February 18, 2021 – A set of weak weather systems will bring light precipitation to Northern California into Saturday morning. Accumulations are expected to be light with the best chances for measurable precipitation expected over the higher terrain. Thereafter, a warming and drying trend is forecast into next week with above average temperatures expected.


Weak trough approaching NorCal this morning will dissipate into the evening hours, as it flattens out while encountering ridging that has been established over the region. Only light showers are expected with this first system with generally less than 0.10 over valley locations and 0.25 or locally a little higher over foothill areas. Less than an inch of snow is expected at pass level through Friday afternoon.

A second system will drop southeast through the area Friday night into Saturday morning. Ensembles are still not in great agreement with this system, as there are a few outlier solutions wetter than the mean. Have went with a blend of WPC and RFC in the short term for QPF this keeps amounts to less 0.10 over the Valley.

This system does have the potential to generate a bit more snow over the mountains at pass level with 2 to 4 inches above 5000 feet over I80 Friday night/early Saturday. Will need to watch next few model runs to see if there is any trend towards wetter ensemble members. Snow amounts are below winter wx adv levels at this time, however, would only give current snow forecast a medium confidence level.

Upper ridge will build over northern California Sunday and Monday with dry weather and a warming trend. High temperatures warm to mid/upper 60’s Sunday and upper 60’s/low 70’s Monday over Valley locations.

Extended discussion (Monday through Thursday)

Models similar on Monday with EPAC upper ridging extending inland over interior Northern California. Deterministic solutions then differ further into the future with EC digging deep trough through NorCal Tue/Wed, while GFS maintains ridging. Ensemble solutions support drier ridging solution through midweek.

Some light overrunning precip advertised by NBM over Shasta county on Thursday. Cooling trend expected through the extended forecast period with above normal high temperatures forecast to return to near normal by Thursday.