As the Labor Day weekend progresses, the National Weather Service in San Diego forecasts slightly warmer temperatures than the previous day for regions west of the mountains in Southern California. Moreover, there's an increased chance of isolated storms today, particularly in the eastern regions of San Bernardino and Riverside counties, which target the mountains.
While the current weather is bringing subtle warming, monsoonal showers and thunderstorms are expected to grace the mountains and parts of the high desert as the weekend unfolds. According to the Area Forecast Discussion, "Subtle warming will occur through the holiday weekend". The marine layer, meanwhile, is predicted to thin out, limiting cloud coverage to coastal and far western valley areas. As high pressure starts to assert by next week's midpoint, such morning clouds are anticipated to become scarcer, allowing temperatures to heat up near 5 to 10 degrees above the seasonal averages.
The forecast from the NWS San Diego indicates the "highest chance for storms across the eastern SBD and RIV county mountains." Dominated by a high-pressure system stationed over northern Utah, this pattern will influence the regional weather, along with monsoonal moisture making a noticeable return to Southern California this afternoon. This sets the stage for greater shower and thunderstorm coverage compared to yesterday, with the eastern San Bernardino and Riverside mountains once again expected to be the primary recipients of rain.
Looking into the Labor Day conditions, Inland Empire residents should prepare for potentially sweltering heat, with "high chances for triple digit heat", as detailed by the NWS San Diego's forecast. Similarly, nighttime temperatures are predicted to veer away from 50s and settle mostly in the 60s to near 70 degrees. Aviation-wise, coastal and valley regions are reminded of the possibility of visibility reductions due to low clouds. At the same time, the mountains and deserts carry a slight chance of showers and thunderstorms after noon, possibly impacting visibility and causing unpredictable wind conditions.
The long-term outlook signals further warming. As stated in the provided forecast, "Our confidence remains high that temperatures will climb through Thursday". This is when high pressure aloft is expected to peak, translating to substantial heat, particularly for inland areas along Orange County's Interstate 5 and San Diego County's Interstate 15 corridor. The desert regions also have a moderate chance of witnessing temperatures soar to or beyond the 115-degree threshold by the week's end.
Maritime activities will be under calmer skies, as the marine forecast predicts no hazardous conditions through Wednesday. While the risk of extreme heat is on the horizon for susceptible individuals in the coming week, the NWS San Diego has not requested Skywarn activation. However, weather spotters are nonetheless encouraged to report significant conditions.
