National Weather Service National Headquarters

• Home
• Site Map
• News
• Organization
• Search for: NWS All NOAA 

-- Discussion containing changed information from previous version are highlighted. --
000
FXUS63 KFSD 231120
AFDFSD

Area Forecast Discussion
National Weather Service Sioux Falls SD
620 AM CDT Tue Apr 23 2024

.KEY MESSAGES...

- Sprinkles to light showers are possible this afternoon, mainly across
  southwest Minnesota.

- Frost will be possible Tuesday night as low temperatures fall to
  the 30s.

- Chances for rain return late Thursday through the weekend.
  Chances for strong to severe storms are possible Thursday
  night and Friday.

&&

.DISCUSSION...
Issued at 339 AM CDT Tue Apr 23 2024

A calmer day is expected today as an upper level trough continues to
pass through the Northern Plains today. Northwest flow within a cold
advective regime will cool 850 mb temperatures down to +2 to +5 C
aloft. Mixing these temperatures to the surface will result in high
temperatures up to the upper 50s to mid 60s this afternoon.
Northwest winds will gust up to around 35-40 mph in the morning when
the strongest push of cold air advection (CAA) will be passing
through the forecast area. Winds will slowly wane to 25-35 mph
during the afternoon. BUFKIT soundings show a hint of instability
along with a small layer of nearly saturated air at the top of the
mixed layer. This suggest that sprinkles to isolated showers are
possible this afternoon as the base of the upper wave pushes through
the region. Sprinkles to light showers look most likely across
southwest Minnesota as the moist layer is a bit lower then locations
further south and west. These locations have more low level dry air
which should keep any rain from reaching the ground. Minimal
rainfall amounts are expected with any rain that does make it to the
surface. Winds will wane during the evening hours as high pressure
moves into the area. With high pressure in control during the
overnight hours, low temperatures will fall to the 30s, coldest
along and north of I-90. Areas to widespread frost is expected
during the overnight hours due to the cold low temperatures.

Wednesday will be a quiet day as the previously mentioned high
pressure system is slow to depart to the east. Highs will warm to
the 60s while overnight low temperatures will fall to the 40s.
Partly cloudy skies and light winds during the afternoon will make
for a lovely afternoon for outdoor activities!

A stronger upper level wave will eject into the Plains on Thursday,
setting the stage for the next chance for rain across the region. As
the wave ejects, warm air advection (WAA) will strengthen out ahead
of the wave, pushing high temperatures to the mid 60s to low 70s
across the area. Southerly winds will gust up to 30-40 mph during
the afternoon but dew points will be moistening during the day. With
relative humidity values only falling to 35% at the lowest, moderate
fire danger is expected. Rain chances will increase during the
evening and overnight hours as positive vorticity advection (PVA)
from the wave begins to encroach on the area. Strong moisture
moisture transport will feed into the area, setting the stage for
potentially heavy rainfall. With a strong low level jet (LLJ) in
place, mid level lapse rates will steepen enough to generate
elevated buoyancy and thus allow convection to develop as the LLJ
encounters an elevated warm front at 850 mb. The GFS, Canadian, and
Euro ensembles all show a broad 50-70% chance for rainfall totals
exceeding a half an inch Thursday night. While severe storm chances
are possible, shear is lacking a bit aloft so think any severe
hazards will come in the form of large hail.

The wave fully pushes into the Northern Plains on Friday, setting
the stage for potential severe weather. Questions still remain
regarding this potential as the GFS continues to be faster with the
wave while the Canadian and Euro are slower. The Euro and Canadian
keep the surface warm front tied to the Missouri River while the GFS
pushes the front into northwest Iowa. These differences in the waves
speed and warm front position will be the main factors that
determine the severe weather potential for the day. Cluster analysis
shows that the most favored cluster has a 60-80% chance for
exceeding 1,000 J/kg of CAPE along and south of I-90 Friday
afternoon. Will closely monitor trends over the coming days. Outside
of severe weather potential, Friday will be a very warm, breezy, and
humid day as high temperatures warm to the 60s and 70s and dew
points warm to the 50s. Overnight low temperatures will fall to the
40s and 50s.

Another upper level wave looks to eject into the Plains states on
Saturday which could lead to additional chances for rain and storms.
This wave looks to slowly progress through the area through Sunday,
continuing chances for rain and storms for the weekend. Medium range
guidance varies in how the wave evolves so have stuck with model
blended PoPs for the weekend. Good news is that rain chances look to
come to an end on Monday, leaving dry conditions for the beginning
of the next work week.

&&

.AVIATION /12Z TAFS THROUGH 12Z WEDNESDAY/...
-- Changed Discussion --
Issued at 620 AM CDT Tue Apr 23 2024

VFR conditions are expected for the TAF period. Northwest winds will
become gusty this morning with gusts up to 30-35 knots expected,
strongest west of I-29. The northwest winds will slowly wane through
the rest of today. A CU field is expected to develop by this
afternoon with cloud bases at approximately 6,000 feet. The CU field
will dissipate this evening as mixing ceases. Winds will go light
and variable during the evening and overnight hours to end the TAF
period.
-- End Changed Discussion --

&&

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

&&

$$

DISCUSSION...Meyers
AVIATION...Meyers