Fall and early winter are not only very volatile, weather wise, but atmospheric patterns are in "birth" mode this time of year, setting up enduring cycles that will dictate our weather for months, making any forecast beyond 7 days an act of complete conjecture.
But I don't care. I want it to snow, and I want to know when that's going to happen.
So here's me trying to predict (ish) the first measurable snowfall in south-central Wisconsin.
Here's how I intend to do that:
- Look at every available weather model (the most ambitious of these goes out to 384 hours, or 16 days);
- Look at the weekly and monthly temperature anomaly projections (which most real weather folks regard as pure entertainment);
- Study jet stream tendencies and forecasts for the slightest sign of an Alberta Clipper or Panhandle Hook or cut off low or even a boring west-to-east zonal low from the Rockies.
- And then, using all that wonderful information, I will guess.
Many of you know that I've already predicted an active winter, with above average snowfall and colder temperatures. That prediction was based partly on the prospect of a weak La Nina (and an examination of Madison winters with similar sea surface temperature anomalies). Since that September 5th prediction, a couple of things have happened:
- La Nina seems to be strengthening, ever so slightly, and;
- The Climate Prediction Center essentially issued the same Winter Outlook that I did, except 6 weeks later.
Now, models are starting to give us the slightest glimpse at what November might look like. We usually average about 2-3 inches of snow in November, but this year may be setting up to be more active.
Here's why I think so:
A large area of high pressure in the southwest U.S. (a "ridge") is forecast to remain in place for roughly the first half of November. This means that our weather systems will form and travel on the north side of that ridge (a "trough"). Those systems generally start by bringing in warm air and rain on the front end, and cold air, wind and rain-to-snow on the back end.
Here's one example of that. After a quick warm-up next weekend (let's say Friday and Saturday, 11/4-11/5), low pressure develops near the Texas panhandle, heads northeast, gets into southern Canada, and essentially stumbles like a New Glarus drunk around the same general area for a few days. Remember that winds move counter-clockwise around low pressure, bringing strong winds from the northwest.
Now, I'm going to show you some images that demonstrate what I mean. But I have to give you the responsible disclaimer: this will change. But that doesn't really matter, because they speak to pattern. Even if GFS doesn't nail the right position on the right day, it speaks, however loosely, to pattern.
These GFS images show you 1pm Saturday (11/5) to 1pm Tuesday (11/8). Watch the low pressure system.
Normally, the northern jet stream would guide this low pressure far off the east coast of Nova Scotia in short order. But it sits. And it spins. And it pulls cold air in behind it. It is cut off from the jet stream.
And I'm going to assume that this pattern repeats in 18-22 days...right around late Thanksgiving weekend...except with colder air already in place.
There's likely not a meteorologist in the world that would agree with this rudimentary conclusion, but I think this event establishes a recurring trough in our neighborhood. And that means the potential for some Alberta Clippers throughout November -- until that ridge breaks down, opening up all kinds of possibilities.
So here's the prediction:
We'll have some flurries and snow showers throughout November (starting on the 7th/8th), but the first real measurable snow will occur 11/26-11/27...the Saturday night/Sunday after Thanksgiving.
If I'm right, let's all go buy lottery tickets. If I'm wrong, at least I made a case.
~Scott
