SPC Mar 25, 2025 1730 UTC Day 2 Convective Outlook

SPC 1730Z Day 2 Outlook

Day 2 Convective Outlook  
NWS Storm Prediction Center Norman OK
1225 PM CDT Tue Mar 25 2025

Valid 261200Z - 271200Z

...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS IN PARTS OF THE
PACIFIC NORTHWEST...

...SUMMARY...
Severe thunderstorms are possible across parts of the Pacific
Northwest on Wednesday afternoon and evening. Coverage should be
mostly isolated, but a more probable corridor for a few supercells
is apparent west of the Cascades. These may produce large hail, a
brief tornado, and locally strong gusts.

...Pacific Northwest...
Confidence is sufficient for an upgrade to level 2-SLGT risk for
large hail, centered along the I-5 corridor in western OR/WA.
Considered a separate upgrade across northeast OR/southwest WA for
wind, but confidence is too low to warrant one at this time. 

A vigorous shortwave trough will approach the Pacific Northwest
coast through the period. A pronounced mid-level jetlet, around
90-100 kts at 500 mb, should overspread the OR coast to west of the
Cascades on Wednesday evening. Near record to record high
temperatures are anticipated downstream amid a preceding highly
amplified mid/upper ridge shifting east. This combined with well
above-normal PW values should yield pockets of 500-1000 J/kg MLCAPE
by Wednesday afternoon. Despite a meridional deep-layer wind
profile, a few supercells will likely develop west of the Cascades
as MLCIN wanes towards peak heating. With weak low-level shear,
large hail should be the primary hazard. A storm or two might
produce significant severe sizes of 2-2.5 inches before storms
weaken over the Cascades. 

Farther east, deep-layer shear will be progressively weaker, but the
boundary layer will be more deeply mixed. Guidance varies greatly
with the degree of convective coverage in this region into the
evening. The more aggressive models suggest a thunderstorm cluster
or two could evolve across northeast OR/southeast WA. Should this
occur, severe wind gusts would be the primary hazard. Given a subtle
delayed/weaker trend in the timing/strength of the parent shortwave
trough, will maintain broad low probabilities for now.

...Lower Rio Grande Valley/South TX...
Minor mid-level impulses are progged to undercut the highly
amplified ridge that currently exists from the Rio Grande Valley to
the Pacific Northwest. Guidance varies in mesoscale spatiotemporal
aspects of when these impulses cross the Rio Grande into south TX.
With rich boundary-layer moisture over Deep South TX and potential
for pronounced diabatic heating, a marginally favorable environment
for isolated severe hail/wind is apparent. While speeds may be
modest, a vertically veering wind profile with height could support
a few slow-moving, transient supercell structures Wednesday
afternoon/evening.

..Grams.. 03/25/2025

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