An atmospheric river is approaching. Here's when rain could hit the drought-plagued West
An early-season atmospheric river could drop nearly a month's worth of precipitation across drought-plagued Washington state, Oregon and British Columbia from Thursday night through Saturday. The same storm will bring showers to Western Oregon on Friday and thunderstorms to far Northern California on Saturday and Sunday.
A revitalized North American Monsoon will raise the chance of thunderstorms and wetting rain across Arizona, New Mexico, Utah and Colorado from Thursday through Saturday. Phoenix could pick up its first measurable rainfall in more than six weeks.
Here's what to know about how the forthcoming rainfall could mitigate drought and fires:
Unseasonable Pacific Northwest atmospheric river
An unseasonably strong low-pressure system is expected to move toward British Columbia on Thursday. This storm will usher a moisture-rich atmospheric river toward Seattle on Friday, setting the stage for significant mountain precipitation, weather more typical of November than August.
Weather models predict precipitable water — the amount of water vapor in the atmosphere — will approach record levels over Washington state and Oregon not just for August, but any time of year.
A month's worth of rain is forecast to fall in one day in Western Oregon and Washington state. Mountain ranges in these states are forecast to receive 2 to 6 inches of precipitation by Saturday afternoon. Some Washington cities, such as Olympia, Bellingham and Quillayute, could set daily rainfall records, with amounts ranging from 1 to 3 inches. Totals in Seattle and Portland, Ore. will be on the lighter side, but each city could still pick up an inch of rain by Saturday afternoon.
Light snowfall is forecast atop Mount Rainier, Washington's tallest mountain.
Wildfire activity ramped up in drought-plagued areas and the rain should help firefighters with containment efforts. Around an inch of rain is forecast to douse the Bear Gulch Fire west of Seattle, which has sent plumes of smoke drifting across the region in recent days. Similarly, the Mount Underwood Fire on Vancouver Island that began Aug. 11 and exploded to more than 5,000 acres in two days is expected to receive significant rainfall.
Active monsoon returns to Arizona
Much of the Desert Southwest gets a significant portion of its annual rainfall from summer thunderstorms, but this year's monsoon has been subdued, particularly in Arizona. After a quiet few weeks, monsoon thunderstorms should become more active across Arizona and New Mexico through the weekend.
Phoenix has received less than 20% of normal monsoon rainfall and fewer lightning strikes than any summer since at least 1990. That should change Thursday, when a mesoscale convective vortex lifts across Arizona on Thursday and could bring measurable rain to Phoenix. By Friday, a strong surge of moisture from the Gulf of California is expected to trigger a thunderstorm outbreak across Arizona and New Mexico, lasting through Saturday, according to the University of Arizona meteorology department.
The precipitation could help moisten vegetation and dampen wildfires across Arizona. Critically dry fuels in July and early August contributed to fast-growing blazes, including the Dragon Bravo Fire, which continues to spread after destroying a historic lodge in Grand Canyon in early July.
What about California?
The monsoon high is expected to be too far east for rain in Southern California, but the remnants of the atmospheric river may hold together just enough for showers in far Northern California this weekend.
Mountainous areas north of Redding have the best chance of picking up a quarter- to half-inch of rain from passing showers Saturday and Sunday. Rainfall totals may be locally heavier beneath thunderstorms, especially around Mount Shasta.
While the Bay Area isn't in line for heavy rain like the Pacific Northwest, the storm will still impact weather around San Francisco.
Moisture and some high-level clouds associated with the system are anticipated to drift all the way over the Bay Area throughout the weekend. However, there won't be enough vertical motion in the atmosphere to condense the water vapor to liquid raindrops.
Ahead of the system, the pressure gradient along the California coast will tighten and whip up moderate northwesterly winds. These winds may be accompanied by enough dry air to mix out the coastal fog by Thursday evening for a mainly clear night over San Francisco Bay. Friday may even begin mostly sunny in San Francisco. Despite the sunshine, northwest gusts up to 35 mph are expected in the city. Even stronger gusts are possible in Point Reyes and through the San Bruno Gap.
As winds ease Friday night, marine layer clouds are expected to redevelop and blanket San Francisco Peninsula by Saturday morning. The thick marine layer will extend far inland over the weekend, keeping temperatures on the cool side of normal.
Try Our AI Features
Explore what Daily8 AI can do for you:
Comments
No comments yet...
Related Articles
San Francisco Chronicle
2 days ago
- San Francisco Chronicle
California weather shift: Heat, monsoon thunderstorms enter forecast
After a breezy and cool weekend, California's weather is about to undergo a big shift. 'The most significant heat wave of the summer season, so far,' is expected to begin midweek and continue through the weekend, according to the National Weather Service. Heat is predicted to peak Thursday through Saturday, but there's a chance it lasts even longer. High temperatures are forecast to be 10 to 15 degrees above normal and flirt with record territory in the mountains, deserts and valleys. San Francisco should be spared from the worst of the heat, as is typical with August heat waves. Subtropical moisture from the North American Monsoon will also bring a chance of thunderstorms and potential wildfire ignitions from dry lightning. The weather service warns of elevated fire weather danger in Southern California beginning Wednesday. Thunderstorms are predicted to spread northward toward the Lake Tahoe area Friday and Saturday. Here's what to expect as temperatures climb this week: Cool start, hot finish to week It'll be a slow warmup across California. An area of low pressure will linger off the coast Monday, keeping temperatures below normal as winds blow from sea to land. Temperatures will inch closer to normal Tuesday, but the big shift is anticipated Wednesday. A high-pressure system that brought hot weather to the East over the weekend will get shunted westward as Hurricane Erin approaches the Atlantic Coast. This area of high pressure will park itself over the Four Corners by Wednesday and warm up the West. By Thursday, triple-digit temperatures are predicted in California's valleys and deserts. The National Weather Service already forecasts temperatures to flirt with record territory in the Mojave Desert and San Joaquin Valley on Thursday, Friday and Saturday. In the Bay Area, Santa Rosa, Walnut Creek, Concord and Livermore are among the cities with a chance of hitting 100 degrees Thursday and Friday. Highs in Lake Tahoe are forecast to be in the mid-80s to low 90s, well above August normals. Nights will be warm, too. Overnight lows may not drop below 70 degrees in the Central Valley from Thursday through Sunday, threatening records. High-pressure systems that move east to west typically don't bring hot weather to San Francisco and Oakland because their position promotes a shallow marine breeze that keeps the coast cool. Still, downtown San Francisco should have a few days in the 70s and Oakland will probably reach 80 degrees at least once, warm relative to recent months. Areas removed from the coast slightly will be significantly warmer. San Jose and downtown Los Angeles have a shot at the 90s Thursday and Friday. Monsoon thunderstorms to hit mountains Hot weather always coincides with increased wildfire danger, but the added possibility of thunderstorms has prompted the weather service to issue a fire weather watch for the mountains of Southern California beginning Wednesday. Monsoon moisture spinning clockwise around the high-pressure system will inch toward the San Diego County mountains on Wednesday and the Ventura Mountains, San Gabriel Mountains, Antelope Valley and southern Sierra Nevada on Thursday. This moisture will increase the chance of mountain thunderstorms, but the exact timing and location of storms will become clearer by midweek. Storms may even extend toward the Tahoe basin Friday and Saturday. A mix of wet and dry lightning could spark wildfires. Flammable vegetation could burn quickly if lightning sparks a fire. Even areas that aren't hit by thunderstorms will be impacted by the monsoon moisture. The humid air mass will trap heat near the ground at night and keeps temperatures much higher than they would be typically. The National Weather Service forecasts record overnight temperatures in the Sierra Nevada and Central Valley from Thursday through Saturday. It is unclear if the hot weather will stick around beyond Sunday, but for now, at least four days of heat and mountain thunderstorms are expected in interior California. Monday Bay Area breakdown San Francisco: Thick morning fog could produce drizzle in the hills, but sunshine should prevail by midmorning at the Embarcadero with partial clearing west of Twin Peaks in the afternoon. Winds will gust 15 to 25 mph in the afternoon. Highs will be in the low to mid-60s in West Portal, Lakeshore and the Richmond and Sunset districts. Downtown, SoMa, the Mission, Dogpatch and Bayview should reach the mid- to upper 60s. Lows will be in the upper 50s with increasing clouds. North Bay: Patchy fog will slowly retreat to the coast for a mostly sunny afternoon across Wine Country. Highs will be in the mid-70s to low 80s in Santa Rosa, Sonoma, Petaluma, San Rafael, Napa and Vallejo. Mill Valley and Sausalito will be cooler, in the upper 60s to low 70s. Fairfield and Santa Rosa should reach the mid- to upper 80s. Westerly winds will gust up to 20 mph in the afternoon and evening. Patchy fog is expected to form overnight with lows in the 50s, coolest in the valleys and warmest in Solano County. East Bay: Dense fog in the Berkeley and Oakland hills could be accompanied by drizzle in the morning. Clouds should be less widespread and are expected to burn off quicker than they did over the weekend. Highs will be in the upper 60s to mid-70s along the bay shoreline from Richmond to Fremont. Upper 70s to low 80s are forecast in Lamorinda, Walnut Creek, Pittsburg and the Tri-Valley. The sea breeze will bring gusts up to 20 mph in the late afternoon. Clouds will increase overnight, especially west of the Caldecott Tunnel. Lows will be in the mid-50s. Pacific Coast and Peninsula: More morning fog is expected at the coast, although it won't be nearly as thick as over the weekend when heavy drizzle totaled up to more than a tenth of an inch in Half Moon Bay. Those clouds could even break up enough for a partly sunny afternoon sunshine at the beaches with highs in the low to mid-60s. More sunshine will be found along the Highway 101 corridor with highs in the mid- to upper 60s in South San Francisco and the mid-70s near the San Mateo-Santa Clara county border. Gusts of 15 to 25 mph are expected in the afternoon. Lows will be in the mid- to upper 50s with increasing clouds. South Bay and Santa Cruz: Clouds will burn off more quickly over the South Bay compared to the weekend, which will yield warmer temperatures. Highs will reach the mid-70s in Santa Clara, Sunnyvale and Milpitas and the upper 70s to near 80 in San Jose, Saratoga and Los Gatos. The hottest weather will be found in Morgan Hill, Gilroy and the Santa Cruz Mountains, with highs in the low to mid-80s. Scotts Valley will be around 80 while Santa Cruz should reach the low to mid-70s. Northwest wind gusts will exceed 15 mph in the afternoon, but shouldn't be much stronger. Lows will be in the mid- to upper 50s with patchy clouds near the bay and coast.
Newsweek
4 days ago
- Newsweek
Thousands of Americans Told To Stop Burning
Based on facts, either observed and verified firsthand by the reporter, or reported and verified from knowledgeable sources. Newsweek AI is in beta. Translations may contain inaccuracies—please refer to the original content. Thousands of people across the United States have been told to stop burning amid concerns over air pollution levels. The National Weather Service (NWS) has issued a series of air quality alerts across parts of Idaho, Washington and Colorado on Friday. The warnings mean that ground-level ozone and particulate concentrations are forecast to reach dangerous levels, largely due to pollution from drifting wildfire smoke. Why It Matters The NWS warned that sensitive groups — children, seniors, and individuals with preexisting respiratory or heart conditions — might experience health effects linked to poor air quality in the affected regions. "Air pollutants can cause breathing difficulties for children, the elderly, as well as persons with respiratory problems," it said. "Those individuals who are sensitive to increased particulate matter or smoke are encouraged to avoid prolonged or strenuous outdoor activity during this advisory." Firefighters battle a wildfire in Hasley Canyon, California, last week. Firefighters battle a wildfire in Hasley Canyon, California, last week. Marcio Jose Sanchez/AP What To Know In Idaho, an air quality alert has been issued for Boundary, Bonner, and Shoshone counties until midday on Friday. Air quality is forecast to be unhealthy for sensitive groups. The Idaho Department of Environmental Quality said: "Open burning is prohibited by air quality rule. It is also recommended that all other individuals limit prolonged or strenuous activity outdoors." In Washington, the Olympic Region Clean Air Agency has issued an air quality alert for Mason County until 9 a.m. due to wildfire smoke from the Bear Gulch Fire. "Health impacts and recommended actions: when air quality is very unhealthy or hazardous, everyone should reduce exposure. Stay inside and filter indoor air to keep it cleaner. Go elsewhere for cleaner air, if needed. Burning restrictions are in effect," the agency said. Meanwhile in Colorado, an air quality healthy advisory for wildfire smoke has been issued until 9 a.m. for large swathes of the northwest and southwest, including the city of Durango. The Colorado Department of Public Health and Environment (CDPHE) said: "The Stoner Mesa fire in eastern Dolores County will create periods of moderate to heavy smoke on Thursday and Friday within the advisory area. The heaviest smoke impacts will likely be in locations near the fire and low-lying areas, including Rico, Dolores, Cortez, and Durango." What People Are Saying The CDPHE said in a statement: "If smoke is thick or becomes thick in your neighborhood you may want to remain indoors. This is especially true for those with heart disease, respiratory illnesses, the very young, and older adults. Consider limiting outdoor activity when moderate to heavy smoke is present. Consider relocating temporarily if smoke is present indoors and is making you ill. If visibility is less than 5 miles in smoke in your neighborhood, smoke has reached levels that are unhealthy." Jonathan Grigg, a professor of pediatric respiratory and environmental medicine at Queen Mary University of London, previously told Newsweek that there are "very clear links" between inhaling particles and earlier death from both respiratory and cardiovascular diseases. He added: "There are vulnerable groups and classically they are children because they've got an extra issue to do with their lungs developing, whereas our lungs are not developing as adults." What Happens Next The warnings are currently set to remain in force until Friday morning in Washington and Idaho, and midday in Colorado. Regular updates regarding air pollution levels are issued on the NWS website and on the Environmental Protection Agency's AirNow interactive map.
San Francisco Chronicle
6 days ago
- San Francisco Chronicle
An atmospheric river is approaching. Here's when rain could hit the drought-plagued West
Two separate weather patterns are forecast to bring substantial rainfall to parts of the West the next few days, alleviating drought and drenching wildfires from Seattle to Phoenix. An early-season atmospheric river could drop nearly a month's worth of precipitation across drought-plagued Washington state, Oregon and British Columbia from Thursday night through Saturday. The same storm will bring showers to Western Oregon on Friday and thunderstorms to far Northern California on Saturday and Sunday. A revitalized North American Monsoon will raise the chance of thunderstorms and wetting rain across Arizona, New Mexico, Utah and Colorado from Thursday through Saturday. Phoenix could pick up its first measurable rainfall in more than six weeks. Here's what to know about how the forthcoming rainfall could mitigate drought and fires: Unseasonable Pacific Northwest atmospheric river An unseasonably strong low-pressure system is expected to move toward British Columbia on Thursday. This storm will usher a moisture-rich atmospheric river toward Seattle on Friday, setting the stage for significant mountain precipitation, weather more typical of November than August. Weather models predict precipitable water — the amount of water vapor in the atmosphere — will approach record levels over Washington state and Oregon not just for August, but any time of year. A month's worth of rain is forecast to fall in one day in Western Oregon and Washington state. Mountain ranges in these states are forecast to receive 2 to 6 inches of precipitation by Saturday afternoon. Some Washington cities, such as Olympia, Bellingham and Quillayute, could set daily rainfall records, with amounts ranging from 1 to 3 inches. Totals in Seattle and Portland, Ore. will be on the lighter side, but each city could still pick up an inch of rain by Saturday afternoon. Light snowfall is forecast atop Mount Rainier, Washington's tallest mountain. Wildfire activity ramped up in drought-plagued areas and the rain should help firefighters with containment efforts. Around an inch of rain is forecast to douse the Bear Gulch Fire west of Seattle, which has sent plumes of smoke drifting across the region in recent days. Similarly, the Mount Underwood Fire on Vancouver Island that began Aug. 11 and exploded to more than 5,000 acres in two days is expected to receive significant rainfall. Active monsoon returns to Arizona Much of the Desert Southwest gets a significant portion of its annual rainfall from summer thunderstorms, but this year's monsoon has been subdued, particularly in Arizona. After a quiet few weeks, monsoon thunderstorms should become more active across Arizona and New Mexico through the weekend. Phoenix has received less than 20% of normal monsoon rainfall and fewer lightning strikes than any summer since at least 1990. That should change Thursday, when a mesoscale convective vortex lifts across Arizona on Thursday and could bring measurable rain to Phoenix. By Friday, a strong surge of moisture from the Gulf of California is expected to trigger a thunderstorm outbreak across Arizona and New Mexico, lasting through Saturday, according to the University of Arizona meteorology department. The precipitation could help moisten vegetation and dampen wildfires across Arizona. Critically dry fuels in July and early August contributed to fast-growing blazes, including the Dragon Bravo Fire, which continues to spread after destroying a historic lodge in Grand Canyon in early July. What about California? The monsoon high is expected to be too far east for rain in Southern California, but the remnants of the atmospheric river may hold together just enough for showers in far Northern California this weekend. Mountainous areas north of Redding have the best chance of picking up a quarter- to half-inch of rain from passing showers Saturday and Sunday. Rainfall totals may be locally heavier beneath thunderstorms, especially around Mount Shasta. While the Bay Area isn't in line for heavy rain like the Pacific Northwest, the storm will still impact weather around San Francisco. Moisture and some high-level clouds associated with the system are anticipated to drift all the way over the Bay Area throughout the weekend. However, there won't be enough vertical motion in the atmosphere to condense the water vapor to liquid raindrops. Ahead of the system, the pressure gradient along the California coast will tighten and whip up moderate northwesterly winds. These winds may be accompanied by enough dry air to mix out the coastal fog by Thursday evening for a mainly clear night over San Francisco Bay. Friday may even begin mostly sunny in San Francisco. Despite the sunshine, northwest gusts up to 35 mph are expected in the city. Even stronger gusts are possible in Point Reyes and through the San Bruno Gap. As winds ease Friday night, marine layer clouds are expected to redevelop and blanket San Francisco Peninsula by Saturday morning. The thick marine layer will extend far inland over the weekend, keeping temperatures on the cool side of normal.
