June 25, 2017

The Hot One Today

Temperatures on Saturday were toasty around the region (see below), with upper 80s reaching into Puget Sound, near 100F in Portland, and over 100F in portions of the torrid Willamette Valley.   As predicted, temperatures surged into the low 90s along the WA coast due to offshore (easterly flow).

Temperatures are warmer this (Sunday) morning over much of the region by roughly 5F, and a key parameter (the Seattle-Yakima pressure difference) suggested a large offshore pressure gradient (that helps warming)...see the table below.  The pressure differences between Seattle and the coast are still negative (higher pressure in Seattle), which suggests no push of marine air during the day today.
A really useful tool for short term forecasts of temperature is to look at time-height cross sections of temperatures and winds from aircraft coming in to Seattle and Portland.   Here is the latest from Seattle (red is temperature, the vertical axis is height in pressure, with 850 being around 5000ft.  Time increases to the left and is in UTC/GMT).   850 hPa temperatures are around 22C (which are very warm) and could support surface temperatures as high as 37C (upper 90s), where there is no marine influence.

In fact, the 850 hPa (about 5000 ft) temperature at Quillayute, on the WA coast, is at record high levels for the date (see climatology at the radiosonde site there, with red being record highs, the dot is the temperature at 5 PM yesterday).

Consistent with this, here is the latest high resolution UW WRF forecast for 5 PM.  Mid to upper 90s away from the water (eastern Seattle suburbs and lower western Cascade foothills). You don't want to know about Portland and the Willamette Valley, where 100F+ will be widespread.

So today is going to be very warm... so be prepared.   I close my shades and fill my house with cool morning air with fans.  But it will be the last day of the uber-heat and there is already a sign of change....low cloud are starting to move up the Oregon coast.  An indication that an onshore push of marine air may be in store for tomorrow.


  1. Dewpoints are trending a little higher today which will make it feel more uncomfortable too. The column integrated water vapor shows rising values region wide. 59 degrees and a SW wind in Astoria. It be fun to watch the car thermometer driving from Portland to there today.

  2. Clouds moving in in Shoreline already.

  3. Tell tell me about it. Whatever happened to 90s with humidity in the teens?

  4. I'm in north Seattle near hwy 99 and we are much cooler than SeaTac. We never approached 90 today. It was comfortable.

  5. Well, it was a great day for swimming in the lake.


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