Severe Thunderstorm Warning 236, NWS Sioux Falls, SD

AREA FORECAST DISCUSSION
National Weather Service Sioux Falls SD
1201 PM CDT Tue Jul 5 2022

.SHORT TERM...(Today and Tonight)
Issued at 404 AM CDT Tue Jul 5 2022

After a mainly quiet holiday night, things look to become more
active this afternoon. Today will be another very hot day across the
region with high temperatures yet again in the 90s and even around
100 degrees, with the highest temperatures poised to be along the MO
River vicinity. This coincides well with where 850 temperatures are
the warmest in the mid 20s over the MO River. Muggy conditions
remain as dewpoints stay in the upper 60s to mostly 70s today,
contributing to hot heat indices maxing out around 105 degrees. With
little change in temperatures and humidity, have not made any
changes to the current heat headlines.

There are a couple of different scenarios that may play out regarding
convective initiation and evolution. Previous 00z guidance showed
continuing convection from Montana pushing into the forecast area
by early this afternoon. However, some of the latest 06z guidance
is showing that complex coming out of Montana weakening before it
gets into southeastern South Dakota and instead fires convection
off of an approaching mid level wave coming up from the southwest.
For now, favor the convective complex scenario coming out of
Montana as the majority of guidance still agrees with it. This
includes the HREF as it depicts a swath of >50 percent of >30
knots of 4hr max wind speed streaking in from Montana through
southeast South Dakota, far northwestern Nebraska, and northwest
Iowa. If the less likely scenario that the HRRR is showing comes
to fruition, may see more scattered storms but still expect cold
pools to merge between storms and create messy clusters. Can't
rule out the risk of localized flooding possible as the NAEFS
ensemble has PWATs in the 97.5th percentile.

Regarding today's environment, models still struggle to pin point
where the quasi-stationary boundary sets up today but has come into
more agreement that it will set up somewhere between highway 20 and
I-90. Northeasterly to easterly flow is likely north of the boundary.
While this typically is not a wind that is conducive for advecting
moisture into our area, surface observations show dew points into
the 60s and 70s across Minnesota this morning, keeping more than
sufficient moisture locked in north of the boundary. Atop of the low
level moisture, mid level lapse rates between 700-500mb will be at
or above 8 degrees Celsius/ km. This will support very large to
extreme instability at or above 2500 J/kg across the entire area,
contributing to large, thick CAPE profiles as per sounding analysis.
Parcels will be able to accelerate very quickly in the vertical in
such an unstable environment, supporting very strong thunderstorm
updrafts. Very large DCAPE in excess of 1200 J/kg, possibly higher
will accompany the already high instability. Despite the high DCAPE,
0-3 km shear is sufficient at around 30 knots but is not oriented
orthogonally to the incoming system from Montana, reducing the
strength of the cold pool. Do think that the extreme DCAPE may be
able to overcome this to keep strong gusts to 75 mph possible.

Models show mainly long and straight hodographs as with little
curvature in the low levels. 0-1 km shear is below 10 knots so do
not think that a tornado is likely. However, still cannot rule out
an isolated tornado if storms pick up additional helicity along the
boundary. Given such long and straight hodographs, 0-6 shear is
around 40 knots, mainly north of the boundary which is supportive of
supercell or supercell structures. Looking further aloft, speed
shear increases as winds above 300 mb strengthen to above 60 knots.
This will create sufficient shear aloft that will advect liquid
hydrometeors away from parent updrafts, allowing for efficient hail
growth within the hail growth zone. Hail up to 2 inches in diameter
will be possible IF discrete to semi-discrete storms can form either
along the boundary or ahead of the main system.

With the more likely scenario as shown by the 00z guidance, should
see storms become more cold pool dominate as they track through the
forecast area as overall shear weakens south of I-90 and especially
south of highway-20. The main timeframe for severe weather looks to
be between 12 pm to 9 pm this afternoon and evening.

.LONG TERM...(Wednesday through Monday)
Issued at 404 AM CDT Tue Jul 5 2022

Heat comes down a bit on Wednesday with highs in the 80s to up to 90
degrees but dew points remain in the 60s and 70s. Given the
persistent muggy environment, storm chances are possible but there
remains uncertainty in how Tuesday's storm will affect what happens
on Wednesday. Still looks like a decent enough environment as
ensembles show >70% chance for CAPE values over 1000 J/kg along with
0-6 km shear values in excess of 20-30 knots. PWAT's remain high as
NAEFS climatology pushes PWAT values into the 99.5th percentile.

Upper level ridge looks to slightly flatten during the middle of the
week before another ridge builds on its heels. Ensembles remain
consistent in developing another ridge by the end of the week, still
centered around the 4 corners region. This places the Northern
Plains in northwest flow aloft. While downstream of a ridge
typically is not the most favorable location for storms, continued
monsoonal waves riding down the downwind side of the ridge will keep
the persistent chances for showers and storms going through the
weekend.

&&

.AVIATION...(For the 18Z TAFS through 18Z Wednesday afternoon)
Issued at 1155 AM CDT Tue Jul 5 2022

A line of strong to severe storms will move through the area this
afternoon into the early evening. Wind gusts of 70 to 90 mph will
be possible with this line. MVFR and IFR conditions are likely
within the stronger storms. The chance for thunderstorms will
linger past sunset into tonight with lower confidence on
convective chances tomorrow morning. There may be some MVFR and
IFR conditions in stratus and fog with the better chances in
southwest MN later tonight.

&&

.FSD WATCHES/WARNINGS/ADVISORIES...
SD...Heat Advisory until 8 PM CDT this evening for SDZ065>071.

MN...NONE.
IA...Heat Advisory until 8 PM CDT this evening for IAZ012>014-020>022-
     031-032.

NE...Heat Advisory until 8 PM CDT this evening for NEZ013-014.

&&

SHORT TERM...Meyers
LONG TERM...Meyers
AVIATION...08

Hazardous Weather Outlook
National Weather Service Sioux Falls SD
457 AM CDT Tue Jul 5 2022

IAZ001>003-MNZ071-072-080-081-089-090-097-098-SDZ038>040-050-052>064-
061000-
Lyon-Osceola-Dickinson-Lincoln-Murray-Cottonwood-Nobles-Jackson-
Pipestone-Rock-Beadle-Kingsbury-Brookings-Gregory-Jerauld-Sanborn-
Miner-Lake-Moody-Brule-Aurora-Davison-Hanson-McCook-Minnehaha-
Charles Mix-Douglas-
457 AM CDT Tue Jul 5 2022

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

.DAY ONE...Today and tonight.

Another hot and humid day is forecast to prevail today, as heat
indices rise into the 90s. Could even see a few locations approach
100 degrees. In addition to this, expect showers and storms this
afternoon and evening.

Storms that become strong to severe may be capable of producing
damaging winds up to 75 mph and hail up to 2 inches in diameter.
These storms may also be capable of producing 2 to 4 inches of
rain in short period of time, which may result in localized areas
of flash flooding, especially across urban areas.

.DAYS TWO THROUGH SEVEN...Wednesday through Monday.

Another round of storms may be possible Wednesday, though chances
remain largely conditional on how the activity from late Tuesday
evolves. Therefore, we encourage you to continue monitoring the
forecast for the latest updates.

.SPOTTER INFORMATION STATEMENT...

Spotter activation will likely be needed from noon to 9 pm today.

IAZ012>014-020>022-031-032-NEZ013-014-SDZ065>071-061000-
Sioux-O'Brien-Clay-Plymouth-Cherokee-Buena Vista-Woodbury-Ida-Dixon-
Dakota-Hutchinson-Turner-Lincoln-Bon Homme-Yankton-Union-
457 AM CDT Tue Jul 5 2022

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

.DAY ONE...Today and tonight.

Another hot and humid day is forecast to prevail today, as heat
indices rise into the 90s to lower 100s. In addition to this, expect
showers and storms this afternoon and evening.

Storms that become strong to severe may be capable of producing
damaging winds up to 75 mph and hail up to 2 inches in diameter.
These storms may also be capable of producing 2 to 4 inches of
rain in short period of time, which may result in localized areas
of flash flooding, especially across urban areas.

.DAYS TWO THROUGH SEVEN...Wednesday through Monday.

Another round of storms may be possible Wednesday, though chances
remain largely conditional on how the activity from late Tuesday
evolves. Therefore, we encourage you to continue monitoring the
forecast for the latest updates.

.SPOTTER INFORMATION STATEMENT...

Spotter activation will likely be needed from noon to 9 pm today.

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PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE SIOUX FALLS SD
217 PM CDT TUE JUL 5 2022

..TIME...   ...EVENT...      ...CITY LOCATION...     ...LAT.LON...
..DATE...   ....MAG....      ..COUNTY LOCATION..ST.. ...SOURCE....
            ..REMARKS..

0210 PM     TSTM WND GST     WOONSOCKET              44.05N 98.27W
07/05/2022  E80 MPH          SANBORN            SD   EMERGENCY MNGR

&&

SST

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE SIOUX FALLS SD
218 PM CDT TUE JUL 5 2022

..TIME...   ...EVENT...      ...CITY LOCATION...     ...LAT.LON...
..DATE...   ....MAG....      ..COUNTY LOCATION..ST.. ...SOURCE....
            ..REMARKS..

0205 PM     TSTM WND GST     3 S CORSICA             43.38N 98.41W
07/05/2022  M60 MPH          DOUGLAS            SD   MESONET

            MESONET STATION 304 SD RWIS CORSICA.

&&

SST

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE SIOUX FALLS SD
220 PM CDT TUE JUL 5 2022

..TIME...   ...EVENT...      ...CITY LOCATION...     ...LAT.LON...
..DATE...   ....MAG....      ..COUNTY LOCATION..ST.. ...SOURCE....
            ..REMARKS..

0205 PM     TSTM WND GST     4 ESE FORESTBURG        44.01N 98.03W
07/05/2022  M59 MPH          SANBORN            SD   MESONET

            MESONET STATION 6 SD RWIS FORESTBURG.

&&

SST

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE SIOUX FALLS SD
225 PM CDT TUE JUL 5 2022

..TIME...   ...EVENT...      ...CITY LOCATION...     ...LAT.LON...
..DATE...   ....MAG....      ..COUNTY LOCATION..ST.. ...SOURCE....
            ..REMARKS..

0210 PM     TSTM WND GST     1 WSW FAIRFAX           43.02N 98.90W
07/05/2022  M63 MPH          GREGORY            SD   MESONET

            MESONET STATION EW7290 BUTTE 8NNW.

&&

SST