029
FXUS63 KFSD 301741
AFDFSD

Area Forecast Discussion
National Weather Service Sioux Falls SD
1241 PM CDT Thu May 30 2024

.KEY MESSAGES...

- Multiple chances for showers and thunderstorms continue into
  next week. Locally heavy rainfall is possible today through
  the weekend.

- A Marginal Risk (Level 1 of 5) for severe storms is in place
  for much of our area today. Damaging wind gusts to 60 mph and
  quarter sized hail are the main threats, with timing between 3
  and 9 PM. Additional strong to severe storms may occur over
  the weekend, especially Sunday afternoon through Sunday night.

- Near normal temperatures and periodic breezy conditions
  expected through the weekend, with above normal temperatures
  forecast to prevail heading into next week.

&&

.DISCUSSION...
Issued at 346 AM CDT Thu May 30 2024

TODAY THROUGH FRIDAY NIGHT: Convection is on-going this morning
across western SD into central NE as the first short waves tracks to
the east. Cloud cover is keeping temperatures above average, with
most in the mid 50s to lower 50s. Already seeing wind gusts this
morning around 20-35 mph from the southeast as the surface pressure
gradient tightens and we mix into the stronger LLJ.

Biggest challenge with this portion of the forecast is how
precipitation will evolve. Main issue lies in which model scenario
will play out. One solution brings a slower fropa, but earlier
initiation of the WAA wing of precipitation. The second solution
speeds up the cold front, and keeps most of the precipitation
development near/just ahead of the front. Have generally
narrowed the highest pops from the previous forecast a bit,
trying to split the difference between the two main scenarios.
Storms should begin to develop into a more defined line just after
daybreak close to the MO River valley (further west if tied more
to the WAA), tracking east with the WAA and front. Severe
weather is not expected this morning with instability lacking,
although storms could produce some brief heavy rainfall.

The next area of precipitation begins to develop once again
near/west of the MO River during the early to mid afternoon hours,
with CAMs keeping this activity tied closer to the surface cold
front with a secondary 700mb wave and WAA. These showers and storms
move east through the evening hours, at least until the front
stalls/washes out. Could see a couple of isolated strong to severe
storms with this round of storms. With southeasterly flow ahead of
the cold front, moisture return and warming could be enough (despite
AM showers/storms) to bring in near/over 1000 J/kg of CAPE, with the
NAM/RAP/Canadian solutions showing more. Although 0-6 km bulk shear
is lacking during the early part of the day, this is expected to
increase to near or above 30 kts through the evening as the surface
front and next mid level wave approach. Mid level lapse rates around
6-6.5 deg C/km could support some hail to quarter size, but hail
threat may be tempered slightly by freezing levels around 12kft.
However, with DCAPE values over 500 J/kg, think that wind gusts to
60 mph would be the main threat. Timing for severe weather would
likely be between 3 and 9 PM.

Today`s mid level wave splits tonight into Friday morning,
stagnating over IA. This along with the washed out surface front
keeps isolated to scattered showers and storms in place Friday into
Friday night until another approaching wave can push things along.
Most of the activity should remain close to the relatively better
forcing aloft in northwestern IA and southwestern MN. However, with
the next short wave edging in from the west, can`t rule out some
isolated activity west of the MO River in the afternoon hours.

Locally heavy rainfall is possible through tomorrow night as PWAT
values climb near to above 1.5". Could see localized ponding and
some rises on smaller tributaries. Flash flooding risk looks low at
this time with guidance across the area above 1.5" per hour, and
very low and isolated probability (< 20%) of hourly rainfall rates
above 0.5" and 1.0 inches. The caveat to this threat would be if
multiple storms train over the same area, especially east of I-29
where most of the 6 hourly FFG is closer to 2.25" than 3"+. Through
Friday night, probability of areas east of I-29 receiving more than
1" of rain is around 40%. Most of the area has moderate to high (>
40%) chances of seeing more than 0.5" in this time, with the lowest
chances in south central SD.

Outside of precip chances, expect highs in the 70s with lows in the
50s to near 60 - with cloud cover keeping things a bit more mild and
limiting the diurnal range somewhat. Winds will be breezy from the
south to southeast through this evening. As the front moves through
and washes out, lighter and somewhat variable winds are expected
into Friday night.

SATURDAY THROUGH MID NEXT WEEK: Those with weekend plans (including
travel) will want to keep an eye on the forecast, with unsettled
pattern leading to continued shower/storm chances. A few storms
could be strong to severe and produce locally heavy rain.

Friday night`s wave/trough axis in western SD will lift to the north
into the day on Saturday with another wave across KS/MO. This split
should provide a break in widespread precip chances through at least
the first half of the day. Next short wave ejects out of the Rockies
and moves into the forecast area by Saturday evening in the quasi
zonal flow. Expect showers and storms to develop ahead of the wave
with the initial push of WAA. More widespread chances with a couple
rounds of showers/storms on Sunday into Sunday night as the more
defined trough axis and surface low move into our area.

Strong to severe storms are possible, with the better chances Sunday
afternoon through Sunday night. Ensemble data continues to show
moderate to high probability (50%+) of CAPE above 1500 J/kg. Highest
probabilities are from the GFS and Canadian ensembles; however, the
ECMWF ensemble still shows a moderate to high (near 40% to 80%)
chance of this value being exceeded. Shear also looks to be on the
increase as well, which could also support severe weather. Again,
there are some issues with timing and location of any development,
so keep an eye on the forecast if you have outdoor or travel plans
this weekend.

Continued chances for locally heavy rainfall, although impacts will
be dependent on what happens today through Friday night. Ensembles
show a moderate (40-60%) chance of more than 0.5" of rain in 24
hours Sunday into Monday for areas east of the James River (greatest
chances in southwestern MN). High (> 85%) chances for PWAT values to
exceed 1".

Models vary in timing and strength of the next wave/trough Tuesday,
but expect more shower and storm chances. Depending on the track and
evolution of this system, additional strong to severe storms may be
possible, but very low confidence at this time. Although details
vary on strength and timing, guidance indicates ridging and surface
high pressure mid week could provide at least a brief reprieve from
showers and storms.

Temperatures remain near to above normal, with a couple of days in
the 80s possible early next week with a short lived ridge. Lows in
the 50s and lower 60s. Periodic breezy conditions prevail.

&&

.AVIATION /18Z TAFS THROUGH 18Z FRIDAY/...
Issued at 1241 PM CDT Thu May 30 2024

Scattered showers and storms continue across the region, with
additional development forecast to occur this afternoon and evening
ahead of an advancing cold front. A few storms may become strong to
severe, with damaging gusts up to 60 MPH and quarter size hail being
the primary hazards. Cigs and vsbys may also be reduced to MVFR
levels at times. In regard to winds, expect breezy S/SE gusts to
gradually diminish this evening, allowing light and variable winds
to prevail overnight. Otherwise, look for showers to linger along
and east of I-29 through daybreak Friday and perhaps mid-morning,
with dry conditions expected elsewhere. Winds during this time will
shift to the northeast.

&&

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

&&

$$

DISCUSSION...SG
AVIATION...SST