Moderate Risk for heat-related illnesses for pets, livestock, and those who are sensitive to heat, especially those without effective cooling and/or adequate hydration. Dry conditions expected the rest of this week with hot weather by this weekend. Isolated mountain thunderstorms are possible Sunday.
Discussion
A few high clouds are cresting the building ridge over NorCal, otherwise skies are clear early this morning. Current temperatures are similar to those of 24 hours ago, and surface pressure gradients are also similar to early Wednesday with a light Delta Breeze continuing. The Delta Breeze will slacken today as ridging builds in, and temperatures will warm around 5-10 degrees compared to Wednesday and will be close to average for mid-May.
The ridge will build over the area through the remainder of the week resulting in warming temperatures. North to northeast offshore flow will also develop Friday and continue into Saturday which will enhance warming over the Central Valley.
Highs are forecast to climb into the lower 90s across the Sacramento Valley on Friday, with 90s expected throughout the Central Valley on Saturday leading to widespread moderate heat risk.
Those without effective cooling and/or adequate hydration should reduce time in the sun during the warmest part of the day, stay hydrated, and stay in a cool place during the heat of the day.
Models continue to forecast a retrograding closed low approaching from the east on Sunday. Though confidence remains pretty low on the track, it is expected to take the edge off the heat a bit and bring a chance for afternoon thunderstorms to the northern Sierra.
Extended Discussion (Monday through Thursday)
Upper low drifts northward over OR Monday as it gradually fills. Interior NorCal then sandwiched between Desert SW high and offshore low. Above normal high temperatures expected with low to mid 90s forecast in the Central Valley.
Afternoon thunderstorms will be possible over the Sierra Nevada Sunday, and again Wednesday into Thursday, mainly near the crest.