May 04, 2017

Thunderstorms Have Begun over the Northwest!

3:35 PM Update
A strong line of convective showers is now approaching south Seattle.  Here is the composite radar image.  You don't see radar images like this around here very often....

Lots of lightning!  Here are the lightning strikes for the half hour ending 3:30 PM


 The latest radar image (around 2 PM) shows precipitation associated with convection and thunderstorms, moving northward over western Oregon and SW Washington.  The red areas are very heavy rain or hail.

A visible satellite image at 2 PM shows the convective clouds, with the storms over the northern Oregon coast

The National Lightning Detection Network showed many lightning strikes for the half hour ending 2 PM along the Oregon Coast.

 And the Space Needle PanoCam was viewing some mid-level cumulus development that is indicative of destabilization and vertical motion.

The air over us is ripe for convection, as indicated by a critical measure (CAPE, Convective Available Potential Energy).  This figure shows the values at 5 PM....very high for around here (generally we don't get to 100, and there are values of 500-1500 over western WA/OR and the Cascades)

The stability of the air lessens as the ground warms and there is clearly a northward-moving upper level disturbance that is releasing the instability.

Expect showers to reach southern Puget Sound country starting around 3PM, reaching central and northern Puget Sound 1-2 hr later.

An onshore push of marine air is beginning and the upward motion from that feature will help rev up the thunderstorms between 5 and 8 PM.

A second patch of showers and thunderstorms will occur overnight as an upper level disturbance (shortwave) moves in off the ocean, with the main action over the Cascades and eastern WA.

The simulated satellite infrared imagery at 5 PM, 8 PM and 5 AM, indicates thunderstorms over our region (the areas that are very white).

There will be plenty of showers and lightning around our region.... so boaters and golfers should be careful.


  1. Great light show and rolling thunder in Kent Valley

  2. Lights flickered at UW about 4:15

  3. Approaching storms from my office window about an hour ago:

  4. Here in edge of Lacey near Yelm Highway...storm came through with winds I have never experienced and driving rain! At times the gusts had to be near 60 or 70mph! Lots of tree damage and flooding!

  5. Looking over Sinclair Inlet, lots of lightning, sudden wind shifts (north and south), and about 7 seconds distance from the flash. Near constant last 15 minutes

  6. Very cool excepting property damage and human injury. Sad to be on the edge of it here in Victoria but the latest radar is pretty incredible.

  7. In Lacey I thought we were in a tornado. Chairs outside were flying around in a swirl

  8. This weather is killing our little league season, and it needs to stop. Lightning and hard rain at game time, then sun. When does that happen? The gods are mocking us.

  9. Northsound 70+ degree weather lasted half-a-day (back to rain again).

  10. It's been a long time since I have seen lighting during day like what rolled through the Kent valley this afternoon around 4pm and then near Lake Tapps around 7pm. Many cloud to ground strikes that were so close, the windows rolled a couple times and the power flickered. Made for an interesting weather day with upper 70's and sun early in the day then storms. Reminded me of something you would see in Dallas not Seattle. Very cool! ;)


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