After a mild weekend, a “substantial change of weather” is coming to California this week, UCLA climatologist Daniel Swain wrote on Twitter. “A prolonged period of much higher temperatures inside is expected, which will be a dramatic shift from the recent cold temperatures to the north.” Sweeney said another upheaval is coming in the state weather this week: “In addition, it looks like an early / pre-monsoon eruption will reach southern 2/3 of California by the middle of the week. “Desert t-storms and possibly even lightning at lower altitudes south of I-80. The details are still unclear, but there could be some dry lightning over the area of the drought peak.” The Central Valley will see some of the hottest temperatures in the northern part of the state, with triple digits that may be maintained in many locations until the weekend. Tuesday and Wednesday are likely to be the hottest days of the week in the Central Valley. Further north, Redding is forecast to hit 104 on Tuesday and 107 on Wednesday. Sacramento is forecast to reach 102 on Tuesday and Wednesday, the meteorological service said. “We do not expect any records, but we will be about 10 to 15 degrees above normal for this time of year,” said Scott Rowe, a forecasting meteorologist at the Sacramento Meteorological Office. In the San Francisco Bay Area, the mercury is expected to reach its peak on Tuesday. Discovery Bay is expected to reach 105, Concord 103, Santa Rosa 100, San Jose 98, Oakland 93 and San Francisco 83. “It’s still toast until Wednesday, Thursday and after Friday it will start to get a little colder,” said Sarah McCorkl, a forecaster with the Bay Area office. A monsoon is expected on Wednesday, but meteorologists said Monday it is too early to know exactly what this low-pressure system will bring to Northern California. In the bay area, meteorologists believe that lightning and thunderstorms are extremely unlikely, but a change in weather is likely to lead to a slight drop in temperature. “Temperatures on Wednesday will continue to be widespread in the 1990s with some low 100 degrees for the interior, but it should be a little colder than Tuesday,” the meteorological service said. Thunderstorms and dry thunderstorms are most likely along the Sierra Peak, Rowe said. “There is very little confidence in the trajectory of this humidity,” he said. “Right now, we have a 10% to 20% chance of dry lighting along the top of the Sierra. It’s one of those things that’s hard to predict.” Dry lightning is a concern in the summer, when it can cause fires, but Rowe said the risk of fire remains moderate in the Sierra due to recent light rain that keeps vegetation somewhat moist. The chances of thunderstorms, both lightning fast and light rain, associated with monsoon humidity are higher in the desert areas of Southern California than in Northern California.
