January 2, 2020 – Dry and mild weather into the end of the week. Precipitation chances return this weekend, mainly north of I-80.
Mostly clear skies have allowed areas of dense fog to develop early this morning, especially over portions of the southern Sacramento Valley, and the Delta. Therefore, have issued a Dense Fog Advisory until 10 AM this morning. Morning fog could be possible again Friday morning.
Dry conditions will prevail across the region through Friday afternoon as ridging over the eastern Pacific amplifies and moves into the West Coast. Mild temperatures are expected over the next few days, with Valley highs generally in the upper 50s to low 60s. These forecast highs range from 5 to 10 degrees above seasonal normal.
A shortwave trough will bring precipitation Friday night into Saturday, mainly north of I-80. QPF amounts will be light, generally ranging from 0.01-0.25 inches. Best precipitation chances will be over the mountains, especially Saturday morning. Snow levels will range from 4500 to 6000 feet, with only light snow accumulations expected. Another short wave trough will pass through the region later Saturday into Sunday. Shower chances appear to be limited to the northern Sierra, with light precipitation amounts.
Extended Discussion (Monday through Thursday)
Upper level ridging builds over California Monday bringing continued dry weather to the forecast area. Ensemble guidance shows a series of weak upper troughs moving through NorCal Tuesday through the weekend, bringing periodic chances of precipitation. At this point the best chances of precip are Tuesday and Thursday, mainly limited to the mountains and northern Sacramento Valley.
However, confidence is low in precip timing and location due to model inconsistencies. Daytime temperatures will cool a few degrees to near normal on Wednesday after the trough passage. Expect Valley temperatures in the low to mid 50s and mountains in the 30s to 40s. Cool overnight temperatures in the 30s for the Valley and teens to the 30s for the mountains expected.