299 
FXUS63 KFSD 252341
AFDFSD

AREA FORECAST DISCUSSION
National Weather Service Sioux Falls SD
641 PM CDT Tue May 25 2021

.SHORT TERM...(This Evening through Wednesday)
Issued at 241 PM CDT Tue May 25 2021

A mild and breezy day across the area with strong cold air advection 
in place into the night. This has allowed very dry air to move south 
with surface dew points in the 40s as winds turn to the northwest. A 
few showers across ND but those look to remain to the north as the 
cold pool aloft move east. In the low levels cooler air will 
continue to filter south through tonight which should keep northerly 
flow from completely dropping off, likely averaging about 5 to 15 
mph through the night. Because of this went with the 75th percentile 
for low temperatures, ranging from the upper 40s near highway 14 to 
the mid 50s in northwest IA.

As this low pressure to the north moves into northern MN a ridge of 
high pressure will move across the Northern Plains and keep dry 
conditions in place for most of the area on Wednesday. There is some 
potential that this air is a little drier than forecast and could 
really limit and activity ahead of the incoming wave Wednesday 
night. Instability ahead of this wave pretty weak with even the more 
aggressive Nam about 500-750 J/kg. There is some shear to work with 
if for some reason the models are not right, but for not not 
anticipated. 

.LONG TERM...(Wednesday Night through Tuesday)
Issued at 241 PM CDT Tue May 25 2021

By Wednesday night a fairly strong shortwave will move into SD with 
decent warm and moist advection racing north ahead of it. This will 
be our next better chance for severe weather. Positives are that 
shear is fairly strong but negatives are that we might struggle with 
moisture a bit and instability still pretty questionable. The 850 mb 
to 700 mb front mostly north of Interstate 90 to north of highway 14 
while the surface to 925 mb front lingers closer to the Missouri 
River. While a very isolated stronger thunderstorm will be possible 
with the elevated front, the better chances will be south of the 
Missouri River. Wondering if we might see a somewhat broad area of 
rain nd embedded thunder around highway 14 and points north, then 
strong thunderstorms south of the Missouri River, maybe a few 
stronger updrafts near the Missouri River, with a stratiform 
precipitation shield just north. That might leave Interstate 90 with 
a little less rainfall with higher amounts to the north and south. 
Will see how it plays out tomorrow but for now not expecting more 
than isolated severe weather.

Still some lingering light rain and very isolated thunder across the 
area on Thursday. While the mid and upper levels scour out moisture 
a bit, the low levels remain fairly saturated and allow for some 
weak instability with lift around 850 mb to 800 mb. By Thursday 
night a little bit more drying and warming in the mid levels seem to 
cut off this showery potential so chances should decrease quickly. A 
cool air mass in place with highs only in the 50s along and north of 
I-90 and 60s to the south.

The air mass cools and dries a bit more going into Friday so highs 
near 60 to the mid 50s will be pretty common. With the upper level 
low pressure lingering around and shearing out clouds should still 
be pretty thick. For now not thinking any showers but there is some 
very weak instability at the top of the moist layer so maybe some 
very light showers or sprinkles.

The weather going into the weekend looks cool with a continued 
chance for showers and isolated thunderstorms. Not really a severe 
threat, just cloudy, cool and potentially showery.

Very gradual warming Monday into Tuesday with decreasing chances for 
showers.

&&

.AVIATION...(For the 00Z TAFS through 00Z Wednesday evening)
Issued at 640 PM CDT Tue May 25 2021

Frequent wind gusts of 25 to 30 kts will fade quickly after 00z
leaving VFR conditions through the period. Will watch for a few
showers to move into areas mainly west of the James River after
18z Thu, but any should remain VFR through 00z.

&&

.FSD WATCHES/WARNINGS/ADVISORIES...
SD...NONE.
MN...NONE.
IA...NONE.
NE...NONE.
&&

$$

SHORT TERM...08
LONG TERM...08
AVIATION...Chapman