We warned you earlier this week about the atmospheric moisture that will bring heavy rain and snow to portions of the West Coast earlier this week. Now the Pineapple Express will come into fruition beginning this Thursday and lasting through Saturday.
On Thursday, rain showers will move in all of Washington, Oregon, and Northern California by the end of the day. A few showers will work far inland, reaching portions of Idaho as well. At this point, there will be a thick layer of warm air at the surface, so snow will only be found at the highest peaks of the Cascades. Further inland, however, there will be freezing air down to the surface in much of Montana, which will lead to snow showers.
As we get into Friday, this will be the main event. A moderate to heavy rain is forecast Friday through Friday night for Northern California. To the north, it will actually be drier with occasional rain and snow showers depending on elevation in the Northwest. Due to the thick layer of warmth affecting California at the onset of the precipitation, only the highest peaks of the Sierra Nevada will deal with snow. It’s not until Saturday when snow levels will drop across the Sierra. By the end of the day Friday into overnight, a widespread light to moderate rain will move into all of Oregon and Washington as well as into much of Idaho and northern Nevada. Much of the Cascades will be experiencing rain and not snow.
That will change on Saturday, however. Snow will break out in much of the Cascades and the Sierra Nevada by the end of the day. Snow levels will mainly be over 7000 feet because the warm air will remain somewhat relentless. In the lower elevations it will be rain. That rain in the form of showers will impact much of California, Oregon, Washington, Idaho, Nevada, and western Montana. A few showers may even move into Southern California and Wyoming. Most of the rain and snow will move out of California as the atmospheric river collapses. Snow will slam much of Rocky Mountains, however, as a new surface low develops and organizes in Colorado. Rain and snow showers will also persist along the Pacific Northwest coast.
By Sunday, the activity will gradually wind down by the end of the day in the Northwest and intermountain West. Over half a foot of precipitation is possible by the end of this storm. This will be an elevation-driven event. In many cases, the higher in elevation you are, the heavier the precipitation will be. Also over a foot of snow is forecast in portions of the Sierra Nevada and the Cascades of Washington.