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000
FXUS63 KFSD 131936
AFDFSD

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

.KEY MESSAGES...

- Very warm, dry, and windy conditions continue to lead to
  widespread high to very high fire danger Saturday. Red flag
  conditions continue into early Saturday evening east of I-29.

- Well above normal temperatures continue Sunday and Monday,
  with the greatest risks for fire danger focused on Monday as
  winds gust over 30 mph at times in the afternoon.

- High confidence in rainfall arriving Monday night and
  continuing into Wednesday. Area average rainfall totals may
  reach between 0.50" and 2.00" by Wednesday morning.

- Some potential for strong to severe convection Monday evening
  and early overnight. Marginally severe hail will be the
  greatest risk, with lower end risk for strong winds Monday
  evening.

- Cooler conditions are expected from Wednesday through Friday.

&&

.DISCUSSION...
Issued at 228 PM CDT Sat Apr 13 2024

THIS AFTERNOON: A hot, dry, and breezy day across the region, as
temperatures soar into the 80s in most locations.  Slightly enhanced
surface dew points in the 40s have advected northeast out of
Nebraska today, but even with the touch more moisture, we`re still
likely to see RH values fall to critical levels.  See separate fire
weather discussion for more details about what falls ahead in the
forecast.

TONIGHT: A weak wave will exit Wyoming and northern Colorado later
this evening. Despite being mostly moisture starved, a few high
based showers could develop and try to track eastward towards the MO
River valley later this evening.  For now, given the dry airmass in
place, will keep PoPs out of a mentionable range.  Otherwise, a weak
surface front sprawled across the Dakotas this afternoon will since
southeast overnight, bringing northerly winds and low-lvl cold air
advection to the Tri-State area after midnight.

SUNDAY: A perfect day is on tap for the region thanks to the
influence of high pressure moving through North Dakota. Temperatures
in the afternoon are likely to rise into the upper 70s to 80s, and
have nudged highs a bit warmer south of I-90.  Winds stay light
through the day, but dew points may fall a bit further than
previously thought.

MONDAY: Eyes begin to turn towards a large upper trough moving
towards the Plains late Monday and Tuesday.  Late Sunday night, a
lead wave ejects into the Dakotas, with a bit of speed convergence
on the LLJ developing scattered shower and a few thunderstorms
in central South Dakota which should track north and away from
the CWA in the morning. A rather gusty day is then anticipated
through Monday as the surface pressure gradient increases. While
I`ve tamed down the NBM winds slightly, we may still see
widespread sustained winds and gusts just under advisory levels.
Have also trended dew points down slightly, especially east of
I-29 through the day. A persistent easterly wind is likely to
tap into the drier air reservoir hanging around across northern
Illinois and southern Wisconsin through the day.

MONDAY NIGHT: The big question into Monday night will be how quickly
low-lvl moisture can return to the MO River valley in the evening.
GFS/ECMWF/CMC all bring higher levels of 850mb moisture transport
out of the lower MO river valley into the evening hours. The NAM
however is still suggesting more of an easterly low-lvl fetch,
bringing moisture northward a bit slower.  If the moisture can reach
the area, then sounding do suggest sufficient moisture for
convection to develop late Monday afternoon and continue
developing northward Monday evening through the MO River valley
into central Iowa. Long thin CAPE profiles sitting around
1200-1400 J/KG, gradually thicken as additional low-lvl moisture
arrives into the evening, potentially leading to isolated to
scattered strong storms south of I-90 into early overnight.
Shear profiles remain marginal, with only modest increases of
vertical winds at the top of the effective sounding. Some
lingering mid-lvl dry air however could signal some early wind
gusts in storm development/collapse. Convection begins to pull
northeast after midnight through Tuesday morning, though broad
upper diffluence and continued low-lvl speed convergence may
keep elevated convection going all the way to the MO River at
times.

TUESDAY: There still remains quite a bit of variance in model data
in how the upper low and resultant surface low develops and
tracks into KS/NE late Monday night. It`s fairly certain that
widespread convection will develop near the surface low given
strong PVA and arrival of 90+ knot 500 mb jet rounding the base
of the trough. This convection is likely to track north towards
the area on Tuesday, prompting nearly widespread 90%+ PoPs. The
severe weather risk by this time should have diminished,
however some ensemble guidance is suggesting potential for a
rapid 1-2" of rainfall. As the upper low tracks northeast, we`ll
watch where the dry slot tracks and then where secondary
deformation rain band forms. Still quite a bit of disagreement
in model guidance on where these features fall, but a fairly
steady rain may persist into Wednesday morning in some areas.

Total QPF from deterministic models remains on the higher end
of guidance. However ensembles continue to also show high
probabilities for widespread rain, with the highest
probabilities focused along the MO River (due to Monday evening
convection) and then east of I-29 (due to secondary convection
Tuesday).

0.50":  GEFS 90-100%, EPS 100%, CMC 90-100%
1.00":  GEFS 70-80%, EPS 80%, CMC 70-80%
2.00":  GEFS 30-40%, EPS 30-40%, CMC 10%

WEDNESDAY-FRIDAY: Temperatures will cool considerably for the middle
and end of the work week as deeper troughing moves into the Plains.
Latest trends continue to lower temperatures below normal in most
locations for the second half of the week. Occasional shortwaves
embedded within the westerly to northwesterly flow could produce
slight risks for showers. However there is no consistency in
guidance to suggest any favored times.


&&

.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 230 PM CDT Sat Apr 13 2024

Despite some increasing dew points, temperatures have risen into
the 80s in most locations, dropping area relative humidity
values between 22 and 30% on average. The strongest wind gusts
remain focused east of I-29 and will continue to slowly weaken
by early evening.

Conditions on Sunday remain favorable for burning. While
relative humidity values may fall as low as 20% at times, a
light northerly wind is only expected. In fact the winds in the
lowest 4000 ft of the atmosphere will be quite weak, which may
make dispersal of smoke plumes not as favorable.

Conditions on Monday are expected to be near critical to
critical. An increasing pressure gradient leads to 20+ mph
sustained winds through the day with afternoon gusts pushing 30
to 35 mph. Dew points will be slow to rise through the day,
with areas of southwest Minnesota expected to see RH values fall
near 25 percent in the afternoon. Widespread very high GFDI
values are likely.


&&

.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...Dux
AVIATION...Dux