We definitely have an interesting pattern shaping up for this upcoming week into next weekend that will give most of the United States relatively wild swings in temperatures. This is somewhat typical to see at the beginning of the astronomical spring, but the colder temperatures that will follow next weekend, which will be especially potent across the Midwest, Great Lakes and Northeast, are going to be pretty impressive. I’ll address the timing on all of this momentarily.
I must admit that what is about to occur is coming about a month later than what I anticipated at the beginning of the winter. Timing means everything in meteorology, and being off by even a couple of weeks can make a huge difference. While the cold plunge will be impressive, especially farther north, this will not be something that will set in for an extended period of time. However, I would be careful about planting crops or a garden since the volatility in the pattern going into April could bring AT LEAST a couple more shots at frost or freezing temperatures.
Meteorological Discussion with Reasoning:
Frost advisories and freezing warnings extend as far south as Oklahoma and Texas tonight, which won’t be the last time that regions fairly far to the south will flirt with temperatures at freezing or even drop below that. The shortwave (disturbance) responsible for this first wave of colder temperatures is currently moving northeastward into the Great Lakes region and will drag a cold front all the way to the Gulf Coast and East Coast by Monday/Tuesday. The cooler temperatures behind the front won’t be anything impressive, and temperatures will once again warm up across the eastern half of the U.S. by mid-week ahead of another system. This will be temporary, however.
As the first system (discussed above) moves out over the Northeast early in the week, a long-wave trough is going to dig southward just to the north of Hawaii. As this occurs, a ridge is going to build just off the West Coast and extend into western Canada and Alaska, and downstream of that ridge, a trough is going to build into the western U.S. as a piece of energy drops southeastward from western Canada/the Pacific Northwest. This kind of pattern configuration is known as an Omega block, and the reason for its name is that the mid and upper-level pattern literally takes the shape of the Greek letter Omega. Where this occurs, the wind flow does not go from west to east like what typically occurs but actually goes up and over the ridge and then back southward. Sometimes these kinds of patterns can stick around for a while, which is why it’s called an Omega BLOCK.
So you’re probably wondering why that is even worth mentioning. Here are a few things to keep in mind. With the building trough over the western U.S. (specifically over the Rockies into the Southwestern U.S.) this will bring below average temperatures for most of the week over those areas. The immediate West Coast, especially over the Pacific Northwest, will actually warm up quite nicely while that ridge hugs close to the coast. Conditions generally will be very dry over the West Coast with snow chances over the Rockies. Again, this is what I thought would have occurred in February instead of this late, but nonetheless, this kind of pattern does cut off the ability for system after system hitting the Pacific Northwest, even if it is temporary.
As I alluded to earlier, the eastern U.S. will warm up after the brief “cool-down” early in the week, but don’t get too comfortable because the real cold is coming in a one-two punch later in the week going into next weekend. I still say that the more impressive cold will be farther north, but freezing temperatures could reach as far south as the northern Gulf Coast states or at the least get into the 30s at night with the weekend Arctic intrusion. This last cold punch in the forecast period should be the most impressive.
A series of shortwaves will drop into the northern U.S. from Canada, with the first shortwave likely picking up energy from the southwest U.S. and triggering an outbreak of severe weather mid-week across the central U.S. I’ll get more into the specifics on the severe weather potential in another update. A cold front associated with a surface low pressure system will drag in the colder air behind it and will probably be further reinforced by another shortwave dropping south from Canada. This will be punch number 1 of colder air coming to the eastern two-thirds of the nation later in the week going into the early weekend. Some will definitely feel this more than others.
Right on the heels of the first punch of colder air, a very potent Arctic air mass will dive southward into the Great Lakes region and Northeast Sunday into Monday of next week (7 days from now) and will bring well-below average temperatures from the Northern Plains to the East Coast. This will occur as the ridge over the western U.S. and Canada flattens out some and comes slightly farther east. This will definitely be an impressive intrusion of Arctic air for this late in the season. Temperatures could be unseasonable cold air far south as the Gulf Coast states, but how potent that cold air will be farther south will be dependent on how far south that lobe of the polar vortex digs southward into the Great Lakes. This is something that we have a few days to watch, so those details can be ironed out this week. Farther north from the Northern Plains eastward, I could definitely see some records being broken.
With that said, I want everyone to understand that temperatures well-below average in late March and early April are much different than the same thing occurring in January or February. It might be significant from a climatological perspective if record lows are broken, but as we progress into spring, the sun angle becomes more direct over the Northern Hemisphere. That doesn’t mean that it can’t get very cold, but it just means that it won’t be as bad as if the exact same event occurred during the winter months.
I didn’t get a chance to address much the flooding situation that could occur over the Southeast regions this week or the severe weather threat coming up this week, although I did post the 5-day rainfall forecast below. I’ll try to have updates on all of that in a day or two.