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Area Forecast Discussion
Issued by NWS San Francisco Bay Area, CA
Issued by NWS San Francisco Bay Area, CA
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449 FXUS66 KMTR 012125 AFDMTR Area Forecast Discussion National Weather Service San Francisco CA 225 PM PDT Mon Jul 1 2024 ...New SYNOPSIS, SHORT TERM, LONG TERM... .SYNOPSIS... Issued at 131 PM PDT Mon Jul 1 2024 Significant and extended warm up still slated to begin tomorrow lasting into the weekend. Multiple days of dangerous temperatures expected inland. Potential for well above average temps lasting through the forecast period and into next week. && .SHORT TERM... (This evening through Tuesday) Issued at 131 PM PDT Mon Jul 1 2024 Temperatures on track today, running a couple of degrees warmer than yesterday as of this afternoon. A sign of things to come if you look at higher elevations though...these locations are running between 8-15 degrees warmer than 24 hours ago. This sharp increase in temps will extended to lower elevations by tomorrow as what is left of the marine layer becomes further compressed by the building high pressure aloft. Not much change in the short term forecast as far as temperatures go. The City of San Francisco was added to the Heat Advisory for Tuesday and Wednesday given a slight nudge upwards in forecast temps. This resulted in moderate HeatRisk for portions of the City, mainly the south and eastern sides where the 90th percentile forecast is around 90 degrees. The current official forecast is still in the low-to-mid 80s, but there is a real possibility of seeing temps briefly spike to around 90 in these areas if the weak offshore winds are more productive than expected during the mid-to-late morning hours. The western side of the City and other locations along the immediate coast will still be on the warmer side, but will still hold on to a bit of marine influence given that there is no synoptic driver of persistent offshore winds with this pattern. Not to say that some offshore winds won`t exist, but any gusty offshore winds that do occur will be relatively short-lived and localized. Higher elevations of the East Bay and North Bay will see increased fire danger due to the winds Tuesday afternoon, particularly over inland Napa/Sonoma and far eastern Contra Costa/Alameda counties. Elsewhere and through the rest of the week, winds don`t seem to be as big of an issue. However, fire starts will still be extremely likely as fuels are VERY dry combined with low RH. More in the FIRE WEATHER section below. && .LONG TERM... (Wednesday through next Sunday) Issued at 131 PM PDT Mon Jul 1 2024 No notable change in temperatures going into Wednesday. There is a weak mid-level shortwave trough embedded in the NW flow across the Pac NW and Northern Rockies that may end up bringing temps down by a couple of degrees for low-lying areas of the North Bay due to "slightly" more marine influence to start the day. However, the overall risk due to heat remains as temps will still be north of 100 degrees. Some of this "cool down" will spread across the rest of the low-lying areas by Thursday taking another couple of degrees off the highs. There is higher confidence now that we will see temperatures peak again by the end of the week into Saturday, thus, the Excessive Heat Warning and Heat Advisory were both extended to Saturday night. Ensemble guidance also exhibits better confidence that we will see a secondary peak late in the week, advertising 850 mb temperatures around 31 C by late Saturday, which would tie the all-time July record for 850 mb temps per the OAK sounding. A further hint that this is a significant, multi-day heat wave that should be taken seriously. Looking further towards the end of the weekend, cluster analysis still exhibits some uncertainty but is gradually coming to a better agreement in the ridge remaining in place well into next week. For now, will keep the expiration of heat highlights as is for Saturday night, but we will need to continue to monitor for the possibility of extending the advisories and warnings further. *While we have all seen temperatures like this before, this event may end up approaching the upper end of what we`ve seen historically, in terms of longevity. While not necessarily in the realm of "unprecedented", this certainly fits the bill as a significant heat wave, especially for inland areas. Please take the proper precautions, as impacts will only worsen day-by-day. A bit on heat safety below. HEAT SAFETY AND IMPACTS: By now youre well aware that it is going to be extremely hot this week with well-above normal temperatures; now lets talk about the impacts of excessive heat and actions we can take to minimize those impacts: With extreme heat, and especially prolonged heat events, it is a marathon, and not a sprint. Our bodies, infrastructure, pets, and livestock will be under duress from heat over the span of days as opposed to just a day or two. Given that there is little overnight relief expected throughout this event, this is where it really becomes a marathon, and precautionary measures are necessitated in order to prevent adverse results such as heat exhaustion and stroke. This is not just for individuals sensitive to heat, but rather, the entire population. Heat for this duration and at these temperatures can be dangerous for everyone. Do your body a favor and if you can, suspend outdoors activities between the hours of 10am and 7pm on days where Heat Advisories or Excessive Heat Warnings are in effect. Remain in air conditioning if you have that available to you in your residence, or seek out air conditioned environments such as stores, movie theaters, restaurants, libraries, and cooling shelters. If you cannot access air conditioned environments, must be outside, work outdoors, or otherwise, there are other precautionary measures you can take to keep yourself and your loved ones safe (including pets!) during excessive heat. Take frequent breaks in the shade and ensure that you are drinking plenty of cool water, or other hydrating beverages such as sports drinks with electrolytes. Avoid DEHYDRATING drinks such as alcohol or caffeinated beverages. That aside, visiting your city public pool or a lake, river, or ocean can also help keep you cool, but dont forget the life jacket! If planning on swimming, stick to where there is a lifeguard, and know the ocean or river conditions before you get in. Although outside of our area, its worth repeating: rivers can run fast and cold with snowmelt in the Sierra Nevada mountains, and cold water shock can set in quickly, which can lead to loss of muscle control, and ultimately, drowning. Cold water shock can also set in for ocean- goers. Have fun at the water, but be smart, be safe, and Know Before You Go! Finally, if you do not have air conditioning or cannot access it, and also cannot access a body of water to stay cool: consider taking cold showers or baths, turn on those sprinklers or garden hose and have a fun time in your own makeshift water park, or lay a damp, cool towel across your head or body. Even just dipping your hands and feet in cool water can help to abate feelings of excessive heat. For pets and livestock, make sure they have access to shade structures or areas, and have clean water freely available to them at all times. They do not have the same resources or ability to notify of feeling heat-stressed as we do, so check in on them! If theyre permanently outdoors, consider giving them a quick rinse- down with the hose or set up misters, as the evaporation will help to keep them cool as well. && .AVIATION... (18Z TAFS) Issued at 1051 AM PDT Mon Jul 1 2024 VFR through the TAF period for all terminals except Monterey Bay. Onshore and breezy winds return this afternoon for all terminals, then ease into the night to become light. Winds will shift overnight to develop very light northerly or offshore flow. Monterey Bay terminals will be under LIFR CIGs through the nighttime. Vicinity of SFO...VFR through the TAF period. W/NW winds resume in the afternoon to become moderate, and with a few gusts nearing 25 knots. Winds then diminish into the nighttime to become light. Some light offshore flow is expected in the morning of Tuesday. SFO Bridge Approach...FEW low clouds will develop over the SF bay in the early morning of Tuesday, but are expected to clear in the late morning. Monterey Bay Terminals...VFR through the early evening today with breezy W/NW winds, then developing IFR CIGs. IFR CIGs are expected to quickly lower to LIFR within a couple hours of stratus pushing into terminal vicinities. Winds ease to become light in the late night. LIFR CIGs and lowered visibilities then linger through sunrise Tuesday. VFR returns by the late morning of Tuesday. && .MARINE... (Today through Saturday) Issued at 937 AM PDT Mon Jul 1 2024 Strong northwesterly breezes continue over the outer waters through the midweek. Winds become more northerly this afternoon and gale force to near gale force gusts become more widespread over the outer waters as high pressure builds. Winds will gradually weaken by mid to late week and become moderate to fresh. Significant wave heights generally build to 10-12 feet through mid-week before abating by the late week. Portions of the northern outer waters may see peak wave heights between 12-16 feet through mid-week. && .FIRE WEATHER... Issued at 901 PM PDT Sun Jun 30 2024 ...A Red Flag Warning is in effect from Monday evening through Tuesday evening for the East Bay Hills, Marin and Sonoma Coastal Ranges, and the North Bay interior mountains Monday evening through late Wednesday afternoon. A Red Flag Warning has been added to the list of hazards along with the Excessive Heat Warning which remains in place for most of our interior locations, and a Heat Advisory for some locations closer to the shoreline that may still see minimal influence of the Marine Boundary Layer. Minimum RH values inland for the upcoming week and beyond will mostly be in the teens, with some single digit values in areas of higher elevation. Overnight RH recover will be poor to non-existent as the heat wave persists through the week, and potentially into next weekend. The hot and dry conditions continue to move ERCs into the 70-80 percent range. With the long holiday weekend, and the many outdoor activities expected, people need to be careful with any campfires, and fireworks should not be used. Any wildfire that ignites will have the potential for rapid spread. Lightning is the only natural ignition for wildfires and there are no thunderstorms in the forecast. && .MTR WATCHES/WARNINGS/ADVISORIES... CA...Heat Advisory from 11 AM Tuesday to 7 PM PDT Wednesday for CAZ006. Red Flag Warning from 11 PM this evening to 11 PM PDT Tuesday for CAZ502-503-515. Excessive Heat Warning from 11 AM Tuesday to 8 PM PDT Saturday for CAZ502>504-506-510-512>518. Red Flag Warning from 11 PM this evening to 5 PM PDT Wednesday for CAZ504. Heat Advisory from 11 AM Tuesday to 8 PM PDT Saturday for CAZ508- 528-529. PZ...Small Craft Advisory until 3 AM PDT Tuesday for Pigeon Pt to Pt Pinos 10-60 NM-Pt Arena to Pt Reyes 0-10 nm. Small Craft Advisory until 9 PM PDT this evening for Pt Pinos to Pt Piedras Blancas 0-10 nm. Small Craft Advisory until 3 PM PDT this afternoon for Pt Arena to Pt Reyes 10-60 NM. Gale Warning until 3 PM PDT Tuesday for Pt Arena to Pt Reyes 10- 60 NM. && $$ SHORT TERM...Behringer LONG TERM....Behringer AVIATION...AC MARINE...AC 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