787
FXUS63 KFSD 241110
AFDFSD

Area Forecast Discussion
National Weather Service Sioux Falls SD
610 AM CDT Wed Apr 24 2024

.KEY MESSAGES...

- Chances for rain and storms return late Thursday and persist
through the weekend. Strong to severe storms are possible on Friday.

- Beneficial rainfall is possible Thursday night, with a 50-80%
chance for exceeding a half an inch of rain.

&&

.DISCUSSION...
Issued at 342 AM CDT Wed Apr 24 2024

Today will be a quiet day across the area as a surface ridge slowly
pushes through the Northern Plains and into the Upper Midwest. Light
winds will begin the day out of the east and slowly turn
southeasterly throughout the day. Soundings do show a small moist
layer between 700-600 mb which is expected to result in some mid
level clouds. This mid level cloud deck will develop over south
central South Dakota and push eastwards throughout the day. With dry
low levels beneath the cloud deck, do not expect any rain to reach
the surface. This mid level cloud deck will keep high temperatures
just a touch cooler with highs warming to the 60s this afternoon.
The near seasonal temperatures and light winds will make for a solid
day for outdoor activities. Get out there any enjoy it if you can!
Elevated southeasterly winds will persist through the night and keep
low temperatures on the mild side, only falling down to the 40s to
perhaps 50 degrees F.

A strong upper level wave will begin to eject into the Plains states
on Thursday. The best lift with the wave looks to stay south and
west of the area during the daylight hours, keeping conditions
mostly dry. High temperatures will remain in the 60s but dew points
will slowly moisten to the 40s. Southeasterly winds will remain
gusty with gusts as high as 30-40 mph. As the wave begins to
encroach on the Northern Plains, warm air advection (WAA) will
strengthen in response to an intensifying low level jet (LLJ). This
will set the stage for increasing precipitation chances Thursday
evening and night. The WAA will encounter an elevated warm front
around 850 mb which should allow for weak elevated convection to
develop. Strong to severe storm chances Thursday night looks low
(<30% chance) as instability will be lacking with only a few hundred
J/kg of CAPE. The other aspect to Thursday night is that 850 mb
moisture transport will increase due to the strong LLJ in place,
which will set the stage for beneficial rainfall. Ensembles have
slightly increased their probabilities, now up to a 50-80% chance
for exceeding a half an inch of rain Thursday night.

The upper level wave pushes into the Northern Plains on Friday,
bringing the potential for strong to severe storms with it.
Questions still remain regarding the severe storm potential as
overnight storms could limit diurnal destabilization during the
afternoon hours via storm outflow cooling the low levels and cloud
cover. Along with potential destabilization issues, medium range
guidance continues to vary how far north the surface warm front
gets. If the warm front is able to push into the Missouri River
Valley, then severe storms may be possible. If not, perhaps elevated
storms will be possible. The deterministic Euro, GFS, and NAM are
generally in support of stable low levels and thus the potential for
elevated convection. However, cluster analysis reveals that the most
favored cluster has the warm front getting into the Missouri River
Valley and about 1,000 J/kg of CAPE and minimal convective
inhibition (CIN). Latest hi-res ensemble does show convection firing
along the warm front as well. Despite some CIN in place, think that
the ensemble develops convection due to strong positive vorticity
advection (PVA) from the wave finally pushing into the forecast
area. On top of the PVA, an upper level jet streak will reside over
the surface warm front which could result in a coupling of the
frontal circulation and the jets indirect thermal circulation via
the lift in the left exit region. Will continue to monitor severe
storm trends. Aside from storm chances, Friday will continue the
trend of near seasonal high temperatures in the 60s and perhaps 70s,
again depending on cloud cover. Dew points will moisten into the 50s
which will make for the first humid day across the area this Spring.
With the previously mentioned LLJ remaining strong throughout the
day, gusty southeasterly winds will continue with gusts up to 30-40
mph. Low temperatures will only fall to the 40s and 50s overnight.

Another upper wave will eject into the Plains on Saturday brining
renewed chances for rain and storms. This chance for storms will
depend on where the surface front sets up. As of now, ensembles keep
the front southeast of the forecast area. This can still change so
trends will be monitored but the fronts position suggest a minimal
chance for severe storms on Saturday. Sunday will be a similar day
as the base of the upper level trough will push through the region.
Severe storm chances will again depend on the waves evolution and
surface front location. Ensembles do show nearly a 100% chance for
exceeding a tenth of an inch of liquid QPF over the weekend, but
with details uncertain, have stuck with model blended PoPs. High
temperatures look to remain in the 50s and 60s for the weekend.

Dry conditions look to return on Monday as the wave lifts north and
subsidence prevails on the wave`s backside. The dry conditions look
to persist into the middle of next week along with warmer high
temperatures, potentially into the 70s as supported by the
ensembles.

&&

.AVIATION /12Z TAFS THROUGH 12Z THURSDAY/...
Issued at 610 AM CDT Wed Apr 24 2024

VFR conditions are expected for the TAF period. Light and variable
winds will slightly strengthen out of the east/southeast today with
speeds between 5-15 knots, strongest west of the James River. A mid
level cloud deck will develop across central South Dakota and push
eastwards through the day, based around 10,000 ft. Southeasterly
winds further strengthen this evening and night with gusts up to 15-
25 knots to end the TAF period.

&&

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

&&

$$

DISCUSSION...Meyers
AVIATION...Meyers