Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0752 AM CDT Wed Mar 26 2025
Valid 261300Z - 271200Z
...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS WESTERN
PORTIONS OF WASHINGTON/OREGON...
...SUMMARY...
Severe thunderstorms are expected across parts of the Pacific
Northwest this afternoon and evening, with supercells possible west
of the Cascades across Oregon into Washington. These storms may
produce large hail, perhaps a tornado or two, and strong wind gusts.
...Pacific Northwest...
A very active early season severe risk is expected regionally today.
A seasonally strong upper low over the coastal Pacific Northwest
will shift eastward today, highlighted by a 100+ kt mid-level speed
max that will overspread coastal areas by evening. Strong height
falls will similarly spread across this region and the associated
synoptic cold front should arc from off the Washington Coast to
southward along the Oregon Coast by evening.
Low-level mean-mixing ratios are notably high, as compared to
typical daily climatological values (highest 5-10%), this morning
based on 12z observed soundings from Salem and Medford, Oregon.
Large-scale forcing for ascent will contribute to a further
moistening of profiles and PW values may approach 1 inch prior to
convective initiation. Cold mid-level temperatures and a plume of
steepening mid-level lapse rates will also notably overspread the
region. Of particular concern are the cold mid-level temperatures,
and the steep lapse rate plume that will overspread this region.
Forecast soundings suggest convective temperatures should be
breached by 21-22z west of the Cascades, and surface-based CAPE
should reach/exceed 1000 J/kg coincident with a favorably sheared
environment for organized, rotating updrafts.
Isolated to scattered robust convection seems likely to develop by
21-22z across western Oregon, immediately ahead of the strong
forcing. This activity should grow upscale and develop
north-northeastward ahead of the approaching speed max, with
profiles favoring supercell development. Hail should be common with
this activity and the strongest updrafts may generate quite large
hailstones, possibly exceeding golf ball size, or even larger with a
few of the most intense storms. Some tornado risk will also exist,
particularly where low-level winds maintain at least a modest
easterly component. Damaging winds may also occur.
...Texas Lower Rio Grande River Valley...
Water vapor imagery depicts a substantial sub-tropical cirrus plume
from the southern Baja Peninsula, across Mexico toward the lower Rio
Grande Valley. A weak disturbance will approach the international
border through mid day, and this will draw a substantial moisture
plume across South Texas. Forecast soundings exhibit modest lapse
rates despite the moistening profiles. While forecast shear is not
particularly strong, especially with northward extent, some
organization is possible and this activity could generate gusty
winds and/or hail. Otherwise, a considerable amount of convection is
expected across this region which may tend to disrupt and limit
organizational potential.
..Guyer/Bentley.. 03/26/2025
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