July 16, 2018 – Hot temperatures continue this week. Slight chance of thunderstorms over the northern mountains this afternoon with northern Sierra thunderstorms possible later in the week. Heat Advisory until 8 PM PDT Wednesday
Clear skies across interior NorCal early this morning. Current temperatures are cooler compared to 24 hours ago and generally range from the 50s in the mountain valleys to the upper 50s to around 80 in the Central Valley. The marine layer remains around 1500 feet deep and steady onshore flow continues through the Delta. Onshore flow is forecast to weaken a bit today as high pressure aloft strengthens resulting in slight warming compared to Sunday.
The short-wave trough that helped to trigger yesterday`s thunderstorms across far northern California will lift further to the northeast today, but enough moisture and instability lingers for a few storms to possibly pop again this afternoon over the mountains around Redding.
High pressure strengthens further Tuesday and Wednesday which will suppress the marine layer leading to hot readings across the region and capping potential for deep convection across most of the region.
A Delta trickle is expected to keep temperatures across the southern portion of the forecast area somewhat in check, but the northern half of the Sacramento Valley will see highs topping out in the 108-113 degree range.
Overnight lows will also be very mild in across the northern Sacramento Valley and across the thermal belts. The ridge is forecast to get nudged eastward slightly beginning Thursday which may take the edge off the heat and allow afternoon thunderstorms to return to the northern Sierra Nevada up to about Lake Tahoe.
Extended discussion (Friday through Monday)
A modest cooling trend is currently projected late this week into next weekend as the Four Corners upper ridge shifts eastward, and as a trough clips the Pacific Northwest. Current progs have temperatures dropping down to within a few degrees of normal for next weekend. We may continue to see isolated afternoon thunderstorms develop over the mountains, but confidence is low in widespread this convection will be.