No watches are valid as of Wed May 20 16:25:02 UTC 2026.MD 0801 CONCERNING SEVERE POTENTIAL...SEVERE THUNDERSTORM WATCH LIKELY FOR PORTIONS OF THE MID-ATLANTIC
Mesoscale Discussion 0801
NWS Storm Prediction Center Norman OK
1123 AM CDT Wed May 20 2026
Areas affected...portions of the Mid-Atlantic
Concerning...Severe potential...Severe Thunderstorm Watch likely
Valid 201623Z - 201800Z
Probability of Watch Issuance...80 percent
SUMMARY...Widely scattered thunderstorms will pose a risk for
damaging wind gusts and isolated large hail this afternoon and
evening. A Severe Thunderstorm Watch will be needed soon.
DISCUSSION...Latest surface observations depict a cold front
extending from central New York southwestward through north-central
and western Pennsylvania into southeast Ohio. Ahead of this cold
front, temperatures are warming into the 90s across portions of the
Mid-Atlantic, with surface dewpoints in the low/mid 60s F. Continued
heating of this air mass is supporting 1000-1500 J/kg MLCAPE, with
further destabilization anticipated through the afternoon hours.
Recent satellite/radar imagery has shown increasing convective
coverage ahead of the aforementioned cold front as remaining
inhibition is eroded. With stronger mid/upper-level flow remaining
displaced to the northwest, only modest effective shear is analyzed
across the region (generally 20-30+ kts per latest mesoanalysis).
This will be sufficient to support updraft organization with
multicells, and perhaps marginal supercells, likely. Steep low-level
lapse rates, well-mixed boundary layer profiles, and surface
dewpoint depressions exceeding 20-25 F will promote the potential
for damaging wind gusts, particularly with any more organized
clusters that develop. Isolated instances of large hail may also
accompany any more robust updrafts despite weak mid-level lapse
rates (as sampled by the 12z PIT/IAD observed soundings). A Severe
Thunderstorm Watch will be needed soon.
..Chalmers/Hart.. 05/20/2026
...Please see www.spc.noaa.gov for graphic product...
ATTN...WFO...PHI...BGM...CTP...LWX...PBZ...RLX...
LAT...LON 40687798 40987676 40987614 40907587 40747568 40397553
39967560 39437589 39147621 38927665 38687793 38597862
38587907 38767959 39117993 39388003 39737992 40107959
40247926 40687798
MOST PROBABLE PEAK WIND GUST...55-70 MPH
MOST PROBABLE PEAK HAIL SIZE...1.00-1.75 IN
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
SPC 1630Z Day 1 Outlook
Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
1101 AM CDT Wed May 20 2026
Valid 201630Z - 211200Z
...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS FROM WEST VIRGINIA
INTO THE MID-ATLANTIC STATES AND SOUTHERN NEW ENGLAND...AND OVER
PORTIONS OF SOUTHWEST 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.
...WV to Southern New England...
A broad upper ridge is present today over the southeastern U.S.,
with the southern fringe of stronger westerlies extending from the
OH Valley into the Mid-Atlantic region. Visible satellite imagery
shows a zone of relatively clear skies from KY/WV into southeast
PA/NJ and southern New England. Strong heating in this corridor
will lead to moderate CAPE by mid-afternoon. Scattered thunderstorm
development is expected, with steep low-level lapse rates and
sufficient westerly flow above the boundary-layer supporting a risk
of damaging wind gusts and some hail in the strongest
cores/clusters.
...Southwest TX...
Water vapor imagery shows a southern stream shortwave trough moving
into northwest Mexico, with large scale ascent approaching west TX.
Considerable cloud cover will persist in this region today, limiting
heating/destabilization. Easterly low-level upslope flow will aid
in the development of afternoon thunderstorms over the Davis
mountains, with storms spreading slowly eastward through the
evening. A few severe storms are possible, capable of large hail
and gusty/damaging winds.
..Hart/Dean.. 05/20/2026
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