But there is more: That 76F was the warmest winter (Dec. 21-March 21) temperature ever observed at the airport, in a record that goes back to the late 1940s.
But before we get too puffed up with thermal pride (or worry), it should be noted that the same winter high (76F) was observed on March 19, 1928. So we only tied the record.
Today we might beat it.
A plot of the temperature at Sea-Tac versus normal highs and lows for the entire winter (below) illustrates the amazing thermal surge. Through Feb 1, our temperatures were a bit on the warm side, but then the bottom dropped out as we entered the freezer. Below-normal temperatures reigned through early March, and then the thermostat was suddenly turned up.
Everything had to be just right to do this. We start with a very strong upper level high centered over southern BC and a trough offshore of California (see upper-level (500-hPa) map for 2 PM Monday). This configuration is associated with warm air over the region and easterly (offshore) flow. An unusual pattern.
The easterly flow is very important, since it produces downslope flow on the western side of the Cascades that warms the air by compression (as the air moves from low pressures aloft to higher pressures at low levels). Just like your bicycle pump.
A plot of winds and temperatures with height above Sea-Tac for the past day shows powerful easterly flow, reaching 30 knots. That is strong. Every major heat wave in late winter and early spring I can remember is associated with strong easterly flow...and this one is no different. (time increases to the left and is in UTC, heights are in pressure--850 is roughly 5000 ft)
With warm air and easterly flow just above the surface, expect a surge in temperatures today, as surface heating and associated mixing taps the warm air aloft. Some locations near the Cascade foothills will get very near 80F.
from Cliff Mass Weather and Climate Blog https://ift.tt/2HGifYQ
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