750
FXUS63 KFSD 192055
AFDFSD

Area Forecast Discussion
National Weather Service Sioux Falls SD
355 PM CDT Sat Oct 19 2024

.KEY MESSAGES...

- Elevated fire danger looks to return to the region for Sunday
  and Monday.

- Chances for rain return on Monday, with locations south of
  I-90 having a 20-30% chance for seeing light rain. The light
  rain may reduce the elevated fire danger in this area.

- A cold front will bring another chance (30-40%) for light rain
  Tuesday night, followed by a brief cooldown on Wednesday.
  Temperatures slowly rebound to above average through the end
  of the week.

&&

.DISCUSSION...
Issued at 354 PM CDT Sat Oct 19 2024

Low to mid level clouds are clearing out this afternoon, allowing
high to reach up to the 60s and 70s. With light winds in place, it
will make for a pleasant rest of the afternoon hours. Winds will
remain light through the overnight hours as the surface pressure
gradient (SPG) remains slightly tightened over the forecast area.
However, soundings do show a strong nocturnal inversion developing
tonight in response to radiational cooling. If winds go calm during
the overnight hours, patchy fog may be possible, mainly west of I-29
and north of I-90. Low temperatures are expected to fall to the
upper 40s to mid 50s from northwest to southeast tonight.

The SPG will tighten a bit more tomorrow, continuing breezy winds
across the area. Mid and upper level flow will turn more
southwesterly aloft, allowing for efficient mixing to take place.
Gusts up to about 30 mph is expected but there could be isolated
higher gusts due to momentum mixing. Dew points will moisten a bit
more tomorrow up to the low to mid 50s. With very warm high
temperatures tomorrow, thanks to 850 mb temperatures pushing into
the 90th percentile of climatology, highs into the upper 70s and 80s
is expected. The higher dew points will keep relative humidity (RH)
values in check with RH falling to 30-40% during the afternoon
hours. Despite RH staying above critical levels, elevated fire
danger is expected tomorrow due to the breezy winds and dry
antecedent conditions. Elevated fire danger will come to an end
tomorrow evening as the boundary layer stabilizes. Low temperatures
will fall to the 50s overnight. Given the very warm overnight
temperatures, a few record high mins could be tied or broken.

A cut off low that was sitting over the southwest CONUS will eject
northeastwards on Monday. This wave is moisture starved though so
any rain that does fall will be very light and has a 20-30% chance
of falling south of I-90. Rainfall amounts up to a few hundredths of
an inch is possible. With abundant cloud cover across the region,
temperatures will be a touch cooler with highs in the 70s to up to
about 80 degrees F. Dew points will remain in the 40s and 50s which
will keep higher RH values, only down to about 30-50%. Breezy
southerly winds will keep elevated fire danger going though despite
the higher RH. Low temperatures will be a bit cooler, falling to the
low to mid 50s.

Tuesday will be a dry day across the area but a stronger upper level
wave will push through the Northern Plains. This wave will drag a
cold front though the area during the daylight hours. The cold air
advection (CAA) behind the front will not be strong initially but it
will be enough to cool high temperatures a bit, down to the 70s. The
strongest CAA will come through during the overnight hours along
with strong frontogenesis (FGEN) in the mid levels. There is enough
saturation in the mid levels that rain is possible Tuesday night.
Like what we have seen so far, this looks to be light rain as the
ensembles only show a 30-60% chance for exceeding a hundredth of an
inch. Low temperatures will fall to the 40s.

Although Wednesday will see high temperatures near to above average
in the 50s and 60s, upper level ridging will build back in aloft for
the second half of next week. Thus, a return to above average high
temperatures is likely. This is supported by the NAEFS ensemble as
it shows 850 mb temperatures warming back to the 90th percentile of
climatology. With upper level ridging in place, the warmer
temperatures look to coincide with dry conditions.

&&

.AVIATION /18Z TAFS THROUGH 18Z SUNDAY/...
Issued at 1237 PM CDT Sat Oct 19 2024

Current satellite shows a mix of VFR/MVFR/IFR ceilings across the
area this afternoon. The lowest ceilings, down to MVFR/IFR levels,
reside along and west of a Marshall, MN to Hartford, SD to Tyndall,
SD line. Mid level clouds to the east of the line remain at VFR
thresholds. These low and mid level clouds are expected to lift
throughout the afternoon hours, returning conditions to VFR levels
across the area. A boundary resides across the area this afternoon.
Light southwest winds lie ahead of the boundary and westerly behind
it. However, winds are expected to turn out of the southwest through
the afternoon with speeds around 5 knots.

Light south/southwest winds will persist through the overnight hours
but there is some uncertainty regarding how light the winds will
become. If winds go light and calm during the overnight hours, then
patchy fog may be possible. Too uncertain to put in a TAF at this
time but trends will be monitored. Southwest winds will restrengthen
tomorrow morning to end the TAF period.

&&

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

&&

$$

DISCUSSION...Meyers
AVIATION...Meyers