Upper Level Lows Making Llfe Dreary, Chilly, In Northeast, Northwest

Schematic view of a cut-off low, though this isn't today's forecast
You see the jet stream going across Canada (thick blue lines and
arrows) with a cut off low left behind it in the center
of the country. 

It's chilly and rainy here on this Sunday and in much of the rest of the Northeast. The Pacific Northwest isn't doing much better.

The common thing causing these dreary spots on the national weather map: Cut off upper level lows.

These things I would say are most common in the spring. The jet stream normally helps bring storm systems generally west to east across the Northern Hemisphere.

The jet stream is basically strong winds in the upper levels of the atmosphere, so things move right along, so a storm usually doesn't sit in one place for very long.

Most storms also have a pool of chilly air with them in the upper atmosphere. The air up there associated with them is cooler than the surrounding air. That helps air rise, cool, condense and drop moisture as rain or snow.

This time of year, in the spring, the jet stream is retreating more and more toward the North Pole. Sometimes the storms within the jet stream are "left behind" to the south. Think of a river that has flooded a neighboring field.

When the river recedes, most of the water in the field goes with it. But pools of standing water remain. That's kind of what these cut-off lows are like.

With no jet stream to push them along, cut-off lows tend to meander and don't move much. Which is why this upper low in the Northeast began to affect us Friday and Saturday and will keep doing so into Monday.

As I said, the air in upper layers of the atmosphere is chilly, compared to the surrounding air in and near these cut-off lows. That helps air rise and we get precipitation. The chilly air up above helps make us cold down here, too.

That's why temperatures are so chilly today - in the 40s to near 50 in Vermont. Snow is likely at elevations above 2,000 feet, though I don't think it will accumulate much, except on northern mountain peaks.

To give you an idea of what a supply of cold air there is with these upper lows, temperatures today are in the low teens at about 9,000 feet above central New York.

Directly beneath that cold upper level center in New York, it was only 35 degrees in Utica, New York as of 9 a.m. today, and the expected high temperature today is only 41 degrees. In high elevation Saranac Lake, New York, it was 33 degrees and snowing as of 9 a.m. Sunday.

The upper low in the Pacific Northwest isn't as strong as the one over us here in Vermont, so the air isn't as cool and it isn't as rainy there as it is here. Still, it's cooler than normal in places like Seattle, and they are under threat of showers today.

The jet stream to the north of these cut off lows still has some influence. That jet stream will gradually nudge the upper level low over us to the east in the coming days.

You'll notice it will be a tad warmer and less showery on Monday, and by Tuesday, it'll be back to spring, with temperatures right there in the 60s with sunshine.

We're lucky. Sometimes these upper lows can sit over or near us for up to two weeks. It's good we'll only have to put up with this one for two or three days.