650
FXUS63 KFSD 171916
AFDFSD

Area Forecast Discussion
National Weather Service Sioux Falls SD
216 PM CDT Mon Jun 17 2024

.KEY MESSAGES...

- Continued uncertainty for severe weather risks today, given
  cloud cover, lingering showers/storms, and the surface warm
  front displaced well south of where previous models had
  projected. May see renewed potential for elevated storms late
  this afternoon and evening, mainly north of I-90.

- A progressive front moves through on Tuesday, bringing yet
  another risk for strong storms and locally heavy rainfall.
  Brief bursts of 60 mph winds and marginally severe hail
  possible.

- An unsettled week is ahead, with numerous thunderstorm risks
  into next weekend. The risk for locally heavy rainfall will be
  possible each day, with slightly more muted severe weather
  risks with lower shear.

&&

.DISCUSSION...
Issued at 204 AM CDT Mon Jun 17 2024

TONIGHT:  Convection continues to track east across the Tri-State
area.  Generally the severe weather risks have lessoned as the
strong mass convergence really gave no opportunity for storms to
stay very discrete. Most guidance has also been focused far too
north through the night, with the true effective low-lvl front
focused south of I-90. Perhaps some residual severe weather
risks will be possible along the Missouri River and then into
portions of NW Iowa into Southern Minnesota, where instability
is a bit higher, DCAPE remains nearly 1000 J/KG, and effective
shear is AOA 40 KTs. However the greatest risk tonight will
remain in the form of heavy rainfall. At this point, see no
reason why convection will jog northward as some of the high
resolution guidance suggests. Also, stronger shortwave energy
continues to approach north central Nebraska, which will travel
along the elevated boundary and continue the focus for heavy
rain along and just north of the Missouri River and then further
east into northern Iowa through 12Z.

TODAY: We`ll need to wait for the Nebraska shortwave to slide east
before some weakening of deeper lift takes place. This may not
happen until nearly mid-morning. However, with broad southwest
flow and continued overrunning of the elevated boundary,
persistent shower and thunderstorm development may continue
north of the surface front through at least early to mid
afternoon. Speaking of that surface front, it`s current location
south of the CWA may remain stationary until afternoon when
some gradual retreat will begin in the afternoon. Convection
risks later this afternoon and evening remain extremely
conditional, partially due to continued capping over the CWA
through the day, and the absence of deep synoptic lift. For now,
will keep PoPs lower into the late afternoon hours, and
temperatures cooler through the day due to cloud cover.

TONIGHT:  With the increase of the LLJ early in the evening, this
could pose a risk for elevated convection to develop along and
north of the retreating warm front over eastern and northeastern
SD and western Minnesota. An additional focus point would be
along a north to south oriented cold front in central South
Dakota. However, unless a subtle wave sneaks through the Plains
(ala the ECMWF) the best synoptic forcing is likely to take
shape northwest of the CWA, so will only maintain a low chance
PoP. The return of southerly surface flow behind the retreating
warm front is likely to keep overnight low temperatures very
warm and humid through the region.


TUESDAY AFTERNOON-WEDNESDAY NIGHT: Uncertainty on where the surface
cold front ends up Tuesday afternoon, but most guidance keeps
this in our area (along/east of I-29) with the main surface low
off to the north. Plenty of convergence along the front with
lift by the evening hours as mid level wave and upper jet begin
to track over the eastern half of the forecast area. Lots of
warm and moist air ahead of the surface front; however,
soundings show a fairly capped environment so afternoon/evening
convection may be more elevated and tied to either the 850 mb or
700 mb front. Regardless, storms during Tuesday afternoon
through night could be strong to severe. Main threats would be
large hail and heavy rainfall. Can`t rule out strong wind gusts,
but this looks to be a secondary threat especially if storms
are elevated. Prevailing storm motion is essentially parallel to
the front so training storms could be a concern if the front is
more slow moving. PWATs approach 2" which with days of
rainfall, additional heavy rain could quickly pose issues with
flooding. Stay weather aware.

Showers and storms linger through Wednesday night as a couple of
weak waves pass across the southwesterly flow regime and are
supported by the right entrance of the upper jet. Some uncertainty
with the subtle waves moving through the overall flow pattern. Not
much in the way of instability during this time, so severe weather
Wednesday into Wednesday night currently looks unlikely. Cooler
temperatures look to prevail.

THURSDAY ONWARD: Unsettled continues to be the theme of the forecast
into next weekend with the blocking high remaining in place over the
Mid Atlantic to TN Valley. Numerous waves/troughs swing through the
mid level pattern, with the upper jet either overhead or just north.
Models vary in the timing/location of each wave, but generally
expect shower/storm chances to continue. Temperatures near
normal.&&

.AVIATION /06Z TAFS THROUGH 06Z TUESDAY/...
Issued at 1127 PM CDT Sun Jun 16 2024

Storms have developed as of 17.04z from just north of KFSD
stretching southwest into northwestern NE. Expect storms to
continue developing and slowly moving northeast through the
overnight hours. Large hail and heavy rainfall are possible.
Expect MVFR and lower conditions with any storms. MVFR to
possibly IFR stratus expected tomorrow with additional rounds of
showers and storms through the period. Lower confidence in
convective timing after daybreak Monday. Winds shift to more
southerly through the period with gusts up to 30 knots. Could
see some low level winds shear area wide after sunset Monday
(18.01-02z) but given the expected gusts have omitted for now.

&&

.AVIATION /18Z TAFS THROUGH 18Z TUESDAY/...
Issued at 144 PM CDT Mon Jun 17 2024

Low confidence forecast with regard to persistence of MVFR
stratus early in the period, as well as timing/location of
thunderstorm chances through the next 12-18 hours. Most likely
scenario lifts current line of thunderstorms with relatively
brief but very heavy rain northeast through southwest MN and the
Iowa Great Lakes. Additional scattered storms will be possible
through the later afternoon and evening, mainly north of the
I-90 corridor.

Broader clearing is expected through the overnight hours, but
could see MVFR stratus again develop after sunrise Tuesday with
a strong push of low level moisture from the south ahead of an
approaching cold front. The front will trigger additional storms
as it moves near and east of I-29 after this TAF period.

A strong southerly low level jet is expected to develop this
evening and persist through just after sunrise Tuesday. This
will result in low level wind shear, with speeds as high as
45-50+ kt within the low level jet.

&&

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

&&

$$

DISCUSSION...Dux
AVIATION...JH