April 6, 2017 – Showers return today, mainly for areas north of Sacramento. Stormy weather is expected to arrive on Friday with strong gusty winds, heavy rain, heavy mountain snow and thunderstorms. Showers are forecast to taper off by Sunday.
Winter Storm Warning from 6 PM this evening to 6 PM PDT Saturday.
High Wind Watch from this evening through Saturday afternoon.
Discussion
Clouds have continued to increase overnight and some showers are beginning to spread inland, mainly north of Sacramento. Temperatures are very mild, ranging from the 40s in the mountains to the 50s and lower 60s elsewhere.
Showers today will occur mainly over the mountains with a few over the valley. The main part of the storm will spread inland this evening. Models rapidly spread rain across the area between 00Z and 06Z.
During that same time period winds will be increasing significantly across the area becoming very strong overnight as the front moves through. The strongest and most damaging winds look to occur sometime between 9 pm and 6 am. Winds look to remain windy during the day on Friday but more advisory level type winds than the stronger high wind warning type of winds.
Snow levels will start out fairly high fluctuating near pass levels to slightly below pass levels into early Friday when colder air will start to lower the snow levels and cause more travel problems.
The coldest air moves in on Saturday and may lower snow levels down to 2500 to 3000 ft, lowest in the north. Multiple feet of snow is still forecast for the higher elevations.
Thunderstorms still look like a possibility and may occur Friday and Saturday. Showers will taper off Sunday, then pick up again Sunday night as the next system spreads inland.
Extended discussion (Monday through Thursday)
Weak Pacific frontal system forecast fairly consistently by mid range models to move through the Pacific northwest Monday. Upper ridging over the Great Basin will direct this system northward so Precipitation will likely remain mainly north of interstate 80. Tuesday looks dry for most of the CWA but models are hinting at a threat of showers over the far north as a weak shortwave tracks through. Very limited precipitation will bring minimal impacts Monday and Tuesday. Weather pattern turns more winterlike as a cold upper low forms over the eastern Pacific.
Current forecast brings light warm sector precipitation to NorCal on Wednesday with moderate snow levels and breezy south winds. Precipitation will start out relatively light but snowfall over the Sierra could be enough to bring minor impacts.
A strong Pacific frontal system pushes through NorCal next Thursday although timing differs a bit between models. Significant rain, mountain snow and gusty winds are likely with this system. Precipitation is likely to continue into Friday but model discrepancy becomes more significant lowering confidence.