There may be problems with water supply and forest fires in summer and autumn. This was La Nina’s second consecutive winter season. La Nina winters generally result in healthy snowpack in the mountains and winter 2020-21 did just that, ranging from around 110-135% of average.
This winter season, the wet period from late November to mid-January resulted in a snowpack in the mountains varying from 100 to 130% of normal. Remember that the Col de la Cascade highways have been closed several times due to heavy snowfall and a high risk of avalanche.
Then, in mid-January, a relatively drier weather pattern set in and continued through mid-February. The month-long drier period in mid-winter resulted in a gash in the snowpack, falling behind average and dipping to 65-95% of average by mid-February.
The snowpack in the mountains generally reaches its peak around April 1st. So there wasn’t much time for the mountains’ snowpack to catch up after the drier mid-winter weather turned wetter.
The latest statistics from the Northwest Avalanche Center show that the mid-winter dry period removed the snowpack. As of April 1stthe snow accumulation at the Olympiques and the Cascades ranged from 60 to 85% of normal. The good storm early next week will add about a foot of fresh snow to the mountain snowpack, but still not enough to reach at least average in most places.
The more limited snowpack in the mountains may present challenges this summer and fall. One concern is an earlier start to the wildfire season, likely in July. The North Sound has experienced periods of wildfire smoke and poor air quality four of the last five years after decades without wildfire smoke problems. Almost all of that smoke was blown into the region from wildfires in British Columbia, eastern Washington or south in Oregon and California.
The lower than average mountain snowpack also means less stored water available in the snowpack. The 1st of Aprilst The Natural Resources Conservation Service’s mountain snowpack water equivalent map shows the Olympic and Cascade Mountain basins ranging from 56 to 97 percent of average. This issue raises concerns about water for irrigation, fish, recreation and drinking this fall.
The latest seasonal weather forecast from the National Weather Service Climate Prediction Center (CPC) shows again what the trend has been so far this century, July to September warmer than average. The chances of another “heat dome” similar to the one experienced at the end of June last year are low, but cannot be ruled out.
Historically, the North Sound experiences periods of temperatures reaching the 90s, an average of three times a year. But so far this century, the North Sound has exceeded that average more than half the time, and periods of excessive heat will be another concern this summer.
The outlook also shows near-average rainfall this summer. Summer is the driest time of the year.
As for this fall, the current Nina is moving towards neutral conditions, which means that sea surface temperatures in the eastern Pacific Ocean have a good chance of being near average. Neutral conditions fall between La Nina (colder than average sea surface temperatures in the eastern equatorial Pacific) and El Nino (warmer than average).
the latest insights from the CPC for this fall shows the likelihood of precipitation shifting to drier than average conditions with warmer than average temperatures. Typically, neutral conditions produce near-average temperatures and precipitation, along with a greater risk of significant fall storms such as high winds and flooding.
In the meantime, prepare for what could be another hot summer with a greater risk of wildfires and wildfire smoke later this summer, as well as more limited water supplies.