Wednesday, December 11, 2019

Conveyor belt of storms to deliver rounds of rain, mountain snow to the northwestern US

Updated Dec. 11, 2019 2:40 PM




After a weak storm brings snow showers to the Intermountain West on Wednesday, a conveyor belt of storms will unleash unsettled weather conditions across the Pacific Northwest through next week.
Winter storm warnings and advisories are in effect for mountainous areas of the interior Northwest into Friday as snowfall is expected to create tricky conditions along heavily traveled passes.
The next system from the eastern Pacific Ocean reached the coasts of Northern California, Oregon and Washington during Wednesday midday.
This image, taken on Wednesday, Dec. 11, 2019, shows the eastern part of the Pacific Ocean and much of the western United States and Canada. NOAA/GOES-West
The rain will spread inland and encounter the Cascades, where it will fall in the form of snow during Wednesday night.
Rain will also expand into Northern California by Wednesday evening. Precipitation will continue to push east through Wednesday night with isolated rain showers expected in most valleys.
Rain is forecast to continue along the coast through Wednesday night and can become locally heavy as the cold front associated with this storm moves through the area.
Meanwhile, colder air aloft will cause precipitation above 6,000 feet to fall as snow, especially in the Blue Mountains.
Moisture will continue to stream into the Northwest through the end of the week as the storm gradually moves inland.
As rain continues at times in the valleys, a push of cold air will help to drop snow levels to around 4,000 feet in the Cascade and Blue mountains by Friday. Travel could become impossible in some of the highest mountain passes with around a foot of snow forecast in these locations.
Snowfall totals can easily climb to around 2 feet in higher elevations, with higher totals possible in the highest peaks of the Cascades.
By late Friday night and early Saturday, the storm is expected to move into the central Rocky Mountains. This will bring a reprieve from rain and snow in the Northwest.
The break will be short-lived for some areas as the next storm on the conveyor belt is expected to arrive late on Saturday.
As the storm moves inland throughout the weekend it can bring another round of rain and mountain snow to Oregon and Northern California.
However, if the moisture associated with this storm gets spread out by the system behind it, it can bring spotty rain and snow showers to much of the Northwest into Sunday.
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AccuWeather forecasters will be monitoring this storm closely as it reorganizes over the central and southern Plains before tracking toward the Northeast.
Outside of a few snow showers lingering in the higher elevations on Monday, the region is expected to be largely dry as the next storm system arrives.
This storm may not bring much precipitation to the Northwest; however, as it could run into an area of high pressure sitting steadfast over the Rocky Mountains. The moisture from this system would spread out and bring only a few stray showers to the area.
If the area of high pressure is not as expansive, more rain and mountain snow would be expected.
The train of storms will continue as another storm may take aim at the region by the end of next week. Again, the significance of the impacts will depend on whether or not high pressure will set up over the Great Basin.
Download the free AccuWeather app to check the forecast in your area. Keep checking back on AccuWeather.com and stay tuned to the AccuWeather Network on DirecTV, Frontier and Verizon Fios.

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