The continental western United States is a hot topic this week, as a major winter storm begins barreling down on the area. As has been noted by several in the weather community, there was a lack of moisture for the west, and this certainly will bring relief in that aspect. The implications for travel, though, may be bigger here as it will cause issues for the densely populated pacific coastal areas. This major winter storm is likely to go on to cause major implications across the Northern Midwest and into the Great Lakes by the weekend. Here is a look at the current enhanced satellite and radar imagery:
We can already see the transition from a moderate to heavy rain to a snowfall past the Cascade Mountains.
Two main factors will be at play, setting up this major storm: and arctic air mass coming out of Canada to meet a low pressure system that will be coming on-shore near California and Oregon. Moisture out of the Pacific will add to the couple inches of rainfall that will impact most of California, especially the southern half of the state. This storm will come in two parts: Wednesday and Thursday-Friday. The latter days will cause the most rainfall for the California region. Snow will be the first part of this storm, causing a mess for parts of southern Washington and into Oregon. Let us review two model runs for this scenario: the Global Forecast System (GFS) and the North American Model (NAM), each stopped at 0z Thursday, or 7 p.m. EST Wednesday:
The GFS model run is the image on the left; the NAM model run is the image on the right. The GFS is notably being slightly more aggressive with the precipitation along the coast of Oregon, but both models are in quite good agreement about the precipitation overall. The GFS also digs the cooler air further southward.
Snow and rain
Along the Cascade Mountains (just inland of Oregon), snow will be greatest. 1 – 2 FEET of snow could fall along the mountains and on the immediate east side. Once you get out of the Cascades, snow totals should be in the 3-6″ range. To a lesser extent, the Blue Mountains will pick up on higher snowfall, as well. Along the Sierra Nevada mountain range in California, 1-2 feet of snow is equally possible. As one would expect, mountain ranges typically see the most snowfall due to topographical reasons.
With regard to rainfall, a couple inches of rain is possible for many portions of California, especially south and central areas, as the moisture continues to stream in with part II of the system that rolls in Thursday into Friday. By this point, the storm will begin its trek eastward toward the central plains and northern Midwest – taking the arctic air and moisture with it. Los Angeles, Las Vegas, and Sacramento are all major cities that will be impacted by the rain side of the storm. With all the heavy rainfall, standing water on roadways throughout California – especially lower-lying ones – will be a great concern for areas that see the heaviest rainfall.
Further implications with major storm for the rest of the country
As mentioned, this storm will not be done with just the western U.S. This winter storm will begin impacting the Midwest and Great Lakes by the weekend. As moisture continues to stream onshore in the west, the arctic air mass it going to produce significant snowfall potential across the Midwest, Ohio Valley, and into the Northern Great Lakes. Coming off a major winter storm last weekend, this comes just in time for another one about a week later. Southern Great Lakes regions – such as Ohio – will be on the warmer side of the storm, where freezing rain and a mixture of rain and snow will be possible Friday night into Saturday.
The arctic air will continue its trek into the Midwest and Great Lakes, as well, as the coldest air of the season will arrive. Wind chills will be well below zero, with overnight lows barely in the single digits or worse for many across those regions.
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