FXUS63 KFSD 190502
AFDFSD

Area Forecast Discussion
National Weather Service Sioux Falls SD
1202 AM CDT Tue May 19 2026

.KEY MESSAGES...

- Pockets of drizzle will continue through Tuesday morning with
  mainly light accumulations expected.

- Areas of frost or freeze will be possible by Wednesday 
  morning, with the better chances north of I-90. Make sure to 
  cover/bring in any sensitive vegetation.

- Cooler conditions will prevail this week. Dry weather 
  expected mid week. Another round of storms will be possible 
  from Thursday through Friday.

&&

.UPDATE...
Issued at 910 PM CDT Mon May 18 2026

While the main severe risk has now pushed east of our area this 
evening, scattered light to moderate showers will likely persist 
into the late evening as a mid-level wave lifts through eastern SD 
and central MN tonight. Given the waning mid-level saturation and 
lower cloud heights according to sounding, can't rule out a few 
pockets of drizzle through Tuesday morning as well. While this could 
lead to persistent dreary conditions overnight, any accumulations 
will likely be on the lower side with another 0.10" of an inch or 
less expected for most areas. Otherwise, should see cloud cover 
begin to gradually clear from west to east starting by Tuesday 
morning. With lingering cold air advection (CAA) aloft and breezy 
northwesterly winds at the surface, expected another cool day with 
highs mainly in the low to upper 50s. With this in mind, make sure 
to take a jacket when heading out on Tuesday as the cooler and 
breezier conditions could make things feel a bit chilly at times 
especially during the first half of the day.

&&

.DISCUSSION...
Issued at 1258 PM CDT Mon May 18 2026

Early this afternoon the surface to 925 mb front was across southern 
NE into southern IA. Given the marginal strength of the incoming 
wave, this boundary should not lift far enough north and west 
by late afternoon to get into the area. This should limit any 
wind and tornado threats and keep them off to the southeast. 
However, some elevated hailers will remain possible across 
mainly northwest IA as elevated CAPE values ramp up to about 
1000-1500 J/KG and deep layer shear is a fairly strong, 
unidirectional 40-50 knots. This would be lifting a parcel from 
above the stratus layer, which would likely be in about the 
800-750mb layer. The better chances will be from about 5 pm to 9
pm.

After this wave pushes the remaining instability out of the area 
this evening, dry and cool conditions are expected for Tuesday and 
Wednesday. The only concerns on these two days will be the potential 
for frost and freeze conditions, mostly north of I-90, as surface 
high pressure is in place. Another weaker wave moves through the 
area on Wednesday but for now this appears to bring mainly mid level 
cloud cover.

The next better chance for showers and thunderstorms will come 
Thursday night into Friday night. At this time severe weather looks 
to remain isolated as model instability fields are hinting at 1000 
J/kg CAPE or less for the most part.

Once this wave passes a warming trend should move in as flat ridging 
aloft develops ahead of a deepening low pressure in the Northern 
Rockies. Saturday should be mild, likely in the 70s, while Sunday 
sees the better chance to warm into the 80s.

&&

.AVIATION /06Z TAFS THROUGH 06Z WEDNESDAY/...
Issued at 1158 PM CDT Mon May 18 2026

Mainly MVFR to IFR conditions will continue this TAF period.
Taking a look at satellite imagery, areas of MVFR to LIFR
stratus continue to blanket the area with a few pockets of
drizzle. While these conditions will likely persist in the 
overnight hours, should see gradual improvements from west to
east by mid-morning on Tuesday returning things back to VFR
conditions. Lastly, breezy northwesterly winds will persist 
intermittently through Tuesday evening to end the TAF period.

&&

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

&&

$$

UPDATE...05
DISCUSSION...08
AVIATION...05