SPC 2000Z Day 1 Outlook
Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0253 PM CDT Fri Apr 22 2022
Valid 222000Z - 231200Z
...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS ACROSS THE
CENTRAL AND SOUTHERN HIGH PLAINS...
...SUMMARY...
At least isolated significant severe weather is possible across
portions of the High Plains late this afternoon and tonight. Very
large hail, damaging straight-line winds, and a few tornadoes are
anticipated.
...20Z Update...
Recent surface analysis depicts a deepening low over the central
High Plains, with surface pressure falls around 3-4 mb over the last
2 hours. A dryline currently extends from western NE southward
through western KS into far eastern NM. Some cumulus is beginning to
form in the vicinity of this boundary, although the character of
this cumulus suggests convective initiation is likely still an hour
or two away. This matches recent runs of the WoFS, which depicts
development around 21-22Z.
Overall forecast outlined in the previous outlook (discussed below)
remains unchanged, with no changes needed. Recent 19Z AMA and DDC
soundings shows very steep lapse rates in place, supporting strong
buoyancy. Kinematics will continue to improve as the upper trough
continues to approach from the west. As noted in the previous
discussion, all severe hazards are still expected, including very
large hail, strong wind gusts over 74 mph, and tornadoes.
..Mosier.. 04/22/2022
.PREV DISCUSSION... /ISSUED 1129 AM CDT Fri Apr 22 2022/
...Southern/central High Plains...
Early morning /12z/ upper-air analysis features relatively rich
mid/late-April moisture across the region, with 12+ C 850mb
dewpoints across western Kansas and all of west Texas
(DDC-AMA-MAF-DRT) with the moist axis roughly centered along 101W
longitude. Early/mid-morning visible satellite trends already depict
a relatively quick erosion of the southern High Plains stratus
field, particularly on its western edge near the New Mexico/Texas
border vicinity. This moisture is beneath a stout elevated mixed
layer and generally coincides with the early day mid-level warm axis
with 700mb temps 10-12C.
Ahead of the upper trough/polar jet spreading from the Southwest
Deserts toward the Four Corners area, robust surface cyclogenesis
will occur today across northeast Colorado toward western Nebraska
by evening. As mid-level height falls occur and mixing and
confluence/convergence increases near the dryline, current thinking
is that at least widely scattered storms will begin to develop by
around mid-afternoon within a north-south corridor spanning areas
from far west Texas to near/just west of the New Mexico/Texas into
southeast/east-central Colorado.
Although some warm-sector mixing/lowering of dewpoints can be
expected, mid 50s to low 60s F surface dewpoints are expected to
generally persist the east of the dryline, supporting a likely
intensification as storms progress eastward. 35-40 kt of effective
shear will support initial high-based supercells capable of very
large hail. Deep-layer/low-level shear will tend to increase through
early/mid-evening, while storms will also encounter increased
moisture content and less mixing. This should result in an increased
potential for tornadoes by early evening, while strong convective
wind gusts are also plausible.
A later round of separate convective development is likely by late
evening as the Pacific cold front moves eastward and impinges on the
western extent of the buoyancy plume near the
Nebraska/Colorado/Kansas border area. This should result in a
north/south-oriented convective line quickly spreading into western
portions of Nebraska/Kansas, while also expanding southward
regionally overnight. Very strong wind profiles should promote a
threat for severe wind and some hail, although duration and spatial
extent overnight will probably be limited by the pervasive cold
low-level theta-e advection in the warm sector, which will reduce
available CAPE with time.
...Far eastern Wyoming/western South Dakota/northwest Nebraska...
A tight baroclinic zone will lie to the north of the slow-moving
warm front/quasi-stationary frontal zone extending from the
deepening central High Plains cyclone. A narrow bent-back plume of
50s F surface dew points should be maintained beneath an initially
stout elevated mixed layer. It seems likely that a few surface-based
storms may ride along the boundary within an SRH-enriched
environment near the SD/NE border area, while additional storms are
possible farther west-northwest. Hodographs will be highly
elongated, yielding the potential for a longer-lived supercell or
two, with the main threat being significant large hail, although a
couple of tornadoes could also occur.
...Upper Midwest...
Pending some additional destabilization near a warm front, isolated
strong to severe storms could occur today near/east of an MCV
currently across eastern Iowa. Otherwise, additional potentially
severe development (mostly hail) is possible later tonight across a
broader part of the Upper Midwest in association with a low-level
warm theta-e advection regime. This potential will be supported by
steepening mid-level lapse rates attendant to an expanding Great
Plains elevated mixed-layer and adequate shear within the
cloud-bearing layer.
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