From the ABC 7 Weather team

March going out like a COLD lion

March 20, 2013 - 06:27 AM
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Ready for spring? The calendar says it's here, but it feels like winter.  What is going on that we are so cool?

Photo: Smithsonian National Zoo

Time for true confessions of a Meteorologist. I know I am supposed to love all kinds of weather, and I know this has not been a harsh winter for us in D.C, but I’m over it.

Meteorological spring arrived March 1. The Vernal Equinox happened at 7:02 a.m. Wednesday, my daffodils are blooming, and I am completely ready for spring! I’m guessing you are too, based on the comments I have been receiving on Facebook and Twitter.

Now, I hate to be the bearer of bad news for you warm weather lovers (I am just the messenger here), but more winter-like temperatures are on the way. March will be going out as a cold lion.

So, what the heck is going on that we are talking about snow showers and well below average temperatures, you ask?

Well, we can blame something called the North Atlantic Oscillation (NAO). The NAO causes changes in weather patterns. When the NAO is in a negative phase, like it is now, it drives the polar jet stream to our south. So, what does that really mean for D.C.? Still with me?

Jet Stream from Intellicast


The polar jet stream is a fast current of air about 5-7 miles up in the atmosphere that divides the cooler air to the north and the warmer air to the south.

When there is a kink or trough in the jet stream, like there is over the Great Lakes and east this week, it allows cool air from Canada to freely descend upon us. In addition, storm systems generally travel from west to east within the jet stream.

So, with cool air in place and storms tracking to our south, it is a more likely set up for snow showers than rain showers in our region. This was the case for many of us last weekend.

And some light snow/flurries can be expected again Wednesday night. In contrast, when there is a bump or “ridge” in the jet stream, warm air builds up under the influence of high pressure. Those under the ridge tend to see calm, sunny and mild conditions. 

Trough and Ridge

These long wave patterns tend to stick around a while and it looks like that is the case for the rest of March. Here’s a look at the GFS computer model forecast for the jet stream next week, Wednesday, March 26th. 

Forecast Jet Stream March 26th

Notice the cool trough still over the Mid-Atlantic. At least one computer model is also trying to bring snow showers back at us early next week with this long wave pattern! Notice the bump out West. I’m heading for the Valley of the Sun next week to rejuvenate. Look out Spring Breakers!

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