9 p.m. on Monday …
We ended up with 0.7 ″ of snow officially in Portland on Sunday. It was a mixture of Sunday morning and Sunday evening again. This brings our winter total to 1.1 ″
Fortunately no freezing rain yet and none in sight!
Today, the southern limit of this cold arctic air mass has shifted across the metropolitan area. It was just at sunrise. A northwesterly breeze settled in, bringing the air 25 to 28 degrees south. The maximum at PDX was just after midnight… 34 degrees. It bottomed out at 26, has now risen to just below zero for most of us as the thin layer of arctic air mixes with the surrounding air. There is no supply of cold air from the north or the east until Wednesday morning. So it’s very cold, in fact the 850 mb temperature of -9.9 degrees in Salem means it is around 18 degrees at 4000 ′ above your head! It is also the coldest measured over Salem since the Arctic epidemic of December 2013.
It’s still snowing tonight! I see dust all over the metro area and the boss says he has 1/2 (fresh) at Lake Oswego. Most of the lower altitudes west of the Cascades are subject to a winter weather advisory. Anything over 1 triggers this notice. I remember back in the 1990s when the criteria was either 2 ″ or 3 ″, but after a few events it became apparent that Portland can stop with 1-2 ″ of snow, so a notice usually means that at less than 1 ″ of snow is expected. I think a 2 inch mark covers it for tonight, although intuition says the majority of us have an inch.
I think the roads will be mostly good at noon and tomorrow afternoon, assuming we really only have less than 2 ″. Secondary roads in neighborhoods could of course remain covered in snow all day
A “BC Slider” (a low surface depression that moves rapidly along the Pacific Northwest coast) provides lift, clouds and light snowfall. The depression is well west of Astoria at this time
At around 4 p.m. tomorrow, the low has weakened and spread somewhat over the southern Oregon coast. We won’t see much wind from any direction for the next 24 hours as it is very weak.
This light snowfall continues until tomorrow morning with flurries following the rest of the day. Temperatures stay below or near freezing most of the time. All models produce snowfall between 1/2 ″ and 2 ″, most around 1 ″. The outline here is the HRRR. GFS is much wetter / whiter… producing 3-5 inches in Salem / Albany areas by tomorrow night! This is due to another weak southward wave descending into the upper atmosphere later tomorrow, prolonging precipitation. There is a decent ‘bust potential’ in the lowlands with this event …
After the depression falls in our south tomorrow night, a new wave of modified arctic air is pouring into the Columbia River Gorge. This should bring drier air, sunshine and high temperatures only to around zero on Wednesday. This will be our third day around freezing point. A 12 cold days of Christmas indeed!
I’m watching the next system closely for Wednesday night and Thursday. All models agree that another small “cursor” descends along the coast, but moves inland through central Washington this time. This gives us a gusty southerly wind for at least a few hours that day. We’ll probably be climbing into the mid-30s at some point on Thursday with the land wind warming, but not until somewhere between 1 and 3 of snowfall.
That’s all for tonight… enjoy the snow! Chief Meteorologist Mark Nelsen
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