684
FXUS63 KFSD 102350
AFDFSD

Area Forecast Discussion
National Weather Service Sioux Falls SD
650 PM CDT Mon Jun 10 2024

.KEY MESSAGES...

- Weakening storms will push into locations along and west of
  the Missouri River this evening. Gusty winds are possible
  with the weakening storms.

- Severe weather remains possible on Wednesday but uncertainty
  remains regarding where storms develop.

- Near to above average temperatures are expected for the next
  week. The warmest day will be Wednesday with high temperatures
  into the 90s.

&&

.DISCUSSION...
Issued at 250 PM CDT Mon Jun 10 2024

Quiet conditions continue this afternoon as shortwave ridging
resides over the area aloft. An upper level wave on the heels of the
overhead ridge is pushing into western South Dakota. A cold front
tied to the upper level wave will serve as a focus for convection
initiation. Sufficient CAPE and shear are in place which will allow
storms to grow into a line of storms as they move eastwards.
However, the western edge of the warm sector will reside across
central South Dakota. The storms will outrun the warm sector this
evening. Thus, the storms are expected to weaken as they approach
the Missouri River. As the storms weaken, gusty winds are possible
in any outflow produced from the storms. While the storms will
continue to weaken into the evening and overnight hours, light
showers look to persist through the overnight hours. Light rainfall
amounts are expected with the showers ranging from a tenth or so
along the Missouri River to a few hundredths east of the river. Lows
overnight will fall to the 60s.

Tuesday will be a quiet day as upper level subsidence prevails on
the backside of the departing upper level wave. High pressure will
swing through the Northern Plains, keeping marginally breezy
northwest winds going for the day. 850 mb temperatures will reside
in the mid to upper teens tomorrow afternoon. Mixing this to the
surface will result in high temperatures into the 80s across the
forecast area. The lighter winds and warm temperatures will make for
a beautiful day for outdoor activities! Especially since humidity
will be lower, down to around 30-40%. Low temperatures will fall to
the upper 50s to low 60s overnight.

The next chance for strong to severe storms arrives on Wednesday as
a mid level wave pushes into the Northern Plains. A strong upper
level jet streak will reside overhead with the core of the jet
anchored over North Dakota. This will place the right exit region
over the forecast area. Given how this is a straight jet streak, the
four quadrant conceptual model will work in this scenario. However,
the low level jet (LLJ) will remain modest beneath the right
entrance region at 20-30 knots. The LLJ will further contribute to
warm air advection (WAA) across the Northern Plains / Upper Midwest
in tandem with the approaching mid level wave. While the right exit
region typically isn`t the quadrant that see`s severe weather,
sufficient lift in the low levels may be able to overcome the upper
level subsidence via the jets indirect thermal circulation. With the
upper level jet in the vicinity, adequate vertical shear will be in
place with 0-6 km shear values up to 40-50 knots. A quick look at
hodographs shows that vertical shear profiles remain mainly straight
with a large magnitude of shear above 6 km. This will result in
adequate updraft/downdraft separation, supportive of severe storms.
At the surface, southerly flow will result in mass response due to
the exit region of the jet which will pull higher moisture air
northwards. Dew points will moisten up to the 60s beneath very steep
mid level lapse rates on the order of 7-8 degrees C/km. This will
contribute to large instability on the order of 2,000-3,000 J/kg of
MLCAPE. A cold front will be passing through the afternoon hours,
providing a potential trigger for storm to develop on. The main
catch with this setup is the timing of the mid level wave. Medium
range guidance still varies on how fast the wave pushes through the
forecast area and struggles where convection develops. If the wave
pushes through the area faster, then a smaller area for severe
storms will be possible, mainly across southwest Minnesota into
central and eastern Minnesota as the nose of the LLJ will reside in
this area. If the wave is slower, then the severe threat will remain
over the bulk of the CWA as convection fires on or just ahead of the
cold front. Still too early to say which scenario is favored but a
look at cluster analysis shows the highest probabilities for
exceeding a tenth of an inch of rain  is across Minnesota from the
most favored cluster. Will continue to watch trends. In terms of
severe hazards, large to very large hail, damaging winds, and an
isolated tornado are all possible. Aside from storm chances,
Wednesday will be a hot day with high temperatures into the upper
80s and 90s with breezy southerly winds.

The end of the work week looks to be mostly quiet as high pressure
returns to the area. High temperatures will be a bit cooler in the
upper 70s to 80s with low temperatures falling to the 50s and 60s.
The next chance for rain will push into the area Friday night as
another upper level wave ejects into the Plains. As of now,
convection that does develop just east of the Rocky Mountains looks
to outrun the warm sector, keeping a low severe weather threat for
the CWA.

Confidence decreases going into the weekend as medium range guidance
shows increasing variance in the upper level pattern. For now, have
kept model blended PoPs through the weekend. In terms of high
temperatures, highs will remain in the 80s with lows falling to the
60s overnight.

&&

.AVIATION /00Z TAFS THROUGH 00Z WEDNESDAY/...
Issued at 650 PM CDT Mon Jun 10 2024

Showers and storms remain on-going across central South Dakota and
will continue to push eastward through the evening and overnight
period. That being said, expect instability to diminish along the
MO River, which should limit the severe threat along and east of the
James River. As alluded to in the previous discussion, a stray
lightning strike and brief wind gust may still be possible though
but confidence remains too low to include mention in the TAFs at
this time. Otherwise, look for winds to turn southeasterly as
showers exit the area early tomorrow morning, with direction
becoming northwesterly during the afternoon.

&&

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

&&

$$

DISCUSSION...Meyers
AVIATION...SST