November 22, 2019 – Dry weather with mild daytime temperatures and light winds through the weekend. Breezy conditions over the Sacramento Valley on Monday with the potential for a significant winter storm by Tuesday into the Thanksgiving holiday. Much cooler temperatures in store for next week.
Discussion
Satellite imagery this morning shows continued mid to low level cloud cover over the Sierra and foothills, generally from Plumas County southward. Current temperatures are quite chilly across the region with Valley temperatures in the mid 30s to low 40s and mountains temperatures in the teens to low 30s.
A weak low pressure system will remain over the Eastern Pacific generally west of the California Coast through the weekend. Weak high pressure will build over NorCal north of this offshore low. Quiet weather is expected with mainly light winds and dry conditions. Daytime temperatures will rise slightly each day, especially over the northern Sacramento Valley and mountains. Above normal daytime temperatures expected ranging around 7 to 15 degrees above normal as Valley temperatures rise to the upper 60s to low 70s and mountains in the 50s to low 60s. Overnight lows will still fall to near or below normal due to light winds and little cloud cover.
Ensembles continue to depict the pattern beginning to change Monday as a series of weather systems are forecast to impact the West Coast next week. For NorCal, a weak weather system moves east of California into the Great Basin on Monday which will create gusty northerly winds across the Valley and wind prone mountain areas. There could be an increased fire weather concern with these winds as vegetation remains very dry and daytime humidity Monday are currently forecast in the upper teens to 20s. However, overnight humidity recoveries will be moderate with most locations in the 40s to 70s except for a few localized areas in the upper 30s. Daytime temperatures will begin to cool Monday, especially in the northern Sacramento Valley and mountains where temperatures are forecast to drop around 5 to 10 degrees from Sunday. Cooler and wet weather return Tuesday with a strong weather system possibly bringing our first significant winter storm leading into the Thanksgiving holiday.
Extended Discussion (Tuesday through Friday)
Cool and wet weather is expected from Tuesday through the Thanksgiving holiday period.
A strong and rather cold system from western Canada will drop southward into the region bringing widespread precipitation starting on Tuesday and impacting the region through Friday. Confidence is increasing that this will be a significant system bringing heavy snow to the Sierra, bringing travel disruption during the busiest period of the year. While model ensembles show a range of possibilities, the most likely storm total amounts (Tue-Fri) at this point appear to be up in the general range of 1-3 feet at pass levels. Cold air with this system could bring some accumulating snow to 2500 feet, potentially lower in heavier convective showers. Anyone considering travel mountain travel around Thanksgiving should closely monitor the forecast.
Valley temperatures are going to be cooler than they have been in a long time, with highs on Wednesday and Thursday (Thanksgiving) only reaching the low 50s! Rainfall amounts in the Valley, Delta, and lower foothills are currently estimated to be in the half inch to inch range. There could be thunderstorms with this system as the cold core moves through Wednesday and Thursday, though, which could bring locally higher amounts. Confidence in timing and details remain uncertain at this time, so will leave out of the forecast for now. The current track of the low along the suggests higher potential along the west side of the forecast area.