SPC 0730Z Day 3 Outlook
Day 3 Convective Outlook
NWS Storm Prediction Center Norman OK
0226 AM CDT Wed Apr 20 2022
Valid 221200Z - 231200Z
...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS LATE FRIDAY
AFTERNOON INTO FRIDAY NIGHT ACROSS MUCH OF THE CENTRAL INTO PORTIONS
OF THE SOUTHERN GREAT PLAINS...
...SUMMARY...
One or two squall lines may evolve across parts of the central Great
Plains Friday afternoon into Friday night, posing a risk for hail
and strong, damaging wind gusts. Additional thunderstorm activity
spreading north of the lower and middle Missouri Valley into parts
of the Upper Midwest may pose a risk for severe hail.
...Synopsis...
Large-scale mid/upper troughing, with several embedded short waves,
appears likely to continue developing inland of the Pacific coast
during this period. Models continue to indicate that this will
include one significant perturbation accelerating northeast of the
lower Colorado Valley into the lee of the Colorado/Wyoming Rockies.
This is forecast to be accompanied by strong surface cyclogenesis
from the lee of the Front Range north-northeastward through central
South Dakota by late Friday night.
This will be preceded by a plume of warm elevated mixed-layer air
advecting through much of the Great Plains and Upper Midwest.
However, models continue to suggest that Gulf moisture return to the
deepening lee surface troughing may begin to become disrupted by
drying associated with low-level ridging building westward toward
the northwestern Gulf coast, beneath a prominent mid-level high
centered over the eastern Gulf States.
While the mid-level ridge axis initially extending to the
north-northwest of this high may gradually pivot across and east of
the Mississippi Valley, the western flank of the broad amplified
ridging may not shift east of the lower Great Plains until late
Friday evening.
...Great Plains into Upper Midwest...
Highest boundary-layer moisture, including surface dew points in the
mid 60s, may become focused along the warm frontal zone shifting
across and north/northeast of the lower and middle Missouri Valley
vicinity, and perhaps in a narrow corridor near the dryline across
west Texas. It appears that the plume of elevated mixed-layer air
will tend to overspread the warm front and provide increasing
inhibition, but this may be preceded by convection supported by warm
advection, which could pose a risk for severe hail.
Stronger/more widespread thunderstorm development seems more likely
to focus near the dryline perhaps as it is overtaken by an eastward
advancing cold front across the central Great Plains Friday evening.
However, to varying degrees, models suggest that this may be
preceded by convective initiation to the east of the dryline,
perhaps aided by a subtle impulse preceding the main upper trough.
This remains unclear, and could considerably impact boundary-layer
instability preceding the developing dryline/cold front convection.
Even so, modestly deep boundary-layer mixing, with CAPE in excess of
1000 J/kg near the dryline, will contribute to an environment with
storms initially posing a severe hail threat, before transitioning
to strong, damaging gusts. This should coincide with an upscale
growing line of storms aided by increasing forcing downstream of the
primary approaching short wave, and southerly 850 mb jet
strengthening from 50-70 kt Friday evening.
..Kerr.. 04/20/2022
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