Just a quick post/explanation about the unsettled weather we’ve seen today! We’ve seen plenty of “showers and sunbreaks” today as an upper-level-trough moves onshore. Upper-level-troughs are associated with both cold air aloft and large-scale vertical motion, and both of these features support the larger process known as convection and the associated “showers and sunbreaks” we all know and love.
Convection is the process by which a warmer, less dense fluid rises in a relatively cooler and denser environment. Lava lamps are great tools for visualizing convection – the heat source at the bottom of the lamp warms the wax and causes it to rise to the top of the lamp, with the wax subsequently sinking as it cools, shrinks in volume, and becomes denser than its surroundings.
The same process works in an atmosphere where temperature rapidly decreases with height. The sun warms the surface, causing a given ‘air parcel’ to rise, and although this air parcel cools as it rises through a process known as adiabatic cooling, it can still remain warmer than the surrounding environment if the environment cools faster.
As you would expect, instability and convection increased throughout the day as the sun warmed the surface. This is most visible over the Columbia Basin – note the clear skies in the morning but the showers developing in the afternoon.
The trough will move east tomorrow and showers should subside as a result, but another system will approach from the NW on Monday, keeping temperatures below-average and giving us a few showers. All of next week looks chilly with highs in the low 50s, but the lion’s share of precipitation from incoming systems should stay over Washington while we see only a few showers at times.
Be sure to keep your radar app handy this evening! That’s your best tool for staying out of these showers.
Charlie
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Hey Charlie. Great analogy with the lava lamp, especially for those of us who actually had one!
I had two rounds of hail yesterday afternoon here in Happy Valley, the first lasting 10 minutes and having both hail and graupel simultaneously; the second was just a 2-minute period of very small hail. There is still some left this chilly, foggy morning where it piled up from bouncing off of the roof.