spc ac 211724
day 2 convective outlook
nws storm prediction center norman ok
1224 pm cdt tue apr 21 2026
valid 221200z - 231200z
...there is a marginal risk of severe thunderstorms for parts of the
high plains...
...summary...
severe thunderstorms capable of hail and gusty winds may develop
during the late afternoon and evening on wednesday across portions
of the high plains.
...synopsis...
a broad trough within parts of the northwest and great basin will
progress eastward through the day wednesday. the mid-level jet will
round the base of this trough and impact the northern high plains
during the evening overnight. a secondary mid-level jet will dig
into the southwest by early thursday morning. the upper-level ridge
across the plains will begin to break down and shift eastward. at
the surface, a deep surface low will track along the montana/canada
border. strengthening flow across the rockies will promote a
moderately strong lee trough. surface moisture will continue to
advect north and west during the period. richer moisture will
generally remain within the southern plains and adjacent high plains
with less certain moisture quality farther north.
...western nebraska...western south dakota...
with greater large-scale ascent and closer proximity to the surface
low, confidence in storm development is higher in these areas. the
main question will be the degree of moisture return that can occur
through the day. model guidance still varies widely in this regard.
dewpoints near 50 f are possible into southwest nebraska, but this
may occur towards 00z or later. farther north, dewpoints in the 40s
f may be the ceiling for late afternoon/early evening. a probable
scenario is that high-based convection develops within the terrain
of eastern wyoming/western south dakota and within the surface
trough. some intensification is possible as this activity encounters
greater surface moisture to the east. severe wind gusts will be the
main hazard given the steep low-level lapse rates and inverted-v
thermodynamic profiles. linear structures would be favored in south
dakota given the deep-layer flow orientation. a supercell or two
could occur in western nebraska, should storms form.
...southern high plains into western kansas...
with the synoptic trough lagging to the west, mid-level height falls
will be very weak during the afternoon. the dryline/surface trough
will be the focus for storm development. temperatures nearing 90 f
behind the dryline appear sufficient for an isolated storm or two to
develop. that said, some guidance does not develop any convection.
deep-layer shear will be roughly perpendicular to the surface trough
and mid-level lapse rates will be steep. storms that can develop
will be supercellular. large hail would be the main concern with
this activity.
...eastern montana...
high-based convection is possible in association with the deepening
surface low. dewpoints will not likely reach 40 f. gusty outflow
winds are possible, but potential for severe gusts is low.
..wendt.. 04/21/2026
click to get wuus02 ptsdy2 product
note: the next day 2 outlook is scheduled by 0600z