The Bay Area is bracing for another bout of intense heat, as temperatures in the Central Valley are forecasted to tip the scales between 100 and 112 degrees, with the hottest conditions anticipated in the Northern Sacramento Valley. Residents should plan accordingly, as the National Weather Service Sacramento has issued a Heat Advisory from 11 AM this morning to 11 PM PDT Wednesday. This heatwave is part of a trend, with well above normal high temperatures expected to persist through at least mid-week.
According to the weather bulletin, the marine layer is thinning, a consequence of an ever-strengthening upper high coming from the Great Basin. As a box of the atmosphere warms, overnight temperatures will likely stay in the sweltering 70s and 80s throughout the valley and foothills – creating what the National Weather Service defines as "areas of major heatrisk." Cities encompassing the Delta region have also been included in the heat advisory, owing to the decreased effectiveness of the Delta breeze, which would otherwise offer a modicum of relief.
Adding a layer of complexity to the scorching forecast, the Sierra Nevada may experience afternoon thunderstorms and showers into the middle of the week, thanks to monsoonal moisture coupled with the mountains' unique heating dynamics. At ground level, locals might see haze or smoke from nearby wildfires, which could reduce visibilities, particularly impacting travelers and residents near active fire zones.
Relief from the heat appears to be on the horizon, with forecasts indicating a dip in temperatures by Thursday, as an offshore upper low makes its way inland, "lowering heights over interior NorCal," per NWS Sacramento. The marine layer is expected to deepen, and onshore flow should increase, dialing back the mercury by 2 to 6 degrees. Although thunderstorm threats in the western N Sierra Nevada may subside, the extended forecast promises dry conditions with a slight uptick in temperatures by next Monday, as the high over the Desert Southwest starts to rebuild.
For aviation, VFR (Visual Flight Rules) conditions will reign over the interior of Northern California for the next 24 hours, though isolated MVFR (Marginal VFR) visibility could feature in areas affected by wildfire smoke or haze. Surface winds should remain relatively tame, not exceeding 12 knots, except near the Delta where gusts might reach 20 knots.
