Massive La Nina Precipitation Coming to the Northwest

Heavy rain and snow?  Check.

Skiing before the holidays?  Check.

Bring reservoirs to near normal levels?  Check.

Threaten flooding on some local rivers?  Check and check again!

The next few weeks are going to be an exciting meteorological ride, so buckle up.

A series of atmospheric rivers will make landfall over our region, resulting in bountiful precipitation, including snow in the mountains.  Let me show you.

The next week will include three atmospheric rivers (water vapor transport is shown below...the key measure of atmospheric river activity)

A modest atmospheric river on Thursday,

A strong one next Monday.

And a GODZILLA atmospheric river next Wednesday.  Directed right towards us.  

Precipitation totals over our region?

Through Friday morning, a good wetting, with the mountains soaked by 3-5 inches.  Just the start.

By Sunday morning, very large precipitation totals will have accumulated in the mountains, with some locations receiving 5-7 inches.

But then the third, crazy-strong atmospheric river hits, and by next Friday, the totals become insane..10 inches and more in much of the mountain areas.

The above are forecasts from the UW modeling system, driven by the NOAA/NWS GFS model.

The European Center modeling system is doing the same thing, which gives us confidence that a major event is ahead.  Below are the totals through next Monday morning.  Mountains are hit very hard.

By next Friday, crazy high totals:

The rivers will rise rapidly, some to flood stage.  Consider the situation for the Snoqualmie River near Carnation (below).  The first two atmospheric rivers will bring the level up to flood stage (see below).  The third, stronger river will cause substantial flooding (not shown below).

Snow in the mountains?  Huge amounts will fall.  Here is the forecast through mid-December by the European Center model.  Yards of snow in some locations.  

The ski season will begin.  Our water resources will be greatly enhanced.  Winter recreation will beckon.  

Hard Freeze This Morning

 Much of the region dropped below freezing this morning, with the main exceptions being locations close to large bodies of water.

Even my neighborhood in Seattle, not far from the water, awoke to glazed cars and icy roofs (see below).

The patterns of the frost were intricate and quite beautiful:

So how cold did it get?   The map below shows the low temperatures this morning.  Below freezing over much of western Washington, while eastern Washington was in the teens or low 20s, with a few single-digit temperatures over northeast Washington.

If you like cold, the Methow Valley did not disappoint, with most stations in the teens.

Keep in mind that the above temperatures are NOT at ground level, but at 2 meters (about 6 feet) above the surface, which is the standard height for surface air temperature.  

On cold, nearly clear nights, like last night, the ground temperatures are considerably cooler than at 6 feet.

I checked that out this morning with a research-quality thermometer over a grassy area.

Frost was evident, and the ground temperature was 29.4°F.

At 6 feet, the temperature was 33°F. An inversion (temperature increasing with height) was evident.

Tomorrow morning should be icy as well....so be careful...