July 7, 2018 – Temperatures warm into upper 90s most areas with around 100 northern Sacramento Valley through Monday. Then slightly cool through next week to around normal. A risk for a few showers and thunderstorms mainly south of Highway 50 towards the end of the week.
Discussion
Northern California will remain in southwesterly flow aloft between a high pressure to the east and a trough of low pressure to the northwest. As a result, dry weather will continue with warm dry air streaming into the forecast area. Temperatures will increase into the upper 90s to near 100 for some spots in the valley. This pattern will continue through the beginning of next week with afternoon temperatures remaining above normal.
Extended discussion (Wednesday through Saturday)
Upper level ridge of high pressure over the southwest U.S. will bring continued very warm temperatures to start off the extended period. Daytime highs Wednesday are forecast to come in several degrees above normal. Weak upper trough over the Pacific Northwest is forecast to move eastward on Thursday allowing southwest U.S ridge to push to the northwest. This places southeast flow aloft over the north state on Thursday. If this model scenario pans out then this southeast upper flow could start to bring monsoon moisture up the Sierra. Models differ on just how much moisture works its way over the region but as least some threat of afternoon Sierra thunderstorms seems reasonable through the end of the week.
Otherwise, forecast area will continue to see above normal temperatures under upper ridging. Daytime RH values will remain quite low for moderate fire danger but winds under the ridge should be relatively light.