PORTLAND, Maine — If you think nearly every storm has behaved the same way this winter, you are definitely right.
Classic coastal storms have been hard to come by, and the reason is pretty simple. The weather pattern has lacked a deep trough in the jet stream over the east coast, allowing disturbances to hit the coast, grow and intensify into a big storm.
Instead, we have dealt with a lot of weaker systems. We call them inside runners, taking a track far to our west. The precipitation is caused by "overrunning" ahead of a warm front.
Cold air is tough to displace, because it's heavy and dense. Warmer air is less dense, and is forced to ride over this cold air. This causes instability, generating clouds and precipitation.
It means most of the time, ahead of this warm front, all of us see a burst of snow that lasts several hours. Then, as the warm front makes progress moving north, the column of air can start to warm above freezing, aloft. This changes snow to sleet (ice pellets) and freezing rain. There has been some rain near the coast too, usually at the tail end of the precipitation.
In this type of a pattern, the mountains and northern Maine very often stay cold. It's meant a ton of snow and ice. As of Wednesday morning, 38 inches of snow were on the ground in Caribou, with two to three feet in the western Mountains.
While the pattern has not been conducive to major coastal storms so far this winter, there is still plenty of time left. We'll see.