So if you hear the buzz around town, it goes something like this: “Is that all?” They’re of course talking about our rather mild La Nina winter/non-winter of 2011-2012. So far we’ve had just a handful (even less than that in the valley) of winter events. Mountains are starting to get back the snow lost in December but still no arctic cold snap acr0ss the state. Most of us think of an “arctic blast” as highs struggling to get into the 30s, and lows maybe in the low teens in the valley, well below zero in the mountains and Central Oregon.
So far this winter (which I am calling from Nov. 2011- Current), we’ve only bottomed out into the teens once in Eugene, a low of 19 on Jan. 16th. The coldest afternoon so far has been back in December, when we saw a high of 34. That’s it. Nada more. A couple of mornings in the 20s, but very short lived. Most of the really cold time has been with an arctic high sitting north of us bringing cold, DRY Canadian air with no chance for some valley snow.
Now I’m a glass half-full guy. Always have been. Think it’s what keeps me sane in this business and honestly in life. There’s always a chance you just have to keep truckin’ along. SO- that said, here’s some potential, and it’s just that, potential for a nice late winter blast by next weekend. Below is the GFS model for 1000-500 mb thickness value for Feb. 25, late Saturday afternoon:
So here’s what I’m looking at: 1) A cold upper low just to our northeast, 2) Counter-clockwise winds pulling in moisture off the ocean, 3) thickness values across Western Oregon between 522 dm and 526 dm. The general rule for freezing levels at 500 mb is the “540 line” or where the rain-snow change over line is, which we’ve talked about. The thickness of the atmosphere tells you how cold the column of air is and thus how easy it is so to speak to pull refrigerated air close to the surface (with snow) because it’s more dense.
Now, this is still 8-9 days out and a LOT can change in that time, but it bears watching over the next week. If, and this is a big if, we can get those ingredients in place, we might just have a nice last hurrah for winter as we round into early spring. We’ll see …
~ Justin Stapleton