Heat wave: Here today, gone tomorrow

Heat wave: Here today, gone tomorrow

SEATTLE -- The one saving grace of Northwest heat waves: they don't last too long.

The current one looks like its reign will be all of three days, before cooler, marine air stages a revolution and reclaims its rightful place at the helm of our late spring weather pattern Thursday night.

In the interim, it was another day of shorts and ice cream as temperatures are climbed to near 90 degrees again under mostly sunny skies.

Seattle, fresh off shattering the record high for June 3 with its 89 degree day Wednesday, easily broke Thursday's record of 88 with a preliminary high of 90 degrees.

Here are some of the highs from Thursday:

  • Olympia: 92
  • Shelton: 92
  • Tacoma: 92
  • Seattle (Sea-Tac): 90
  • North Bend: 90
  • Gig Harbor: 89
  • Renton: 89
  • Arlington: 88
  • Mount Vernon: 87
  • Friday Harbor: 86
  • Bellingham: 84
  • Port Angeles: 83
  • Everett: 83

Friday will be markedly different, with low clouds and fog giving way to partial clearing in the afternoon. Highs will drop to the low-mdi 70s.

Friday will be a marked change from today with some morning clouds but also some lingering sunshine.  Highs will be a good 15 degrees cooler, possibly more. It'll depend on how much we get in the way of morning clouds, but could be as cool as 65 but look more like mid 70s.

Saturday will be the full effect of the marine push so it'll be mostly cloudy with areas of drizzle and limited afternoon sunshine. A weak trough sliding down from the north might also squeeze out a few isolated light showers, but not a washout. Highs will drop into the 60s.

A bit of a rebound for Sunday and Monday with morning clouds then afternoon sunshine and highs near 70.

Forecasting models now show a better chance of scattered light showers on Tuesday while we cool back to the low-mid 60s, and then rebounding back to near 70 for the balance of the week.

I think we'll take it!

Why don't heat waves last too long here?

We can send our thank you note to the Pacific Ocean. With the Earth's rotation, weather generally moves from west to east. For the Northwest, it means our weather typically comes off the ocean, which off the West Coast stays in the 50s for temperature year round.

That's why we stay relatively cool in the summer and mild in the winter. To get a heat spell, we have to get air to come from the east where it's hot and dry. That does three things: 1) The air is already warm, 2) it warms further when it sinks down the Cascade Mountains, and 3) it holds the marine breeze back from pushing inland.

But you can't hold back the natural westerly progression for too long. This isn't the actual physics -- but to get a general idea of how this works, imagine the cool air being pooled behind a dam being built by that east wind. The longer the east wind goes and the hotter the heat wave, the more pressure gets built behind the dam.  Eventually, the dam breaks and the cold air comes rushing inland. That's what will occur tonight.

(Actually, it's more like the dam moves east into Eastern Washington and just allows the cold air to move east, but close enough for this relative explanation.)

How hot did it get Wednesday?

Here is the list of high temperatures from Wednesday evening (preliminary high temperature readings from 5 p.m.)

    * Shelton: 90
    * Bremerton: 90
    * Vancouver, WA:90
    * Seattle (Sea-Tac): 89
    * North Bend: 89
    * Tacoma: 89
    * Olympia: 89
    * Gig Harbor: 88
    * Renton: 87
    * Kelso: 86
    * Mount Vernon: 86
    * Arlington: 84
    * Friday Harbor: 84
    * Everett: 83
    * Bellingham: 83
    * Hoquiam: 82
    * Forks: 81