The last three out of four snowy winter seasons have been blamed, at least in part, on La Niña, the cooler-than-normal sea-surface temperature pattern along the equatorial regions. As of early May, ocean waters in this area are still cooler than normal. But sea-surface temperatures along the equator have been moderating, which indicates that La Niña is weakening.
Over the last month, new but small regions of warmer-than-normal sea-surface temperatures have developed near the South American coastline. Although it has been looking like a back-and-forth pattern of ocean warming and cooling for much of this year, it appears that La Nina will continue to weaken into the late spring and summer season.
It’s also possible that the new warming along the west coast of South America may indicate the development of a new El Niño later this year. Our previous winter of 2009-’10 was practically snowless due to the El Niño pattern.
For the rest of May, and if La Niña continues to at least maintain its current strength, I expect to see more clashes of cooler air to the north combining with the warm and moist air from the south in the central and eastern parts of the U.S. Therefore, more severe thunderstorms and tornado activity will be likely in regions east of the Rockies and toward the Southeast.
In terms of our weather, the cool and wet pattern that has been dominating the far West should finally change toward drier and warmer late this month. We’re already seeing more days of sunshine and milder temperatures in between the cool and showery ones.
I am still hopeful that we’ll see a warm and dry summer season this year as La Niña finally dies off in the south-central Pacific Ocean.
If current weather patterns continue on the same course, a strong stationary ridge of high pressure should build into our region in June and last through July, August and at least early September. This should mean hot days this summer with afternoon highs near or above 90 degrees. Don’t be surprised to see at least three or four days with maximum readings near or above the century mark in the Inland Northwest.
But, if we do see unusually hot, dry and windy weather this summer, it could mean big trouble for this area’s parched grasslands and forests. The abnormally wet weather will likely lead to increased foliage, which will eventually dry out.