Area Forecast Discussion
Issued by NWS San Francisco Bay Area, CA
Issued by NWS San Francisco Bay Area, CA
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880 FXUS66 KMTR 071149 AFDMTR Area Forecast Discussion National Weather Service San Francisco CA 449 AM PDT Sun Jul 7 2024 ...New AVIATION, MARINE... .SYNOPSIS... Issued at 1236 AM PDT Sun Jul 7 2024 Day 6 of the inland heat wave. The peak of the event is finally behind us and some minor relief is on the way this week before a more substantial cool-down next weekend. && .SHORT TERM... (Today and tonight) Issued at 1236 AM PDT Sun Jul 7 2024 ACARS data from Oakland flights are showing the 850 mb temperature is 31C. The highest 850 mb temperature ever observed from the Oakland weather balloon is 31.0C. This means we are experiencing the hottest low level heat since records began 75 years ago. Inland areas reached triple digits yesterday with a few over 110. Higher elevations are seeing some of the hottest daily max and min temps on record. For example Pinnacles National Park reached 116 degrees yesterday (all time record 117 9/6/20), and Mallory Ridge (north of Livermore @ 1948 ft) only got down to 90 Saturday morning before jumping back up to 106 in the afternoon. Fortunately onshore winds and a shallow marine layer are keeping coastal areas cool. As the ridge axis moves across California, temperatures will begin to cool a bit Sunday. The only record we are threatening is at King City (105 forecast). Otherwise, most inland areas will stay out of the 100s today. Higher elevations are still seeing very warm conditions, but they will also begin to cool a few degrees Sunday. Coastal areas will be much cooler (similar to yesterday) with marine layer clouds breaking in the afternoon and returning in the evening. && .LONG TERM... (Monday through Saturday) Issued at 1236 AM PDT Sun Jul 7 2024 The cool-down will continue through Tuesday as the ridge continues to slide east. While this is certainly welcome, it is not a drastic improvement. To put it in perspective, the 850 mb temp is currently in the top 99.99% (30.2 C) of historical observations. We are anxiously awaiting it to drop back to the the 98% (25 C) by Tuesday. We are still going to be well above average this week with inland areas remaining in the 90s. By Wednesday, the cooling trend flattens, and temps may tick back up a few degrees Wed-Fri before a more substantial cool-down arrives this weekend. This heat wave has been going for 5 days now and we are just now getting on the back nine. The warm mornings and back-to-back record breaking temperatures can cause cumulative effects that make the situation more dangerous. Heat is the number 1 weather related killer in the United States. Unfortunately lives will be lost during this heat wave. Follow these tips to protect yourself, your loved ones, and your animals. -Stay inside in an air conditioned environment between 10am and 7pm. -Suspend unnecessary outdoor activities during the extreme heat, but if you must be outdoors, take frequent breaks in the shade or AC and drink cool water. -Know the signs and symptoms of Heat Exhaustion vs. Heat Stroke! Heat Stroke can be deadly if not treated immediately by a medical professional. Call 911 if you suspect someone is suffering from Heat Stroke. -Wear a lifejacket, swim near a lifeguard, and check conditions before entering the water if going to a river or ocean to cool off. Rivers and the ocean are extremely cold, and Cold Water Shock can turn into paralysis and drowning if you are not careful. -Use a cool and damp towel on your body if you do not have AC and are feeling hot. Or, take a cool shower or bath. -Do not leave kids or pets in a parked car. You can put your cellphone/wallet or even your shoe in the back seat as a reminder. -Ensure pets and livestock have access to shade and water. && .AVIATION... (12Z TAFS) Issued at 448 AM PDT Sun Jul 7 2024 Mix of VFR and LIFR conditions across the board. Night Fog shows stratus moving inland towards STS, APC, and OAK with stratus already located at MRY and SNS. Stratus is expected to reach STS, APC, and OAK shortly (between 12-13Z) with five minute obs at all three airports showing low level clouds already present. Elevated fog potential remains for STS, MRY, and SNS with visibility most likely to drop between 12-16Z. For OAK and SFO - stratus has been slightly slower to filter into the SF Bay than previously expected. Stratus arrival has been pushed back for SFO and OAK with moderate confidence that stratus will reach SFO. Onshore flow continues through the period with moderate winds persisting into the evening before weakening overnight. Vicinity of SFO...VFR becoming IFR during the early morning hours. Low to moderate confidence that stratus will reach SFO. Stratus has been filtering into the SF Bay slower than originally forecast resulting in beginning of IFR conditions being pushed back several hours. Ensemble guidance continues to indicate a brief period of IFR CIGs but confidence remains low to moderate given the slower stratus arrival time. Onshore flow persists through the period with moderate, gusty winds returning during the afternoon before diminishing overnight. Ensemble guidance indicates stratus is likely to return tomorrow night but low confidence on the exact timing. SFO Bridge Approach...Similar to SFO. Monterey Bay Terminals...LIFR conditions continue through mid to late morning before VFR returns briefly during the afternoon/evening. Low to moderate confidence that visibilities will degrade significantly this morning. For now leaning towards minimal visibility interruptions, however, elevated fog potential does remain with 12-16Z the most likely time for larger dips in visibility to occur/for fog to form. Onshore flow continues through the TAF period with moderate winds expected during the day before lighter, more variable winds return overnight. Stratus is expected to return by the late evening with CIGs expected to quickly transition from IFR to LIFR. && .MARINE... (Today through Friday) Issued at 448 AM PDT Sun Jul 7 2024 High pressure continues over the Pacific Ocean with gentle to moderate northwest winds persisting into the early work week. Fresh to the occasional strong gusts will briefly develop over the northern outer coastal waters Monday before diminishing into Tuesday. Widespread fresh to strong northwest winds return across the coastal waters by mid-week. Significant wave heights will build to 10-14 feet in the outer waters beginning Wednesday. && .FIRE WEATHER... Issued at 920 AM PDT Sat Jul 6 2024 Just finished up coordination calls with agency fire partners and neighboring offices. No updates needed for ongoing fire headlines. Red Flag Warnings remain in effect for the North Bay Interior Mountains, East Bay Hills and Santa Cruz Mountains until 9 PM Saturday. Red Flag Warnings are also in effect for the Santa Lucia Mountains, San Benito County, and the Southern Salinas Valley until 9 PM Saturday as well. Marine layer brought some overnight relief for lower elevations, but higher elevations (specifically Red Flag Locations) saw no relief with temps in the 80s/90s and RH less than 30 percent. Winds are breezy at times too. Needless to say critical fire weather conditions. While the Red Flag Warning is set to expire this evening with weakening winds, lack of humidity recovery tonight over higher elevations will lead to near critical conditions. For Sunday, areas of concern will be focused away from the coast with another hot and dry day. Area of greatest concern will be the East Bay were afternoon gusty pass/gap winds combined with hot/dry conditions will lead to isolated pockets of critical fire weather. Not widespread enough for another Red Flag, but critical nonetheless. MM && .MTR WATCHES/WARNINGS/ADVISORIES... CA...Excessive Heat Warning until 11 PM PDT Wednesday for CAZ502>504- 506-510-512>518. Heat Advisory until 11 PM PDT Wednesday for CAZ508-528. PZ...Small Craft Advisory from 3 PM this afternoon to 9 AM PDT Monday for Pt Arena to Pt Reyes 10-60 NM. && $$ SHORT TERM...Flynn LONG TERM....Flynn AVIATION...Kennedy MARINE...Kennedy 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