After taste of spring, stormy pattern returns to the West later this week
March 17, 2019; 11:02 AM
Spring fever has been in the air across the West over the past few days, but the cooler and wetter pattern will be making a return this week.
This most recent round of warmth was the warmest it has been in a while. Seattle and Portland both reached 60 degrees Fahrenheit for the first time since November. Downtown Los Angeles surpassed the 80-degree mark on Saturday for the first time since November.
This will continue in the short term, with Seattle set to be close to record highs from Monday to Wednesday with high temperatures near 70.
East of the Cascades, the ridge in place will lead to moisture getting trapped and there will be the potential for some pockets of low clouds and fog (freezing fog in some areas) in eastern Washington and northeastern Oregon. This, however, should not be as widespread or persistent as earlier rounds of low clouds and fog this winter.
This forecast sounding from the NAM shows the inversion in Walla Walla, Washington, early Tuesday morning. In areas that remain clear and the temperature falls to the dew point, there can be areas of low clouds, fog and even freezing fog.
Farther south across California, the warmth will not last as long, as clouds will start to increase on Tuesday and precipitation will not be too far behind.
An upper-level trough will swing eastward into California late Tuesday night into Wednesday, which will combine with a cold front at the surface to get some showers going during that time.
Snow levels will need to be watched in the Sierra, as they'll fall from ~10,000 feet now to 6,000-7,000 feet by late Tuesday night and Wednesday.
This system will not be as big of a snow-maker as some of the other storms recently, but over a foot of snow will be a possibility in the Sierra, mainly above 7,000 feet.
With the 540 thickness line charging southward across California, this is a pretty chilly air mass for this time of year. Obviously, snow levels have been much lower than this in recent weeks, but there will be a noticeable change in the air as temperatures in Los Angeles and San Diego will struggle through the 60s.
With this cold pocket aloft swinging through, the precipitation on Wednesday and even into early Thursday looks convective, which could lead to localized downpours, thunderstorms and even small hail in some of the strongest cells.
The best chance for these localized, heavier showers will be across Northern and Central California, although a handful could even develop over Southern California as well.
The surface low associated with this trough will move into Northern California early Wednesday, and weaken as it moves northeastward. As this happens, showers will struggle to make it too far northward into Oregon. It will likely get into southwestern Oregon, but never make it northward into Portland.
Later in the week, a cold front will approach the Pacific Northwest, coming onshore late Friday or Friday night with some showers from western Washington southward through Northern California. That does not look to be a major system at this point, but we'll take a closer look at it in the next few days.
The views expressed are those of the author and not necessarily those of AccuWeather, Inc. or AccuWeather.com