Just like it’s supposed to be.
Tuesday, January 4, 2022
El Ninos get most of the attention, but little sister (La Nina) can step to the plate just as well. Both systems can be traced back centuries and they tend to operate in irregular cycles. Over a cycle of decades we’ll see long periods where El Ninos are more frequent and stronger than La Ninas. One of those started fading about 5-10 years ago. We’re now in a cycle where the La Ninas dominate.
We are currently in a moderate La Nina phase. During a La Nina time, the jet stream over the Paciific is pushed northward so that heavy winter precipitation hits northern California, Oregon and Washington while leaving southern California and Arizona very dry. Example: snowfall in Oregon in December set a record high.
After the west coast, the jet stream generally runs along the U.S.- Canadian border before dipping into the northeast. That was the story for December as most of the U.S. had a very warm December. Meanwhile, Canada was very cold compared to normal.
But, as the cold dome builds to our north, it eventually has to break under the jet stream and head south. Right on schedule, that’s what is happening now. The cold dome is breaking free. The past couple of days have actually produced below normal temperatures. And another lobe of even colder air will arrive tomorrow. That should keep temperatures below freezing Thursday and maybe Friday.
In addition, a weak disturbance will form along the cold front to our south and spread some snow as far north as southern Indiana. The water content will be very low, but with temperatures in the 20’s light snow should be able to “fluff up” to about 1-2″ Thursday afternoon and evening.
When the cold air dips out of Canada, history shows that the below normal temperatures and snow chances increase for two-three weeks. So look for unseasonable cold weather into mid January. By that time Canada has lost most of its excessive cold dome. Rebuilding begins up north, and abnormally warm weather returns to much of the U.S. Translation: February will be very warm. However, often a La Nina winter ends with another round of the cold air escaping Canada in early March.
Such is life in an La Nina winter!