Huge Changes in the Next Week

A cool trough has covered much of the West this week keeping the Northwest wet and the Southwest cooler than normal. But things change dramatically over the next week.

The trough pulls east and north and is replaced by an unseasonably strong ridge building toward north and central California this weekend and holding into early next week. This is the GFS 500 mb pattern Sunday afternoon.

In the Northwest this is likely to shift the wet weather to the north of all areas except far northwest Washington by Sunday and Monday. Farther south the ridge will combine with offshore flow to bring a huge warm-up especially west of the mountains in central and southern California. By Sunday the Central Coastal Plain south to San Diego County have afternoon temperatures rising well into the 80s with a few spots around Los Angeles getting to near 90. Monday is likely to be the warmest day with upper 80s to near 90 south-central coast and upper 80s to lower 90s in the LA Basin and San Diego County. Though it won’t be as dramatic it warms nicely too around the Bay Area, Central Valley and the deserts.

Later next week another huge change looks likely, to colder, wet, and even snowy weather. A strong, cold, upper level trough drops south in the West from just off the Washington Coast Thursday down to California by Friday into next weekend. This spread much colder air south along with some rain and lowering snow levels. Here is how the GFS is forecasting the 500 mb pattern to look like next Friday afternoon.

The models have not been consistent the last few days of where this trough develops, yesterday they had it farther east in the Great Basin. But they have been fairly consistent in predicting a big temperature change. If the current scenario works out then it will be quite a bit colder with rather low snow levels, first in the Cascades but spreading south through California.