Potential Category 4 atmospheric river to hit Northern California - CBS News

Southern California experienced a drastic driblet successful temperatures connected Monday, with bedewed upwind expected done the week, portion a almighty wintertime tempest deed Northern California starting precocious Monday and brought respective inches of rainfall and dense winds.  

An atmospheric river, oregon a upwind strategy that moves precocious concentrations of h2o vapor extracurricular of the tropics, could connected Tuesday bring up 1 to 3 inches of rainfall to the coastal areas, with higher elevations receiving upward of 3 to 5 inches, the National Weather Service told CBS San Francisco. The atmospheric stream could beryllium arsenic beardown arsenic a Category 4, with a standard that tops retired a 5.

Accompanied by a medley of upwind alerts, a surging pitchy watercourse pushed the almighty wintertime tempest strategy toward California's Bay Area connected Monday, CBS San Francisco reported. The National Weather Service issued a bid of updated warnings targeting communities successful the area, including a flood ticker for cities similar San Francisco, Watsonville, Pacifica, Santa Cruz, Scotts Valley and Boulder Creek. Those warnings took effect precocious connected Monday nighttime and are presently acceptable to stay progressive done Tuesday afternoon.

By Tuesday morning, experts forecasted that important runoff from surrounding upland ranges could bring flooding to rivers, creeks, streams and low-lying areas, the upwind work said successful an advisory, adding that flooding could hap successful municipality areas arsenic good arsenic areas with mediocre drainage systems. Storm drains and ditches could go clogged with debris, the upwind work warned.

"Locally up to 7 inches are imaginable implicit favored peaks and higher terrain of the Sonoma Coastal Range wherever prolonged mean to dense precipitation and higher rainfall rates are presently forecast," the NWS told CBS San Francisco. "Last but not least, if that was not enough, determination is simply a flimsy accidental of thunder which has expanded southward to conscionable astir San Francisco. Not expecting overmuch much than a rumble of thunder present and there."

The National Weather Service said a flood ticker is successful effect for North Bay, San Francisco and the coastline. A upwind advisory is besides retired for the coastal areas from Sonoma County to Santa Cruz County. 

The agency's San Francisco bureau shared updated guidance during the aboriginal hours of Tuesday morning, and, astatine the time, noted that "moderate to dense rain" is anticipated passim the day, with 5 inches expected to deed locally and betwixt 2 and 4 inches expected on the coast. Between 2 and 3 inches of rainfall are expected further inland, with somewhat little precipitation forecasted for vale communities, the upwind work said. The advisory is scheduled to stay successful effect until 6 p.m. PST connected Tuesday evening.

NOAA

"Localized flooding volition apt occur, peculiarly successful municipality areas wherever ponding connected roadways oregon mediocre drainage is simply a communal issue," upwind work forecasters said. "Excessive runoff whitethorn effect successful flooding of rivers, creeks, streams and different low-lying flood-prone locations. Commuters should program connected a bedewed travel connected Tuesday and let for other clip to get astatine their location."

The @NWSWPC has updated its excessive rainfall outlook, and determination is precise small alteration successful the hazard of excessive rainfall for our work area. Any preparations for imaginable flash flooding should beryllium completed by the clip the rainfall arrives tonight! pic.twitter.com/ZszWgC11vX

— NWS Bay Area 🌉 (@NWSBayArea) December 26, 2022

Wet upwind connected Monday evening was already causing proscription issues connected BART trains passim the Bay Area, the bureau reported, saying astatine the clip that transit riders should hole for delays of up to 20 minutes system-wide. The upwind work noted that rainfall was opening to make successful the areas surrounding San Francisco Airport astatine astir 5:50 p.m. connected Monday, according to CBS San Francisco.

The upwind work has besides issued a upwind advisory that took effect precocious connected Monday nighttime and was scheduled to stay progressive done Tuesday morning, for coastal communities stretching from Sonoma County to Santa Cruz County.

"South winds 20 to 30 mph with gusts up to 50 mph expected," the upwind work said. "Local gusts up to 60 mph implicit the ridges and peaks."

California officials warned of the imaginable for falling trees and histrion limbs, arsenic good arsenic imaginable powerfulness outages, arsenic a effect of the upwind forecast, CBS San Francisco reported, noting that formation hazard statements and precocious surf advisory warnings were besides issued for coastal beaches owed to "dangerous swimming and surfing conditions."

Meanwhile successful Southern California, the National Weather Service forecasted drastic changes successful upwind with temperatures dropping up to 20 degrees, arsenic a tempest strategy sweeps done the country into Wednesday.

"Say goodbye to the warmth," NWS Los Angeles tweeted. "Big driblet successful temperatures connected way betwixt contiguous and time (Tuesday). Expect 15-20 degrees of cooling acknowledgment to the approaching tempest system"

Say goodbye to the warmth. Big driblet successful temperatures connected way betwixt contiguous and time (Tuesday). Expect 15-20 degrees of cooling acknowledgment to the approaching tempest system. #cawx pic.twitter.com/ly8MBN7WRA

— NWS Los Angeles (@NWSLosAngeles) December 26, 2022

NWS forecasts temperatures successful downtown Los Angeles are expected to driblet from a precocious of 79 degrees connected Monday to 61 degrees connected Thursday, CBS Los Angeles reported. 

A low-level unit strategy presently forming is acceptable to propulsion done Washington precocious Tuesday and propulsion a plume of precise moist aerial implicit California aboriginal Tuesday done aboriginal Wednesday, according to the NWS. 

The plume volition determination dilatory done San Luis Obispo and Santa Barbara Counties each time Tuesday resulting successful 1.5 to 3 inches of rainfall, with immoderate foothills similar the Santa Lucias garnering up to 5 inches, the NWS said. 

Ventura and Los Angeles Counties could spot anyplace betwixt fractional an inch to an inch of rainfall betwixt 4 to six hours, the NWS said. 

When is it going to rain? Hope this helps. #cawx #larain pic.twitter.com/hJyz60ntYX

— NWS Los Angeles (@NWSLosAngeles) December 26, 2022

Meanwhile, Northwest Oregon and Southwest Washington look a tempest strategy that is expected to bring dense rainfall and beardown winds starting Monday evening that could pb to insignificant flooding on rivers and creeks, according to NWS Portland. 

"A beardown frontal strategy brings dense rainfall and beardown winds to NW OR and SW WA done Tuesday," NWS Portland tweeted. "Strongest winds on the coast, expanding contiguous into Tuesday. Windy conditions inland precocious Tuesday greeting and afternoon."

A beardown frontal strategy brings dense rainfall and beardown winds to NW OR and SW WA done Tuesday. Strongest winds on the coast, expanding contiguous into Tuesday. Windy conditions inland precocious Tuesday greeting and afternoon. Could spot immoderate insignificant flooding on rivers and creeks. pic.twitter.com/MtglFYxZlM

— NWS Portland (@NWSPortland) December 26, 2022

The displacement successful upwind comes arsenic millions of Americans woody with a frigid winter storm that has gripped overmuch of the United States.

CBS News has confirmed astatine slightest 62 weather-related deaths nationwide from that storm.

The scope of the tempest has been astir unprecedented, stretching from the Great Lakes adjacent Canada to the Rio Grande on the borderline with Mexico. About 60% of the U.S. colonisation faced immoderate benignant of wintertime upwind advisory oregon warning, and temperatures plummeted drastically beneath mean from eastbound of the Rocky Mountains to the Appalachians, the National Weather Service said.

Thousands of U.S. flights were canceled Saturday, and astir 3,000 arsenic of Sunday night, according to the tracking site FlightAware.