SPC AC 251725

   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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