Much of the Northwest is enjoying a break in precipitation after persistent regional storms and post-frontal showers. A low pressure system heading for Alaska will bring that to an end from north to south with the first of several cold fronts moving in.
Rain and mountain snow from this begins during the day Thursday for the northern British Columbia Coast. In Washington, Oregon, and southern British Columbia, high clouds move in from west to east on Friday though most should remain dry.
Precipitation from this first round aims mostly at the northern two-thirds of Vancouver Island so that major Northwest cities come away with between a quarter and three quarters of an inch (5 to 15 mm) of rain and not much overall in the Columbia Basin through Saturday. This trajectory will add quite a bit of snow to the mountains of British Columbia and Washington where snowpack continues to struggle. One storm won’t be enough to clear the deficit but at this point all snow in that area is good snow.
Becoming breezy along the I-5 corridor, including Seattle and Portland, Saturday afternoon. Wind gusts in well exposed locations may reach 40 mph (65 km/h). Breezy through the weekend across the rest of the Northwest but wind gusts won’t be as strong except on the Coast.
The next system comes in Sunday, this time with the low pressure system passing much closer to the Northwest. Heavy rain west of the Cascades is likely early in the morning, snow in the mountains, and some light rain a few hours later in the Columbia Basin. It will be followed by post-frontal showers including isolated thunderstorms in lowland areas on both sides of the mountains.
A third storm comes Tuesday with showers and isolated thunderstorms tapering off Wednesday. In total, these three storms may bring 3 inches (75 mm) of rain to major Northwest cities. The Tri-Cities are looking at between a tenth and a quarter of an inch (2 to 5 mm) of rain. Snow totals in excess of a foot (30 cm), much higher in southern British Columbia, are expected above 3,000 feet (900 m) elevation.
It looks like the region will be warming up after the storm train ends. Models continue to favor upper level ridging dominating western North America. It’s too far out to say for sure, but highs into the upper 60s (around 20°C) appear possible around Portland and the Tri-Cities. Cooler to the north, such as in Seattle, Spokane, and Vancouver.
This pattern appears to last for a while, possibly producing dry and seasonally warm conditions for much of the middle portion of March. Snowpack is likely to decline throughout the West under this weather pattern. The Climate Prediction Center holds above average temperatures and below average precipitation in place for at least three weeks but there is a chance this pattern starts to break down a little after the 20th.
The featured image is satellite imagery for the Pacific Northwest and adjacent portions of the Pacific at 10:00 PST Thursday via College of DuPage.
