A Relatively Dry Week Ahead--And Hope for Some California Rain

 It is not unusual to have a dry period during the second or third week of January and this will be the case this year.

The really wet systems tend to hit our region in mid-November, when the jet stream is directly aimed at our region (see probability of 0.10 inch below at SeaTac.   By mid-January, the jet stream often goes south of us, giving California much needed rain.

There will be serious drying this week with periods of sun for many Northwest locations.  

In fact, the weather.com forecast, which is quite good in general, has low probability of rain at SeaTac for the entire week (see below).   But there will be a price to pay for the dry conditions: relatively cool temperatures with plenty of frost away from the water and urban areas.

The origin of this dry boon is major West Coast ridging (high pressure) aloft and at the surface.  Below is the upper-level map at 500 hPa pressure (about 18,000 ft).  Red colors indicate higher than normal pressures/heights.   

Big/strong high pressure offshore, with produces sinking air over the Northwest and cool, northwesterly flow.   

The ridge is still there on Sunday morning at 4 AM, but has moved a bit closer.

By Monday morning the ridge is now crossing into BC-- a very dry pattern for the NW.

But look carefully to our south...a trough is developing over California, a change that could bring some cooling and light precipitation.

And then something very hopeful for California.  The trough moves westward off of Southern California and becomes a strong closed low.  This could bring some significant precipitation to portions of the wildfire zone.

Here is the predicted rainfall total through Friday morning.  Welcome precipitation over southern CA!  Not heavy, but enough to help.

'