WeatherWatcher: Snow level flirting with the lowlands all week

Clouds and precipitation over Puget Sound
Photo by Frank Kleyn

The photo is an impressive capture by Frank Kleyn of some convergence zone action over Puget Sound. At the north end of that cloud is a nice column of precipitation reaching the ground.

Cold and Snow potential:

Forecast models have been painting a picture since last Wednesday of the potential for several arctic waves to move through this coming week. There is still a lot of uncertainty, especially for mid- and late-week but expect the snow level to fluctuate between sea level and 1,000 feet all week. 

Plenty of showers are expected, as well as a cold front moving in through Tuesday night into Wednesday morning.

There is a winter weather advisory issued for western Snohomish county, including Woodway, Edmonds, Lynnwood and Everett. Shoreline might be snagged into a little of that fun as well. 

The winter advisory is in effect from 10pm Sunday evening until 10am Monday morning. Some snow showers are possible, and there could be some spotty accumulation of a dusting to an inch or so in some neighborhoods.

An active convergence zone is hanging out in Snohomish and north King counties overnight into Monday morning. Heavier showers could temporarily bring the snow level down to the surface and produce a small wet accumulation. Things should warm above freezing Monday as the sun rises and takes care of any frozen stuff left over.

Monday afternoon through Tuesday morning is expected to be mostly sunny and clear. Look for it to be breezy with winds gusting to 30mph and temperatures near 40°F for a high, and lows in the 20's. The next event arrives Tuesday afternoon into the evening, with winds increasing as the storm approaches.

Tuesday-Wednesday potential for snow:

Tuesday evening south winds are expected to increase, gusting to 30mph initially and increasing to 40mph late into Tuesday night. Rain or snow is likely with a snow level starting around 400 feet (most of the higher parts of Shoreline and Lake Forest Park). 

A few inches of snow accumulation are possible, but it's not certain with this event. Current high-resolution forecasts from the UW WRF GFS model show snowfall of around 4-6 inches in the Shoreline and Lake Forest Park area, but this is not accumulated on-the-ground snow. A lot of that snowfall will likely melt.

Wednesday it is expected that we warm up and transition to all rain for the day, but rain will taper off to showers, with winds still breezy through the day. Snow levels will still be hovering near 500 feet so it's marginal whether we will actually see snow on the ground.

Remainder of the week and into the weekend:

For Wednesday night through the weekend, the chance of rain or snow showers continues in the forecast. There are hints of another storm on Friday but for now they're backing off and calling it just showers likely. Thursday night into Friday could be our coldest window, with snow showers forecasted for Friday morning and a snow level at sea level.

Bottom line:

This is a week of uncertainty, and things could change rapidly. My best advice is to be prepared to deal with winter weather this week, especially before Tuesday evening. We could be dealing with the wintry mix weather for more than a week. A slight change in a storm track or strength could make all the difference in a big snow event or a mild rain event. 

Be sure to keep checking back on our webpage for updates in the forecast. I will try to keep my twitter feed updated as well on my weather station webpage if things change with short notice.

For current weather conditions visit www.shorelineweather.com