896 FXUS66 KSTO 212230 AFDSTO Area Forecast Discussion National Weather Service Sacramento CA 230 PM PST Thu Dec 21 2023 .Synopsis... Quieter and more seasonable weather returns through the Christmas holiday with only a few light mountain showers. Areas of fog will be possible through the weekend. Precipitation chances return by mid next week. && .Discussion... Happy Winter Solstice! Mostly cloudy skies are being observed around the Sacramento area and up into the surrounding foothills while clear skies prevail further north. Valley highs today will be in the mid 60s with overnight/morning lows in the low to upper 40s. After an unsettled weather pattern that brought rain and thunderstorms to our area earlier this week, quiet and mostly dry weather is expected today through Christmas with gradually cooling temperatures. The high pressure ridge responsible for the aforementioned dry weather, will also bring about decreased wind and clear skies through the overnight hours this week. As a result patchy fog will likely develop in the Valley during the overnight and early morning hours. A weak cold front will push through the area on Friday bringing the chance for sprinkles over Shasta County, but little to no impacts are expected. North winds are expected to increase Friday into Saturday (strongest winds expected early on Saturday) with gusts up to 30 mph along the I-5 corridor in the northern Sacramento Valley which will work to mitigate fog development through the Sacramento Metro Area. Winds decrease by Sunday morning which will increase the chances of fog development. Additionally, chilly morning lows in the low to upper 30s are in the forecast for the Valley on Sunday, with the coldest temperatures centered over the northern Sacramento Valley. && .EXTENDED DISCUSSION (Monday THROUGH Thursday)... Ensembles and clusters advertise upper-level ridging in place over Northern California through Christmas. As this ridge remains in place over our area, dry weather and light winds are expected. By mid-week a low pressure system will begin to influence our area bringing showers to the Coastal Range and foothills Wednesday morning. Showers will become more widespread Wednesday into Thursday with a 40-70% chance of 0.5" inch or more of rain in the Valley. This system is anticipated to be colder resulting in snow levels from 5,000 to 6,000 feet and which may result in travel impacts at pass levels. The NBM is indicating a 45-60% chance of 6 inches of snow over the Sierra on Wednesday, but uncertainty persists with this system, especially regarding timing and amounts so make sure to stay tuned for forecast updates! && .AVIATION... VFR conditions prevail through the afternoon and evening for all NorCal TAF sites. MVFR/IFR/LIFR conditions may begin to develop around 09Z-18Z Friday across the Valley due to patchy BR/FG. Surface winds generally at or below 12 knots from the North. && .STO WATCHES/WARNINGS/ADVISORIES... None. && $$