Merry Christmas! Sorry a little late, but hey, it’s only the 2nd day of Christmas; I’ve got 10 more days in which I can say that.
I’m working this evening and I’ll put together a blog post about this upcoming week after 00z models are in.
But, I notice a band of precipitation which no models seem to have accounted for is crossing the Coast Range. It’s REALLY light stuff, but taking a look at the 4pm Salem balloon sounding:
It’s pretty obvious the atmosphere is cold enough for snowflakes to survive down into the lowlands. Temperatures are a degree or two above freezing up around 2,000′, but it’s dry air and precip falling into that dry air will evaporate, cooling the atmosphere. That’s what we call Evaporational Cooling or, as slang, Wetbulbing. The highlighted column is what the temperature will be if the airmass “wetbulbs”. Note below freezing all the way down almost to the surface.
So IF the precipitation survives the drier low levels and IF the band doesn’t fall apart entering the valley? Then you may see snow or snow/rain mixed in the next couple of hours in the metro area. It’s cold enough so that IF the precip holds together a dusting could accumulate at the top of the West Hills, Mt. Scott, Western Gorge etc…
A lot of IFs, but you get the idea.
Chief Meteorologist Mark Nelsen