512
FXUS63 KFSD 181924
AFDFSD

Area Forecast Discussion
National Weather Service Sioux Falls SD
224 PM CDT Fri Apr 18 2025

.KEY MESSAGES...

- Rain should return to the area on Sunday, with the better
  chances to the east of I-29. Some locations could see a half
  an inch of rain, mainly in northwest IA.

- Temperatures look to be seasonally warm for most of next week,
  generally 5 to 10 degrees above normal. Occasional chances for
  showers and isolated thunderstorms through the week, with the
  better chances most likely on Thursday.

&&

.DISCUSSION...
Issued at 223 PM CDT Fri Apr 18 2025

Cool high pressure will settle south tonight and drop overnight lows
into the upper 20s to mid 30s. Some patchy frost will be possible on
Saturday morning.

This high pressure will drift east and allow southerly flow to
return for Saturday, albeit fairly light. Temperatures will remain
somewhat cool, but creep up right to around normal for this time of
year with highs averaging the mid 50s to lower 60s. Other than some
afternoon diurnally driven cumulus, dry conditions are expected.

The upper level trough to the west will eject onto the Plains
Saturday night into Sunday and bring increasing clouds and a chances
for rain into the area. While the models are fairly consistent in
ejecting this low pressure into the Central Plains during this time.
The main questions will be how deep the low pressure gets and how
much of a negative tilt the wave takes. With some dry air in the
lower levels there should be a fairly sharp western gradient to the
rainfall. The 12z Nam does a pretty good job of indicating this
potential tight western gradient with rainfall amounts ranging from a
tenth of an inch to near a half inch just across Sioux Falls. For
now, this Nam solution also looks a tad too far west as the latest
GEFS only showing about a 30-40 percent chance for a tenth of an
inch along this gradient, dropping to about 10-15 percent for a half
an inch or more of rain. The latest EC Ensemble is even drier with
all those higher chances suppressed farther south. Overall this
looks like a fairly nice trowal, it is just a matter of how far
westward the warm and moist air aloft can wrap. Did lower highs a
bit across northwest IA given the cloud cover and rainfall
expectations.

Rainfall will gradually shift east Sunday night into early Monday
morning. A weak surface ridge will move through the area on Monday
with mild temperatures expected. So overall Monday should be a
pretty nice day with decreasing clouds, lighter winds and highs
mainly in the 60s.

A fast moving wave will track north of the area Monday night and
bring the next chance for showers and maybe a little isolated
thunder. Overall the environment is a bit on the dry aide so will
need to get some mid level moisture in to help produce a little
instability so that some activity can get going. Saturation in the
dendritic layer looks unlikely.

Once this system passes there should be periodic chances for showers
throughout the week with temperatures running a bit above normal, so
highs mainly 60s to lower 70s. At this time Wednesday night into
Thursday looks like the next better chance for rain.

&&

.AVIATION /18Z TAFS THROUGH 18Z SATURDAY/...
Issued at 1203 PM CDT Fri Apr 18 2025

Spotty high based showers and sprinkles will remain possible
through this afternoon. Otherwise northerly winds will gust to
25 to 30 mph at times this afternoon. After sunset, light winds
and mostly clear to partly cloudy skies are expected.

&&

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

&&

$$

DISCUSSION...08
AVIATION...08