National Weather Service Weather Forecast Office

• Home
• Site Map
• News
• Organization
• Search for: NWS All NOAA 

000
FXUS63 KFSD 201945
AFDFSD

Area Forecast Discussion
National Weather Service Sioux Falls SD
245 PM CDT Sat Apr 20 2024

.KEY MESSAGES...

- Temperatures will drop below freezing again tonight into
  Sunday morning. Be sure to protect sensitive plants from the
  cold.

- Monday and Tuesday will be windy days with gusts peaking 30 to
  45 mph. While vegetation is greening up from recent rains,
  afternoon humidity levels will likely drop to 25 to 35
  percent, leading to elevated fire danger for some locations.

- A low (< 40%) chance of isolated showers and storms returns
  Monday afternoon and night. High confidence in less than a
  tenth inch of rainfall.

- Chances for showers and thunderstorms continue to increase for
  Thursday and Friday. There is a low to moderate (20 to 50%)
  chance of over a half inch of rain occurring by Friday
  afternoon. The heaviest amounts looking most likely south of
  the I-90 corridor, where locally heavier amounts exceeding one
  inch are possible with storms.

&&

.DISCUSSION...
Issued at 243 PM CDT Sat Apr 20 2024

THIS EVENING AND OVERNIGHT: Satellite images around 2 PM show
stratocumulus across the region continues to break up with afternoon
mixing. Upstream, an upper trough axis brings a brief increase in
mid level clouds that will slide through early this evening, but
skies should clear pretty quickly after sunset. Northwest winds
gusting 20 to 30 mph will weaken this evening as diurnal mixing
shuts off and surface high pressure builds south through the central
Dakotas and Nebraska.

With clear skies, lighter winds, and height falls aloft, we`re ripe
for temperatures to drop substantially overnight. Given the somewhat
favorable pattern for nocturnal radiative cooling, dropped lows to
range from the lower 20s to lower 30s, warmest in portions of
southwest Minnesota. Issued a Freeze warning through early Sunday
morning given the high probability for sub freezing temperatures.

SUNDAY: We will see pleasant conditions to end the weekend with
slightly warmer air and weaker winds as weak ridging aloft and broad
warm air advection develop. Though drier air slides in Sunday with
relative humidity values dipping into the 20s, fire danger will be
limited by weak winds aloft. Expect gusts to peak in the teens and
20s, giving a brief period of relief from windy conditions.

MONDAY: Broad warm air advection makes for an even warmer start to
the week ahead of a deepening, positively tilted upper trough
tracking east through the Canadian Prairie. Expect highs in the 60s
to mid 70s Monday, warmest across northwest Iowa ahead of a passing
weak cold front. Models suggest broad upper lift ahead of an
approaching jet streak coupled with destabilization from a deep
elevated mixed layer would be enough to support isolated showers or
weak thunderstorms, but dry low level air and the weaker nature of
the front should keep rainfall amounts pretty light at less than a
tenth inch of rain for any location. The bigger impact Monday will
be gusty southwest winds ahead of the front, turning northwest
behind the front. Ahead of the front east of I-29 and/or with
showers, mixing into a strengthening low level jet may result in
gusts in the 40s (nearing Wind Advisory criteria) Monday afternoon.
Further west, gusts look to peak in the 30s to lower 40s. Areas
behind the front near and west of the James River Valley may see
elevated fire danger between gusty winds and dry post frontal air
dipping humidity levels into the 20s Monday afternoon.

TUESDAY: Colder, cloudy, and windy weather is the theme by Tuesday
as cold air advection spills in and the upper trough digs through
the Upper Mississippi Valley. Though temperatures should rise into
the 50s to mid 60s by Tuesday afternoon, model soundings support 1)
a weakly unstable stratocumulus layer with sprinkles possible as
well as 2) gusts in the 30s and 40s with efficient mixing. Given
another day with humidity levels dropping below 30 percent for much
of the region, elevated fire danger and windy conditions will be
main concerns.

TUESDAY NIGHT AND BEYOND: Mostly dry surface ridging settles in mid
week with near normal temperatures - highs in the 60s and lows in
the 30s to 40s. Late week, attention turns to a strong, progressive
Colorado Low poised to track into the Central Plains Friday into
Saturday. Chances for showers and storms continue to increase
Thursday into Friday with the SPC Day 7 outlook highlighting
potential for severe weather Thursday night and Friday. This is
favored by some CIPS analogs and CSU machine learning guidance with
a focus further south for Nebraska through northern Texas and also
the operational Euro/Canadian models painting a northern sfc low
track near the I-90 corridor. However, there is still major
uncertainty in the timing and low track at this stage, so
will continue to monitor this period.

&&

.AVIATION /18Z TAFS THROUGH 18Z SUNDAY/...
Issued at 1227 PM CDT Sat Apr 20 2024

VFR conditions will prevail through the period. Stratocumulus
at 3-5 kft lingers across the region through mid afternoon with
northwest winds gusting 15 to 25 kts and occasionally a bit
higher. Expect diurnal heating/mixing to scatter ceilings closer
to 4-7 kft late this afternoon with skies clearing out after
sunset. Winds will weaken after sunset as well, turning more
west or west- northwest overnight.

&&

.FSD WATCHES/WARNINGS/ADVISORIES...
SD...Freeze Warning from midnight tonight to 8 AM CDT Sunday for
     SDZ055-056-061-062-066-067-069>071.
MN...Freeze Warning from midnight tonight to 8 AM CDT Sunday for
     MNZ071-072-080-081-089-090-097-098.
IA...Freeze Warning from midnight tonight to 8 AM CDT Sunday for
     IAZ001>003-012>014-020>022-031-032.
NE...Freeze Warning from midnight tonight to 8 AM CDT Sunday for
     NEZ013-014.

&&

$$

DISCUSSION...BP
AVIATION...BP