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000
FXUS63 KFSD 101620
AFDFSD

Area Forecast Discussion
National Weather Service Sioux Falls SD
1120 AM CDT Wed Apr 10 2024

.KEY MESSAGES...

- More light rain chances (20%-40%) will return this afternoon
  and Thursday afternoon with only a few hundredths of
  accumulation expected. Showers late this afternoon and evening
  could produce wind gusts of 40 to 50 mph.

- A Fire Weather Watch has been issued for portions of
  southeastern and southcentral SD along with far northeastern
  NE for Thursday afternoon.

- The combination of mild, dry, and breezy conditions will lead
  to more elevated fire weather concerns over the weekend.

- The uncertainty continues in the extended portions of the
  forecast with ensemble guidance continuing to show up between
  a 10-15 degree spread in potential highs over the weekend.

&&

.UPDATE...
Issued at 1118 AM CDT Wed Apr 10 2024

No big changes. The late afternoon/evening isolated to
scattered showers could produce wind gusts of 40 to 50 mph. Dry
subcloud layer, weak instability and some hints from the hi res
models are suggesting this potential.

&&

.DISCUSSION...
Issued at 435 AM CDT Wed Apr 10 2024

The Short Term (Today & Tonight):

Another warm and breezy day will be on tap for the day. Taking a
look at satellite imagery, mostly clear conditions continue with
morning temperatures hovering in the mid 30s to low 40s. The mostly
quiet conditions will continue into the afternoon hours as deeper
mixing helps transport warmer and drier air to the surface along
with increasing northwesterly winds. However, with the 850 mb LLJ
mostly centered over the central portions of South Dakota the
strongest winds will likely be isolated to areas west of the James
River with gusts between 25-35 mph expected this afternoon. With
today being a similar set up to yesterday, deeper mixing and strong
northwesterly winds will likely cause temperatures to slightly
overperform.

As a result, ended up nudging our temperatures towards the
50th percentile of guidance with highs peaking in the upper 60s to
low 70s for the day. This combined with the mostly dry and breezy
conditions will lead to some marginal fire weather concerns.
Shifting gears to our precipitation chances, a weak cold front will
continue to drift southeastwards across the area throughout the day
ahead of an incoming trough. Areas of light to moderate showers
will likely develop starting this afternoon as an area of
increased lift interacts with 200-300 J/kg of instability across
the area. However, with limited saturation available aloft;
accumulations are expected to be light with only a few
hundredths expected at best. Otherwise, the showery activity
will likely continue into the overnight hours before dissipating
around daybreak tomorrow as our overnight lows dip into the
upper 30s to low 40s for the night.

The Long Term (Thursday-Tuesday):

Heading into the extended period, any lingering precipitation east
of I-29 should begin tapering off just after daybreak Thursday
morning giving way to quieter conditions with mostly clear skies
west of I-29. With linger cold air advection (CAA) aloft and deeper
mixing, our overall temperatures will feel a touch cooler than the
previous day with highs expected to peak in the mid 50s to low 60
for the day. As the surface pressure gradient (SPG) continues to
tighten, northwesterly surface winds will strengthen throughout the
day with gusts between 35-45 mph possible throughout the day.
Looking aloft, another quick shortwave is expected dive
southeastwards across areas east of I-29 Thursday afternoon bringing
an area increased isentropic lift.

As this lift interacts with about 100-200 J/kg of instability, a
cumulus field will develop with a few embedded sprinkles to light
showers through Thursday evening. With PWAT values running in the
10th percentile according the the ESAT Tables which means dry air is
present; expecting accumulations to be limited to a few hundredths at
best. Lastly, deeper mixing will likely transport drier air to the
surface dropping our RH values into the lower 20s to low 30. The
combination of mild temperatures, stronger northwesterly winds, and
drier air will lead to high to very high fire danger across most of
the area with the greatest concerns being along the Missouri River
and west of the James River. With all this in mind, a fire weather
watch has been issued for these areas from 17z on Thursday through
01z on Friday. Otherwise, quieter conditions return by Thursday
night as a broad surface high moves through the region with
overnight lows falling into the low to mid 30s for the night.

Looking into the weekend, quieter and potentially warmer conditions
are ahead as the upper-level component of the ridge builds across
the area by Friday. Southerly to southwesterly surface flow along
with increased WAA underneath the ridging could lead to some fairly
impressive temperatures with most guidance continuing to show highs
potentially in the upper 70s to low 80s through Sunday. While the
spread continues gradually shrink in recent model runs, both
deterministic and ensemble guidance continue to show a 10-15 degree
spread for high temperatures over the weekend. Looking at ensemble
guidance, the GEPS continues to be the warmest solution among
guidance with both the Euro and GEFS trending towards the mean (low
to mid 70s). However, with temperatures continuing to trend towards
the 90th to 97.5th percentile of climatology at 850 mb according to
the ESAT Tables; its still a bit hard to discount the NBM
temperatures at this time. Lastly, continued warmth along with
breezier conditions over the weekend will lead to more elevated fire
weather concerns area wide.

By early next week, a pattern shift is likely on the horizon as more
concrete rain chances return to the region with a potentially strong
system lifting out of the Desert southwest. However, uncertainty
still remains with location and intensity differences among long-
range deterministic guidance.

&&

.AVIATION /12Z TAFS THROUGH 12Z THURSDAY/...
Issued at 625 AM CDT Wed Apr 10 2024

VFR conditions are expected this TAF period. Taking a look
across the area, mostly clear conditions continue with a few
high clouds over the Missouri River Valley. The quiet and mostly
clear conditions will presist through the afternoon hours
before increased rain chances bring some VFR stratus through
most areas. Otherwise, light and variable winds will become more
northwesterly throughout the day and increase in speed with
gusts up to 35 mph expected mostly west of the James River.

&&

.FIRE WEATHER...
Issued at 500 AM CDT Wed Apr 10 2024

As alluded to above, deep mixing will help transport drier air
and stronger winds down to the surface today with minRH values
expected to be in the upper 20s to low 30s for the day. This
along with warm temperatures and increasing northwesterly winds
with gusts up to 35 mph will lead to some marginal fire weather
concerns especially west of I-29. Otherwise, the better day for
fire weather concerns will be on Thursday. Lower dewpoints in
the upper teens to 20s will lead to MinRH values in the lower
20s to lower 30 percent range. Combine this with deeper mixing
and strong northwesterly winds with gusts between 35-45 mph and
high to very fire danger will be possible. As a result, a fire
weather watch has been issued for areas west of the James River
and along the Missouri River Valley starting Thursday afternoon.

&&

.FSD WATCHES/WARNINGS/ADVISORIES...
SD...Fire Weather Watch from Thursday afternoon through Thursday
     evening for SDZ050-052-053-057>060-063>066-068>071.
MN...None.
IA...None.
NE...Fire Weather Watch from Thursday afternoon through Thursday
     evening for NEZ013-014.

&&

$$

UPDATE...
DISCUSSION...Gumbs
AVIATION...Gumbs
FIRE WEATHER...Gumbs