329
FXUS63 KFSD 221700
AFDFSD

Area Forecast Discussion
National Weather Service Sioux Falls SD
1200 PM CDT Tue Apr 22 2025

.KEY MESSAGES...

- Elevated fire danger is expected along and south of highway-14
  this afternoon due to warm and dry conditions along with
  winds gusting up to 20-25 mph.

- Chances for rain remain on track to return for Wednesday and
  Thursday. The highest probabilities for accumulating rainfall
  remains for locations along and south of highway-20 though
  some uncertainty remains.

- Another chance for rain looks to come over the weekend and
  into early next week, mainly on Sunday and Monday. Details
  remain uncertain.

&&

.DISCUSSION...
Issued at 334 AM CDT Tue Apr 22 2025

Quiet conditions begin the day today as yesterday`s thundershowers
have pushed east of the area. Mainly clear skies are expected this
afternoon which will allow for afternoon high temperatures to warm
to the upper 60s and 70s. However, the warm, well mixed environment
will result in low humidity values and breezy winds, leading to
near critical to critical fire danger across part of the area. More
details about the fire danger can be found in the fire weather
discussion. Should see some increase in cloud cover aloft as a weak
shortwave trough pushes into the area from the west. There looks to
be just enough moisture to develop some light showers this evening.
No instability will be present so thunder and lightning are not
expected with the light showers. In fact, given the dry air in the
low levels, could see more virga rather then plain rain showers. Any
chance for rain will come to an end during the overnight hours as
the wave moves east of the area. Low temperatures will fall to the
40s overnight.

The next chance for rain returns late Wednesday through Thursday as
additional weak shortwave troughs push into the area from the
southwest within the right entrance region of an upper level jet.
The cold front that pushed through the area on Tuesday looks to
stall just south of the forecast area. This will keep any
instability tied to along the front and generally out of the
forecast area as well though some minor instability could bleed over
into parts of northwest Iowa. With marginally saturated thermal
profiles in place, rain looks to return to the area Wednesday
evening. Given that this chance for rain is being forced by weak
shortwaves, there is some uncertainty in rainfall amounts and
location. As of now, the ensembles show the highest probabilities
with a 50-80% chance for exceeding a tenth of an inch of rain along
and south of highway-20.

The previously mentioned cold front will get shunted further south,
down to around I-80 on Thursday. Forcing for ascent looks to be
enough to allow for rain chances to continue, especially with more
warm air advection (WAA) in the low levels. Despite the fronts
location, rain looks to continue through the day on Thursday. Any
appreciable instability looks to remain tied to along the front so
do not expect any severe storms at this time though rumbles of
thunder appear possible. The ensembles show higher probabilities, up
to a 50-90% chance, for rainfall on Thursday exceeding a quarter of
an inch. The highest probabilities lie across parts of northwest
Iowa, especially the highway-20 corridor. Chances for rain look to
continue through the overnight hours on Thursday before decreasing
for Friday. Highs in both Wednesday and Thursday look to span from
the 60s and 70s on Thursday to the 50s and 60s on Thursday.

Friday will be a generally dry day as upper level ridging builds
over the Northern Plains. This will allow for high temperatures to
rebound back to 60s. The break from chances for rain will be short
lived though as probabilities for precipitation will increase on
Saturday and especially Sunday as an upper level trough over the
western CONUS begins to eject into the Plains. Moisture return looks
potentially more impressive with this wave with medium range
guidance suggesting dew points could reach into the 60s. This is
somewhat supported by the ensembles as they show a 20-60% chance for
dew points to reach 60F. The highest probabilities come on Monday.
This could lead to severe storm chances on Sunday and Monday though
this waves evolution is uncertain. A lot can still change over the
coming days so this potential will be monitored.

&&

.AVIATION /18Z TAFS THROUGH 18Z WEDNESDAY/...
Issued at 1124 AM CDT Tue Apr 22 2025

VFR conditions expected to continue into the overnight hours.
Winds will gradually weaken by this evening, with considerable
variability in both speed and direction.

A broken mid-lvl cloud deck will form and spread through the
forecast area, through mostly stay focused along and north of
I-90 into Wednesday morning. Scattered light rain may develop
along highway 14 after dark.

&&

.FIRE WEATHER...
Issued at 334 AM CDT Tue Apr 22 2025

High temperatures are expected to warm to the upper 60s and 70s this
afternoon. This will result in a well mixed boundary layer that will
bring down drier air aloft. This drier air will lower dew points to
the upper 20s to low 30s, resulting in critical humidity levels
being reached across the entire area. Winds remain the most
questionable part today but a look at BUFKIT soundings shows that
there is no inversion above the mixed layer. Wind profiles are also
unidirectional, further supporting efficient mixing. However, the
magnitude of the winds looks to be on the weaker side of things. The
strongest winds look to occur along the highway-14 corridor with
gusts up to about 25 mph expected. Do not have enough confidence to
issue a Red Flag Warning at this time but have issued a Special
Weather Statement (SPS) to account for the remaining uncertainty.
Trends will be monitored throughout the day today for any potential
upgrade to a Red Flag Warning.

Wednesday will be another warm days with high temperatures remaining
in the 60s and 70s. Dew points however will moisten to the 30s, 40s,
and even up to about 50F across parts of northwest Iowa. This will
keep humidity levels above critical levels while winds remain on the
lighter side of things. Thus, fire danger is not expected.

&&

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

&&

$$

DISCUSSION...Meyers
AVIATION...Dux
FIRE WEATHER...Meyers