Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0750 AM CDT Thu May 21 2026
Valid 211300Z - 221200Z
...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF
THE CENTRAL/SOUTHERN HIGH PLAINS...
...SUMMARY...
Thunderstorms capable of producing large hail and isolated severe
gusts should occur across parts of the central/southern High Plains
this afternoon and evening. A tornado or two may also occur.
...Central/Southern High Plains into South Texas...
Within large-scale upper troughing over the northern Rockies/Great
Basin, an embedded mid-level shortwave trough and associated jet
will translate southeastward across the central Rockies and adjacent
High Plains this afternoon and evening. Forcing for ascent preceding
this feature will encourage initial isolated to scattered
thunderstorm development across the higher terrain of central CO by
mid afternoon. A weak southern-stream perturbation should also
foster scattered convection farther south across the southern High
Plains as well.
The airmass across the central/southern High Plains should gradually
destabilize today, as modest moisture in a persistent low-level
upslope flow regime continues streaming northwestward across these
regions beneath steepened mid-level lapse rates. Weak to moderate
instability is forecast to be in place by mid afternoon, with
sufficient deep-layer shear for a mix of multicells and supercells.
Initial development should pose a threat for large hail, before
eventual clustering this evening potentially results in a greater
threat for severe winds. The primary change with this update was to
expand the Marginal Risk across parts of west into south TX, where
any convection which develops eastward may pose an isolated
hail/wind threat this afternoon through tonight.
...Southern Virginia into North Carolina...
Daytime heating south of a cold front should help steepen low-level
lapse rates across parts of southern VA into NC by this afternoon.
While both mid-level flow and lapse rates are expected to remain
fairly modest across this area, an isolated threat for damaging
winds may exist with loosely organized clusters that can develop
along the higher terrain and/or sagging cold front this afternoon.
...Coastal Texas into the Lower Mississippi Valley...
Another expansive MCS has moved offshore from the lower TX Coast
this morning. Generally weak offshore surface flow continues across
the middle/upper TX Coast into southern LA. Eventually, a more
southerly component to the low-level winds may encourage greater
low-level moisture to advance inland later today across parts of the
lower MS Valley. While a couple of stronger thunderstorms with gusty
winds appear possible, modest mid-level flow and poor lapse rates
aloft should tend to limit the overall severe threat.
..Gleason/Marsh.. 05/21/2026
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