High Risk of Flooding And Feet Of Mountain Snow Expected on West Coast

AccuWeather Global Weather Center – March 6, 2023 – AccuWeather meteorologists are closely monitoring the potential for a high-impact storm along the West coast late this week. There is the potential for flooding rainfall, mudslides, road closures, feet of mountain snow, and very strong wind gusts between Thursday night and Saturday. People and businesses are already cleaning up from previous storms, meaning that the latest storm has the potential to become a disaster upon previous disasters, further compounding any impacts. Additional storms are expected into next week – which also may tap into a 2,000-plus-mile feed of deep subtropical Pacific moisture yielding heavy rain at lower elevations and heavy snow in the mountains.

While these latest installments in the series of moisture-laden storms this wet season across California will once again bring a variety of life-threatening impacts while promoting the risk of property damage, the storms will also provide additional drought relief, building on the relief from previous storms. AccuWeather meteorologists expect that the majority or even all of the short-term drought across California can be wiped out by mid-April! This is a staggeringly positive development, especially given the severity of the drought across California as recently as a few months ago. Some longer-term drought impacts, including the recharging of deep aquifers, can persist despite the major short-term drought turnaround.

The latest atmospheric river of moisture could end up targeting California and Oregon with an extreme amount of moisture late this week. Due to the historic winter season already observed so far in California, the threshold for flooding in lower elevations is rather low. The massive snowpack across the mountainous terrain has also presented its own set of challenges, resulting in major travel disruptions, logistical challenges and difficulties for residents and visitors in the area.

The new impacts are expected to unfold beginning Thursday night into Friday across California and Oregon. Initially, snow levels can start out rather high, which could pose a threat of flooding across towns located in the foothills of the mountains. Recent storms have featured unusually low snow levels, so the combination of falling rain and melting snow can quickly lead to flooding concerns, which can rapidly escalate to major, life-threatening flooding in some areas. Dangerous and property-destructing mudslides can also occur, and the combination of mudslides and flooding rainfall may result in roads becoming impassable once again, especially in the higher terrain. There can even be an avalanche in the higher terrain. 

As the storm marches inland Friday into Saturday, prolific rainfall and snowfall rates are anticipated. Areas that are expected to reside within this zone include southern Oregon, as well as Northern and Central California. This time frame is expected to feature the worst conditions from the incoming storm. Saturday night into Sunday, the storm is expected to shift inland, bringing along a round of heavy mountain snow to the Intermountain West and potentially into the center of country.

Across some mountain towns across California, the extreme amount of snow this season has cut off access to daily necessities, leading to life-threatening conditions. With additional snow in the forecast across Central and Northern California this week, the situation can continue to worsen. With a deep snowpack extending down to low elevations, the risk of flash flooding and landslides late in the week can be very high due to the expected higher snow levels from this event. Currently, the areas at the highest risk for this include Central and Northern California. In addition to the flash flooding risk, rivers can end up quickly rising well beyond their banks as a result of the rain and snowmelt.​​​​​​​

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