34 inches of rain in 24 hours breaks continental record

 By Mary Gilbert, AccuWeather meteorologist

Updated Oct. 7, 2021 12:13 PM EDT

Parts of northern Italy are recovering from a historic deluge earlier this week that produced a new continent-wide record for rainfall over a 12-hour period and left one city with nearly a year's worth of rainfall in one day.

Rossiglione, Italy, located in the Genoa province, found itself in the absolute worst of Monday's extreme rainfall. The city ended up with a mind-boggling 34.8 inches (883.8 mm) of rainfall over the course of 24 hours.

The annual rainfall total for the nearby city of Genoa itself tops out at just over 42 inches, which is fairly representative for the region at large, according to AccuWeather forecasters. This means that Rossiglione recorded 82.9 percent of the average rainfall that falls over the course of an entire year in the region in just 24 hours.

In order to record rainfall totals that extreme, rainfall rates have to be extraordinary, perhaps even record-breaking.

In 12 hours, from 5:40 a.m. to 5:40 p.m. local time, the city recorded a staggering 29.2 inches (740.6 mm), which broke the record for the European continent, according to climatologist Maximiliano Herrera.

"That's ridiculous rainfall," AccuWeather Senior Meteorologist Adam Douty said.

Accumulated rainfall for portions of northern Italy. (AccuWeather)

Outside of Rossiglione's new records, at least two other Italian cities set records Monday. The Italian record for greatest six-hour rainfall now belongs to Montenotte Inferiore with an incredible 19.5 inches (496 mm). According to the Regional Agency for the Protection of the Ligurian Environment (Agenzia Regionale per la Protezione dell'Ambiente Ligure or ARPAL), the previous record belonged to Brugnato, Italy, with 18.6 inches (472 mm) in six hours on Oct. 25, 2011.

The Italian record for greatest three-hour rainfall also fell when Vara Superiore picked up 14.9 inches (377.8 mm) Monday. The previous record belonged to Vicomorasso, Italy, when 13.3 inches (336.6 mm) of rain in three hours on Nov. 4, 2011, according to ARPAL.

According to reports from The Associated Press, flash flooding and mudslides were common across the region Monday. No casualties were reported, but at least one bridge in Quiliano, Italy, collapsed following the torrential rainfall.

Genoa, a popular port city, was forced to close its schools, parks, cemeteries, sports facilities and open-air markets Monday as the torrential rain unloaded across the region.

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While Rossiglione now holds the European record for greatest 12-hour rainfall, Monday's rain total fell well short of the global record. The global record was set in January of 1966 and belongs to Foc-Foc, La Réunion, with 45 inches (1,144 mm) of rainfall in just 12 hours, according to the World Meteorological Organization. This rainfall was a result of Tropical Cyclone Denise and a meteorological phenomenon known as upslope flow or upsloping.

"Upslope flow can commonly be defined as air that is flowing towards higher terrain -- such as a mountain range -- and is forced to rise," AccuWeather Meteorologist Brandon Buckingham explained. "Because of the higher terrain, the air has nowhere to go except up."

When the air is forced upwards over higher terrain, the intensity of precipitation also tends to increase.

While Italy did not need a tropical system to achieve record-breaking rainfall, upsloping was likely a factor for Monday's extreme event.

AccuWeather forecasters say torrential rainfall from a storm moving across southern and central Europe targeted portions of Italy Monday and unleashed significant flash flooding issues. Italy's Liguria region, which is located in the northern half of the country and borders the Mediterranean Sea, was in the bull's-eye for extreme conditions.

The Liguria region wasn't the only portion of Italy in the line of dangerous storms early this week.

On Tuesday, severe thunderstorms impacted portions of Sicily and brought heavy rainfall, damaging winds and a possible tornado to the island. AccuWeather forecasters say tornado reports poured in from Catania, Italy, and video taken by residents showed roads underwater, trees down and damaged structures downtown.

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A possible tornado tore through downtown Catania, Sicily, on Oct. 5, 2021. Damage from flooding and high winds was reported.

Tuesday's storms also caused flights to Catania–Fontanarossa Airport to be diverted to Palermo Airport on the other side of the island due to the hazardous conditions.

As residents work to clean up following the unprecedented deluge, better weather is in the forecast.

"As the storm system that brought the extreme rainfall moves southward and stalls across southern Italy through the end of the week, dry conditions are expected to prevail across the area," Douty explained. "There can be a gusty wind at times into the weekend, but it should not hinder cleanup and recovery efforts."

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1st substantial snowfall of season on the way for Rockies

 By Ryan Adamson, AccuWeather meteorologist

Updated Oct. 7, 2021 8:39 PM EDT

A significant change in the weather pattern will have some residents wondering if summer simply transitioned into winter across parts of the Northwest and Rockies.

Temperatures were well above normal in the northwestern United States through much of the summer, and that trend has continued into early fall. October began with temperatures more representative of July or August in the northern Rockies. Helena, Montana, soared to 84 degrees on Tuesday, easily surpassing the daily record high of 81 degrees set in 1958. A typical high for Oct. 5 there is 64 degrees.

Over the next few days, temperatures will begin a gradual downward trend. Cooler air already arrived in the Northwest on Tuesday in the wake of a cold front. Seattle managed a high of only 55 degrees, which is 10 degrees below normal.

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With the front moving farther inland, many locations that were in the 80s on Tuesday only reached the 60s and 70s on Wednesday.

By Thursday, highs struggled to get out of the 50s in some instances with cooler air combined with clouds and precipitation. Helena, Montana, which had seen temperatures rise into the 80s on Tuesday, breaking a record, saw a high of only 57 degrees on Thursday.

"A storm will begin to cool things down across the northern Rockies on Thursday and Friday, with areas from northern Nevada into Montana, Wyoming and Idaho getting some rainfall," said AccuWeather Senior Meteorologist Rob Richards.

Outside of the highest mountain peaks, temperatures will be too high for precipitation to fall as anything other than rain through the end of the week. However, a second cold front with much colder air behind it will arrive by this weekend.

"This will cause temperatures to fall further and set the stage for a more impressive ripple in the jet stream to usher colder conditions into the Rockies," said Richards.

A bit of snow may fall on Sunday in the Cascades of Washington and Oregon.

By Monday and Tuesday, a dip in the jet stream will become very pronounced across the Southwest. Much colder air combined with a stalling storm may lead to significant snowfall in parts of the West.

"A storm will blossom and produce windy conditions with snow across most of the northern Rockies, leading to travel disruptions due to the season's first snowfall of consequence across this part of the country," said Richards.

While travel could be hazardous as low as 4,000 feet in Montana, affecting locations such as Bozeman and Helena, snow levels will not dip as low farther to the south. However, with snow levels of 5,000-5,500 feet in Wyoming, Casper and Riverton could be in line for the first accumulating snow of the season.

Even farther to the south, accumulating snow is not expected in major cities such as Salt Lake City and Denver, but a few wet snowflakes mixing in with the rain will not be completely out of the question.

At an elevation of 7,000 feet, Flagstaff, Arizona, may also be in line for its first snowflakes of the season, with a small accumulation possible.

Any snow that does fall will begin to melt later next week, with even the highest elevations having temperatures above freezing during the day.

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3 months' worth of rain falls over 48 hours in French city

 By Mary Gilbert, AccuWeather meteorologist

Published Oct. 5, 2021 12:01 PM EDT | Updated Oct. 7, 2021 12:17 PM EDT

Parts of southern France were left underwater to start the week after a robust storm unleashed several months' worth of rain in just two days across the region.

AccuWeather forecasters say torrential downpours targeted southern France Sunday and Monday. This triggered a deluge that led to significant travel disruptions, more than 1,000 emergency calls and at least one fatality, according to multiple news outlets in France.

Videos showed harrowing scenes of cars stuck in raging floodwaters while aerial images captured swollen rivers inching toward the top of a bridge around the port city of Marseille. Some residents around the area were forced to evacuate.

One person was killed on a highway in the Bouches-du-Rhône department when a truck and car collided during the adverse weather on Monday, according to La Provence.

A screen shot taken from video footage showing the swollen Huveaune River surging through Marseille, France, and nearly breaching a bridge.

(Hugues Barthes via Storyful)

The areas in the south of France that were in the bull's-eye for the worst impacts included the departments of Bouches-du-Rhône, Var and Alpes-Maritimes. All three departments border the Mediterranean Sea.

Marseille, located in the Bouches-du-Rhône department, recorded about three months' worth of rainfall in just two days. According to Météo-France, the French meteorological service, Marseille received a staggering 7.64 inches (194 mm) of rain Sunday and Monday.

To put that number in perspective, the city typically records about 3.33 inches (85 mm) of rain on average for the entire month of October. According to AccuWeather forecasters, the combined average rainfall for the area for the three months from September to November is 7.58 inches (193 mm).

This amount of torrential rainfall in such a short period of time quickly overwhelmed nearby roadways, rivers and streams.

Dozens of road closures forced traffic to come to a grinding halt across portions of multiple departments as some roadways were rendered impassible. In addition to road traffic, all Transport Express Régional (TER) rail lines passing through Marseille were shut down Monday afternoon, stranding hundreds of passengers, according to BFM TV.

In the Bouches-du-Rhône department alone, 1,500 calls for help were relayed to the region's fire department, according to BFM TV. Of these calls, 610 rescues were carried out on Monday by the department's fire and rescue workers. No fatalities were reported.

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All schools in the Var, Bouches-du-Rhône and Alpes-Maritimes were closed on Monday when the scope of flooding issues became clear. Multiple schools in Marseille remained closed on Tuesday as damage assessments continued, according to La Provence.

Even as floodwaters began to recede, many areas were left with what is likely to be a substantial cleanup period. Members of the Marseille firefighter battalion, the largest unit in the French Navy, were seen working to cleanse streets of a thick layer of mud left behind after floodwaters made roads unrecognizable.

The timing of the flooding rain could not have been worse for some portions of Marseille, with floodwaters arriving just days after local waste collectors ended a weeklong strike. According to EuroNews, there are fears that "catastrophic" waste can make its way into the ocean when floodwaters further recede.

The storm that unleashed torrential rainfall across the south of France early this week was fueled by a deep layer of moist air over the western Mediterranean Sea. Winds at the lower and middle levels of the atmosphere essentially directed this moisture right at the southern coast of France.

Drier weather is on the way, which should aid in cleanup efforts as floodwaters recede.

Through the upcoming weekend, largely dry weather is in store for Marseille and the surrounding area as high pressure settles into place, according to AccuWeather Meteorologist Tony Zartman.

While the weather will remain largely dry, there is one thing that residents beginning to pick up the pieces left by the deluge will have to monitor.

"It was rather windy Wednesday and Wednesday night as a storm strengthened over Italy, but those winds should start to diminish on Thursday," Zartman cautioned.

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