2023年北美重大天气事件追踪（存档）

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California set to get needed break from storms. How long will it last?
Story by Alex Sosnowski • 4h ago

Amuch-needed break from the relentless train of storms from the Pacific is set to unfold across California, and AccuWeather meteorologists believe the pause in major rain and mountain snow events should last through the end of January.

During much of late December and the first half of January, storms from the central Pacific continuously plowed into California while grabbing plumes of subtropical moisture along the way. The storms brought drought-easing rain and yards of snow to the mountains but also triggered deadly and damaging flooding and mudslides as snow shut down travel over the Sierra Nevada passes.

While storms will continue to roll along across the northern Pacific in the coming weeks, a zone of high pressure will build at most levels of the atmosphere along the West Coast of the United States.


California set to get needed break from storms. How long will it last?
© Provided by AccuWeather

This setup will force the storms to swing well to the north and far away from tropical moisture before plunging southward over the interior Southwest, rather than along the California coast.

Storms of this nature are often referred to as "inside sliders" by meteorologists.

One such storm will continue to produce patchy low-elevation rain showers and mountain snow into Thursday over California before it pushes eastward. This storm has much less moisture to work with and will be a drop in the bucket compared to many prior storms this month.


California set to get needed break from storms. How long will it last?
© Provided by AccuWeather

The changing weather pattern will allow the ground to dry out and streams to recede gradually. However, the runoff will continue to fill area lakes and reservoirs over the next couple of weeks.

As the storm into Thursday pivots over the interior Southwest, breezy conditions can cause some trouble. Since the soil will remain moist and tree canopies have absorbed some of the wet weather, moderate amounts of wind can cause some top-heavy trees to come crashing down without notice.

A storm at the jet stream level of the atmosphere over the Southwest could be more problematic this weekend into next week.


California set to get needed break from storms. How long will it last?
© Provided by AccuWeather

The combination of this storm high in the atmosphere and an area of high pressure that will build from the coastal Northwest to the Great Basin will stir up gusty winds, AccuWeather Long-Range Meteorologist Joe Bauer explained.

"This setup supports the risk for Santa Ana winds in Southern California and perhaps similar Diablo winds around San Francisco to develop next week, potentially for a string of days," Bauer said.


California set to get needed break from storms. How long will it last?
© Provided by AccuWeather

"The northeast winds can lead to gusty conditions over the mountains and northeast-facing canyons and breezy conditions extending into the valleys and some coastal areas," Bauer added.

AccuWeather's long-range forecasting team believes that some storms may return to California during early February. Drenching rain, mountain snow and travel problems are likely to resurface in early February but probably not to the scope of the past few weeks.

There has already been an incredible amount of snow over the Sierra Nevada this winter, compared to recent years, and more snow is expected.


California set to get needed break from storms. How long will it last?
© Provided by AccuWeather
Snowpack levels are well above average in the Sierra Nevada as of Jan. 18, 2023.

"It appears as though the northward bulge in the jet stream will shift position and drift westward and well off the Pacific coast for a time in early February," AccuWeather Lead Long-Range Meteorologist Paul Pastelok said. "This will open up the opportunity for storms to drop southward over California, rather than slide inside over the interior Southwest."

Pastelok's team believes that the return of storms may last only a week or so during early February before the bulge in the jet stream returns to the Pacific Coast states.

"One difference in the upcoming pattern in early February is that we do not foresee a merge in the jet stream that allows a great deal of tropical moisture to be drawn in," Pastelok said. As a result, upcoming storms in early February will not be as potent with less wind, rain and mountain snow compared to late December and the first half of January.


California set to get needed break from storms. How long will it last?
© Provided by AccuWeather
Reservoir levels across California as of Jan. 18, 2023.

More rounds of storms may follow later in February, March and perhaps in April. This would make a dramatic difference when compared to the 2021-2022 winter when storms became much less frequent after a busy December.

That lack of storms helped lead to exceptional drought last summer across the Golden State. This winter, rain is already well ahead of last year's pace and is filling reservoirs as a result. The state is also no longer experiencing any exceptional drought conditions, according to the U.S. Drought Monitor.

With the surplus of rain thus far this winter, grass and other brush will likely grow rapidly heading into the spring before drying out in the heat of the summer. That excess amount of brush could serve as more fuel for wildfires.

"We believe that La Niña will continue to weaken and an El Niño may develop this summer to this autumn, but how strongly and how fast that occurs has implications on the upcoming fire season," Pastelok said.

Experts say the brush will dry out heading into the summer and early autumn, no matter how wet or dry the winter storm season was. How many fires erupt will depend on human interaction as well as the amount of lightning and intensity of wind storms that develop.

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Severe storms will threaten Ohio, Tennessee Valleys on Thursday
Story by Bill Deger • 5h ago

The threat of severe thunderstorms will shift east on Thursday to target portions of the Midwest and Southeast, one day after racing through the southern Plains and Mississippi Valley. The storms will unleash soaking rains and could even trigger strong winds and tornadoes, according to AccuWeather forecasters,

Storms will track unusually far to the north for the middle of winter. Some areas that will be at risk of damaging storms on Thursday are more used to cold and snow this time of year than the loud roar of thunder.

"The thunderstorms will be in association with a strong storm tracking across the southern Great Lakes," said AccuWeather Senior Meteorologist Tyler Roys. The same storm will spread a swath of accumulating snow from the Rockies to the Upper Midwest through late this week.


Severe storms will threaten Ohio, Tennessee Valleys on Thursday
© Provided by AccuWeather

A cold front extending south from the storm to the Gulf Coast will also prove to be a focal point for thunderstorm development as it moves to the east.

Thunderstorms are expected to be ongoing from the northern Gulf Coast to the Tennessee Valley early on Thursday. The storms are forecast to track eastward in a line, which can reach as far east as northern Georgia and the western Carolinas by nightfall.

Farther north, thunderstorms may come in two rounds in parts of the Ohio Valley and southern Great Lakes. The first round will be ongoing in the morning and produce heavy, soaking rain. By the afternoon, storms will operate in one or more individual lines.

The storms later in the day are expected to be the strongest, likely first developing in eastern Indiana or western Ohio then expanding and rolling east through far southern Michigan, Ohio and Kentucky then into West Virginia and western Pennsylvania.

There will likely be a few lines of storms with brief heavy rains that can lead to flash flooding, as well as damaging winds, according to Roys.


Severe storms will threaten Ohio, Tennessee Valleys on Thursday
© Provided by AccuWeather

Due to the fast-moving nature of the storms, the flooding threat should mainly be confined to highways and poor drainage areas rather than creeks and streams. However, it could coincide with the evening commute. Damaging wind gusts in excess of 50 mph could accompany that heavy rain in a few storms, dramatically reducing visibility for motorists, while also bringing down tree limbs and power lines.

There is also a small chance that a tornado or two could develop in Ohio and nearby areas late in the day on Thursday. This area is closer to the overall storm system and where winds will be changing with increasing atmospheric height, indicating a higher chance that a tornado could spin up.


Severe storms will threaten Ohio, Tennessee Valleys on Thursday
© Provided by AccuWeather

Some cities and highways that may have to contend with the threat of gusty, drenching storms include portions of I-20 between Birmingham, Alabama, and Atlanta; I-75 from Chattanooga, Tennessee, to Lexington, Kentucky; I-64 from Louisville, Kentucky to Charleston, West Virginia; and I-76 from Akron, Ohio, to Pittsburgh.

The threat of severe thunderstorms as far north as Michigan, Ohio and Pennsylvania in January is rare and will be driven by an intrusion of unusually moist and mild air into parts of the Great Lakes and Northeast.

Lightning and thunder can even advance to the north of the severe weather risk area into parts of the Lower Peninsula of Michigan, western New York and southern Ontario, Canada. In the heart of winter, when snow and bitter cold are often more on the mind of residents in these locales, the loud roar of thunder will seem very misplaced.

The cold winds of winter will make a quick return in the wake of the thunderstorms, as a cooler air mass could trigger lake-effect snow showers downwind of the Great Lakes from Thursday night into Friday. Only a modest drop in temperature is expected behind this front in the South.

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Drone footage shows dramatic improvement in California reservoir levels
Story by Bill Deger • 7h ago

In the wake of the atmospheric rivers that have brought an onslaught of rain, wind and snow to California over the last few weeks, short-term drought conditions and reservoir levels have improved, but the Golden State is not in the clear yet when it comes to the long-term drought, according to AccuWeather forecasters.

According to the latest version of the U.S. Drought Monitor, released on Thursday morning, extreme drought conditions have been completely eliminated in the state. Since mid-October, the area covered by severe drought conditions or worse has shrunk from 92 percent to just 43 percent.

The storms that clobbered the state from late December into the first half of January were deadly and damaging, but one silver lining has been the dramatic recovery in water level in many reservoirs crucial to the state's water supplies and the snowpack in the mountains, a water supply in-waiting once the snow melts and runs downstream during the spring and summer months. It has been estimated that 24 trillion gallons of water fell over the state during the stormy streak.

Drone footage shot by storm chaser Brandon Clement showed the improvement in water level and snowpack in places such as Folson Lake, Lake Oroville and Donner Pass, since last summer.

The winter months are a crucial time of year for California's water supply. It is the state's wet season, the time to stockpile water for the drier months that run from the spring into the fall. In recent wet seasons, periods of stormy weather have been brief or even nonexistent, causing reservoir levels to drop and drought conditions to expand. This season, the storms have almost been too much of a good thing, due to the deadly flooding and damaging mudslides they have caused.

Despite the improvement in drought conditions, more than 99 percent of the state remains at least abnormally dry, and 92 percent is experiencing at least moderate drought conditions, according to the latest drought monitor report. This underscores the long-term, multiyear nature of the current drought, which would only be eradicated if soaking storms continued to reach the state over the course of months, not days or weeks.

According to AccuWeather's long-range forecasters, drought improvement is likely to continue over the next few weeks, but the degree of improvement will be uneven across the state.


Drone footage shows dramatic improvement in California reservoir levels
© Provided by AccuWeather
Nearly the entire state of California remains in some type of drought or abnormally dry conditions, despite the recent barrage of storms.

"Drought conditions will continue to improve greatly across Central and Northern California, but only some improvement is expected in Southern California," said AccuWeather Lead Long-Range Forecaster Paul Pastelok. This is because Pastelok expects the storm track for the rest of the winter to target mainly the Pacific Northwest and the northern half of the Golden State, leaving the southern portion drier.

Still, the long-term effects from the period featuring frequent and robust atmospheric rivers will have powerful effects, even without much additional precipitation. "Reservoirs will continue to fill through spring due to snowmelt and some rain, while increased vegetation from the rainy period will hold low-level moisture through much of the spring months," added Pastelok.


Drone footage shows dramatic improvement in California reservoir levels
© Provided by AccuWeather

The downside will be a greatly enhanced risk of river flooding as snow melts later this season into the spring, mainly from the western slopes of the Sierra Nevada into California's vast Central Valley region.

In the short term, dry weather is expected for much of California for the rest of January. "The dry conditions will be due to an area of high pressure forcing the jet stream and storm track off to the north," said AccuWeather Meteorologist Alex DaSilva.

In addition to the storm track lifting north, the drying will also come via warm, offshore winds next week, which will dramatically drop humidity values and make for gusty, locally damaging winds on occasion, especially in the parts of Southern California prone to Santa Ana wind events, and also for the region north of the San Francisco Bay Area.

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The Daily Weather Update from FOX Weather: Winter storms bringing snow to Northeast this weekend
Story by Aaron Barker • 1h ago

Welcome to the Daily Weather Update from FOX Weather. It’s Friday, Jan. 20, 2023. Start your day the right way with everything you need to know about today's weather. You can also get a quick briefing of national, regional and local weather whenever you like with the FOX Weather Update podcast.

The first of two winter storms impacting the Northeast this weekend is bringing snow to interior portions of the Northeast today, while rain is possible near the coast. A second storm is forecast to arrive by Sunday, bringing with it even better chances for snow in the interior.

The Northeast has been largely snow-free so far this winter. New York City has yet to see its first measurable snowfall and is closing in on the record for its latest first snow.

The latest three-month outlook from NOAA's Climate Prediction Center (CPC) is out, and you’re out of luck if you’re a fan of the cold, it seems. According to the CPC, warmer-than-average temperatures are likely from February through April across the southern U.S. and along much of the East Coast. If you want cold, head to the Northwest.


Snowfall forecast in the Northeast between Sunday and Monday.
© Provided by Fox Weather

Need more weather? Check your local forecast plus 3D radar in the FOX Weather app. You can also watch FOX Weather wherever you go using the FOX Weather app, at foxweather.com/live or on your favorite streaming service.

It’s easy to share your weather photos and videos with us. Email them to weather@fox.com or add the hashtag #FOXWeather to your post on your favorite social media platform.

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Storms to bring flash flood, severe weather risk to southern US
Story by Alex Sosnowski • 4h ago

A pair of storms will bring rounds of drenching rain to portions of the south-central and southeastern United States through this weekend and into next week. Both storms could trigger localized flash flooding, travel problems and isolated severe weather, but the storm next week has the potential to unleash severe thunderstorms over a larger area, AccuWeather meteorologists warn.

The initial storm will gather clouds and rain along the Interstate 10 and 20 corridors on Saturday, and a few rumbles of thunder may occur. The rain into Saturday evening will cause roads to become slippery and disrupt outdoor activities from central Texas to the western part of the Florida Panhandle and southern Alabama.


Storms to bring flash flood, severe weather risk to southern US
© Provided by AccuWeather

More moisture will be pulled into the storm as it moves to the northeast, and as it moves farther along, the rain will taper off in Texas and Louisiana Saturday night. However, the rain will ramp up in intensity farther to the east across northern Florida to Georgia and the Carolinas during Saturday night and Sunday.

During this time period, thunderstorm activity may increase to the point where a few cities and towns may experience flash flooding and locally strong wind gusts.

Rain of a lighter, more intermittent nature will occur farther to the north over the Mississippi and Tennessee valleys this weekend.


Storms to bring flash flood, severe weather risk to southern US
© Provided by AccuWeather

A general 1-2 inches of rain will fall with locally higher amounts possible from southern Alabama to parts of Georgia and the coast of the Carolinas mainly from Saturday night through Sunday afternoon and evening.

Rainfall of this intensity could cause water to collect in poor drainage areas, create large puddles on area highways and trigger rises on some small streams, forecasters say.

Low cloud ceilings and areas of fog for a time on Sunday may lead to airline delays at some of the major hubs, such as Atlanta and Charlotte, as well as regional airports.


Storms to bring flash flood, severe weather risk to southern US
© Provided by AccuWeather

The second storm is likely to be the more potent of the two systems and will be a more widespread rain and thunderstorm producer.

Since a similar amount of rain -- generally 1-2 inches with locally higher amounts -- will fall from the second storm on top of the rain that fell a day or two earlier, the risk of flash flooding will be higher with the second storm from Tuesday to Wednesday. Drenching rain will also reach farther to the north with the second storm and spread into the middle Mississippi, Tennessee and Ohio valleys, as well as the zone from the southern Appalachians to the Virginia coast.

The stronger storm system has the potential to produce severe thunderstorms on a regional basis in the Southern states.

"There is the likelihood for thunderstorms to erupt and begin triggering damaging wind gusts and perhaps tornadoes on Tuesday from Louisiana to Mississippi and western Alabama," AccuWeather Senior Meteorologist Brett Anderson said.


Storms to bring flash flood, severe weather risk to southern US
© Provided by AccuWeather

Depending on the track of the storm system, it is possible that the risk of severe thunderstorms and tornadoes may extend farther to the north into portions of Tennessee.

On Wednesday, the risk of severe thunderstorms capable of producing tornadoes will extend farther to the east and is likely to reach across much of Georgia and South Carolina, as well as portions of North Carolina and northern Florida, Anderson said.

While direct airline delays from severe weather may be limited to a few hours of the arrival of thunderstorms in the southern U.S. hubs, storms responsible for areas of snow and/or heavy rain farther north can also have an impact on flights in the region as well as across the nation and southern Canada through the middle of next week.

Much of the zone from the central Gulf coast to the Tennessee Valley and southern Appalachians has already been targeted by severe weather and tornadoes multiple times this winter. A recent outbreak of severe weather and tornadoes took the lives of nine people on Jan. 12. Dozens of tornadoes were confirmed, and more than 300 incidents of severe weather, including hail and damaging winds, were reported.

In addition to an active storm track across the U.S., unusual warmth with temperatures averaging 5-10 degrees Fahrenheit above normal has been partially to blame for the rounds of severe weather. The Gulf of Mexico has also been rather warm as well, as water temperatures have been averaging 2-5 F above normal in January. Warmer air and warmer Gulf waters support more moisture and potential fuel for severe weather.


Storms to bring flash flood, severe weather risk to southern US
© Provided by AccuWeather

After the storm departs on Wednesday, colder air will settle across much of the central and eastern U.S.

This spread of more dense and stable air is likely to greatly reduce the number of severe thunderstorms through the end of January. However, it may still be possible for some robust thunderstorms to develop on one or more occasions in parts of South Texas, the Florida Peninsula and perhaps right along the central Gulf Coast.

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32 trillion gallons of water in 3 weeks: California storms by the numbers
Story by Ian Livingston • 4h ago

From late December to the end of this week, a parade of storms slammed California, unleashing tremendous amounts of rain and snow along with bouts of damaging winds and punishing surf.


32 trillion gallons of water in 3 weeks: California storms by the numbers
© Melina Mara/The Washington Post

Even as the storms made a big dent in the state’s multiyear drought, they were harmful and costly. Coastal erosion, toppled trees, flooding, mudslides and rockslides left behind destruction. And the storms killed more people than any California wildfire since 2018.

Here are some of the key numbers that help put the storms into perspective:

9 atmospheric rivers — Nine separate atmospheric rivers — or narrow plumes of deep moisture generated by ocean storms — walloped California from Dec. 27 to Jan. 16, according to atmospheric scientist Marty Ralph and his colleagues at the Center for Western Weather and Water Extremes in La Jolla.

Ralph said the strongest of the atmospheric rivers hit Northern California and Oregon on Dec. 27. It was rated Level 4 of 5, only missing Level 5 because of its quick movement. Nonetheless, the intensity of that particular river was exceptional, Ralph said in an email.

11.47 inches of rain — The statewide average rainfall for California was just shy of a foot, according to the National Weather Service Weather Prediction Center. Many locations received almost their entire annual rainfall over the approximate three-week period.

Several locations in the San Francisco Bay Area saw near record amounts.

Here are some notable totals:

Honeydew: 47.72 inches
Santa Cruz: 39.55 inches
Blue Canyon Airport: 34.28 inches
Shasta Dam: 26 inches
San Francisco downtown: 17.74 inches
Death Valley: 0.29 inches.

Locations that saw their wettest 23-day stretch on record include:

Mount Hamilton (east of San Jose): 20.05 inches
Oakland International Airport: 16.48 inches
Redwood City: 16.00 inches
San Francisco International Airport: 15.29 inches
South Lake Tahoe: 14.46 inches
Merced: 10.26 inches

An analysis of rainfall data suggests maximum amounts reached around 65 inches in mountainous areas of coastal Northern California. It also showed that more than 20.2 percent of the state saw totals of 20 inches or more, focused on the Sierra Nevada and coastal ranges.

32 trillion gallons of water — The nearly one foot of rain averaged over the entire state equates to about 32 trillion-plus gallons of water. California was not the only state to be doused by the series of atmospheric rivers. The moisture pushed into much of the Intermountain West, bringing record-challenging amounts of precipitation to numerous locations.

60-foot water rise — The water level has risen 60 feet in the past month at Shasta Dam — vastly improving Lake Shasta’s water supply.


Water levels at Lake Shasta are up. (California Department of Water Resources)

Lake Shasta’s water level is 85 percent of its historical average for the date, and at 53 percent of its capacity. Reservoirs are fuller than they’ve been in at least a few years, but more precipitation is still needed.

20 feet of snow — Mammoth Mountain ski resort in the central Sierra Nevada reported 243 inches since the days after Christmas, including an additional three inches Thursday morning. It received at least 30 inches of snow on three days during the stretch. Palisades Tahoe — about 150 miles to the north — reported 203 inches, including nine new inches on Thursday. About 12 miles to the northwest, UC Berkeley Central Sierra Snow Lab registered 192 inches of snow during the span.

An analysis of snowfall data suggests totals of 300 to 400 inches fell in the snowiest locations between the wilderness east of Yosemite and Mount Whitney, the highest peak in the Lower 48.


A snowboarder slides after one of the most significant storms of the season on Big Bear Mountain in southern California dropped 17 inches of snow on Jan. 15.

250 percent more snow water than average — As the atmospheric rivers wound down, snow water equivalents — or amounts of water contained within the snowpack — were as high as 288 percent of the norm in the southern Sierra, 248 percent in the central Sierra and 209 percent in the northern Sierra. The statewide average peaked at around 250 percent of normal.

On Thursday, the entire Sierra Nevada region’s snow water equivalent was around 126 percent of the April 1 norm or above the average amount received over an entire season.

160 mph wind gust — A wind gust reached a roaring 160 mph near the summit (at around 8,700 feet) of Palisades Tahoe on Dec. 30. At least 10 locations reported gusts of 100 mph-plus over the stretch, mainly in the Sierra Nevada but a few such gusts were also noted in the mountains of Southern California east of Los Angeles.

On Jan. 8, high winds toppled thousands of trees around Sacramento because of the combination of high winds and saturated soils from heavy rain.

20 deaths — The onslaught of storms has killed at least 20 people. A 5-year-old boy separated from his mother in floodwaters remains missing.

More than 1 billion dollars in damage — The cost of the storms is expected to top 1 billion dollars, making it the first such disaster of this magnitude of 2023. Six counties — Santa Cruz, Merced, Sacramento, Monterey, San Luis Obispo and Santa Barbara — were declared major disasters by the Biden administration. Few counties were untouched.

2.1 million without power — At least 2.1 million people lost power, according to Pacific Gas & Electric, which covers the core of the state from Eureka to Santa Barbara and inland. The utility called it “the single largest winter storm response in PG&E’s history.”

0 percent of state left in extreme or exceptional drought — Three months ago, the federal drought monitor classified 41 percent of California in its top two tiers of drought: extreme and exceptional. That number is now zero. However, more than 90 percent of the state is still classified under more mild drought levels.

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中国气象爱好者

#历史上的今天# 1977年1月19日，超级寒潮南下美国，迈阿密下雪，为近200年来仅见。

天一色

天一色 发表于 2023-1-21 06:53
中国气象爱好者

#历史上的今天# 1977年1月19日，超级寒潮南下美国，迈阿密下雪，为近200年来仅见。

罗利RDU站有气象记录以来平均气温最低的月份就是1977年1月，该月平均气温仅-3.0度，比倒数第二低的1970年1月低了3.4度

https://www.tybbs.org.cn/forum.p ... p;extra=&page=9