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Breezy onshore winds expected each afternoon and evening through early midweek

Gradual warming starting midweek, with Moderate HeatRisk for interior locations

Elevated fire weather threat across the Diablo and Santa Lucia Ranges this week

Hazardous beach conditions at the Pacific Coast with an increased risk for sneaker waves and rip currents through the end of the week

Short Term

Pleasant conditions persist this afternoon across the Bay Area and Central Coast. 24 hour tendencies in temperatures indicate most areas are running anywhere from 1-4 degrees lower than this time yesterday. While the stratus footprint has dwindled to the San Mateo coastline, persistent onshore flow is likely the culprit for the cooler conditions. As troughing continues on Tuesday, we'll contend with another period of onshore flow. There's some uncertainty with regard to the inland extent of marine stratus, but overall, mostly sunny skies are anticipated late morning and into the early afternoon on Tuesday.

Long Term

Wednesday will be the start of our warming trend. The region will be on the backside of the aforementioned upper level trough with the Pacific Southwest Ridge projected to gradually expand westward Wednesday and into Thursday. While another compact upper level wave will move eastward onto the Oregon Coast late Thursday, it's impact on our weather seems to be an increase in the winds over the marine environment thanks to the development of several coastal jet features. This, in theory, could help induce upwelling which may promote marine stratus development. However, forecast soundings from traditional NWP along with cross- sections from the PG&E/SJSU WRF indicate the marine layer compressing to under 1000 feet (potentially lower through the end of the week). As such, infiltration of marine stratus should be limited spatially and at a minimal if at all. If stratus does develop, it'll likely dissipate rather quickly by mid to late morning. This promotes moderating temperatures, particularly across the interior and poor to moderate humidity recovery (30-50%) at elevation. More intel on this in the fire weather section below.

Temperature wise, guidance remains in fair agreement with moderating conditions on Wednesday and into the weekend across the Bay Area and Central Coast. We still maintain some very diffuse troughing aloft on the synoptic scale, but the ridge expands more noticeably Thursday and into the weekend. Confidence has increased that the ridge will expand sufficiently enough to compress the marine layer, particularly across the Central Coast where the areal extent of Moderate HeatRisk increases quickly. There's still a chance that current MaxT forecasts may need to be trended upward across interior sections, but likely only on the order of 1-3 degrees. Across the Santa Lucia and Galiban Ranges, pockets of Major HeatRisk enter the forecast with some on Wednesday, but especially Thursday and into the weekend. Those recreating across this region should ensure they are adequately hydrated with plenty of water and have access to shade. Moderate HeatRisk becomes most expansive Thursday and into Friday across the remainder of the Central Coast and this is when the potential for more formal heat products increases.

While there's strong consensus for hot conditions across the interior, coastal regions, including the population centers, model forecasts exhibit a much more significant spread. For instance, the KSFO MaxT interquartile ranges from the mid-60s on the low end to low to mid-80s on the high end Thursday and into the weekend. What will likely modulate just how hot it gets for coastal locations will be onshore vs. offshore flow. 925mb flow in the deterministic guidance starts to diminish especially Friday and into the weekend. As flow drops below 10 knots, there's the potential for a large degree of variability in direction and should a given location experience periods of either very weak onshore flow or offshore winds, MaxT will likely verify on the higher end of the spread. In the case of KSFO, mid-80s would be nearly 10-15 degrees warmer than normal. For now the forecast currently resides on the warmer end of things through at least Thursday, but additional adjustments will be made as we venture closer to mid- week. Regardless, it'll be important for those across the area to remain hydrated with plenty of water, stay cool and limit strenuous outdoor activities to the cooler portions of the day. Never leave kids or pets unattended in vehicles! In addition, if headed to our Pacific coast beaches for relief, be mindful of the increased risk for sneaker waves and rip currents.