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 1 Wind Risk
Area (sq. mi.)
Some Larger Population Centers in Risk Area
Kansas City, MO...St. Louis, MO...Overland Park, KS...Kansas City, KS...Topeka, KS...
Kansas City, MO...Overland Park, KS...Kansas City, KS...Topeka, KS...Olathe, KS...
SPC AC 241252
Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0752 AM CDT Thu Jun 24 2021
Valid 241300Z - 251200Z
...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS OVER PORTIONS
OF NORTHERN KANSAS...SOUTHERN NEBRASKA AND NORTHERN MISSOURI....
A corridor of severe weather (including destructive hail, severe
wind and a few tornadoes) is possible today into tonight near the
Kansas/Nebraska line, eastward over northern Missouri.
In mid/upper levels, a series of shortwave troughs from the northern
Rockies to the Great Lakes -- including a few that are convectively
generated/enhanced -- will contribute to the formation of a
positively tilted synoptic trough. By 12Z, the broader 500-mb
trough should extend from the northern High Plains across the Great
Basin, connecting to a low near (or just offshore) from the SFO
area. To its east, a somewhat confluent, nearly zonal pattern will
prevail across the central/northern Plains, Upper Midwest, and upper
Great Lakes. An MCV over IA, from an ongoing MCS over IA and
northern MO, is expected to move eastward across eastern IA and
northern IL today. The associated perturbation should weaken as it
crosses southern Lower MI, northern IN and northwest OH tonight.
West of the synoptic trough, a northern-stream shortwave trough --
apparent in moisture-channel imagery over the BC/AB Rockies -- will
move east-southeastward to the MT/AB/SK border region by 00Z, then
weaken and move more slowly southeastward over eastern MT tonight.
At the surface, the 11Z analysis showed a quasistationary frontal
zone just offshore from the Carolinas, arching across southern GA,
then becoming a weakening warm front over northern MS, northern AR
and central MO. The western limb of this boundary will become more
diffuse today as it moves northeastward over the mid Mississippi
Valley. A cold front was drawn from northwestern ON to near the MN
North Shore, through a weak low near MSP, across southeastern SD and
central/southwestern NE to eastern CO. By 00Z, that cold front
should extend from WI southwestward across IA to a low over central
KS, then to southeastern CO. By 12Z, the low should reach
central/eastern Upper MI and southeastern IA, becoming slow-moving
to stationary southwestward over northwestern MO, central KS and the
OK Panhandle. A dryline initially near the KS/CO border, and over
eastern NM, will mix eastward today to west-central/southwestern KS,
the eastern TX Panhandle, and the lower Pecos Valley area of west
TX. Cyclogenesis and frontogenesis also are expected this afternoon
and evening over eastern MT ahead of the northern-stream
...Central Plains to mid Mississippi Valley...
The ongoing MCS over southern IA and northern MO is moving into
lower boundary-layer theta-e on the cool side of the diffuse warm
front, but may produce isolated gusts near severe limits over the
remainder of the morning as it encounters a marginally favorable but
destabilizing boundary layer. An outflow boundary -- trailing
southwestward and westward from the complex across northern portions
of KS and MO -- will decelerate this morning, then retreat northward
Scattered thunderstorms are expected to form this afternoon near the
boundary, with isolated to scattered convection also occurring near
the dryline and perhaps part of the nearly cold front. Large to
giant hail is possible in early-stage convective evolution, when
supercells are most favored, with severe gusts and a few tornadoes
also possible (especially near the boundary). Clustering and
upscale organization to one or more complexes should occur through
the evening, concentrating the wind threat better.
Possible foci for initiation this afternoon and evening include the
boundary, cold front and dryline/lee trough. The outflow boundary
will be the main focus for severe potential today. In the absence
of substantial cloud cover, the air mass on both side of the western
and perhaps eastern portions of the boundary (KS and MO
respectively) will destabilize substantially today amidst strong
insolation and rich low-level moisture, with surface dew points
commonly in the upper 60s and 70s F, under favorable midlevel lapse
rates. Modified model soundings for along and just north of the
boundary indicate MLCAPE may reach 2500-4000 J/kg, while slightly
weaker (but still moderate-strong) buoyancy occurs to its south,
amidst stronger heating and deeper warm-sector mixing.
Meanwhile, with some reinforcement from the front, the surface flow
on the north side of the boundary will remain relatively backed,
leading to enlarged shear and storm-relative flow vectors in the
boundary layer. Modest mid/upper winds will impede venting and
likely contribute to messy/heavy-precip modes in fairly short order,
but the backed winds north of the boundary still may yield around
40-50-kt effective-shear magnitudes. The extent of outflow-boundary
return northward remains uncertain, and further mesoscale
adjustments to the outlook area (including tornado probabilities
tied largely to the vorticity/hodograph enhancement along and to its
north) are possible.
...Northern High Plains...
Widely scattered thunderstorms are expected to develop this
afternoon across portions of western through north-central/
northeastern MT, offering the potential for isolated, marginally
severe hail and gusts. This activity should form as a plume of
large-scale DCVA-related lift ahead of the shortwave trough
superimposes with a diurnally destabilizing boundary layer with
weakening MLCINH. Also contributing will be increasing low-level
convergence near the area of cyclogenesis. Additional convection
should develop over parts of eastern WY, western SD and northwestern
NE, near the Black Hills and along a lee trough, with potential for
isolated severe gusts for a few hours. Across the northern Plains
corridor, residual moisture (surface dew points 40s to 50s F) and
steep low/middle-level lapse rates will contribute to peak MLCAPE in
the 500-1000 J/kg range, atop deep/well-mixed subcloud layers.
Activity should diminish markedly this evening with near-surface
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