FastCast—Friday, Mar. 10 to Monday, Mar. 13:
Due to a low pressure center offshore, strong winds have been drawn out of the gaps in the Cascades. Expect gap winds to peak at 25-40 mph for the lowlands, mainly from Tacoma to South Seattle, strongest late Thursday night. In the foothills, gusty winds of 30-50 mph will continue through early Friday morning, strongest near North Bend, Enumclaw, and Maple Valley. Expect scattered showers on Friday, mainly in the morning. Sporadic showers are possible on Saturday, with partly sunny conditions expected through midday Sunday. Widespread rain arrives later on Sunday, continuing through Monday. Rainfall accumulations of 0.5-1.5” are expected, but stay tuned for more on that storm. In general, expect highs in the upper 40s to mid 50s (warmest on Sunday), with lows in the mid 30s to low 40s. Additionally, expect 4-8” of snow at the passes through Sunday, with brief travel impacts possible.
——————————————————
Continue reading the full blog below!
A strong pressure difference across the Cascades, due to low pressure over the Pacific Ocean, has caused gap winds to increase across the lowlands Thursday night. Below is the NAM high-resolution forecast for peak gap wind gusts, around 11 PM Thursday.
Generally, expect gusts of 25-40 mph in the lowlands, strongest from Seattle to Tacoma and around Everett/Lake Stevens. In the foothills, expect gusts of 40-50 mph. These patterns also bring strong offshore winds on the Washington & Northern Oregon Coasts. Expect peak gusts of 35-45 mph from roughly Tillamook northward to La Push.
There is a good visual representation of these winds, found in pressure maps, like the one below from the UW WRF forecast for 10 PM Thursday. Note the black lines inside the red box.
Inside the red box, lines of constant pressure are close together. The closer the lines, the stronger the wind, since winds are caused by a difference in pressure.
Peak gusts as of 10:15 PM are below.
The angled region of strongest winds is clear, stretching from Enumclaw toward Tacoma, Federal Way, and SeaTac, with another area of strong winds around Kent/Maple Valley and along I-90, with significant winds near North Bend. The strongest gusts have been 30-40 mph around SeaTac Airport and Federal Way, with 45-55 mph in Enumclaw and North Bend, and a peak of 60 mph on the ridges above Snoqualmie Pass.
Expect winds to peak late Thursday night, decreasing early Friday, except lingering into Friday morning for the foothills.
With a chance of showers on Friday, isolated showers on Saturday, and widespread rain arriving late Sunday, let’s take a look at this weekend’s rain forecast, seen below on the European model through Sunday night.
Through Sunday night, expect 0.2-0.4” of rain for the lowlands, with 0.5-1” from Olympia southward. Most of this will fall from Sunday evening onward. On the coast, expect 1-2”. Eastern Washington will receive 0.3-0.4” of rain, but this will most likely be snow from areas near I-90 and northward.
Speaking of snow, let’s take a look at the total snowfall expected through Sunday night, also from the European model.
Through Sunday night, expect 4-8” at the passes and 1-4” in Eastern Washington, most likely from around I-90 northward. The Oregon Coast Range may pick up 2-6” as well, but that greatly depends on temperature.
Finally, a quick look at the NWS Weather Prediction Center Excessive Rainfall Outlook for Friday in California.
Notice that most of California has a risk for excessive rainfall, with a very rare moderate to high risk (red and magenta) for the coastal mountains, parts of the Central Valley, and the Northern Sierra Nevada. The magenta (high risk) means a 50% or greater chance of excessive rain, which is very problematic due to the massive amounts of snow that have recently fallen.
With a potent atmospheric river already impacting California, urban/river flooding, flash flooding, avalanches, and landslides are expected. Be sure to check up on your relatives and friends in impacted areas!
I am still waiting for Spring to show up.
ReplyDelete