The National Weather Service in Sacramento has issued a forecast that spells out another hot day for the interior of Northern California today, with a cooling trend expected to start from Thursday and carry on into the weekend. The heat advisory remains in effect until 11 PM PDT this evening, targeting a wide area including the Central Valley, Motherlode, and the northeastern foothills, according to National Weather Service.
The National Weather Service reports that an upper high centered over the Great Basin will continue to usher in heat across the region today, with high temperatures potentially inching slightly lower than Tuesday's figures. The Sacramento Valley, Southern Sacramento Valley, Northern San Joaquin Valley, and particular areas within the Carquinez Strait and Delta are expected to feel the bulk of this heat impact. In tandem, the Delta breeze is set to be somewhat stronger, although its cooling effect will be blunted as the marine layer stays shallow under the oppressive subsidence.
There's an added spice of localized elevated fire weather concerns today and Thursday due to increased afternoon to evening gusty winds and lower humidity levels in the forecast. Alongside the rising mercury, there's also a slight chance of afternoon showers or thunderstorms over the higher elevations near the Sierra Nevada crest, but the bulk of this activity is expected to occur farther east.
Hope for cooler days comes in the form of a cooling trend that will develop Thursday into Friday as the region begins to feel the effects of a deep short wave trough moving through the Pacific Northwest. The cooling is compounded by a marine layer that is forecast to deepen and increased onshore flow. "Below normal temperatures Saturday with mid 80s to lower 90s for the Central Valley and upper 60s to lower 80s for mountains and foothills," as pointed out by National Weather Service. Despite these reprieve, gusty winds in the afternoons remains a probable scenario, especially as the humidity levels start to climb again by Friday.
Looking ahead, the National Weather Service anticipates that a broad upper trough will maintain its presence along the West Coast heading into the weekend, keeping temperatures on the lower side of normal. There is some uncertainty early next week, however, with weather models suggesting variations ranging from an unseasonably deep short wave trough potentially hitting the Pacific Northwest Tuesday, to a strengthening desert Southwest high that might expand northwestward over Northern California through midweek. National Weather Service leans towards a prediction of a gradual warming trend with "high temperatures returning to near or slight above normal Tuesday into Wednesday."
Regarding aviation, VFR conditions are expected over the interior of Northern California in the next 24 hours. In the Central Valley, surface winds from the south could reach up to 20 knots at times between the hours of 20z to 05z. Travelers through the Delta should expect southwest surface winds at 15-25 knots. The threat of isolated showers or thunderstorms remains in the vicinity of the Sierra Nevada crest between 20z to 03z.
