Tornadoes and Flash Flood in South Dakota, May 7, 2022

Area Forecast Discussion...UPDATED
National Weather Service Aberdeen SD
1228 PM CDT Sat May 7 2022

.UPDATE...
Issued at 1224 PM CDT Sat May 7 2022

See updated aviation discussion below.

UPDATE Issued at 1012 AM CDT Sat May 7 2022

No major changes made to the forecast this morning. The area of
clouds that has been in place over the central CWA is now
beginning to dissipate, but more clouds approaching from the west
will overspread the area late this morning and this afternoon. No
changes made to winds or temperatures at this time.

&&

.SHORT TERM...(Today through Sunday Afternoon)
Issued at 359 AM CDT Sat May 7 2022

Southerly winds will be on the increase by late morning and expect
speeds to be strong and gusty through the afternoon. Went with a
50/50 blend of NBM/NBM90 for winds today, which did give some low
end criteria for parts of the CWA. Straight NBM90 winds do give a
bit more coverage of advisory speeds, but with the strength of the
capping inversion in place today, was a bit hesitant to go all-in
with the NBM90. Held off on a Wind Advisory at this time but will
certainly need to monitor obs throughout the day for a possible
need for a headline. Tonight, a 50 knot low-level jet sets up over
the Coteau region, which almost always brings rather strong winds
in that area, so made the Coteau an edit area and leveraged
higher end wind here, such as NBM90.

Low-level moisture will also begin increasing today, modestly. Only
expecting 50s dewpoints, but it's something nonetheless. Will also
be watching the progress of the surface trough this afternoon into
central SD as this is expected to be the focus for thunderstorm
development. Strong capping will be in place across the CWA today,
but models do show erosion over central SD as the mid-level height
falls approach. The surface convergence should also aid in help
breaking the cap. Expecting some degree of scattered areal coverage
of storms from central ND into central SD. Then, activity will move
eastward overnight aided by the low-level jet. Overall instability
is lacking a bit with MLCAPE/MUCAPE this afternoon/overnight
generally around 500-1500 J/KG based on deterministic and ensemble
output. Although, lapse rates are fairly steep and 0-6km shear is
strong - over 50 knots. All this would support potential for a
couple strong to perhaps severe storms, but would like to see more
instability to be overly concerned about overall impacts/threats.

.LONG TERM...(Sunday Evening through Friday)
Issued at 359 AM CDT Sat May 7 2022

A somewhat amplified flow pattern aloft is forecast across the CONUS
through the long term. Energy will gradually carve out an upper trof
over the western CONUS early in the period. That trof is then
expected to slowly retrograde as upper ridging exerts itself over
the Southern Plains/mid to lower Mississippi valley. By the end of
the period, energy is then expected to eject northeast into the High
Plains and Northern Plains. The models are in general agreement with
this scenario, but of course differ with the details. The best
chance for rain/storms for the early part of the forecast will be
Sunday night into Monday morning. At that time an induced sfc low is
expected to track northeast across the eastern part of SD. WAA/lift
ahead of this system combined with elevated instability should result
in some nocturnal convection over the eastern Dakotas and western
MN. After that a post-frontal drier and more stable airmass advects
into the forecast area for a couple days, with nil chances for rain.
Toward the end of next week it may start to get more active again.
However, a pretty warm EML to the tune of H7 temps exceeding 10C
advects into the forecast area, and MLCIN values increase greatly.
So, convection formation may be hampered to a decent degree for at
least part of the time period toward week's end. Temperatures
overall look to be normal or above for the entire period.

&&

.AVIATION...(For the 18Z TAFS through 18Z Sunday Afternoon)
Issued at 1224 PM CDT Sat May 7 2022

Terminals KABR,KATY,KPIR,KMBG

VFR conditions will prevail through much of the afternoon. A
frontal boundary will track from west to east across the area late
this afternoon and this evening, and will be the focus for showers
and thunderstorms. Some of the storms may become severe, with
gusty winds and large hail being the main threats. Periods of
IFR/MVFR cigs and vsbys will be possible with the stronger storms.
The precipitation will exit the area overnight. VFR conditions
will then prevail across central South Dakota, but IFR/MVFR cigs
will remain across northeastern South Dakota and west central
Minnesota through the morning on Sunday.

&&

.ABR WATCHES/WARNINGS/ADVISORIES...
SD...None.
MN...None.
&&

UPDATE...Parkin
SHORT TERM...TMT
LONG TERM...TDK
AVIATION...Parkin

Hazardous Weather Outlook
National Weather Service Aberdeen SD
424 AM CDT Sat May 7 2022

MNZ039-046-SDZ003>011-015>023-033>037-045-048-051-080930-
Traverse-Big Stone-Corson-Campbell-McPherson-Brown-Marshall-Roberts-
Walworth-Edmunds-Day-Dewey-Potter-Faulk-Spink-Clark-Codington-Grant-
Hamlin-Deuel-Stanley-Sully-Hughes-Hyde-Hand-Jones-Lyman-Buffalo-
424 AM CDT Sat May 7 2022 /324 AM MDT Sat May 7 2022/

This Hazardous Weather Outlook is for west central Minnesota,
central South Dakota, north central South Dakota and northeast
South Dakota.

.DAY ONE...Today and tonight.

Scattered thunderstorms are expected across central South Dakota late
this afternoon, with activity pushing eastward through the evening
hours. A few storms could become strong to severe with hail being the
main threat.

.DAYS TWO THROUGH SEVEN...Sunday through Friday.

A chance for thunderstorms exists across the area Sunday and Monday,
although the severe threat looks minimal at this time.

.SPOTTER INFORMATION STATEMENT...

Spotter activation is not expected at this time.

TMT