March 16, 2020 – Showers will continue early this week with periods of heavy mountain snow into Tuesday. Below average temperatures continue through the week and may be accompanied with unsettled weather at times.
Discussion
Deep closed upper low continues to drift slowly south off the north coast of California. Radar imagery shows the main band of moderate precipitation is oriented north to south across the southern Sacramento Valley and northern San Joaquin Valley with lighter precipitation to the east over the northern Sierra Nevada.
The low will continue to drop southward through Tuesday, and flow will become more northeast to east across the northern Sierra as it does, resulting in weakening orographics and lighter precipitation with time. Band of heavier showers rotating around the low center will likely remain closer to the western edge of the forecast area with time.
Generally drier and milder weather is expected by mid-week, but the mountains may see a continuing chance of showers as weaker disturbances drop down from the north as the large trough evolves over the western US.
Extended discussion (Friday through Monday)
Usettled and cooler weather is expected over Interior NorCal through the extended forecast period. Timing differences continue Friday on the exiting of the slow moving low currently over the region and the approach of another low along the Pacific Northwest coast. Friday forecast has a general slight chance of showers over the mountains, with the Valley remaining mainly dry. For the weekend, uncertainty on the track of the coastal low is fairly high, with ensembles showing the potential for relatively light precipitation across the area.