By now, I’m sure most of you have heard about the record heat in California and the Desert Southwest. On Sunday, San Francisco obliterated its previous heat record of 86 degrees with an unbelievable 97-degree high, and yesterday, Palm Springs reached an egg-frying 122 degrees! Phoenix even had to cancel nearly 50 flights yesterday due to the heat.
So far, the Pacific Northwest has escaped this record-breaking heat wave. But that will change this weekend!
The chart above shows the current 500 hPa geopotential height and the geopotential height anomalies. If you don’t know what “geopotential” means, don’t fret… for these purposes, the physical difference between geopotential and geometric height is negligible. Geopotential height is simply the geometric height adjusted for changes in the Earth’s gravitational field due to variations in latitude and surface elevation, and meteorologists use it because it simplifies their equations.
As you can see in the graphic above, there is a HUGE ridge offshore and WNW flow aloft over our area. As the week goes on, this ridge will drift eastward over our area, dramatically warming the air aloft and at the surface.
This ridge will direct a tongue of hot air known as a “thermal trough” northward from California into Western Washington. Saturday evening’s chart below shows a textbook thermal trough. ALL of our record-breaking heat waves come from thermal troughs.
Credit: UW Atmospheric Sciences
Temperatures will incrementally warm from the 80s on Thursday to near 100 on Sunday for the Willamette Valley. In Western Washington, expect highs in the mid 70s tomorrow warming to the low 90s by Sunday, warmer away from the water. This weekend will be a wonderful time to hit the beach, but be sure to wear lots of sunscreen! With nary a cloud in the sky and the sun oh-so-high, you will get fried if you don’t apply.
As is often the case, this thermal trough will gradually drift to the east, resulting in a strong marine push that will bring temperatures back down to normal. The coastal areas will cool significantly on Monday, but the interior lowlands west of the Cascades should experience another day with well above-average temperatures. We’ll cool down significantly on Tuesday to near or slightly-above-average temperatures.
Enjoy the heat wave, and WEAR SUNSCREEN! 🙂
Charlie
