Probability of a tornado within 25 miles of a point. Hatched Area: 10% or greater probability of EF2 - EF5 tornadoes within 25 miles of a point.
Day 2 Tornado Risk
Area (sq. mi.)
Area Pop.
Some Larger Population Centers in Risk Area
5 %
19,964
68,681
Rapid City, SD...Rapid Valley, SD...
2 %
83,701
460,257
Garden City, KS...North Platte, NE...Pierre, SD...Spearfish, SD...Sturgis, SD...
Probabilistic Damaging Wind Graphic
Probability of damaging thunderstorm winds or wind gusts of 50 knots or higher within 25 miles of a point. Hatched Area: 10% of greater probability of wind gusts 65 knots or greater within 25 miles of a point.
Day 2 Wind Risk
Area (sq. mi.)
Area Pop.
Some Larger Population Centers in Risk Area
15 %
149,705
886,004
Rapid City, SD...Bismarck, ND...Garden City, KS...North Platte, NE...Aberdeen, SD...
SPC AC 221727
Day 2 Convective Outlook
NWS Storm Prediction Center Norman OK
1227 PM CDT Sat May 22 2021
Valid 231200Z - 241200Z
...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF
THE CENTRAL AND NORTHERN HIGH PLAINS INTO THE NORTHERN PLAINS...
...SUMMARY...
Severe thunderstorms capable of severe gusts and large hail are
possible across portions of the northern Great Plains tomorrow
afternoon and evening.
...Synopsis...
A mid-level trough will eject into the northern High Plains, with
surface lee troughing encouraging the northward advection of a warm,
relatively moist airmass across the northern and central CONUS
tomorrow. Deep-layer ascent associated with the approaching trough,
and strong surface heating with upslope flow will support scattered
strong to severe thunderstorm development along the lee of the
Rockies, from the U.S./Canada to Mexico borders. Upper ridging and
surface high pressure will dominate much of the Ohio Valley into the
Southeast, with deep-layer northwesterly flow prevailing across the
Northeast, where scattered storms (some strong to locally severe)
are likely tomorrow afternoon ahead of a cold front.
...Northern High Plains into the Dakotas...
Weak surface low development is expected along a warm front across
the northern High Plains during the morning hours, with the low
expected to be positioned across western SD by afternoon peak
heating. Ahead of the low, low 60s F dewpoints will reach northern
SD during the afternoon, overspread by 7+ C/km mid-level lapse
rates, supporting widespread 1500 J/kg MLCAPE. 30-50 kts of
effective bulk shear is expected ahead of an eastward moving cold
front given ample speed shear. However, troposheric flow will be
meridional, with unidirectional wind shear above 700 mb expected
across the central/northern Plain states tomorrow. As such, storms
should rapidly grow upscale into linear segments, with damaging
winds and large hail expected as the primary severe hazards. Ahead
of the surface low and along the warm front across portions of
western SD, relatively greater backing of the surface winds will
contribute to locally better low-level veering vertical wind
profiles. Modestly enlarged hodographs/200+ m2/s2 effective SRH will
promote some tornado threat with circulations embedded in line
segments, along with any storms that can manage to stay discrete
ahead of the line.
...Central into the southern High Plains...
Low-level convergence due to upslope flow and afternoon peak heating
will encourage scattered thunderstorm development along the lee of
the higher terrain. Ahead of the storms, a moist low-level airmass
(characterized by low 60s F dewpoints) will contribute to 1000-1500
J/kg MLCAPE. Relatively weak deep-layer and low-level shear will
foster cold pool mergers with multicellular clusters/transient
supercells upscale-growing into line segments an hour or so after
maturity. Large hail may occur with the initial, more discrete storm
modes, with damaging gusts becoming more prevalent after upscale
growth.
...Northeast...
Mid 60s F dewpoints beneath 5.5-6 C/km mid-level lapse rates will
foster 500-1000 J/kg MLCAPE ahead of the cold front, where at least
isolated thunderstorm development is expected tomorrow afternoon.
While tropospheric flow will be unidirectional (northwesterly),
40-50 kts of effective bulk shear suggests that some of the storms
may become organized/strong. As temperatures warm into the 80s F,
modest boundary-layer mixing may encourage downward momentum
transport of the stronger flow aloft, with a couple of damaging
gusts possible with the stronger storms.
..Squitieri/Gleason.. 05/22/2021
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