SPC AC 051944
Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0244 PM CDT Sun Jul 05 2020
Valid 052000Z - 061200Z
...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS THE
Severe thunderstorms are expected through this evening across the
Northern Plains, including northeast Wyoming to the Dakotas and
The previous outlook remains on track, and no changes have been made
with this update cycle. Please see the previous discussion below
.PREV DISCUSSION... /ISSUED 1153 AM CDT Sun Jul 05 2020/
...Northern Plains - southern MT/northeast WY to northwest MN...
Scattered thunderstorms are expected to develop this afternoon along
and near the front over the Dakotas, moving into a very moist and
unstable warm sector, while widely scattered thunderstorms initially
form on the higher terrain of southern Montana and northern Wyoming
within a post-frontal environment. In both regimes, supercells and
organized multicells will be possible, with large hail and severe
wind gusts as the primary hazard.
Strong destabilization is expected along an eastward-advancing
front, with 2500-3500 J/kg MLCAPE plausible especially across
northern South Dakota into eastern North Dakota/northwest Minnesota.
Low- to middle-level flow will be modest, but convective
organization should be aided by ventilating anvil-level winds, as
200-500-mb layer flow strengthens with the approach of the mid/upper
trough. Isolated large hail cannot be ruled out relatively early in
the convective cycle, before activity congeals into clusters with a
continued hail/wind potential into this evening.
Farther west across the northern High Plains, moisture will be more
limited behind the front, but still sufficient amidst steep
low/middle-level lapse rates to support surface-based convection
away from the mountains. Activity should move into a well-mixed and
diurnally heated boundary layer supporting maintenance of hail/gusts
to the surface. The northeasterly flow behind the front will
elongate hodographs and augment the deep shear, beneath stronger
mid/upper-level winds than experienced by frontal convection farther
east. Forecast soundings show effective-shear magnitudes potentially
reaching 50-60-kt. When combined with MLCAPE in the 1000-1500 J/kg
range, supercells capable of large hail can be expected through
early/mid evening. The storms may ultimately merge/cluster with one
or more small MCSs continuing into/across South Dakota late tonight.
...Southern High Plains...
On the western fringe of multiple MCVs from southeast Colorado into
the Texas Panhandle (and related lingering cloud cover/some
precipitation), widely scattered thunderstorms should redevelop late
this afternoon across eastern New Mexico/southeast Colorado into
west/northwest Texas. While some hail cannot be entirely ruled out,
isolated severe-caliber wind gusts should be the primary hazard,
particularly given the potential for some upscale growth/linear
organization as they spread southeastward into the Texas South
Widely scattered to scattered thunderstorms are expected this
afternoon, particularly near a southeastward-advancing cold front
and a preceding/southward-extending weak surface trough. Sufficient
low-level moisture is present to support a narrow corridor of
500-1000 J/kg MLCAPE. Although low-level shear will be weak, veering
with height will contribute to 30-40-kt effective shear and
quasi-straight low/middle-level hodographs. This suggests a blend of
multicell and somewhat-organized supercell modes capable of isolated
severe hail and locally damaging wind gusts.
Widely scattered thunderstorms are expected to develop and intensify
across the region today within a moist/unstable air mass, with
upwards of 2000-3000 J/kg MLCAPE expected across the region. Some of
the stronger storms this afternoon through early evening will be
capable of localized wind damage.
NOTE: THE NEXT DAY 1 OUTLOOK IS SCHEDULED BY 0100Z