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000
FXUS63 KFSD 131712
AFDFSD

Area Forecast Discussion
National Weather Service Sioux Falls SD
1212 PM CDT Sat Apr 13 2024

.KEY MESSAGES...

- A Red Flag Warning has been issued along and east of the I-29
  corridor across southwest Minnesota and portions of eastern
  South Dakota and northwest Iowa for this afternoon and
  evening. Exercise caution to avoid unintentionally sparking a
  fire today, as fires can spread quickly under these
  conditions!

- Unseasonably warm weather today through Monday brings highs
  in the 70s and 80s, 20 to 30 degrees above normal for mid
  April. This heat combines with breezy conditions on today and
  Monday to bring periods of near critical to critical fire
  danger.

- Periods of showers and storms are expected for Monday evening
  through Tuesday with a high (60-90%) chance of at least a half
  inch of rain across the region by the time rain ends. With
  threat for severe weather Monday night and periods of locally
  heavy rainfall, be sure to continue to monitor the forecast.

&&

.DISCUSSION...
Issued at 411 AM CDT Sat Apr 13 2024

TODAY: A northern stream clipper system slides east through the
Dakotas today. In response, strong warm air advection and stout
upper level ridging (in the top 10% of heights aloft for the EPS and
NAEFS climatology) for this time of year set the stage for summer-
like heat. Abundant sunshine kicks off diurnal mixing into a deep
nocturnal inversion, resulting in southwesterly and eventually
southerly winds sustained at 10 to 25 mph. A largely favorable
heating pattern coupled with mixing into 850mb temperatures in the
top 3% of ensemble climatologies for this time of year should yield
widespread highs in the 80s. Thus continued the trend of bumping
highs above the operational NBM toward bias-correct guidance. Highs
of 20 to 30 degrees above normal will be within a few degrees of
today`s record highs at Huron (90) and Mitchell (91).

High confidence in today`s dry heat combined with gusts of 25 to 35
mph means near critical to critical fire weather conditions are
expected, especially near and east of the Interstate 29 corridor.
Additionally the Hot-Dry-Windy Index (HDWI) has a high (>90%) chance
of exceeding its 75th percentile today, suggesting weather
conditions will make it more difficult to manage a wildland fire.
Thus have issued a Red Flag Warning for this afternoon through early
evening. West of the warning area, have high confidence in dry air
but lower confidence in winds exceeding 25 mph as gradient winds
weaken with the approaching sfc trough late this afternoon. Can`t
rule out occasional gusts around 25 mph in this area, but it`s less
likely than further east. Nevertheless, it is a day where much of
the region should avoid burning and use caution to avoid sparking a
fire. More details are available in the Fire Weather section.

TONIGHT: Winds weaken considerably and shift north for a pleasant,
mostly clear evening as a weak front slides through. Temperatures
only fall into the 40s to lower 50s overnight.

SUNDAY: Slightly cooler but still summer-like warm weather is
expected Sunday with weak surface high pressure sliding through.
Winds are much lighter and variable, making for another day great
for outdoor activities.

MONDAY AND TUESDAY: Monday starts off warm and breezy ahead ahead of
a strong closed upper low tracking from the Four Corners region
toward eastern Nebraska. Despite increasing low level moisture, dry
fuels, unseasonably warm air, and gusts in the 20s and 30s prompt
another period of near critical fire danger Monday afternoon.
Tuesday will be cloudy, windy, and notably cooler with highs
mainly in the 60s.

Rain chances remain quite low (<30%) during the day Monday until the
strong surface low ejects into the High Plains and a warm front
lifts north into the area. Rain chances increase considerably
heading into Monday night as height falls aloft to trigger
convection somewhere in the Central and Southern Plains, tracking
northeast through the night. We are now included in the severe
weather threat for Monday night amidst a broad area of up to 2000
J/kg MLCAPE, though there is still notable uncertainty in the
details - the deep layer shear profile, whether capping can break,
positioning of the low level jet and the warm front and dryline.
Coupled with severe weather threat, multiple rounds of rain (Monday
night, Tuesday, and/or Tuesday night) and precipitable water values
nearing the top of ensemble climatology favors the threat for
locally heavy rainfall. By Wednesday, ensembles support a high
(>60%) chance of most sites seeing at least a half inch of rain and
low chances of isolated 2+ inch amounts.

WEDNESDAY AND BEYOND: High confidence in cooler, drier, and more
seasonal spring weather for the second half of the week. Low
confidence in rain chances as a stronger northern wave treks into
the Northern Plains, placing the Central Plains in zonal flow
aloft.

&&

.AVIATION /18Z TAFS THROUGH 18Z SUNDAY/...
Issued at 1210 PM CDT Sat Apr 13 2024

VFR conditions continue through the afternoon and overnight
hours. Scattered ACCAS continues to move through the region
early this afternoon. One area to watch would be in south
central SD into northern Nebraska where we could meet
convective temps later this afternoon resulting in very high
based showers and cirrus debris.

Otherwise a front will move through the area overnight turning
winds to the north into Sunday morning.


 &&

.FIRE WEATHER...
Issued at 411 AM CDT Sat Apr 13 2024

High confidence in dry, unseasonably warm air with highs in the 80s
coupled with dry fuels and gusts in the 20s to lower 30s will cause
near critical to critical fire weather conditions across much
of the region this afternoon through early evening.

Areas west of the Interstate 29 corridor can look to see the warmest
conditions, but confidence in winds reaching critical thresholds is
lower as gradient winds relax in the afternoon. Can`t rule out gusts
approaching 20-25 mph and a few sites briefly reaching critical
conditions.

Areas near and east of the Interstate 29 corridor and north of the
U.S. Highway 20 corridor can expect near critical to critical fire
weather conditions this afternoon through early evening. Thus have
issued a Red Flag Warning for this area.Am particularly concerned
about fire danger in southwest Minnesota where local terrain effects
associated with the Buffalo Ridge may locally increase gusts and/or
warm/dry downsloping effects.

Summer heat continues on Sunday and Monday, causing elevated fire
danger in the afternoons to early evenings. On Sunday, winds will be
notably weaker, reducing fire danger compared to today. Humidity
levels begin to increase with an approaching system on Monday, but
winds will be stronger again.

&&

.FSD WATCHES/WARNINGS/ADVISORIES...
SD...Red Flag Warning until 7 PM CDT this evening for SDZ040-055-
     056-062-067.
MN...Red Flag Warning until 7 PM CDT this evening for MNZ071-072-
     080-081-089-090-097-098.
IA...Red Flag Warning until 7 PM CDT this evening for IAZ001>003-
     012>014-021-022.
NE...None.

&&

$$

DISCUSSION...BP
AVIATION...Dux
FIRE WEATHER...BP