April 20, 2017 – Shower chances will diminish by this afternoon. Dry and warmer weather for Friday and into the weekend. The next chances for precipitation return for the start of next week.
Discussion (Today through Sunday)
Model height analysis showed an upper level trough of low pressure continuing to move across northern California overnight as water vapor imagery indicated dry air behind the trough moving onshore. Radar trends showed scattered rain and snow showers across the forecast area with intensity starting to diminish.
Latest short term model forecasts show precipitation trends diminishing this morning and eventually ceasing by the early afternoon hours. Some isolated light rain or snow cannot be ruled out for the higher terrain this afternoon, but chances are unlikely as an upper level ridge is forecast to build into the region this evening.
Temperatures will warm to near to slightly above normal for Friday under stable conditions provided by the ridge. Another weather disturbance will approach the west coast and head towards the Pacific northwest on Saturday. Main portions of jet stream and associated instability will remain to the north of the forecast area, however some precipitation is possible for the northern mountains and extreme northern Sacramento valley for Saturday night. Any developing precipitation will be light with small accumulations. Sunday should remain dry, but a small chance for an isolated shower is possible for the northern mountains.
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Extended discussion (Monday through Thursday)
Extended forecast will be controlled mainly by flat upper ridging over the eastern Pacific and west coast. Unfortunately, model agreement in timing of shortwave troughs passing over this ridge is quite poor. In general, areas north of about Chico will see a continued threat of showers through the extended period. This threat may extend farther southward Tuesday or Tuesday night as models show a bit more consistency in tracking a bit deeper of a shortwave through NorCal. Overall, QPF still on the light side during this time as with the remainder of the extended period so impacts should remain minimal. May see breezy south winds at times as shortwaves pass through but again winds are not expected to have major impacts during the extended period.