Generally, when we have mentioned Omega blocks in the past, we have referenced them as the cause of heat waves and exasperating wind and fires in the southwest during the summer months. This winter has offered it’s own blocking pattern, and while it has been unusually warm over the Christmas Holiday, it has also brought about quite a bit of something else.

Precipitation. While the ridge in the middle of this block, like a Ω shape, the Greek letter Omega, gets a lot of attention, the winter has been all about the troughs on the west and east of the main feature. We discussed the rain that hammered Redding in our recent verification, but rain and snow has smothered California, with flooding and deadly consequences from San Francisco to San Diego. All of this was after the deadly flash flooding up around Redding.

The rain was heavy, certainly, but what really brought about the problems was the persistence of the pattern. The blocking ridge in the center of the country ensured that the seasonally omnipresent low in the Gulf of Alaska was able to funnel moisture to a low off the California coast, which made for a much wetter stretch than even California’s rainy season is accustomed to.

It isn’t all bad, of course. Anyone in tune with the economics of California knows that the snow in the Sierras is often the only moisture that the Valley will get through the summer months, supplying crops and thirsty residents. A large snowpack, while terribly inconvenient right now, will be a boon for regional agriculture this summer.

On the other coast, the trough has been a good environment for the development of low pressure in the Gulf Stream. This has enhanced some clippers moving out of the Canadian Prairies, as well as more localized development, both features contributed to the travel hassles along the coast over Christmas. The continued winter storm warnings for Lake effect snow in the Great Lakes are all ongoing because of a feature that has rotated and become embedded over Hudson Bay.

For the foreseeable future, this is the outlook. The Plains and particularly the Front Range will remain quite warm. As with most Omega features, even ones in the winter, the West Coast will remain above normal as well, given flow moving down from the mountains when the low pressure off the coast ebbs. Throughout all of it, look for above normal moisture nearly nationwide to start the new year.