On the west coast of North America, the jet stream extends far to the south. The associat low pressure system form in the Seattle/Vancouver region and is now moving south along the US west coast. Since Thursday evening and until Sunday (local time), the low pressure system has been bringing persistent moisture to California.
Graphic showing jet stream from the west coast of North America.
Jet stream on the west coast of North America on Friday at 4 p.m. local time. The wind spe at 300 hPa (approx. 9 km altitude) is shown in color, starting at 60 kt (= 111 km/h). Arrows indicate the wind direction. The black lines show the height of the 300 hPa level in decameters, the “T” marks the lowest point. (Source: ECMWF/MeteoSwiss)
Snow
All the moisture will be direct towards the coast and then to the Sierra Nevada mountains, where a lot of precipitation is expect. The low pressure system is not only bringing a lot of moisture with it, but also cold air at all altitudes. This will result in an unusually low snowfall line of 500 to 800 meters. This means that there will be snow in areas where it is very rare. And in large quantities too: the US National Weather Service is expecting 15 to 30 cm of new snow above 800 meters, and 60 to 150 cm above 1400 meters, and locally up to 2 m of new snow!
Graphic showing new snowfall amounts in California and Nevada
Expect snowfall amounts from Friday to Sunday, in inches. (Source: NOAA/WPC)
Rain
But even in the lowest areas of California, there is a lot of precipitation, taiwan phone number library in the form of rain. A total of 50 to 120 mm of rain is expect. This can quickly lead to flash floods in rivers and streams, which is why weather warnings are active there too.
Weather map for the west coast of North America
Ground pressure and humidity at 700 hPa (approx. 1500 m) on Friday at 4 p.m. local time. The how to quickly find broken links on a website arrow indicates the wind. (Source: ECMWF/MeteoSwiss)
wind
The whole thing is also accompani by strong winds. In the mountains, the wind blows with alb directory gusts of 90 to 120 km/h. A lot of snow and wind together create a winter storm, also known as a blizzard in the USA. This means that visibility will be very limit in some places, traffic will come to a standstill in many places, and power outages and avalanches are to be expect. According to the National Weather Service in Los Angeles, this is the first blizzard warning for this region since 1989. This shows how unusual this winter storm is.
