Not as hot heading into next week. Isolated mountain thunderstorms continue. As the remnants of Hurricane Hilary progress northward, there will be increasing chances for rain early next week. At this time, impacts are expected to be limited across the area. Significant rain impacts will be limited to south of our area.
Discussion
For the first time in many nights, skies are clear across the region early this morning. IR difference imagery shows stratus has returned to the coast (profiler data indicate the marine layer depth is around 1.5-2k ft) and surface pressure gradient has begun to trend toward onshore. As a result, current temperatures are running considerably cooler (10-15 degrees) across the Central Valley and foothills compared to 24 hours ago with readings in the 60s to around 70 in the Delta Breeze influenced areas, and in the mid 70s to lower 80s across the northern Sacramento Valley.
It won’t be as hot going forward as the low remains near the central California coast. Low to moderate heat risk is expected through the weekend. Highs today will be around 5-15 degrees cooler compared to Thursday. A pause in the cooling is expected Saturday as onshore flow wanes.
Thunderstorm chances will continue the next several days, but will likely return to mainly diurnal over the mountains. Activity likely won’t be as extensive as the past several days, but stronger storms will still be accompanied by lightning, brief heavy rain, small hail and gusty outflow winds.
Then, moving into the latter half of the weekend into early next week, there is still a chance that interaction will take place between the trough off the coast of California and the eventual remnants of Hurricane Hilary.
At this time frame, the most likely solution will be just a deepening of the trough, as the tropical system remains further to the south of this forecast area on Sunday.
Still, given the influx of moisture to the region and an abundance of lift from the approaching system, shower and possibly a few thunderstorm chances are expected to begin to creep northward into the CWA. Exact amounts and location of attendant precipitation remain highly uncertain though as this will be tied to the overall track that Hilary takes.
Extended Discussion (Tuesday through Friday)
Models have slowed progression of closed upper low that has resided off the CA coast. Feature weakens Tuesday to trough as it pushes thru the CWA. Models differ with amount of associated precip Tuesday. NBM favors more widespread precip similar to the GFS as it interacts with remnant moisture from Hillary. Best precipitation chances expected over the mountains Tuesday.
Upper troughing off the CA coast gradually deepens to another closed upper low through remainder of the week. NBM showing continued threat of afternoon showers or thunderstorms over higher elevations of the Sierra Nevada Wednesday and Thursday. Mainly 80s forecast in the Central Valley Tuesday, then low to mid 90s through Friday.