Area Forecast Discussion
Issued by NWS San Diego, CA
Issued by NWS San Diego, CA
448 FXUS66 KSGX 032053 AFDSGX Area Forecast Discussion National Weather Service San Diego CA 153 PM PDT Wed Jul 3 2024 .SYNOPSIS... A long-duration heat wave will continue for the deserts through at least much of next week. Friday and Saturday are expected to bet the hottest days for most areas, with the only relief from the heat occurring toward the coast. The marine layer will slow the warming near the coast with night and morning coastal low clouds spreading into the western valleys late each night. The extended period of hot and dry weather will lead to elevated fire weather conditions each day. && .DISCUSSION...FOR EXTREME SOUTHWESTERN CALIFORNIA INCLUDING ORANGE... SAN DIEGO...WESTERN RIVERSIDE AND SOUTHWESTERN SAN BERNARDINO COUNTIES... The dominant synoptic-scale feature through the forecast period will be strong high pressure, currently along the California coast, slowly building in and becoming anchored over the Western US. This will favor an extended stretch of hot and dry weather across much of the Western US, away from the immediate coast line where marine layer low clouds each morning will keep temperatures relatively cool. Highs today will be generally be 2-7 degrees warmer than yesterdays highs, topping out 5-10 degrees warmer than average for early July. Temperatures tomorrow remain relatively steady, perhaps a degree or two warmer/cooler depending on location. Friday and Saturday look to be the overall peak of this heat event, when highs along and near the coast top out 5-10 degrees above normal, while highs across all other inland areas range from 10-17 degrees warmer than seasonal average! Some areas in the Coachella Valley and San Diego County Deserts, as well as localized areas in the mountains and coastal valleys, look to set multiple daily high temperature records. Friday in Palm Springs will be an exceptional case, when the all-time daily high temperature record of 123 degrees will be challenged. Despite the numbers and stats just provided, there will undoubtedly be at least a few thoughts and mindsets of, 70s and 80s along the coast and almost 100 inland isnt irregular, its summer, just turn on the A/C, the last of which isnt an option for every coastal resident and certainly isnt the case for outdoor workers and unhoused populations. It definitely isnt an option if ones A/C equipment fails. And, lets be real. A bunch of folks are likely going to be outside, in the heat, playing games, grilling, and drinking alcohol. All of this is a recipe for dehydration (not to mention sunburn) if you arent careful and mixing in a water here and there and re-applying sunscreen. The fact of the matter is, heat is the most frequent cause of weather- related illnesses and deaths, and we have an abundance of it coming in. Were gonna take this incoming heatwave seriously. Excessive Heat Warnings remain in effect for all desert zones, and are likely to remain in place through at least early next week. Excessive Heat Warnings also go into effect for the mountains of San Bernardino/Riverside/San Diego Counties, the Inland Empire, and the San Diego County Inland Valleys on Friday/Saturday, while Heat Advisories are hoisted for Inland Orange County and the Santa Ana Mountains on Friday/Saturday as well. There will be a slight drop in high temperatures on Sunday, followed by a relatively steady high temperature forecast for early next week. Keep in mind, its still going to be rather hot, with highs each day topping out 5-10 degrees warmer than seasonal averages per latest latest NBM guidance and derived HeatRisk guidance. The aforementioned tools suggest that an extension of all heat warning/advisory products through more of next week very well may be warranted. What must absolutely not be lost in this story are the overnight low temperatures in the deserts. Lows in the Coachella Valley and San Diego County Deserts look to routinely only fall into the middle to upper 80s overnight while the High Deserts see lows in the middle to upper 70s, providing little to no overnight relief and added stress on power grids. && .AVIATION... 032045Z...Coast/Valleys...Marine layer low clouds lingering along beaches this afternoon. Just inland clear skies and unrestricted vis will continue through the early evening. Low clouds with bases 400- 800 MSL returning vcnty coastal sites earlier this evening than last, 02-06Z Thu. Inland extent will be similar to last night, with BKN-OVC cigs to 5-10 miles inland. Lower confidence in timing of low clouds at KSNA, which will be more on the edge of the marine layer. Clearing to beaches again 15-18Z Thu, but low clouds lingering along immediate coast. Mountains/Deserts...Mostly clear skies with unrestricted VIS will continue through tonight. Local south/west winds near 20-30 kts at times through the San Gorgonio Pass 23Z Wed-07Z Thu. Similar winds Thursday afternoon/evening to today`s. && .MARINE... No hazardous marine conditions are expected through Monday. && .BEACHES... Fresh south swell will continue to build into SoCal today through the weekend, peaking Friday into Saturday. This will lead to elevated surf with breaking wave heights up to 7 feet, mainly on exposed south and southwest-facing beaches in Orange County. Rip and longshore current risks will be high as well now through next Monday. && .FIRE WEATHER... The long-duration period of hot and dry weather across Southern California will aid in a persistent downward trend in both dead and live fuel moisture. The low humidity combined with gusty sea breeze winds will bring elevated to near critical fire weather conditions each afternoon and evening. The marine layer will keep areas near the coast cooler with higher humidity. As evidenced by the recent Kitchen, McCain, and numerous other fires, local grass fuels are cured and very available to burn. The primary factors limiting any more critical fire weather potential are a lack of strong winds (outside of the typical diurnally-driven winds) any given day, as well as live fuel moisture. In other words, theres still plenty of green as opposed to brown vegetation in the trees and brush. Live fuel moisture will, however, be steadily dropping/drying out as we head through the weekend and into early next week. This will increase the ability of larger fuels (especially dead/dry and brown fuels) like brush, chaparral, and trees to burn. Energy Release Components, which can be thought of as somewhat of an available energy for a fire to burn, are steadily trending upward toward the 40th percentile and expected to approach the 45th-50th percentile next week. In other words, fuels are finally drying out back to normal levels for July, after being below normal for so long following this winters precipitation. With fuels becoming drier and more receptive to burning, residents need to exercise additional caution with this holidays 4th of July fireworks. If possible, please leave the fireworks shows to professional displays where firefighting resources are likely already on site. Please also take extra caution to ensure that any grills are kept far away from any potential grass/brush that would be receptive to burning. && .SKYWARN... Skywarn activation is not requested. However weather spotters are encouraged to report significant weather conditions. && .SGX WATCHES/WARNINGS/ADVISORIES... CA...Beach Hazards Statement from Thursday morning through Sunday afternoon for Orange County Coastal Areas-San Diego County Coastal Areas. Excessive Heat Warning from 11 AM Friday to 9 PM PDT Saturday for Riverside County Mountains-San Bernardino County Mountains-San Bernardino and Riverside County Valleys-The Inland Empire-San Diego County Mountains-San Diego County Valleys. Heat Advisory from 11 AM Friday to 9 PM PDT Saturday for Orange County Inland Areas-Santa Ana Mountains and Foothills. Excessive Heat Warning until 9 PM PDT Wednesday for Apple and Lucerne Valleys-Coachella Valley-San Diego County Deserts- San Gorgonio Pass Near Banning. PZ...None. && $$ PUBLIC/FIRE WEATHER...Adams AVIATION/MARINE...CSP