Severe Thunderstorm Warning 251, NWS Sioux Falls, SD

AREA FORECAST DISCUSSION
National Weather Service Sioux Falls SD
1018 PM CDT Thu Jul 21 2022

.SHORT TERM...(This Evening through Friday)
Issued at 305 PM CDT Thu Jul 21 2022

The main story for tonight will be increasing thunderstorm chances
over portions of the area. This will be triggered by increasing
midlevel war air advection as a low level jet develops over central
NE late this evening, veering to the east during the overnight
hours. Most CAMs have elevated thunderstorms developing through the
lower MO river corridor around 06Z, then expanding to the east
through parts of southeastern SD, northwestern IA, and southwestern
MN during the later overnight hours. Model instability continues to
vary quite a bit among model soundings, with the GFS on the lower
end with MUCAPE less than 1000 j/kg, while the HRRR/RAP are closer
to 1200 j/kg, and lastly the NAM continuing to be the most aggressive
with MUCAPE of 1500 j/kg or slightly higher. Effective bulk shear
will be running around 40 kts or more, so cannot rule out a few
severe storms if higher instability verifies, with the main threats
being large hail and damaging winds - which is in line with the
current SPC Marginal risk generally south of Interstate 90.

Convection then tapers off by mid morning on Friday as the low level
jet weakens and veers eastward. This will lead to a a very warm day
with NAEFS ensembles pointing toward 700/850 mb temperatures in the
the 90th percentile with respect to climatology, and highs are
looking to reach the lower to mid 90s. A couple CAMs (primarily the
NAM Nest) want to produce some convection over our far southeastern
IA zones on Friday evening with some low level convergence in that
vicinity, but this seems unlikely so kept with only slight chance
pops for that time frame. If something were to develop, there will
be enough instability and shear that an isolated severe storm would
be possible.

.LONG TERM...(Friday Night through Thursday)
Issued at 305 PM CDT Thu Jul 21 2022

Our next best chance of thunderstorms will come on Saturday as a
cold front slides across the region during the day. Models are still
struggling a bit with timing of the front, with the GFS, which has
consistently been the fastest solution, now being the slowest
solution of the models. At the same time, the NAM has now sped up to
look like the previous GFS solutions - so confidence remains rather
low on timing. In any event, there is a potential for severe storms
on that day, mainly in the afternoon and evening, especially if a
slower solution verifies. There looks to be plenty of instability
and bulk shear in place during that time frame, so scattered severe
storms would definitely be possible. Of course timing of the front
and any convection will play a part in high temperatures, but
looking at 90s to even 100 at this point.

With the boundary well into the Central Plains by Sunday, it will be
a pleasant and cooler day with less humidity as dew points fall into
the 50s. Highs will be in the lower to mid 50s.

Monday will be another seasonable day, though a little more humid as
a southerly low level flow returns to the region. This will lead to
a warmer day on Tuesday with highs back into the mid to upper 80s,
and a possible uptick in convection chances later on Tuesday into
Wednesday as a frontal boundary slides through the area - though
model differences remain in regard to timing.

Behind this system, cooler temperatures will return for Wednesday
and Thursday with lessening convection chances on those days.

&&

.AVIATION...(For the 06Z TAFS through 06Z Friday night)
Issued at 1016 PM CDT Thu Jul 21 2022

Scattered showers and thunderstorms are expected into early Friday
morning. The better chances should be across parts of southwest MN
and northwest IA later tonight, the better chances from about 9z
to 12z. While severe weather is unlikely a few stronger storms
with lightning and locally heavy rain are likely. Any showers and
storm activity should be gone by 15z. Outside of any thunderstorms
VFR conditions are expected.

&&

.FSD WATCHES/WARNINGS/ADVISORIES...
SD...NONE.
MN...NONE.
IA...NONE.
NE...NONE.
&&

SHORT TERM...JM
LONG TERM...JM
AVIATION...08

Hazardous Weather Outlook
National Weather Service Sioux Falls SD
1146 AM CDT Thu Jul 21 2022

MNZ071-072-080-081-090-097-SDZ038>040-052>056-221700-
Lincoln-Lyon-Murray-Cottonwood-Jackson-Pipestone-Beadle-Kingsbury-
Brookings-Jerauld-Sanborn-Miner-Lake-Moody-
1146 AM CDT Thu Jul 21 2022

This Hazardous Weather Outlook is for southwest Minnesota, central
South Dakota and east central South Dakota.

.DAY ONE...This afternoon and tonight.

Scattered showers and thunderstorms are possible overnight. Severe
weather is currently not expected.

.DAYS TWO THROUGH SEVEN...Friday through Wednesday.

Additional chances for thunderstorms arrive Saturday and perhaps
again early to middle of next week. Thunderstorms on Saturday may
have the potential to be strong to severe.

.SPOTTER INFORMATION STATEMENT...

Spotter activation is not expected at this time.

IAZ001>003-012>014-020>022-031-032-MNZ089-098-NEZ013-014-SDZ050-
057>071-221700-
Lyon-Osceola-Dickinson-Sioux-O'Brien-Clay-Plymouth-Cherokee-
Buena Vista-Woodbury-Ida-Nobles-Rock-Dixon-Dakota-Gregory-Brule-
Aurora-Davison-Hanson-McCook-Minnehaha-Charles Mix-Douglas-
Hutchinson-Turner-Lincoln-Bon Homme-Yankton-Union-
1146 AM CDT Thu Jul 21 2022

This Hazardous Weather Outlook is for northwest Iowa, west central
Iowa, southwest Minnesota, northeast Nebraska, south central South
Dakota and southeast South Dakota.

.DAY ONE...This afternoon and tonight.

Showers and thunderstorms are possible late this evening through the
overnight hours. While the overall risk for severe weather is low,
an isolated stronger storm may be capable of hail to around the size
of half dollars and wind gusts to around 60 mph.

.DAYS TWO THROUGH SEVEN...Friday through Wednesday.

A very small chance of thunderstorms exists Friday afternoon and
evening, mainly across northwest Iowa. Additional chances for
thunderstorms arrive Saturday and perhaps again early to middle of
next week. Thunderstorms on Saturday may have the potential to be
strong to severe.

.SPOTTER INFORMATION STATEMENT...

Spotter activation is not expected at this time.