Brookings South Dakota Weather Forecast Discussion

335
FXUS63 KFSD 081121
AFDFSD
Area Forecast Discussion
National Weather Service Sioux Falls SD
621 AM CDT Wed Oct 8 2025
.KEY MESSAGES...
- Dry conditions are expected to persist into Saturday.
- Increasing southerly winds, warm temperatures, and lower
  humidity will make for elevated fire danger this afternoon.
  Locations west of the James River have the highest chances for
  seeing the elevated fire danger.
- The next chance for rain will not arrive until the weekend.
  Coverage remains uncertain at this time but there is only
  30-50% chance, at the highest, for rainfall amounts to exceed
  a tenth of an inch at this time.
- Additional chances for rain are possible into the middle of
  next week though details are very uncertain.
&&
.DISCUSSION...
Issued at 347 AM CDT Wed Oct 8 2025
Quiet conditions begin the day early this morning. Surface high
pressure continues to depart to the east, turning surface winds to
out of the east/southeast in its wake. A cold front is also situated
near the Missouri River Valley as well. Temperatures have been
falling quickly across portions of highway-14 and adjacent areas in
southwest Minnesota. Have lowered temperatures to near to above
freezing in this area to keep trends on track. Patchy frost remains
possible due to the cold temperatures. At the same time, with light
southeast winds in place, wind chills will fall to near to below
freezing, coldest along and north of I-90, especially across
portions of southwest Minnesota. Make sure to bundle up as you head
out the door for work this morning.
Temperatures will quickly warm through the morning hours, reaching
into the 60s come the afternoon time frame. High temperatures will
peak in the upper 60s to low 70s, especially with the previously
mentioned cold front transitioning into a weak warm front and
pushing a bit further northeastwards. With the previously mentioned
surface high now east of the area, the surface pressure gradient
will tighten, leading to breezy southerly winds. Gusts up to 20-40
mph is expected with the strongest winds occurring across south
central South Dakota. With the warm and breezy conditions in place,
elevated fire danger remains possible for this afternoon as humidity
values lower to about 30-35% across the area. The highest fire
danger will occur west of the James River where the best overlap of
strongest winds and lower humidity will reside. Any fire danger will
come to an end this evening as temperatures cool. The low level jet
(LLJ) will strengthen overhead, keeping breezy southerly winds going
through the night. This will also keep low temperatures on the mild
side with lows falling to the upper 40s to 50s. With warm air
advection (WAA) strengthening in response to the LLJ, there could be
just enough moisture to squeak out some sprinkles late tonight into
tomorrow morning. Confidence is not high enough to deviate from the
NBM but something to watch.
Thursday and Friday will see a continuation of above average
temperatures with highs warming to the 70s. Breezy winds will
persist through Thursday as the surface pressure gradient remains
tightened over the forecast area. Humidity levels will be higher on
Thursday, keeping fire danger capped at moderate levels. A cold
front will push through the area Thursday evening, ending breezy
conditions across the region. This will make for a pleasant Friday
with lighter winds and warm temperatures.
Medium range guidance has come into better agreement in the upper
level pattern for the weekend. The deterministic models now show a
slightly stronger closed low that will slowly push through the Great
Lakes area through the weekend. This closed low along with a
stronger upper level wave moving in from the northwestern CONUS will
strengthen the shorter wavelength ridging between the two systems.
This will keep above average temperatures in place with highs in the
upper 60s, 70s, and low 80s. Sunday looks to be the warmer of the
two days. The ensembles differ quite a bit in their rainfall
probabilities with the Euro being the highest with a 30-50% chance
for exceeding a tenth of an inch of rain. The Canadian is the lowest
with a 0% probability for exceeding the same amount of rain and the
GFS is between the two. Looking at the dynamics, Saturday night
looks to be the timeframe when rain could become more likely as the
exit region of the northwest CONUS upper level trough begins to
encroach on the Northern Plains, strengthen WAA. This same wave will
keep rain chances going through Sunday as sufficient quasi-
geostrophic (QG) forcing remains in place. The overall consensus
from the ensembles shows slightly lower chances, down to a 20-40%
chance for exceeding a tenth of an inch of rain on Sunday. The cold
front tied to this upper wave will push through the area on Sunday
as well.
Surface ridging will quickly pass through the Northern Plains on
Monday, resulting in mostly dry conditions and slightly cooler high
temperatures in the 60s to mid 70s. This mainly dry day will be
short lived as broad troughing and a strong upper level jet will
continue to sit over the Northern Plains. Confidence in the upper
level patterns evolution decreases at this point but the troughing
and forcing for ascent should lead to additional chances for rain
into the middle of next week. The variance in the upper level
pattern also keeps the ensemble probabilities for rain generally
below 30% as well as highs near seasonable in the 60s and 70s.
&&
.AVIATION /12Z TAFS THROUGH 12Z THURSDAY/...
Issued at 621 AM CDT Wed Oct 8 2025
VFR conditions are expected for the TAF period. Light and variable
winds this morning will strengthen out of the south today. The
southerly winds will gust up to 15-35 knots, strongest across south
central South Dakota. Winds will weaken a little bit but remain
breezy through the evening and night thanks to the strengthening low
level jet (LLJ). Low level wind shear (LLWS) is not expected due to
the continuation of breezy winds overnight. Winds however will back
a bit to out of the southeast. The breezy southeast winds will
finish out the TAF period.
&&
.FSD WATCHES/WARNINGS/ADVISORIES...
SD...None.
MN...None.
IA...None.
NE...None.
&&
$$
DISCUSSION...Meyers
AVIATION...Meyers

NWS FSD Office Area Forecast Discussion