Warming and drying trend with triple digit heat today through Friday for the Central Valley. The hottest day will be Friday, with little overnight relief from the heat. There’s a chance for showers and thunderstorms for the northern mountains and northern Sacramento Valley later this weekend. Excessive Heat Warning from 11 AM to 10 PM PDT Friday.
Upper level ridge will start to build into the four corners region today and will amplify into the end of the week. This will bring hot temperatures to NorCal as we will be on the western edge of the ridge.
The hottest day is still looking to be Friday but highs will push to just above the 100 degree mark today in the lower elevations with widespread 100s for Friday. This will bring widespread risk to the Valley and foothills and heat products have been issued for these areas.
We are seeing a Delta Breeze tonight though. As the ridge builds in the Delta Breeze you can get cut off and we can expect hot temperatures even in the Delta region the next few days.
Overnight lows are also going to start tomorrow morning and continue into Saturday morning. Lows in the Valley will be in the upper 60s to lower 70s with low to mid 70s throughout the thermal belts. Short waves spinning into the PacNW off of the Gulf of Alaska will bring some high clouds to the region today with less cloud cover expected on Friday.
We will also see some increased northerly flow on Friday with lowering humidity. This could bring some increased weather concerns to the Valley, with the heat providing additional drying fuels.
This upper level will begin to push east on Saturday and the west side of the creek will dig over the Pacific reach CA on Sunday. This has slowed down some Saturday night and the heat products may need to be extended an extra day. We will see the return of onshore winds later in the day along with the Delta Breeze developing. This will bring some relief to the heat but will not come until the evening.
A cold front associated with the digging trough will push into the northern part of our area late in the day. This will bring light rain to the Coastal Range. Shower activity will be pretty limited in northern Sacramento Valley initially due to air below 700 mb but profiles should become a bit more saturated overnight with some light showers possible. The QPF does not have much to do with PWATs pushing above 1.0 ″ but the drier low levels will limit some of the QPF. Most of the rain accumulation will be over the northern mountains with some light accumulation possible in the northern Sacramento Valley.
The trough axis will be pushing through the northern part of the area during the day Sunday. We do see instability build over the northern mountains and northern Sacramento Valley by the afternoon. This will bring the chance for some afternoon thunderstorms. The latest GFS is quite high with CAPE values but when you dive into some of the ensembles things are becoming a bit more mixed. This makes sense in the afternoon along with what the environment will look like. Right now it looks like we’ll see some thunderstorms with some heavy rain along with some hail.
Temperatures will be much cooler on Sunday running as much as 20 degrees cooler than Friday. Sunday evening as the trough pushes east.
Extended Discussion (Monday through Thursday)
High pressure builds inland through the first half of the new week with warming temperatures and some gusty north to east wind. This could lead to increased potential weather conditions.
Heating peaks Wednesday as associated upper ridge shifts through interior NorCal. Increasing onshore flow Thursday with some cooling as troughing in the Pacific approaches.