540
FXUS63 KFSD 302004
AFDFSD

Area Forecast Discussion
National Weather Service Sioux Falls SD
304 PM CDT Tue Apr 30 2024

.KEY MESSAGES...

- Strong to severe storms remain on track for this afternoon.
  Large hail from quarter/half dollar size is expected for most
  of the area. The largest hail, up to 2 inches in diameter,
  remains possible across the highway-20 corridor. Damaging
  winds to 70 mph and an isolated chance for a tornado will
  continue for the entire area through this evening. Brief heavy
  rain is also possible which could result in minor flooding.

- A Tornado Watch is in effect for Dakota, Woodbury, and Ida counties
  until 10 pm this evening.

- A second round of additional rainfall is possible Wednesday
  night where rainfall amounts may exceed a half an inch of
  rain. Locations south of I-90 have a 50-80% chance for
  receiving rainfall totals greater then a half an inch.

- Seasonal temperatures with highs into the 60s and 70s and lows
  down to the 40s will continue through the weekend. &&

.DISCUSSION...
Issued at 303 PM CDT Tue Apr 30 2024

Showers and storms have developed across the area early this
afternoon. Instability has been struggling a bit which has kept a
more limited severe storm threat early this afternoon. However,
current satellite shows some clearing ahead of the line which will
help to destabilize thermal profiles a bit more. This looks to allow
instability to increase up to around 1,000 J/kg of MLCAPE, highest
along and south of highway-20. This same area has the potential for
2 inch hail given the sufficient instability and shear in place.
North of this area, a line of storms has developed along I-29 and
will push east through the evening hours. Damaging winds up to 70
mph are expected along with large hail up to quarter to half dollar
size. An isolated tornado remains possible with the line as it
pushes through the forecast area. Aside from the severe component of
these storms, brief heavy rain is possible with any storm that
develops which could yield minor flooding. Storms will persist
through the afternoon hours before pushing east of the area this
evening. Isolated showers and storms are possible after the line of
storms passes through but these storms are not expected to be
severe. These additional showers and storms will diminish this
evening as instability runs out, leaving quiet conditions for the
overnight hours. Low temperatures will fall to 40s overnight.

Wednesday will be a mostly quiet day during the daylight hours.
Surface high pressure will slide through the area resulting in light
winds along with slightly cooler high temperatures up to the 60s.
Cloud cover will be building overhead throughout the day as the next
chance for rain arrives Wednesday evening. Another upper level wave
will push out of the Rockies and into the Northern Plains. The cold
front from Tuesday will reside well south of the area Wednesday
evening but will slowly push northwards through the night. While the
surface front will not reach the forecast area, the elevated front
at 850 mb will as warm air advection (WAA) strengthens in response
to a strengthening low level jet (LLJ). Moisture transport will
increase between 925-850 mb while precipitable water (PWAT) raise to
the 90th percentile of climatology per NAEFS ensemble. Soundings do
show elevated instability up to a few hundred J/kg. Given the
lacking instability, severe storms are not expected. Ensembles
continue to support heavier rainfall as the Euro and Canadian
ensembles have a broad 50-80% chance for exceeding a half an inch of
rain with the highest probabilities south of I-90. The GFS ensemble
is a bit of an outlier as it has its highest probabilities for
exceeding the same amount of QPF across the Nebraska, Iowa, and
Missouri border.

Any chance for rain will push east of the area on Thursday,
resulting in mainly dry and slightly cooler conditions with highs
warming to the upper 50s to mid 60s. The next chance for rain comes
on Friday as medium range guidance shows another shortwave trough
rotates into the Northern Plains. However, surface winds will be out
of the west/northwest which will keep drier low level air in place
and thus keep instability to a minimum. Ensembles do vary on
precipitation potential so have stuck with model blended PoPs as of
now. Outside of rain chances, high temperatures look to warm to the
60s with lows falling to the 40s.

The weekend looks to be mostly dry as upper level ridging prevails
across the Northern Plains. High temperatures will warm to the 60s
and 70s with lows only falling to the 40s and 50s. The next chance
for rain looks to come early next week as ensembles show another
upper wave ejecting into the Plains. Too much uncertainty resides
with the wave evolution regarding rain and storm chances. Again have
left model blended PoPs. Aside from rain chances, high temperatures
look to remain in the 70s for the new work week.

&&

.AVIATION /18Z TAFS THROUGH 18Z WEDNESDAY/...
Issued at 1231 PM CDT Tue Apr 30 2024

Current satellite shows scattered cloud cover mixed in with scattered
showers and storms across the area early this afternoon. Cloud bases
reside at VFR levels as of now but do expect expect that to change
quickly as strong to severe storms develop. These strong to severe
storms look to develop around 2 pm west of I-29 and race eastwards
through the rest of the afternoon hours. Large hail is expected as
storms initially form but storms will quickly grow into a line and
transition to a damaging wind threat. While ceilings have been kept
at VFR levels in all TAFs, even during storms, brief drops to
IFR/MVFR ceilings are possible. Winds will turn out of the northwest
as a cold front passes through the area while gusts strengthen up to
around 30 knots. Storms look to exit the area no later then 7 pm
this evening, allowing quiet conditions to return for the rest of
the TAF period. Winds will be waning through the evening hours
before going light and variable tomorrow morning to finish out the
TAF period.

&&

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

&&

$$

DISCUSSION...Meyers
AVIATION...Meyers