tonight, and a ridge builds into the High Plains. Alas, this will
begin to draw upper level smoke into the region from Canadian
wildfires, and will begin to see murky/hazy skies develop later
tonight through at least Friday evening. Fortunately, at least
through Friday, our surface flow does not appear to tap into this
elevated smoke layer, so surface impacts are not expected. May
have to monitor this into the weekend, though, as deeper northwest
flow develops across the northern Plains.

SATURDAY-MONDAY: Aside from the aforementioned potential for smoke
issues, this period looks to be relatively quiet with the upper
ridge providing opportunity for our temperatures to warm to above
seasonal normals as we head into meteorological summer on Sunday.
Highs in the 80s will be most common. However, as the thermal
ridge continues to strengthen early next week, ensembles begin to
show moderate (50-70%) probabilities for highs topping 90 degrees
in some areas by Sunday and over a greater area on Monday.

MONDAY NIGHT-WEDNESDAY: The upper ridge shifts east of the area
late Monday-Monday night, placing the northern Plains in a more
active southwest flow pattern Monday night. Some models maintain
this southwest flow into the middle of next week, while some
solutions show a more dominant northern stream trough pushing
east into the northern Plains by Tuesday-Wednesday. While the
transitions to southwest or westerly flow will lessen our impacts
from distant wildfire smoke, we should see periodic rain chances
as various shortwaves slide across the region. However, these
aforementioned differences in pattern evolution lead to a lower
confidence forecast. That said, some machine-learning tools do
suggest at least low probabilities (5-10%) for strong-severe
storms during the Tuesday-Wednesday timeframe. Those with outdoor
plans will want to monitor forecast trends as we move through the
days ahead.

&&

.AVIATION /12Z TAFS THROUGH 12Z FRIDAY/...
Issued at 615 AM CDT Thu May 29 2025

Valley fog near and south of I-90 corridor is resulting in some
METARs showing LIFR-VLIFR visibility, but area web cams show this
is mainly shallow fog near the river valleys and prevailing vsby
appears to be MVFR at worst. Will carry MIFG (shallow fog) to
start the TAF period at KSUX, but similar to yesterday, expect
visibility to quickly improve by 13Z-14Z.

Could again see some hit or miss spotty light showers this
afternoon, but thunder chances are minimal. Even the shower
chances at any single point are too low to mention in the TAF,
but northwest Iowa (KSUX) appears to have a better chance than
locations farther northwest.

Finally, as our upper level flow turns more northerly tonight, we
will likely begin to see a layer of smoke from Canadian wildfires
advance southward across the region. Model projections indicate
the smoke layer may be as low as 8-10kft AGL, but surface impacts
to visibility are not expected.


&&

.FSD WATCHES/WARNINGS/ADVISORIES...
SD...None.
MN...None.
IA...None.
NE...None.

&&

$$

DISCUSSION...JH
AVIATION...JH