Temperatures have begun their gradual upward trend today as a trough is leaving the region, bringing daytime highs across the coastal plains into the 70s, with low 80s for the valleys.
Onshore flow will persist through Wednesday, limiting the immediate coastal warmth, and inland areas will continue to see rising temperatures. Expect marine layer clouds to affect most coasts and some valleys each night and morning. These clouds may cling to some beaches into the afternoons, especially on Wednesday.
Temperatures are expected to climb well above normal by Thursday and peak on Friday. While inland valleys will experience considerable heat, coastal areas will see milder conditions due to a persistent marine layer. Gusty northerly winds are also anticipated at times. Looking ahead to the late weekend and early next week, a shift to cooler and potentially unsettled weather is possible.
Why will we see a Warm-Up?
This is due to a broad ridge of high pressure building over the western United States. Simultaneously, a low-pressure system is expected to break from the main steering flow and become a cutoff low, stalling over the Pacific Ocean west of Baja California. This cutoff low will somewhat dampen the full impact of the ridge over our region.
Wednesday night through Thursday, this cutoff low will also reorient surface pressure gradients, bringing areas of northerly upper-level winds. This will result in gusty north-to-northwesterly winds across the coastal waters and the Central Coast on Thursday.
Peak Heat Friday, Potential Records:
Friday is expected to be the hottest day of the week. The broad ridge of high pressure is likely to dominate over the influence of the cutoff low to our south, leading to daytime highs 10 to 18 degrees above normal. Coastal areas will see temperatures in the mid-70s to mid-80s, while deeper coastal valleys and foothills will experience temperatures in the upper-80s to upper-90s. Some northern inland valleys, such as the Paso Robles area, could approach or even exceed 100 degrees. There is an increasing chance (30 to 40 percent) that Friday's highs will approach or break daily records in these warmer inland locations. A Heat Advisory will likely be needed for Friday across many interior areas.
The high-pressure pattern will significantly compress the marine layer, meaning clouds will be mostly confined to the immediate coastal plains on Friday and Saturday. Dense fog will be possible within this shallow marine layer, particularly Friday night through Saturday morning at the beaches.
Weekend and Early Next Week: Uncertainty Looms
Saturday will see temperatures trend downwards but remain well above normal, around 8 to 15 degrees above average.
The forecast for Sunday through Monday becomes more uncertain due to the nature of the cutoff low, which is favored to move west over land just south of our region. This scenario would bring southerly flow, an increase in moisture, and instability, along with a significant drop in temperatures, especially on Monday when highs are likely to be several degrees below normal. There's currently a small chance of showers or thunderstorms Saturday afternoon through early Monday, with the greatest chance of convection over the mountains.
Looking further into next week, some forecast models hint at an unseasonably cold pattern with more chances for precipitation.
