A Pineapple Express event will take place the end of this week, which occurs when a thin but deep plume of moisture delivers highly-anamolous moisture from Hawaii to the US West Coast. These events are known for producing heavy rain and in some cases heavy snow. This event will be no different.
Impacts will begin by Thursday evening and will continue through Saturday. The heavy of rain will occur Friday night as the deepest moisture moves onshore from the eastern Pacific Ocean. This will primarily be a Northern California and southern Oregon event while most of Southern California remains dry. By the time this event comes to an end Saturday night, up to 7 inches of precipitation would have come down in isolated locations. A more widespread 1 to 2 inches of rain in the Central Valley is expected while the higher elevations receive 2 to 4 inches. Isolated flooding and mudslides are possible.
Speaking of the higher elevations, this will be mainly an all-snow event. The only areas expected to get snow will be much of the Sierra Nevada above 7000 feet as well as the mountain peaks in Northern California. Those peaks will receive as much as 1 foot of snow while the peaks of the Sierra Nevada measure as much as 2 feet. Unfortunately, this will not make up the snowfall deficit. On average, the snowpack is currently at only 49 percent of average.
April 1st snow survey results are coming in for California, with the snow pack 59% average as of this morning (data from CADWR). Measurements taken today at Phillips Station in the northern Sierra were 49% of average. @CA_DWR #cawx pic.twitter.com/pIlfTjqN4X
— NWS Sacramento (@NWSSacramento) April 2, 2018