LIVE MAP (ABOVE) ... SPC 1300Z Day 1 Outlook
Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0730 AM CDT Wed May 20 2026
Valid 201300Z - 211200Z
...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF
THE CENTRAL APPALACHIANS INTO THE MID-ATLANTIC AND SOUTHERN NEW
ENGLAND...AND PARTS OF WEST/SOUTH-CENTRAL TEXAS...
...SUMMARY...
Scattered severe/damaging winds and isolated hail will be possible
with thunderstorms from the central Appalachians into the
Mid-Atlantic and southern New England this afternoon and evening.
Severe thunderstorms with large hail and isolated severe gusts may
also occur today across parts of west/south-central Texas.
...Ohio Valley into the Mid-Atlantic and Southern New England...
On the southern fringe of upper troughing over eastern Canada and
the Great Lakes, a weak/convectively augmented mid-level shortwave
trough will progress northeastward across the OH Valley and central
Appalachians through the day, eventually reaching the Mid-Atlantic
tonight. Robust daytime heating of a modestly moist low-level
airmass (surface dewpoints generally in the low to mid 60s) ahead of
a surface cold front will aid in the development of moderate
instability by early afternoon. Ongoing convection across OH/KY this
morning may eventually strengthen as it encounters this
destabilizing airmass, and additional thunderstorms are expected to
develop along/near the cold front by mid afternoon from the central
Appalachians into portions of the Mid-Atlantic and southern New
England.
Stronger flow aloft will tend to lag/remain north of the cold front,
but modest enhancement to the west-southwesterly mid-level flow
along/near the front should support around 20-30 kt of deep-layer
shear. This will be sufficient for some updraft organization with
mainly multicells expected, although marginal supercell structures
may occur. Low-level lapse rates are expected to become quite steep
through the day, evidenced by a general lack of clouds on recent
visible satellite imagery from central/eastern WV into the
Mid-Atlantic. This will likely aid efficient downward momentum
transfer in convective downdrafts, with scattered severe/damaging
winds possible as multiple clusters spread east-northeastward
through the afternoon/evening. Isolated hail may also occur with the
stronger cores. A Slight Risk for severe/damaging winds has been
introduced from parts of WV to southern New England given increased
confidence in multiple clusters traversing a narrow zone along/ahead
of the front.
...Eastern New Mexico into West/South-Central Texas...
A squall line has generally moved offshore the lower/middle TX Coast
this morning. In its wake, a post-frontal low-level upslope flow
regime will persist today across west TX into eastern NM. Embedded
within large-scale upper troughing over the Great Basin/Southwest, a
low-amplitude shortwave trough over northern Mexico this morning
will move northeastward across the southern High Plains by this
afternoon. A relatively early start to convective development
appears probable across the higher terrain of far west TX, possibly
as early as 17-19Z. With a combination of moderate instability and
40-50 kt of deep-layer shear forecast, supercells with mainly a
large hail threat should be the primary mode initially. Additional
robust thunderstorms may form later in the afternoon/early evening
across a broader portion of the southern High Plains, and also pose
a threat for large hail and isolated severe winds. Some potential
for clustering this evening remains apparent into south-central TX,
and supercells from north-central Mexico could also move into this
region this evening/overnight.
..Gleason/Marsh.. 05/20/2026
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