April 2, 2017 – Dry and warm continues through Wednesday except for a slight chance of light showers over higher portions of the Sierra Nevada Sunday night. Some afternoon breezy winds today and stronger Monday. Potential exists for significant precipitation Thursday into the weekend.
Short term discussion (Today through Wednesday)
Upper ridging over NorCal has flattened as a short wave trough moves into the PacNW with some associated high cloudiness today and breezy northerly winds. High temperatures in the Central Valley this afternoon are expected to top out around 10 F above normal. This coming trough is fairly weak with limited moisture and thus only expect a slight chance of showers with some breezy conditions over the higher Sierra Nevada Sunday night.
Upper ridging re-amplifies behind this wave Monday returning stronger offshore wind to Interior NorCal. Downslope warming will be offset by stronger low level cold air advection, resulting in additional minor cooling over the area Monday.
The air mass continues to warm Tuesday and Wednesday with lighter wind as upper ridge shifts inland over NorCal Tuesday and NV on Wednesday.
Extended discussion (Thursday through Sunday)
Wet pattern returns beginning Thursday as a weak shortwave rides up the western side of a retreating upper level ridge. Impacts with this first system will be relatively minor as much of it`s energy will be absorbed by the ridge. After that, much wetter stormier pattern sets up over NorCal as a winter-like atmospheric river pattern takes aim on the north state.
First wave fairly consistently modeled to come through the forecast area on Friday. Have increased both QPF and winds as models trending towards this being a more potent system. Even averaged QPF puts on the order of a couple of inches of precipitation over parts of the Sierra Friday.
Snow levels start out fairly high so only the higher passes will see significant snowfall. Strong pressure gradients indicate significantly strong winds Friday afternoon and have increased windspeeds in the grids accordingly. Southwest flow aloft continues flow of moisture into Norcal going into the weekend.
Next wave of energy pushes through on Saturday but precipitation will remain fairly continuous between the Friday and Saturday systems. Snow levels will be dropping on Saturday so snowfall issues will be on the increase and under current scenario, winter products will likely be necessary dispute the fact that we are now a couple of weeks into spring.
Even colder air filters into the region on Sunday making for fairly low snow levels but precipitation amounts should be on the decrease between systems.