479
FXUS63 KFSD 191101
AFDFSD

Area Forecast Discussion
National Weather Service Sioux Falls SD
601 AM CDT Sat Apr 19 2025

.KEY MESSAGES...

- Pleasant conditions are expected today, great for outdoor
  activities.

- Rain returns to the area on Sunday, with the best chances
  residing east of I-29. A quarter to three quarters of an inch
  of rain is likely though wobbles in storm track can have
  meaningful changes on rainfall amounts.

- Temperatures look to be near seasonable to a bit above average
  for most of next week. Chances for rain continue throughout
  the week but details are uncertain at this time.

&&

.DISCUSSION...
Issued at 328 AM CDT Sat Apr 19 2025

Today begins on a quiet note as high pressure continues to slowly
push into the Northern Plains. This high will meander across the
forecast area throughout the day today, resulting in a wonderful
Saturday. High temperatures will warm to mid 50s to low 60s while
winds remain light. Humidity levels will drop to near critical to
critical levels but with such light winds in place, no fire danger
is expected today. Today will be a great day for outdoor activities,
so get out and enjoy it! Low temperatures will fall to the 30s
overnight.

Rain returns to the area on Sunday as a shortwave trough over the
southern Plains takes on a negative tilt and ejects northeastwards.
Given its proximity to the Northern Plains, the best dynamics will
be east of the forecast area. That said, rain is still likely for
locations east of I-29. With the best lift and warm sector east of
the area, thunderstorms are not expected. However, as the mid and
upper level wave closes off, moisture will be wrapped around to the
backside of the system. Latest hi-res guidance has backed off on the
start time of the rain though with rain not beginning to fall until
late Sunday morning/early afternoon. Rain looks to continue to fall
through the rest of Sunday before pushing east of the area come
Monday morning. Despite the best dynamics being east of the area,
latest medium range guidance shows the dendritic growth zone (DGZ)
saturating along with sufficient omega (upward motion) values up to
around 10-15 ubar/s in the DGZ. There also looks to be some
potential for banding within the precipitation shield as medium
range guidance does show frontogenesis (FGEN) at 600 mb. While
forcing and moisture will be in place for rain, there is still
disagreement in rainfall amounts. This is due to small changes in
the storms track having meaningful changes on rainfall amounts. As
of now, the GFS shows the highest rainfall amounts east of I-29 with
amounts up to around three quarters of an inch to an inch of rain.
The HRRR on the other hand is the driest model as it shows rainfall
amounts less then a tenth of an inch. The ensembles help ease this
spread in rainfall amounts as they show a 40-80% chance for rainfall
amounts to exceed a quarter of an inch east of I-29. The
probabilities decrease for exceeding a half an inch of rain, down to
a 30-60% chance. The highest probabilities reside across parts of
northwest Iowa. This seems to be a more reasonable rainfall estimate
and currently think a quarter of an inch to up to about three
quarters of an inch of rain is likely but trends will be monitored.
Northwest Iowa remains the area to see the highest rainfall. Aside
from rainfall amounts, high temperatures will be a bit cooler with
highs in the mid 50s to mid 60s expected. The warmest temperatures
will occur west of I-29 where little if any rain is expected.

Dry conditions will briefly return on Monday with high temperatures
warming to the 60s and even low 70s. There could be some elevated
fire danger across parts of central South Dakota as humidity levels
lower to near critical levels along with light to marginally breezy
winds. Another shortwave trough will push into the Northern Plains
Monday evening and night. This looks to be the next chance for rain
as the ensembles show high probabilities (~80-100% chance) for
exceeding a hundredth of an inch of rain. The probabilities quickly
drop off with amounts of a tenth of an inch or more so this round of
rain looks to be quite light. Low temperatures will fall to the 40s
overnight.

Chances for rain look to persist throughout the week as a somewhat
more active, zonal flow pattern sets up. Tough to say how much rain
could fall each day at this time range but details will be ironed
out in time. In terms of temperatures, highs look to remain near to
above average in the 60s and 70s with lows falling to the 40s
overnight.

&&

.AVIATION /12Z TAFS THROUGH 12Z SUNDAY/...
Issued at 601 AM CDT Sat Apr 19 2025

VFR conditions are expected for the TAF period. Light and variable
winds this morning will pick up generally out of the west/northwest
by this afternoon. The light winds will back to out of the southeast
by this evening as surface high pressure moves through the area. The
light to marginally breezy southeast winds will finish out the TAF
period.

&&

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

&&

$$

DISCUSSION...Meyers
AVIATION...Meyers