Another attempt for low elevation snow on Tuesday

Weather

PORTLAND, Ore. (KOIN) – We’ve waited a long time this winter for a chance for snow around the valley and our moment may be coming.

The weekend opened the door to some minor action and with colder air hanging around, we may have another opportunity for snow Tuesday.

Snow levels have been hovering around 1,000 since Sunday and it won’t fluctuate all that much until Tuesday night. Like most winter events here, we are playing an elevation game around the valley. We are also waiting to match up the precipitation with the cold air to really solidify a widespread event. It cannot be stressed enough: this is not going to be a widespread snow event. However, snow is possible.

What do we have to work with? We have an east wind that is not exceptional, but, it is there. We also have a decent amount of moisture out there that may impact some regions more than others by Tuesday night. The east wind will help support the colder air and the moisture should help encourage that as well.

GENERAL PICTURE

A cold pool of air moves in with a trough digging down through the day Tuesday. An area of low pressure meanders off shore a bit and an occluded front extends across the area by the evening. You can see how the shield of moisture extends over the valley and to central Oregon. What we know is that the timing is going to be in the second part of the day starting around dinner and continuing into the night.

Wind will start to increase out of the east around the surface as the occluded front nears the coast. This should help usher in some colder air from the Columbia Basin, which is modest. Temperatures cooling to the upper 30s at this time. The graphic below is detailed, but if you’re interested in something that is more complex, you can digest that image below. We will use this to look at the wind direction, which is supporting and east wind by tomorrow afternoon.

MODEL DIFFERENCES

Right now models are not in complete agreement. They are fairly close, but the difference is the projection for snow coming off the coast range and some of the areas around the Greater Portland Metro Area.

If you cycle through the slideshow below, you will gather three different weather models and the projection for snow by Wednesday morning. Right now, cold air is trying to hold firm out near Hillsboro and the 47 route communities. This is also going to be the area that will have likely the greatest precipitation rate and intensity. Coast range travel is likely going to be impacted and travel south to California (more below). Additionally, temperatures look to drop to freezing through the Columbia River Gorge. The problem there is the moisture may be slightly limited as this system pulls south. Be prepared in areas of Hood River and portions of Skamania county across the street.

Portland? It may be a rain event with a wintry mix. However, temperatures may have a hard time to actually warm up on Tuesday and with the rain, that may be enough to cool us down for snow to the floor. Models again, projecting anywhere from zero to an inch. Sylvan Hill and locations higher in elevation will be the vulnerable spots. If it snows, it will come in the evening hours and it may impede local commutes.

TOTAL PRECIPITATION

This is where models are differing and this is where we need to really focus the forecast come Tuesday. We know that snow levels can be projected around 1,000 feet but in locations near mountains and hills, the precipitation can quickly change the situation over to accumulating snow. Right now, plenty of moisture for the coast and coast range. As it spreads inland on Tuesday night, is it going to be light or will there be more depth to this. One model has .15 inches by Wednesday morning and the other has .30 inches by 10 p.m. Tuesday night. That is a massive difference when it comes to a snow forecast! THIS IS WHERE THE FORECAST IS GOING TO ADJUST. With the path of that area of low pressure cutting south, I think we will find ourselves closer to the .20-.30 inches range by Wednesday morning. That is probably somewhere in between the two. With a heavier shower, that will likely be enough to help out the areas off the coast range for snow. This may be good to bring that snow to the valley floor by night.

PATTERN

This is an exciting weather pattern for us right now. However, it is really more of an impact for southern Oregon and northern California. Notice that the jet is focusing on that area aloft! This is going to support a lot of snow for the mountains and it is driving this system right to them by Wednesday. This is likely too warm for the coast communities but it is definitely going to wet and the travel is going to be tough.

Check out the snow totals for the mountains in southern Oregon and northern California as of Wednesday morning. This is going to make travel through areas of California very dangerous.

The Siskiyou summit will probably catch half a foot of snow by Wednesday and the Sierra Nevada mountain range is really going to collect.

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