520Bridge640
We are entering the time of year when western Washington gets its greatest number of days with unstable air. (WSDOT photo)

Ready for unstable spring weather?

What is stable air as opposed to unstable air? You hear those terms by many weather authorities, but what do they mean? We are entering the time of year when western Washington gets its greatest number of days with unstable air.

The difference:

The primary weather ingredients in the lower atmosphere are heat and moisture. Both of these elements play key roles in whether an air mass is stable or unstable. An unstable air mass usually is warmer and more moist closer to the surface than the air above it.

Like letting a helium balloon go, if a parcel of air near the surface rises and keeps going, that is unstable air and the air mass is considered convective. A stable air mass would result in the parcel of air either to rise and stop or rise rather slowly with little cloud development thanks to relatively warmer air aloft.

During our spring season, the longer days and higher sun angle result in warmer temperatures in the lowlands of western Washington.

Yet we still get cooler air aloft rolling inland from the Gulf of Alaska. This pattern often results in an unstable air mass. If moisture is present and it often is, clouds, showers and even thunderstorms develop. On the calendar, our western Washington convective season usually begins around March 1.

Transitional season:

Spring, the transition season between winter and summer, is the peak season for showers and thunderstorms in western Washington. The other transition season in the fall has a secondary peak. If you encounter rain and then sunshine, and it repeats seemingly again and again, those are usually showers associated with an unstable air mass. And that is why they are called spring showers.


Ted Buehner, NWS Meteorologist, Warning Coordination Meteorologist for the National Weather Service
Ted Buehner is the Warning Coordination Meteorologist for the National Weather Service (NWS) in Seattle, a key customer liaison position.
Top Stories

  • Joining the LOB
    It's never easy being the new guy, but Tharold Simon is already making his mark

  • Smartphone Safety
    Our phones entertain us, inform us and now might protect us

  • Pumpkin Assault
    Pumpkin-flavored items are coming to store shelves whether it's fall or not
ATTENTION COMMENTERS: We've changed our comments, but want to keep you in the conversation.
Please login below with your Facebook, Twitter, Google+ or Disqus account. Existing MyNorthwest account holders will need to create a new Disqus account or use one of the social logins provided below. Thank you.
comments powered by Disqus
Sign up for breaking news e-mail alerts from MyNorthwest.com
In the community
Do you know an exceptional citizen who has impacted and inspired others?
KIRO Radio and WSECU would like to recognize six oustanding citizens this year. Nominate them to be recognized and to receive a $2,000 charitable grant.