186
FXUS63 KFSD 220819
AFDFSD

Area Forecast Discussion
National Weather Service Sioux Falls SD
319 AM CDT Wed May 22 2024

.KEY MESSAGES...

- Breezy westerly winds today with gusts up to around 20 mph.

- Winds become southerly and strong for Thursday afternoon with
  gusts around 30 mph. Strongest winds expected along the James
  River Valley

- There is increasing potential for strong to severe
  thunderstorms Thursday night into Friday. Greatest threat
  with these storms will be large hail and damaging wind gusts.

- An active patter continues through the weekend and into next
  week with multiple chances for showers and thunderstorms.

&&

.DISCUSSION...
Issued at 311 AM CDT Wed May 22 2024

WEDNESDAY: Westerly flow aloft today as the low pressure system that
brought thunderstorms yesterday continues to move off to the north
into Canada. Clouds will also flow out as the morning continues. At
the surface, west-northwesterly winds remain on the breezy side
around 10-15 mph. Gusts will be around 15-20 mph, with the highest
gusts remaining east of I-29. Winds will become light as they turn
southerly overnight. A push of strong CAA early in the day will
limit our highs in the upper 60s to low 70s with lows in the
50s.

THURSDAY-FRIDAY: Mostly sunny skies and southerly winds bring a push
of WAA that will help Thursday warm into the upper 70s and 80s,
which is about 5 or so degrees warmer than normal for this time of
year. Winds will increase after sunrise due to an approaching low
pressure out of Wyoming tightening the SPG. Winds should peak around
20-25 mph with gusts up to around 30 mph. Strongest winds look to be
along the James River Valley in the mid-afternoon. Thursday night
into Friday morning brings the next chance for thunderstorms. 1500-
2500 J/kg of MUCAPE collocated with an elevated mixed layer
indicates the potential for convection. 0-6km bulk shear in the
40 kt range, with SRH in the 150 m2/s2 in the 0-1 km layer, and
around 200 m2/s2 in the 0-3 km layer indicate the potential for
initial updraft rotation. Steep lapse rates around 8 C/km in
both the low levels and in the mid-levels indicate air parcels
will accelerate quickly once triggered. If convection initiates
over central South Dakota, where the forcing is mostly
perpendicular, cells will be initially surface based and
discrete. Gradually growing upscale into a line and becoming
elevated as they move east. If they initiate over eastern South
Dakota, forcing is a little more muddled and instability is more
elevated, indicating elevated convection in more of a line/MCS.
Current CAMS favor the more central South Dakota initiation
scenario, and hold the strongest convection along and south of
I-90. With all of this in mind, I feel that the current SPC day
two outlook with a Slight risk (level 2 of 5) over central South
Dakota to be in good shape. The greatest threats with these
storms will be large hail (1.25-1.75 inches) and damaging wind
gusts. There remains some uncertainty in track, with the GFS and
ECMWF taking the low northeast faster than the Canadian which
brings it directly through southeastern South Dakota. Storms
should be clear of the area by Friday afternoon. Highs will be
cooler thanks to the CAA behind the storm system, reaching the
low to mid 60s. Lows will be in the 40s.

SATURDAY AND BEYOND: An active pattern continues through the weekend
and into next week. Saturday night into Sunday there is another low
pressure system ejecting out of Colorado that brings chances for
thunderstorms. Monday a low tracks out of Montana and Wyoming. Highs
will be around normal in the upper 60s to low 70s.

&&

.AVIATION /06Z TAFS THROUGH 06Z THURSDAY/...
Issued at 1018 PM CDT Tue May 21 2024

VFR conditions are expected through the overnight hours as winds
continue to quickly weaken.

Some mid-high level clouds will drift into areas west of the
James River at times, though this activity should dissipate for
Wednesday.

VFR conditions and light winds continue Wednesday with a
reasonable risk for afternoon CU developing.

&&

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

&&

$$

DISCUSSION...AJP
AVIATION...Dux