We’re in an unusually cool interval forward and, imagine it or not, extra snowflakes are anticipated over the western lowlands in the course of the subsequent few days
However earlier than I focus on the forecast, we have to discuss.
There’s a substantial quantity of confusion in regards to the variations between predicted snowfall and snow accumulation or snow depth.
This distinction is especially true when temperatures are marginal for snow.
Even when the environment is under freezing, the depth of a snowfall on the bottom can fluctuate immensely.
If the bottom is above freezing (because it typically is across the gentle western lowlands), the snow can soften, leading to far much less (or NO) accumulation. That is significantly true on asphalt or concrete streets that assist the conduction of warmth from under.
Snow can even compress underneath the burden of the snow under.
Backside line: occasion with chilly circumstances within the environment, the depth of snow can find yourself a lot lower than anticipated.
However the scenario is “worse” than that with temperatures are on the margin for snow. In marginal conditions, the place the freezing degree is above the floor, the snow is ALREADY melting. The mannequin diagnostics take into account moist snow as snow, so a snowfall map will be spectacular (5 inches!!), however far much less assumulates on the bottom the place the moist slop quickly melts away.
For these causes and others, I always word the distinction between snowfall and snow accumulation on this weblog. Maybe I must stress this extra. Maybe I would like to point out snow depth forecasts!
OK, let me attempt to do it proper on this weblog.
Throughout the subsequent few days, we are going to keep unseasonably chilly, with a low heart forming off the coast (see forecast sea degree stress map and low-level temperatures a 7 AM Saturday). Temperatures shall be marginal for snow over Puget Sound land close to sea degree, however some flakes within the precipitation is possible. Blue colours point out areas chilly sufficient for snow to achieve the floor.
However Portland is in a greater place for snow. A major stress distinction from west to east throughout the Columbia Gorge (greater to the east), will push colder air into the northern Willamette Valley. The air shall be drier as effectively, facilitating evaporative cooling.
Beneath is the forecast SNOWFALL complete by means of Sunday morning at 4 AM. A great deal of snow within the mountans. However solely gentle quantities (snow flurries) round Puget Sound and NW Washington at decrease elevations. Way more over SW Washington the place precipitation shall be heavier and the terrain is greater, and several other inches of snowfall round Portland.
However what about forecast snow DEPTH round western Washington?
NOTHING close to sea degree round Puget Sound and NW Washington. Nothing alongside the coast, the place snowfall is considerably larger than zero. QED.
Snowfall maps are enjoyable to take a look at, however they are often misleading.
