Heavy Rain in Forecast For West Coast – Atmospheric River to Blame

A new weather pattern will be taking over much of the West Coast and Pacific Northwest for the next several days, soaking Northern California and even delivering snow to some mountainous regions. This pattern that will soak the region follows one of the driest Januaries that the U.S has on record for the Golden state, and San Francisco reported that there was no rain during the whole month; this is the first time that this has happened since the recording of weather patterns started in 1850.

So why is this going to happen and what is the cause? A little pattern called an atmospheric river can be to blame, and it will be bringing large amounts of rain along with it. As we move into the weekend and the beginning of next week, a ribbon of moisture will move into Northern California and the Pacific Northwest, leaving inches of snow and rain in its wake.

So what exactly is an “atmospheric river”? Meteorologists refer to it as a long plume that transports moisture from the tropics into mid-latitudes. One of these that you may or may not have heard of was named “Pineapple Express”, which tapped moisture from the Hawaiian Islands and impacted the U.S West Coast, dousing the region with rain.
According to computer models that can predict particular weather patterns, the heaviest rain associated with this system will dump down onto northwest California and southwest Oregon. Because the areas of those states include higher terrain, the rainfall totals could total up to 10 inches or higher.

Also, a precipitation forecast also indicates that heavy will not only fall in those areas, but also will affect the coastlines of Oregon and Washington. The Olympic Mountains of northwestern Washington may also see up to 10 inches of rain as well. Since there is still some time before this event is expected to occur, it isn’t completely clear just where the most rain will fall, meteorologists can only make educated assumptions based on computer models and statistic data. But, it seems that the extent of the significant rainfall will fall just south of the Bay Area. This is good news for San Francisco, as the area will now see their first rainfall since before Christmas time. As for rainfall totals in this area; residents can expect to see 1-3 inches through the weekend. The higher elevation areas that are located around the Bay Area (south of San Francisco) will see much heavier totals.

These areas aren’t the only ones that will see heavy rainfall though; eastern Washington, northern Idaho, western Montana, and the northern Rockies will also see significant totals. Because there is heavy rain in the forecast, this means that there is a higher risk for landslides, urban flooding, debris flows, and even steep increases in stream and river water levels. High winds are to be expected with this atmospheric river, and in the coastal areas and mountain ranges, the gusts may even reach near 75 mph.

Southwest Oregon and northwest California have been alerted that the areas are under flood watches, and high wind advisories and warnings have been posted all across the west, from California to Oregon and even western Nevada.
Along with the heavy rain will come heavy snow to mountainous ranges such as the Cascades of Washington and Oregon, as well as the northern portion of the Sierra Nevada in California.

It is predicted that in the northern Sierra Nevada, the snow levels will rise from near 5,000 feet on Thursday to 7,000 feet this weekend. Because the snow levels are going to rise so high it is unlikely that there will be any improvement for the snowpack situation.

The first low pressure area that started this pattern reached the West Coast on Thursday, and this pattern is sending wet weather to Washington and Northern California. After this system has passed, even more low pressure disturbances will reach the West Coast; meaning that it will be a very wet weekend.

Check out The Weather Channel for more information!

Comments are closed