It has been an unusually active weather day with multiple hazards.
Of first note, the strong winds in the lowlands will be subsiding slowly through the evening but still, a few gusts over 40 mph are likely with 50+ mph across Whidbey Island and surrounding areas.
In addition, heavy rain (possibly mixed with small hail, graupel, or wet snow) will be possible this evening along with a chance for an isolated thunderstorm.
Strong winds will continue in the mountains into tonight with power outages and wind gusts over 55mph continuing into the morning with another foot or more of snow. Travel through the passes will be hazardous into tonight with the snow tapering slowly through the day Wednesday.
Coastal flood threats are beginning to wane as the winds start to subside and we get away from the higher tides of today earlier.
SNOW CHANCES SOUTH TONIGHT
A weak weather system will be moving through southern Washington tonight and that will bring some rain and then a rain/snow mix or all snow to areas mainly south of Tacoma later this evening (after about 9-10pm) and overnight into Wednesday morning. Temperatures will be just barely cold enough for any snow accumulation in Lewis, Thurston, and Pierce counties into the morning and mainly we can expect this on grassy surfaces and elevated surfaces but a quick inch to two inches could accumulate. Then by daybreak, many other spots around the lowlands could see flakes fly but mainly little to no accumulation, with the possible exception of southern Whatcom County. Overall, this quick hit of wintry weather looks quite minor, and temperatures will remain mainly above freezing for most locations with highs back in the upper 30s to lower 40s on Wednesday afternoon.
COLDER AIR LATE WEEK AND WINTER STORM THREAT?
Cold air will plunge south on Thursday as Fraser River outflow develops. Wind gusts could be over 40mph near Bellingham with frigid wind chills. Elsewhere, we’ll be watching the push of cold air and the possibility that as it moves south it wrings out some light snow or flurries, but this air is going to be very dry and the overall atmosphere will not be rich with moisture during this transition, so I’m not expecting significant snow potential on Thursday. But do expect falling temperatures through the day with the mercury falling below freezing by Thursday night.
There remains considerable uncertainty as to the threat for a winter storm in Western Washington Friday afternoon through Saturday. There is a chance that snow will develop on Friday afternoon, then as a potent area of low pressure moves ashore Friday night and Saturday morning, a transition to a mix of snow, sleet, or freezing rain could occur. But the actual location of the low pressure area is critical. A number of forecast models have the low going farther south over Oregon, which would limit impacts of snow to mainly the southern third of our area. A farther north track (as continued to be forecast by the U.S.-based GFS forecast model) have Western Washington being impacted by a major winter storm with some ice storm implications too.
We hope that the forecast models converge on a common solution in the next couple of days, and that will happen eventually as the models better resolve these fast-developing features out over the Pacific and their eventual strength and motion, but it is true there is an unusually wide range of impact possibilities right now as we’re three to four days out. We will update as the forecast details come into better focus, but we should at least be thinking about home and business preparations for winter weather impacts Friday and Saturday.
We would expect drier conditions with slowly warming temperatures (but staying cold with morning temperatures below freezing) into next week.