Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0248 PM CDT Tue May 26 2026
Valid 262000Z - 271200Z
...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS FOR PORTIONS OF
CENTRAL INTO DEEP SOUTH TEXAS...
...SUMMARY...
Scattered severe thunderstorms appear possible this afternoon and
evening across parts of southwest into south-central Texas. Large
hail, severe wind gusts, and a couple of tornadoes may occur.
...20Z Update...
Much of the forecast remains generally on track. Across central into
southern Texas, Slight risk probabilities were trimmed from the west
to account for the passage of an ongoing MCS. Severe probabilities
were increased into deep south Texas for the possibility of
preceding supercells developing ahead of the eastward-meandering MCS
this evening, which may be accompanied by a severe wind/hail threat.
Finally, 5 percent wind probabilities were expanded eastward across
MT, and farther west from the Midwest into ND, to account for trends
in both observations and the latest guidance consensus.
..Squitieri.. 05/26/2026
.PREV DISCUSSION... /ISSUED 1129 AM CDT Tue May 26 2026/
...Texas...
Ongoing thunderstorms late this morning across west TX are being
aided by ascent associated with a weak mid-level trough over the
southern High Plains. While an isolated hail/wind threat may persist
with this activity in the short term, expectations are for an
increasing severe risk to materialize this afternoon downstream
across parts of south-central TX. Recent surface observations and
area VWPs show modest low-level east-southeasterly flow occurring
across this region, with surface dewpoints generally in the mid 60s
to low 70s. Some clearing/cloud breaks are noted on latest visible
satellite imagery, and filtered daytime heating of this moist
low-level airmass combined with modestly steepened mid-level lapse
rates (reference 12Z observed DRT sounding) will aid in the
development of moderate to locally strong MLCAPE by mid afternoon.
While low-level flow should remain modest, strong veering of the
winds with height through mid/upper levels and a gradual increase in
magnitude associated with the weak mid-level trough will support
around 30-40 kt of deep-layer shear across the narrow warm sector. A
mix of supercells and multicell clusters should spread from northern
Mexico/west TX into southwest/south-central TX through the afternoon
and early evening. Large hail will be possible with any sustained
supercells, while severe/damaging winds may occur with clusters as
low-level lapse rates become steepened with continued daytime
heating. The tornado threat remains less clear, as modest low-level
flow and muted effective SRH suggest low-level mesocyclones may
struggle. Still, some risk for a couple of tornadoes remains
apparent across a small part of southwest TX. Severe probabilities
have been adjusted to account for both ongoing convection and the
potential for one or more clusters with some wind threat to persist
this evening/overnight across south-central into coastal TX.
...Upper Midwest...
A weak/dissipating MCV will move into parts of the Upper Midwest
today, as modest westerly mid-level flow continues to the north of a
mid/upper-level anticyclone centered over the northern Plains into
IA. A weak surface front will remain draped generally west to east
from eastern ND into central MN/WI through the day. South of this
front, diurnal heating of a seasonably moist low-level airmass will
support moderate instability by mid afternoon. While large-scale
ascent is expected to remain fairly weak/nebulous, the remnant MCV
may foster isolated to scattered thunderstorm development this
afternoon and early evening along/near the front. Around 20-30 kt of
deep-layer shear should be sufficient for some updraft organization.
Isolated large hail and severe/damaging winds may occur with loosely
organized multicells and marginal supercell structures, before this
activity eventually weakens this evening with the loss of daytime
heating.
...Northern Rockies/High Plains...
A closed upper low over western OR/northern CA this morning will
continue to move slowly southward through the period. A belt of
modestly enhanced southerly mid-level flow will exist of parts of
the interior Pacific Northwest into the northern Rockies and
adjacent High Plains. Even though low-level moisture will remain
limited, the boundary layer is forecast to become very well mixed
with daytime heating. High-based showers/thunderstorms that develop
across this region will spread northward through the afternoon and
evening, and may pose an isolated threat for severe gusts and
perhaps some hail.
...Ohio Valley/Southeast...
A broad zone of 20-30 kt south-southwesterly mid-level flow will
likely remain over much of the Southeast and parts of the OH Valley
today. 12Z observed soundings from across these regions show poor
lapse rates and generally saturated profiles aloft, which should
temper the degree of instability which develops this afternoon with
filtered daytime heating. Due to the expected thermodynamic
limitations, it remains unclear how productive thunderstorms will be
in producing damaging winds. Water-loaded downdrafts capable of
producing occasional strong to locally damaging winds appear
possible across a broad area of the lower/mid OH Valley into much of
the Southeast, especially where low-level lapse rates can become at
least modestly steepened. However, a more focused corridor for a
tornado and damaging winds may exist this afternoon across KY, in
closer proximity to a weak mid-level perturbation noted on visible
satellite imagery over the Mid-South and a subtle surface boundary.
For now, have opted to expand the Marginal Risk to include more of
KY, but additional expansions may occur across parts of the
Southeast if mesoscale corridors of isolated damaging wind potential
can be delineated.
...Northern Maine...
A mid-level trough with attendant strong (40-50+ kt) westerly jet
will move eastward across Quebec today, and will impact parts of ME
this afternoon/evening. Most guidance suggests that a band of
thunderstorms will spread quickly eastward across northern ME later
today in a weakly unstable but strongly sheared environment.
Isolated severe/damaging winds may occur with this activity.
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