We have had no shortage of rain the last couple of weeks. In fact, we’ve had quite the surplus with many parts of the Mid-Columbia exceeding April rainfall averages by the middle of the month. It looks like this unsettled pattern is coming to a close as the atmospheric river shuts off. While Pasco still sits below average for the year for rainfall, the recent pattern of frequent rain has helped close the gap. On top of this, it has brought copious amounts of snow to the Cascades.
Some parts of the Columbia Basin have seen over three times as much rain as they expect for the first half of April. Most of us have seen four to six days of rainfall since the 1st, and many of those days deposited more than a tenth of an inch of rain.
This change to a drier weather pattern won’t be abrupt. A last round of showers is expected for western Washington, but this will be weaker and is unlikely to bring rain to the lowlands east of the Cascades, with the exception of places adjacent to mountains (such as Walla Walla and Pendleton).
While rain is unlikely, some higher clouds are expected to invade to keep us mostly cloudy until Thursday. As is usual after rain storms, we can look forward to breezy conditions Monday and Tuesday. Winds will not be damaging or extreme by any stretch of the imagination but could be an inconvenience.
The shutting off of the atmospheric river is due to larger weather patterns finally moving out. Unsettled winter weather patterns like the one ending this week are dependant on a persistent low-pressure system in the Gulf of Alaska termed an “Aleutian Low.” Wind patterns that result from this setup are the driving force behind funneling vast amounts of moisture into the Pacific Northwest.
The atmospheric river also served to moderate our temperatures somewhat. High temperatures have been around average, but lows have been above average. The increased cloud cover made it so that heat couldn’t escape as well as normal. Highs for the first half of the week will be below average, but toward the weekend, temperatures will rise into the mid-60s.
Looking beyond this week, current indications show that temperatures will be close to average, with no major cold snaps or heat waves expected through the two-week period.
Also during the two-week period, we will generally remain dry. This isn’t going to be an oppressively dry period, but compared to the last few weeks it may seem like summer to some folks. Some of the longer range returns for the GFS model are hinting at another rainy system coming in next week, but there is no good reason to put any weight into that this early.
So, while I’m not saying we are done with rain for the month, it is looking like the last half of April will see us dry out quite nicely as we inch closer to the dry season.
If you’re wondering about conditions west of the Cascades, go to Charlie’s latest post – A gloomy April, but sunny days ahead.
