166
FXUS63 KFSD 022029
AFDFSD

Area Forecast Discussion
National Weather Service Sioux Falls SD
329 PM CDT Thu May 2 2024

.KEY MESSAGES...

- Low level stratus continues to clear from west to east this
afternoon, allowing for sunshine to return. Isolated showers remain
possible north of I-90 through sunset.

- Rain returns Friday afternoon and continues through Saturday
morning. Rainfall amounts between a quarter to up to a half an inch
are expected. Ponding on roads along with minor stream and river
flooding are again possible.

- A strong low pressure system looks to bring renewed storm chances
on Monday but details are uncertain as of now.

&&

.DISCUSSION...
Issued at 328 PM CDT Thu May 2 2024

Current satellite shows low level stratus beginning to clear from
west to east this afternoon, allowing sunshine to return. The edge
of the stratus is currently sitting over I-90 but will continue to
push east for the rest of the daylight hours. A weak boundary has
sparked a few weak showers along highway-14 but could continue to
produce light showers down to about I-90 through sunset. Minimal
rain is expected from the showers. A weak surface ridge will slide
through the area this evening and night which will allow for light
winds and low temperatures to fall to the upper 30s to low 40s
overnight.

Friday begins on the quiet side but rain chances will return to the
area as a cold front tied to an upper level wave pushes into the
area. Cloud cover will gradually build in but 850 mb temperatures up
between +3 to +7 degrees C should allow for highs to warm to the
upper 50s to about 70 degrees. Rain looks to begin for locations
towards central and south central South Dakota after noon as the
front initially pushes into the forecast area. This front will be
highly frontogenetic and result in strong lift along it. Vertical
cross sections also show strong omega (upward motion) and negative
equivalent potential vorticity (EPV) above the front. This signals
that a tight band of rain will develop right along the front. The
front will be a bit slow to move southeastwards as it looks to reach
the I-29 corridor around midnight. As the front hits the interstate,
the frontogenetical forcing will wane a bit leading to a more diffuse
and weaker rain band. However, a mesoscale convective system (MCS)
looks to develop in Nebraska and push eastwards through the night.
While the MCS looks to stay south of the area, the MCS`s northern
precipitation shield looks to connect with the weaker rain band and
bring additional rainfall to locations along and east of I-29. Still
some uncertainty though as the MCS evolution is not definite just
yet. Slight shifts in its track can result in more or less rain for
this area. As of now, between a quarter of an inch to up to around a
half an inch is expected generally along the James River Valley.
Isolated higher amounts are possible. East of the James, rainfall
totals look to be closer to around a quarter of an inch. This can
still change though depending on the track of the MCS. Ensemble
guidance shows parts of northwest Iowa with a 30-40% chance for
exceeding a quarter of an inch, therefore continuing this chance.
While this is not as much rain compared to our last event, saturated
soils will yield the potential for ponding on roadways along with
minor flooding on some rivers and streams.

Any chance for rain will come to an end Saturday morning, leaving
dry conditions for the rest of the weekend. Highs will remain in the
60s and lows will fall to the 40s and 50s, warmest Sunday night. The
next chance for rain will come on Monday as a strong upper level
wave ejects from the Rockies into the Plains. Medium range guidance
is very consistent in this wave taking on a negative tilt as it
pushes into the Northern Plains. This will result in strong upper
level divergence and set the stage for more rain chances. Ensembles
show a near 100% chance for exceeding a tenth of an inch of rain and
a 30-60% chance for exceeding half an inch of rain. The ensembles
also show a 30-60% chance for exceeding 500 J/kg of CAPE, suggesting
the potential for thunderstorms. CIPS analogs do have some
probabilities for strong to severe storms, highest across the
central Plains. However, mesoscale details remain highly uncertain
at this time. As such, have left model blended PoPs but this system
will continue to be monitored over the coming days. Outside of storm
chances, Monday will be a warm day with highs in the upper 60s and
70s with lows falling to the 40s.

The same upper level wave will occlude and spin over the Northern
Plains through the middle of next week. This will keep chances for
rain going throughout this period of time along with near seasonal
highs in the 60s.

&&

.AVIATION /18Z TAFS THROUGH 18Z FRIDAY/...
Issued at 1224 PM CDT Thu May 2 2024

MVFR/IFR ceilings blanket the majority of the area early this
afternoon. Sprinkles to very light showers remain possible beneath
the stratus, mostly north of highway-20. As such, have added VCSH to
KHON and KFSD`s TAF for the first few hours of the TAF period. Good
news is that the stratus is clearing from west to east and will push
out of the area by this evening.

Clear skies will prevail after the stratus exits the area. Light
northwest winds will turn out of the southwest overnight and
continue for the rest of the TAF period. A cold front will begin to
move into the are to end the TAF period.

&&

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

&&

$$

DISCUSSION...Meyers
AVIATION...Meyers