Cooler high temperatures today, will continue through next week. A quick moving weather system will bring the potential for light mountain showers and gusty Valley winds this Wednesday & Thursday. Potential for another weather system to enter the area early next week.
Discussion
Temperatures vary across interior NorCal, with some locations around 2 to 5 degrees cooler in the Sacramento area and 3-6 degrees warmer in the northern Sacramento Valley. Broad zonal flow with offshore troughing is the current synoptic pattern, and heights are expected to lower as a trough in the PacNW will begin to move into the region today. The lowering of heights will help reduce afternoon temperatures today and with the enhanced onshore flow, daytime humidity values will increase as well into the upper teens to low thirties, which will help alleviate fire weather concerns. Afternoon high temperatures will be in the low 80s to low 90s, with the warmer temperatures in the northern Sacramento Valley.
On Wednesday, a closed low will develop north of our area and dig towards the southeast, following a synoptic pattern close to an inside slider. The low will bring precipitation and thunderstorm chances, mainly for far north and northeast Shasta and Lassen counties Wednesday morning through the evening. The National Blend of Models (NBM) advertises around a 5-15% chance of precipitation exceeding 0.10 inches in the aforementioned areas, so any precipitation that falls will be light with little to no accumulation. Thunderstorm chances slightly increased this morning for far north and northeastern Shasta county, with around a 10-15% probability Wednesday morning and afternoon. As the low continues to dig and amplify into the Great Basin area, increased westerly flow in the Delta and northerly winds will develop, with the NBM projecting around a 50-90% chance of wind gusts up to 30 mph Wednesday, with the higher probabilities along the I-5 corridor and western Sacramento Valley/Delta areas.
Thursday the low continues it’s trek out of the area, and interior NorCal will be on the backside so northerly winds will develop for most of the area. The strongest winds are expected to develop along the wind prone areas of the Valley, namely the I-5 corridor and the western Sacramento Valley. Strongest winds are expected in the morning hours, with the NBM projecting a 20-60% chance of wind gusts at least at 30 mph, with a larger chance, 40-90%, of northerly wind gusts of 25 mph. Temperatures will continue to be in the mid to upper 80s across the Valley through Thursday. Friday, we will warm back up slightly as weak ridging to our north and weak troughing to our south will bring heights slightly higher, with temperatures in the upper 80s to low 90s, highest temperatures in the northern Sacramento Valley.
Extended Discussion (Saturday through Tuesday)
Heights trend down over the weekend into early next week as multiple short wave troughs drop into long wave trough that takes residence along the West Coast. Models differ with timing of waves leading to some forecast uncertainty with POPs and amount of cooling. NBM forecasting increasing precipitation potential N of I-80 Sunday night, spreading over the entire CWA Monday. Decreasing POPs Tuesday before another short wave increases precip potential midweek. Periods of gusty wind will accompany the short wave troughs. High temperatures cool from the upper 80s to lower 90s in the Central Valley Saturday, to upper 70s early next week.