SEATTLE - It remains below freezing across Western Washington for most of Monday as an Arctic airmass remains in place.
However, winds aloft are beginning to turn northwesterly to westerly. That is bringing some modified (slightly warmer) air with more Pacific moisture into the coastal regions of Washington.
This moisture several thousand feet aloft is producing light snow showers falling to the surface on the south coast. A weak disturbance is also contributing to lift along the lower Washington coast and, therefore, precipitation.
This disturbance moves into Oregon this afternoon. Meanwhile, onshore flow increases slightly across the state.
Light snow showers possible today through tonight
In conjunction with increasing amounts of moisture, some light snow showers will be possible across inland locations of the state -- including Puget Sound starting late this morning and lasting through tonight.
Best chances of light snow showers from about lunchtime through mid-afternoon will be along the coast, the Strait of Juan de Fuca, from Everett north toward the Canadian border and northwest through the northern islands, as well as the Cascades and foothills mainly from King County northward. Accumulations are likely to be a dusting to an inch or so in some of the heavier showers. We'll also be watching far southern areas between Olympia and the Oregon border for some snow showers.
Toward dark, we could see a few more snow showers down to the Seattle area, though we're likely to see areas from near downtown Seattle south through Tacoma stay mainly snow-free through the evening commute. However, some flurries can't be ruled out. Accumulations in the central Sound should be light with most areas seeing no accumulation at all.
Foothill locations of Pierce and King counties, though, will see some occasional snow and one to three inches of snow could occur in locations like Gold Bar and higher elevations around North Bend.
Of course, with the scattered nature of precipitation, many areas will receive no snow today while some isolated spots could get more than noted above.
Transition to mix of snow and freezing rain or drizzle possible overnight into Tuesday
Overnight, the atmosphere just off the surface and aloft continues to warm as we start to make the transition to more typical weather.
However, there will be a period early Tuesday morning into early Tuesday afternoon where we could see a mix of light snow and light freezing rain.
Freezing rain occurs when liquid water droplets (instead of snowflakes) are produced within clouds where the temperature is near or above freezing. As cold air still is in place at the surface, road temperatures are below 32 degrees, causing the raindrops or drizzle droplets to freeze upon contact. This can produce a thin glaze of ice on less-traveled and untreated road surfaces.
The best chance for accumulation and significant snowy or icy travel problems Tuesday morning will be north of Seattle and in foothill locations.
However, we will be on alert throughout the area as this "last gasp" of the Arctic chill holds the potential for producing travel problems in any lowland location.
By late Tuesday afternoon, we begin to see some drying and lingering precipitation in the lowlands falls as cold rain.
Temperatures return to normal (mid-to-upper 40s in Seattle) late this week with several rainy cold fronts bringing only liquid precipitation to the lowlands but much-needed mountain snow.
During the upcoming thaw, pipes may leak or burst
We have already received reports of some burst pipes and water mains around the area, and as temperatures warm mid-to-late week, pipes containing frozen water will thaw out. Some pipes will have cracked due to ice in this cold period, and once the thaw occurs, we could have plenty of issues with broken pipes!