The air aloft has warmed considerably during the past day under southerly flow, and an offshore pressure gradient has initiated easterly (from the east) flow over the Cascades. To illustrate the profound warm up of the next few days, here are the surface air temperature forecasts for 4 PM today (Saturday), 5 PM tomorrow (Sunday), and 4 PM Monday. A big surge of warmth over the next 48h.
Sunday will get into the mid-60s for most. But look at Monday..wow... lots of folks in western WA will experience 70s F.
One driver of the warmth will be easterly flow, with strong downslope warming over the western slopes of the Cascades. Air get compressed as it descends from higher to lower altitudes, and compression causes warming (like you notice when you use an air pump).
Here are the wind gusts predicted for 5 PM on Monday. 20-30 knot gusts from the southeast, particularly from central/south Seattle and eastward. Another area east of Everett. Why? Because there are major low-areas in the Cascades: Stampede Gap south of I90 and the Steven's Pass gap to the north. When there is a large pressure difference across the Cascades, air accelerates eastward through these low regions.
Such southeasterly winds often produce turbulent flights for those landing/taking off from Sea-Tac Airport.
But what will be really unusual next week will be the large amount of precipitation that will hit California due to a strong low center setting up west of northern CA.
Here are the two 72 hr totals for the next next 144 hours. In WA state we will get some sprinkles, but California, and particularly the Sierra Nevada, will get hit by many inches of water and feet of snow over high terrain. And more is predicted the following week. I suspect fewer people will be talking about California drought when the next few weeks are over.
