Damaging Wind in South Dakota, May 24, 2020

AREA FORECAST DISCUSSION
National Weather Service Sioux Falls SD
1038 PM CDT Sat May 23 2020

.SHORT TERM...(This Evening through Sunday)
Issued at 326 PM CDT Sat May 23 2020

Early this afternoon, a cold front has sparked convection out west
in the vicinity of the MT/WY/SD border. An upper shortwave aloft and
associated sfc low ejecting from the Rockies into the High Plains
tonight will progress eastward, tracking convection gradually across
the Dakotas and Nebraska and into the forecast area late tonight
through Sunday morning. With 0-6 km deep layer shear oriented more
parallel to the cold front with initial storms this afternoon and
evening in western SD/NE, expect storms to merge into one or several
complexes of storms. With northeastward storm motion and the
stronger mid level lapse rates, elevated instability, and moisture
remaining confined in close proximity to the cold front, convection
will take a while to reach the forecast area. The latest CAM
guidance has a complex progged to reach the MO River Valley of
central SD around midnight or as late as a few hours after; thus
expect the main severe weather threat to move into the region in the
predawn hours of Sunday morning and progress eastward across the
region early Sunday morning. Given the elevated nature of the storm
complex combined with 0-3km shear vectors quasi-parallel to the
front and precipitable water values peaking around 1.5 inches,
expect large hail, damaging winds, and locally heavy rainfall to be
the main threats.

Temperatures will only drop into the upper 50s to mid 60s tonight,
with clouds and warm air advection ahead of the sfc low tempering
nocturnal cooling. Sunday's temperatures should peak in the 70s with
increased humidity.

Sunday morning's complex of storms is expected to move east out of
northwest IA/southwest MN by mid day. However clouds and chances for
scattered showers and thunderstorms persist through much of the
Sunday with the inverted sfc trough/frontal boundary and an elevated
unstable layer remaining in the region. Amidst a moist airmass with
dew points in the mid to upper 60s, steep mid level lapse rates, and
adequate deep layer shear in the upper 20s to 40 kts, ingredients
will be sufficient for afternoon strong to severe thunderstorms. The
initial limiting factor appears to be meager but increasing broad
upper level ascent between shortwaves. Heading toward the evening,
severe weather threat increases as destabilization increases and low
level lapse rates steepen, as well as height falls from the
advancing longwave trough coupled increasing deep layer shear and a
weak shortwave disturbance or two would support better chances for
strong to severe storms across eastern NE and areas along and east
of the I-29 corridor.

.LONG TERM...(Sunday Night through Saturday)
Issued at 326 PM CDT Sat May 23 2020

Less than ideal weather for outdoor activities on Memorial Day as
cloudy weather persists amidst highs in the 60s to mid 70s. In the
vicinity of an approaching longwave trough, weak shortwave
disturbances and weak instability in southwesterly flow aloft will
continue to bring showers and isolated thunderstorms to the region
on Monday and Monday night. Rain is most likely to affect areas
along and east of I-29 for a longer duration Monday, but is
certainly possible for areas further west at times as well.

For Tuesday through the rest of the work week, the forecast is
mainly dry. The aforementioned longwave trough closes off over the
Southern Plains, inducing split flow aloft. Cannot rule out
scattered showers and storms along and east of the I-29 corridor on
Tuesday, but otherwise the forecast area is mainly under the
influence of drier zonal flow aloft with Gulf moisture blocked by
the closed low to the south. With large spread in the probabilistic
guidance and no significant influence to temperatures aside from
cloud cover, stuck with a blended solution yielding near to slightly
above normal temperatures.

&&

.AVIATION...(For the 06Z TAFS through 06Z Sunday night)
Issued at 1035 PM CDT Sat May 23 2020

Thunderstorms will move eastward across the area tonight into
Sunday morning. Some of the storms could be strong west of
Interstate 29 with large hail, gusty winds and heavy rain.
Ceilings will lower into the MVFR range behind the thunderstorm
activity and persist into Sunday afternoon. Additional
thunderstorms will be possible on Sunday evening, mainly through
the lower MO River corridor into northwestern IA.

&&

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

SHORT TERM...BP
LONG TERM...BP
AVIATION...JM

Hazardous Weather Outlook
National Weather Service Sioux Falls SD
619 PM CDT Sat May 23 2020

IAZ001>003-012>014-020>022-031-032-MNZ071-072-080-081-089-090-097-
098-NEZ013-014-SDZ038>040-050-052>071-242330-
Lyon-Osceola-Dickinson-Sioux-O'Brien-Clay-Plymouth-Cherokee-
Buena Vista-Woodbury-Ida-Lincoln-Murray-Cottonwood-Nobles-Jackson-
Pipestone-Rock-Dixon-Dakota-Beadle-Kingsbury-Brookings-Gregory-
Jerauld-Sanborn-Miner-Lake-Moody-Brule-Aurora-Davison-Hanson-
McCook-Minnehaha-Charles Mix-Douglas-Hutchinson-Turner-Bon Homme-
Yankton-Union-
619 PM CDT Sat May 23 2020

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

.DAY ONE...Tonight

Strong to severe thunderstorms are possible tonight. Large hail and
damaging winds are the main risks. Thunderstorms may produce locally
heavy rainfall, leading to ponding of water or minor flooding. The
higher risk of severe weather will be west Interstate 29.

.DAYS TWO THROUGH SEVEN...Sunday through Friday

Scattered thunderstorms are expected on Sunday evening. A few of
these storms could become strong to severe with large hail and strong
winds are the primary threats. The higher risk of severe weather will
be east of Interstate 29.

.SPOTTER INFORMATION STATEMENT...

Spotter activation may be needed tonight after midnight.