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000
FXUS63 KFSD 110347
AFDFSD

Area Forecast Discussion
National Weather Service Sioux Falls SD
1047 PM CDT Wed Apr 10 2024

.KEY MESSAGES...

- Light rain chances (20%-40%) continue through tonight, and
  return again Thursday afternoon with only a few hundredths of
  accumulation expected.

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

- Uncertainty remains in the extended portions of the forecast,
  though ensembles continue to converge now showing a 10 to 15
  degree spread in potential high temperatures Saturday through
  Sunday. Elevated fire weather concerns possible.

- After the ridge breaks down early next week, a period of more
  active weather looks likely into the middle of the week.

&&

.DISCUSSION...
Issued at 240 PM CDT Wed Apr 10 2024

Spotty showers late this afternoon and evening will be driven by a
quick moving jet streak dropping south out of ND. Some weak
instability as this energy passes will likely drive showery
activity, but with CAPE values generally under 300 J/kg lightning
will be even spottier. Hail is unlikely with any of these showers
with freezing levels plenty high and not enough instability. Some
stronger wind gusts, maybe 40 to 50 mph, will be possible with a dry
sub cloud layer and some support from hi-res models. Otherwise a
cool front will swing through and bring some cold advection and an
increased surface pressure gradient, leading to breezy night time
winds. This will allow for some mild lows, generally upper 30s to
lower 40s.

Thursday will see a return of elevated fire weather. Northwest winds
will likely gust to 35 to 45 mph through the day, but for now many
locations lowest afternoon relative humidity will be borderline.
For more on fire weather, please see the fire weather section
below. Weak instability, especially east of the James River,
may allow for a few sprinkles or light showers on Thursday
afternoon, but any amounts would be light.

Thursday night will see winds subside as high pressure builds into
the Dakotas. Lows generally in the 30s.

Friday into the weekend will see a strong ridge build across the
western CONUS, with a developing surface high pressure along the
TX/LA border. As the surface ridge axis extending north out of the
surface high will be sliding eastwards, southerly return flow sets
up which will bring the start of our warm-up into the weekend. Most
of the warming will be occurring during the afternoon hours, as
that is when winds become more unidirectional throughout the
boundary layer and thus capable of mixing down the warmer
temperatures. With 850mb temperatures ranging from 4-8 deg C,
temperatures in the mid to upper 60s are expected for most,
while portions of SW MN will remain in the lower 60s given the
cooler air aloft.

The warming trend ramps up sharply into Saturday continuing
into Sunday, with 850mb temperatures now in excess of 15 deg C
across majority of the area. Ensemble situational awareness
tables now show 850mb temperatures largely in the 90-97.5th
percentiles of climatology, with a small pocket exceeding the
99th percentile. The GEPS continues to be the very warm outlier
suggesting temperatures in the mid 80s to lower 90s are
possible, with the GEFS and other ensembles not running quite as
hot in the mid 70s to mid 80s. Ensemble clustering analysis
reveals there is now a dominant cluster, which carries 49% of
all ensemble members (57% GEFS/50% EC/35% GEPS), which suggests
the NBM is running a touch warm for Saturday but is overall in
line with what this cluster is suggesting.

Ensembles continue to show a dry surface low pressure developing
over the area by the afternoon hours, with a weak cold front
moving through overnight into Sunday. Will have to see how
quickly we can rebound into the 70s, with the dominant cluster
unconvinced that we`ll see 80s on Sunday. So, the NBM is
starting to catch onto the GEPS warm bias for Saturday, so
wouldn`t be surprised to see cooler temperatures in additional
model runs, albeit still in the 70s. Another warm day is
expected for Monday as the ridge aloft begins to breaks down,
with another surface low pressure moving towards the area.

A period of more active weather looks likely into the middle of the
week as a couple troughs look to move onto the central plains,
accompanied by a surface low pressure or two. Still expecting above
normal temperatures to continue, though a bit more modest by next
Wednesday getting closer to normal temperatures.

&&

.AVIATION /06Z TAFS THROUGH 06Z FRIDAY/...
Issued at 1044 PM CDT Wed Apr 10 2024

Isolated showers/sprinkles will slide southeast across the
region tonight, with chances lingering east of I-29 through
Thursday. A period of MVFR ceilings may accompany or follow the
showers later tonight into early Thursday, with MVFR conditions
currently expected to remain northeast of our TAF sites.

Northwest winds occasionally gusting to 20-25kt through early
Thursday will increase behind a cool front, with gusts 30-40kt
becoming more widespread by Thursday afternoon. The stronger
gusts will diminish with sunset Thursday evening.

&&

.FIRE WEATHER...
Issued at 240 PM CDT Wed Apr 10 2024

Thursday will see a return of elevated fire weather. Northwest winds
will likely gust to 35 to 45 mph through the day, but for now many
locations lowest afternoon relative humidity will be borderline. The
best combination will be west of I-29 where RH values drop to about
20 to 30 percent, lowest in south central SD. Given such strong
winds, the 25 percent RH values are not quite as strict, and any
area with roughly 30 percent or less will be quite dangerous to burn
in. Luckily fuels are not completely cured as some green is
beginning to pop up and recent rains have left soils somewhat wet in
various locations. Regardless percent greens are still less than 30
percent, and in many locations 10 to 20 percent, so fuels will
likely be responsive if a fire gets going. Weak instability,
especially east of the James River, may allow for a few sprinkles or
light showers on Thursday afternoon, but any amounts would be
light.

&&

.FSD WATCHES/WARNINGS/ADVISORIES...
SD...Fire Weather Watch from Thursday afternoon through Thursday
     evening for SDZ038-039-054-055-061-062-066-067-070-071.
     Red Flag Warning from noon to 8 PM CDT Thursday for SDZ050-052-
     053-057>060-063>065-068-069.
MN...None.
IA...Fire Weather Watch from Thursday afternoon through Thursday
     evening for IAZ001-012-020-031.
NE...Fire Weather Watch from Thursday afternoon through Thursday
     evening for NEZ013-014.

&&

$$

DISCUSSION...APT/08
AVIATION...JH
FIRE WEATHER...08