The first major heat wave of the year is living up to the hype! Portland and Salem hit 98 and 101 respectively yesterday, and today, they simply switched highs. According to Mike Newman (a fellow weather buff from the Portland area), today’s high of 101 at the Portland Int’l Airport was just 1 degree below the all-time June high of 102.
Thankfully, temperatures will come crashing back down to Earth for everyone west of the Cascades tomorrow courtesy of a strong marine push, and by Tuesday, most areas should be sitting near or even slightly below their average temperatures for this time of year.
Credit: NASA Worldview
A look from NASA’s TERRA satellite shows a layer of low stratus developing along the coast, and today’s visible satellite loop shows this layer slowly moving northward. Layers like these form when there is a strong inversion (cool air at the surface and warmer air aloft), and it is a classic indicator of cool temperatures along the coast and an impending marine push into the lowlands of Western Washington and Oregon. Astoria’s high temperature today was 29 degrees cooler than yesterday, and comparing today’s TERRA image to yesterday’s (below), it’s not hard to see why!
Credit: NASA Worldview
One of the best ways to track these marine pushes is via pressure gradients. Having spent the vast majority of my life in Seattle, I’m most familiar with using the HQM-SEA (Hoquiam-Seattle) pressure gradient to track pushes, but you can deduce the strength of an impending marine push from any observed pressure gradient between a coastal station and inland station of roughly the same latitude. As a rule of thumb, weak marine pushes occur when the HQM-SEA gradient is between +1 and +2 mb, moderate ones occur between +2 and +3.5 mb, and strong ones occur above 3.5 mb (credit to Scott Sistek of KOMO news for this factoid). As of 5 pm, the HQM-SEA pressure gradient is +3.5 mb and still increasing, so we can expect a strong marine push tonight. You can track the pressure gradients throughout the night via this link.
The current observations show a remarkably strong east-west gradient in temperatures, with 100+ degree temps in the Willamette Valley and an isolated reading of only 52 degrees off the mouth of the Columbia River (this doesn’t appear to be an erroneous reading, I checked!) with 16 mph gusts from the SW.
Credit: NWS
This marine push will be strong enough to cool tomorrow’s highs off by 15-20 degrees in the Portland metro area. Long-term-forecasts were previously showing the potential for another warm period next week but have since flipped to normal or even slightly cooler-than-normal conditions, with morning clouds and afternoon sunshine most days.
Finally, I have some important news regarding WeatherTogether… model charts are finally up and running! I’ll have a more detailed post tomorrow evening about them.
Hope you are looking forward to some relief from the heat!
Charlie
