Northern California will experience calm weather today, with clear skies and temperatures near seasonal averages. The valley will see comfortable temperatures in the low to mid-80s, while higher elevations will be cooler, in the 60s to 70s. However, this peaceful weather is expected to be short-lived, as a system is forecasted to bring cooler temperatures and a chance of light rain by midweek. "Near normal temperatures, light winds, and dry weather are expected to persist through today," according to the National Weather Service Sacramento.
The forecast indicates that on Wednesday, a shortwave trough will bring lower daytime temperatures and increase the chances of light rain in the region. This system is expected to disrupt the calm conditions, especially in eastern Shasta County and Lassen National Park, where the National Weather Service predicts some instability that could lead to isolated thunderstorms.
Looking ahead to Thursday and the end of the week, the trough will bring even cooler temperatures and a chance of light precipitation at higher elevations, possibly including light snow down to 6,000 feet. The main concern is the system moving into the Great Basin, creating a pattern known as an "Inside Slider," which brings gusty winds and low humidity, increasing fire weather risks. According to the National Weather Service Sacramento, "The NBM has probabilities for gusts 30 mph or higher at 50 to 90% in these areas, and minimum daytime relative humidities look to be between 10 and 25% on Friday and Saturday." A Fire Weather Watch has been issued, indicating heightened vigilance for the latter part of the week.
As we head into the weekend and early next week, the National Weather Service forecasts a shift in weather patterns, starting with warmer temperatures before a new cooling trend due to onshore flows from an expansive trough in the Eastern Pacific. However, there is some uncertainty, as different models show varying predictions for the incoming system. The National Weather Service notes discrepancies in forecasts, but if precipitation does occur, it is expected to mainly affect the Northern Sacramento Valley, northern Sierra, southern Cascades, and northeast foothills. Overall, any expected precipitation is likely to be light and focused in these areas.
The National Weather Service also addresses aviation concerns, predicting general VFR (Visual Flight Rules) conditions across interior Northern California. However, there may be local MVFR/IFR conditions, especially north of certain areas, where precipitation is expected after 08z. The report notes possible surface winds below 12 knots, except in the Delta region from 00z to 12z Wednesday, where southwest winds could reach 15-20 knots. Navigational cautions are advised due to these expected conditions.
