393
FXUS63 KFSD 161737
AFDFSD

Area Forecast Discussion
National Weather Service Sioux Falls SD
1237 PM CDT Wed Apr 16 2025

.KEY MESSAGES...

- Warm, dry, and breezy conditions today results in elevated to
  near critical fire danger this afternoon and evening -
  especially along and east of I-29.

- Shower and thunderstorm chances return Thursday morning into
  Friday morning. The highest chances (50-70 percent) are east
  of Interstate 29. Some storms may be strong to severe,
  especially Thursday afternoon and evening, mainly along and
  southeast of a line from Yankton to Windom.

- Periodic low precipitation chances and near normal
  temperatures return for the weekend into early next week.

&&

.DISCUSSION...
Issued at 335 AM CDT Wed Apr 16 2025

NOW-TONIGHT: Pleasant start to the morning with temperatures in the
30s and 40s. Mostly clear skies, although beginning to see cirrus
develop and advect in from the west. Southeasterly winds are
occasionally gusting around 20 to 25 mph.

For the rest of today, south to southeast flow continues to
increase. Gusts around 20-30 mph (strongest east of I-29) are
expected with peak mixing and as the SPG compresses. Warm and dry
air leads to RH values plummeting to 20-25% over the area; however,
the lowest RH and highest winds are offset. Elevated to near
critical fire danger is expected today, especially along and east of
I-29 where the winds will be the strongest. Take precautions to
prevent fire start today. For now, will hold off on any Fire Weather
Headlines and allow the day shift to monitor trends. Highs today
will warm into the 70s.

Clouds increase tonight as the first wave approaches the region.
Further west, elongated mid and upper level positively tilted
troughing deepens into the Four Corners region bringing
southwesterly flow aloft. Southerly surface flow and WAA keep
temperatures mild tonight, with lows in the mid 40s to mid 50s.

THURSDAY: As the first vorticity max/mid level short wave approaches
and a weak surface low slides into central SD, expect isolated to
scattered showers and thunderstorms to develop. Soundings do show a
cap in place, which may hinder development. CAPE values around 500-
1000 J/kg along with support from the LLJ increasing shear, and
steep mid level lapse rates over 7.5 deg C/km could lead to quarter
sized hail - if storms can break the cap. Convection could also be
more elevated in nature (toward the 700 mb front) if we can`t fully
break the cap, which would still maintain the quarter sized hail
threat during the morning through about noon.

Shower and thunderstorm chances return during the afternoon and
evening hours Thursday, although uncertainty in timing and coverage
of development remains. This is mainly due to some timing issues in
the frontal boundaries and embedded short waves, in addition to the
robust cap in place - evident on soundings across the region. CAMs
are struggling in resolving the coverage and timing of showers and
storms as well, leading to lower confidence. However, if the cap can
break, storms may become strong to severe quickly in the warm
sector/just ahead of the surface cold front. Greatest risk of severe
storms looks to be along and southeast of a line from Yankton to
Windom during the afternoon and evening hours. MUCAPE values are
roughly 1000-1500 J/kg, combined with 0-6 km shear values at or
above 35 knots and mid level lapse rates near/above 7.5 deg C/km
would support large hail (half dollar size). Strong wind gusts to
60 mph are also possible with DCAPE values up to 700 J/kg.

Highs on Thursday will be dependent on how quickly the cold front
moves through, but generally expect highs in the 60s west of the
James River to the 70s east. Showers and thunderstorms linger into
the overnight behind the surface front, with lows in the 30s.

FRIDAY: Showers and isolated storms may linger through the first
half of the day on Friday. Cooler and breezy with strong northerly
winds. Highs in the 40s and 50s. Lows in the 20s and 30s.

SATURDAY-WEDNESDAY: Mid and upper level trough continues to slide to
the east during the first half of the weekend. By Sunday, another
surface low passes to the south of our forecast area, which may
bring some light rain chances to the region. Guidance varies in the
evolution of this system as well as the next short waves early next
week, so may see periodic low rain chances during this time. Left
the NBM as is given low confidence. Temperatures remain near
normal.

&&

.AVIATION /18Z TAFS THROUGH 18Z THURSDAY/...
Issued at 1237 PM CDT Wed Apr 16 2025

Mostly clear skies for the first half of the period, with clouds
increasing after 17.09Z as a wave approaches from the west. Winds
will be southeasterly between 10-15 kts, with gusts up 20 kts. The
strongest winds along and east of I-29, where winds of 15-20 kts are
expected with gusts up to 25 kts. Winds begin to shift as the
aforementioned wave approaches, gradually becoming northerly from
west to east through the morning and afternoon. Behind the wave
winds will increase after the end of the period, to 25-30 kts gusts.
A brief period of LLWS is possible at KSUX Thursday early morning,
however confidence is too low to include in the TAF cycle.

Ceilings will decrease with the increasing clouds, but look to
remain in the VFR to low VFR category. Areas east of the South
Dakota/Minnesota/Iowa border could see ceilings down to MVFR for a
brief period Thursday morning. Isolated to scattered showers and
thunderstorms are possible Thursday morning through about noon. A
second round of possibly stronger showers and thunderstorms are
expected for Thursday afternoon and evening, though there remains
some uncertainty due to frontal passage timing.

&&

.FSD WATCHES/WARNINGS/ADVISORIES...
SD...None.
MN...None.
IA...None.
NE...None.

&&

$$

DISCUSSION...SG
AVIATION...AJP