This is the forecast discussion from Melissa Frey Saturday.
A great wrap up on our wintry and messy weekend! Enjoy . . .
Freezing rain, what a mess! It's not something that we see that
often, but when we do, closures and accidents are always soon to follow.
Winter weather in western Oregon is typically relatively mild. We
have the huge Pacific Ocean, which does a good job of moderating our
temperatures.
During the Winter, we'll have the occasional "arctic blast" when the
jet stream sets up over Alaska and Canada, bringing in the
sub-freezing, but very dry air. This is what we experienced all last
week.
From time to time, that jet stream will move out over the Pacific,
just enough to pick up some moisture, but not long enough to warm
up...with this case we see snow.
The pattern that brought the freezing rain Friday and Saturday,
actually took two separate systems to make it happen. First we had
that cold arctic air in place...too dry to bring any precipitation with
it. Then we had a small storm move in from the south...too warm to
bring anything but rain. But because of the timing, the cold air was
still in place, but only at the surface, meaning any rain that fell,
was rain and not snow, but froze on contact.
Unlike what many people think, freezing rain is never actually
frozen when falling. When the atmosphere is below freezing from the
surface all the way to the cloud, we see snow. But if any part of the
atmosphere is above freezing that snow melts into rain, but if the
surface itself is below freezing, the rain simply freezes once it
touches the roadways, cars, etc. and is called "freezing rain"
Now that all of the cold air is all mixed out, we'll be seeing just
regular old rain. The jet stream has shifted back to the west, and is
tapping into moisture, and heat over the pacific. This means rainy,
but above freezing conditions will be the norm for the next week.
Keep that rain gear handy,
Meteorologist, Melissa Frey
