Area Forecast Discussion
Issued by NWS San Francisco Bay Area, CA
Issued by NWS San Francisco Bay Area, CA
Versions:
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
853 FXUS66 KMTR 020530 AFDMTR Area Forecast Discussion National Weather Service San Francisco CA 1030 PM PDT Mon Jul 1 2024 ...New AVIATION, MARINE... .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. && .UPDATE... Issued at 855 PM PDT Mon Jul 1 2024 Low level marine stratus over southern Monterey Bay is expected to persist through late morning Tuesday, with mostly clear skies for the remainder of the area overnight. See details below for the Red Flag Warning beginning at 11pm tonight, that now includes the Santa Cruz Mountains. Otherwise the forecast remains on track for a strong dome of high pressure to begin exerting its influence across our region tomorrow, and slowly migrate east through the remainder of the extended forecast. The highest temperatures for some locations inland are forecasted for tomorrow and Wednesday, but that does not mean the impacts of this event end after Wednesday. As the heat builds and continues well into next weekend, so too do the hazards associated with it to vulnerable people and communities. Also, we cannot stress enough that fireworks should not be used this year. Any wildfire thats ignited has the potential for rapid spread. && .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... (06Z TAFS) Issued at 1029 PM PDT Mon Jul 1 2024 IFR-LIFR ceilings continue at the immediate coast south of HAF, with the only inland intrusion around the Monterey Bay region and into the northern Salinas Valley, expected to retreat to the coast Tuesday morning. Very low confidence in the development of stratus across the rest of the region tonight. Light winds tonight will develop into breezy onshore flow Tuesday afternoon. Marginal LLWS concerns continue during the overnight periods, especially at the coast and in the North Bay. Vicinity of SFO...High confidence of VFR through the TAF period. Light winds overnight, building to a breezy west-northwest flow on Tuesday afternoon with gusts up to 20-25 knots. Winds diminish in the evening. SFO Bridge Approach...Similar to SFO. Monterey Bay Terminals...LIFR ceilings will impact the terminals through late Tuesday morning. Model output is showing visibility reductions sometime overnight but confidence in timing is low. Added a TEMPO group for visibilities below 1 SM based on persistence from the previous morning. Breezy northwest flow develops Tuesday afternoon, with ceilings returning to the terminals during the evening. && .MARINE... (Tonight through next Sunday) Issued at 1029 PM PDT Mon Jul 1 2024 Fresh to strong northerly winds with gale force gusts possible continue over the outer coastal waters into Tuesday. Winds will diminish and become moderate to fresh by mid-week as surface high pressure strengthens and moves eastward. In general, north to northwest winds prevail through the forecast period but wind direction may become more variable by late week as winds weaken. Elevated significant wave heights between 10-12 feet continue 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 330 PM PDT Mon Jul 1 2024 A Red Flag Warning will be in effect starting at 11pm tonight for some elevated locations in the North Bay Hills, East Bay Hills, Marin and Sonoma Coastal Ranges through late tomorrow evening with the North Bay Hills RFW continuing until 5pm Wednesday. RH values are generally in the teens with gusty north/northeast offshore flow. As the hot and dry pattern persists, fuels continue to dry. ERCs are drying in to the 70-90 percentile range across our region. Combine that with the expected surge of campers over the long holiday weekend and obvious risks of fireworks, putting our area in a combustible situation through next weekend. Fireworks should not be used this year, and campers should be very careful with anything dragging from trailers and securing campfires. && .MTR WATCHES/WARNINGS/ADVISORIES... CA...Coastal Flood Advisory until 11 PM PDT Wednesday for CAZ006-506- 508. Heat Advisory from 11 AM Tuesday to 7 PM PDT Wednesday for CAZ006. Red Flag Warning until 11 PM PDT Tuesday for CAZ502-503-512-515. Excessive Heat Warning from 11 AM Tuesday to 8 PM PDT Saturday for CAZ502>504-506-510-512>518. Red Flag Warning until 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. Gale Warning until 3 AM PDT Wednesday for Pt Arena to Pt Reyes 10-60 NM. && $$ SHORT TERM...Behringer LONG TERM....Behringer/Clouser AVIATION...DialH 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