at 3:15 PM by Pierce Larkin

The West Coast is Getting Hammered By Storms

The storm that affected the northwest last night. h/t NOAA GOES Satellite Archive
The storm that affected the northwest last night. h/t NOAA GOES Satellite Archive

Over the past week, the west coast of the US has been getting absolutely hammered by severe winter storms. The pacific jet stream has been very active, with storm after storm after storm rolling into the region. These have produced absolutely ridiculous amounts of precipitation across California. Much of the state, especially the central and southern half, was in an exceptional drought no more than a week ago.

The current drought in California. h/t US Drought Monitor
The current drought in California. h/t US Drought Monitor

In the past week, multiple plumes of anomalous precipitable water values have moved northeastward out of the central Pacific to affect the west coast. This moisture streamed directly into the Sierra Nevada Mountains in California, and the Cascades in Oregon and Washington. In addition to already favorable synoptic scale ascent foster by strong low pressure systems, the strong onshore flow was aided by orographic ascent, which is just air that is forced to rise along geographical boundaries, such as mountains.

The precipitable water associated with the atmospheric rivers that affected the west coast. h/t Wisconsin Tropical Page
The precipitable water associated with the atmospheric rivers that affected the west coast. h/t Wisconsin Tropical Page

All of this has combined to create one of the most ridiculous weeks of winter storms in several years in that region. Heavy rainfall has plagued the central California valleys, with extremely heavy snowfall impacting the mountains. In fact, some of the snowfall levels even rose above what they normally would be in a storm like this, creating heavy rainfall on top of a thick snowpack in the mountains. This only enhanced the flooding threat in the valleys.

Storms over the past week have brought just about everything you can think of in terms of weather. There was a weak tornado in northern California, damaging wind gusts across much of the region, heavy snowfall, freezing rain, etc. The past week truly has been crazy in that region.

The Sierra Nevada has seen some insane snowfall over the past 7 days, with some areas seeing upwards of 144″ of snowfall. Many mountain roads that traverse this region have been impacts, and even closed for several days. Snow continues to fall across the region.

The reported 7 day snowfall in the Sierra's. h/t NWS Sacramento
The reported 7 day snowfall in the Sierra’s. h/t NWS Sacramento

The most recent storm brought warm temperatures and a largely moisture rich atmospheric column. This system caused widespread impact, but really caused some major heavy, wet snow to fall in the Sierra Nevada. One reporting station reported over 8″ of liquid precipitation, that yielded 29″ of snow. That is approximately a 3:1 snowfall ratio, which is incredibly low snowfall ratio. Usually it is 10″ of snow is equal to 1″ of liquid precip.

h/t giphy.com
h/t giphy.com

Portland, Oregon has been hit very hard with all of this, as well. Portland saw the second significant ice storm to impact Orgeon within a couple months over the weekend. Many areas saw ice accumulation in the 0.5″ range, with some areas seeing a higher amount.

With very little time to recover from this, a major storm system rolled into the region yesterday afternoon and into last night. This storm was initially forecast to produced heavy amounts of snow, but nothing like what they received. The NWS in Portland had a warning out for 1-4″ of snowfall, but the storm wellllll over-produced.

The initial snowfall forecast for Portland and the surrounding areas. h/t NWS Portland
The initial snowfall forecast for Portland and the surrounding areas. h/t NWS Portland

The dynamics associated with it led to heavy convective bands of snowfall developing, and then a strong deformation band developed to the north of the low pressure system, aiding in the longevity of the snowfall across the region as well. This led to high snowfall rates, and amounts. Travel was significantly impacted, as was life in general. The snowfall was heavy and wet, and caused tree limbs to fall on power lines and for power outages. Additionally, this snowfall was associated with thundersnow, just indicating the dynamical support for the snow.

The west coast has been dealing with a lot, and hopefully it will let up soon. I would love a good winter storm in our region, but what they have gone through has been a bit too much at once.