FXUS66 KMTR 062349 AFDMTR Area Forecast Discussion National Weather Service San Francisco CA 449 PM PDT Fri Sep 6 2024 ...New AVIATION, MARINE... .SYNOPSIS... Issued at 133 AM PDT Fri Sep 6 2024 Hot and dry conditions again for Friday, resulting in a moderate to major risk of heat-related illness and near critical fire weather conditions. A pronounced cooling trend starts on Saturday and continues into next week. && .SHORT TERM... Issued at 202 PM PDT Fri Sep 6 2024 (This evening through Saturday) One final day of inland heat before temperatures cool across the Bay Area and Central Coast. First and foremost...Heat Advisories remain in effect through this evening for moderate HeatRisk across the interior. Another pretty impressive temperature spread from the coast to inland again this afternoon. 60s at the coast and lower 100s inland and those 100s fall under the Heat Advisory. The upper level ridge that brought the most recent round of heat will ease tonight as an upper level low approaches the OR/CA border. The weakening ridge will allow for increased onshore flow at the surface along with lower 500mb height/cooling 850mb temps. Simple put, the marine layer will deepen ever so slightly tonight and move farther inland. Some patchy fog will be possible late tonight and early Saturday, especially at the coast. For Saturday...marine layer and cooler/wetter start to the day. Given the transition to a changing longwave pattern and increased onshore flow no Heat Advisories will be needed for Saturday. HeatRisk values for the most part return to Minor with a few pockets of Moderate across the interior. High temperatures on Saturday will cool 5-10 degrees from Friday to Saturday with temps in the 60/70s coast, 70s/80s Bay Shoreline, and 80s/mid 90s far interior. The one exception, and hottest locations, will be southern Monterey/San Benito where high temps will exceed 100 degrees again. Fire Weather Wise - No real change from previous thinking. Near critical conditions will linger into Saturday away from the coast. Hot/dry conditions with typical breezy onshore winds will lead to elevated fire weather concerns. Not expecting much in the way of humidity recoveries tonight into Saturday above the compressed marine layer either. Given the recent heat, fine fuels are highly receptive and any spark has a high likelihood of starting a fire. Be One Less Spark and be mindful with outdoor activities heading into the weekend. It should be noted that National Preparedness Levels returned to level 5 (highest) today. In other words, fire resources are heavily committed to incidents around the CONUS. Fire season is far from over. && .LONG TERM... Issued at 250 PM PDT Fri Sep 6 2024 (Saturday night through next Thursday) The aforementioned upper low will progress through the OR/CA border and become an open wave Saturday night into Sunday morning. Marine will deep a little morning as a result with slightly better stratus coverage by Sunday morning. Only subtle changes in the seasonable weather on Sunday and Monday. Night and morning marine layer clouds with inland sunshines. Temperatures cool a few degrees, but remain above seasonal averages. The longwave pattern continues to evolve the middle of next week as an anomalously deep trough develops over the PacNw. At this time, any chance of precip looks to be farther north. Much higher confidence in more widespread cooling for the Bay Area with temperatures returning to seasonal averages. && .AVIATION... (00Z TAFS) Issued at 449 PM PDT Fri Sep 6 2024 It's VFR except for coastal stratus and fog /LIFR-IFR/ moving locally inland this evening with a greater inland intrusion tonight and Saturday morning. Stratus and fog mixing out to VFR back to the coastline by late Saturday morning and afternoon. Vicinity of SFO...VFR prevailing until 10z Saturday when IFR in stratus is forecast to develop, stratus mixing out by 17z Saturday. West to northwest wind near 20 knots until 04z this evening then diminishing to around 10 knots for the overnight hours, west wind increasing to 15 to 25 knots Saturday afternoon and evening. SFO Bridge Approach...Similar to SFO Monterey Bay Terminals...VFR until mid evening then increasing areal coverage of stratus and fog /LIFR-IFR/ overnight and Saturday morning. Stratus and fog mixing out by late Saturday morning and afternoon. Onshore winds 5 to 15 knots diminishing to light and variable winds tonight, winds onshore 10 to 15 knots Saturday afternoon and early evening. && .MARINE... (Tonight through next Wednesday) Issued at 441 PM PDT Fri Sep 6 2024 Moderate to breezy northwest winds continuing through the weekend. Occasional gusty conditions are possible over the southern waters, particularly along the Big Sur coastline, but don't look to be consistent. Widespread strong northwest winds return into the next work week with rougher seas following. && .MTR WATCHES/WARNINGS/ADVISORIES... CA...Heat Advisory until 8 PM PDT this evening for CAZ502>504-506-510- 512>518. PZ...None. && $$ SHORT TERM...MM LONG TERM....MM AVIATION...Canepa MARINE...Murdock Visit us at www.weather.gov/sanfrancisco Follow us on Facebook, Twitter, and YouTube at: www.facebook.com/nwsbayarea www.twitter.com/nwsbayarea www.youtube.com/nwsbayarea