Snow? Sputter, Sputter, Snow!

April Snow


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After a warm and relatively dry winter and early spring, April brought snow!

A huge April Nor’easter slammed the Northeast and Mid-Atlantic states. Some areas got over a foot of snow!

More than 75,000 people were left without power.

What in the world is happening? Why did this happen?

Here's some insight …

Happy April! SOURCE: NOAA

Blame it on the NAO, the crossing guard of the Atlantic. The North Atlantic Oscillation is an air pattern that allows cold Arctic air to whiz across the Atlantic. For most of this winter, it has been either positive or neutral. This meant that it either stopped the cold polar air from entering North America (a positive NAO) or allowed it to leave the continent very quickly (a neutral NAO).

Blame the NAO, the crossing guard of the Atlantic, for the snow. Credit: Microsoft

Now it is negative.

The North Atlantic Oscillation is shaped by air pressure. When the low-pressure atmospheric area around Iceland is similar to the high-pressure around the warm Azores Islands in the mid-Atlantic, it forms a negative NAO. This air pattern blocks cold fronts from crossing the Atlantic. Cold front after cold front enters North America and lingers. The temperatures drop and the frozen air plunges south.

The negative NAO is keeping cold air from crossing the Atlantic SOURCE: NOAA

At the same time, the Gulf Stream is flowing very fast, heating the ocean water off our shores. The air above the ocean is very warm and wet. This warm, wet air is flowing up the coast and has set everything up for a classic Nor’easter. When the Arctic air hits it, it is like a car crash. The Atlantic air cools and all the moisture falls out.

Unfortunately, for some of your gardens, some of this fallout is snow, lots and lots of snow. Indeed, the amount of snow is record-breaking in some areas, including Central Park in New York City. However, this is a spring storm, not a winter blizzard. Most of the precipitation will be much needed rain for the thirsty Northeast.

Most models seem to indicate that the negative NAO will not last very long. The NAO will be alternating between positive and negative over the next few months. With luck, we will get rain and then more warm, balmy weather. It all depends on the crossing guard of the Atlantic.


About This Blog

Evelyn Browning Garriss doesn't just blog about the weather forecast; she provides insight on WHY extreme weather is happening--and a heads up on weather to watch out for. A historical climatologist, Evelyn blogs about weather history, interesting facts about the weather, and upcoming climate events that affect your life--from farming to your grocery bill. Every week, we look forward to another great weather column from Evelyn. We encourage our weather watchers to post their comments and questions--and tell us what they think!

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Bye summer.. well certainly

Bye summer.. well certainly miss you :( I guess we wont be seeing you this year. I knew having a summer this year just wasent going to happen. March brought sun and 70 degree days and May is bringing rain and 50 degrees. Will it ever warm up Evelyn? Or is this just going to be a chilly, rainy summer like accuweather claims here in DC area? Please bring me good news! I dont want a cool summer! Were all thinking its too good to be true to get hot on time! We are all worried about this summer and im thinking it will be cool and miserable.. winter never arrived so i guess summer wont happen either. Please be hot!!

please be hot this summer!

please be hot this summer! please be hot in Virginia! its already hot now but im afraid the NAO will go negative this summer and cause us to be cool and soggy like April was! I want some heat

Another 100° every day

Another 100° every day summer. Ugh! I like warm, but that was nuts last year.

Keep it positive Evelyn keep

Keep it positive Evelyn keep it positive! lol. No more freakish cold snaps please!! Will we likely have more heat waves in the coming months as the NAO and jet stream shift upward? Also when will the effects of el nino kick in?

so that explains why I got 2

so that explains why I got 2 inches outside of my house in Amherst, Virginia! but ive seen worse! we had this snow storm that turned out to be one of the biggest ive ever seen before in my life! then followed by an ice storm that left us without power in April!. So if were having a positive NAO this summer then this summer will be quite the sizzler? How is May looking also? I wanna see some 90s! thanks evelyn for the great blog!

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