FXUS63 KFSD 241659
AFDFSD

Area Forecast Discussion
National Weather Service Sioux Falls SD
1159 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 /18Z TAFS THROUGH 18Z THURSDAY/...
Issued at 1159 AM CDT Wed Apr 24 2024

VFR conditions are forecast to prevail this TAF cycle. Should see 
south/southeasterly winds continue through the afternoon, with 
direction becoming more predominantly southeasterly after sunset. Will 
then see winds gradually strengthen through the overnight period 
with gusts between 20 to 25 MPH possible by daybreak. Winds 
strengthen even more Thursday, especially along and west of I-29, 
with gusts forecast to range between 25 to 35 MPH. Otherwise, expect 
scattered showers to develop by the end of the period, though 
confidence in any one location remains low at this time - thus, have 
opted to exclude mention for the time being. 

&&

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

&&

$$

DISCUSSION...Meyers
AVIATION...SST