Aloha Moisture Approaching the Northwest

There are many wonderful imports we enjoy from the Hawaiian Islands, from Kona coffee and macadamia nuts, to music and wonderful foods.   

But during the next fews days, we will enjoy the imports in a more visceral, direct sense, as moisture streams to us from southwest.

The satellite moisture imagery this afternoon shows the a plume of enhanced water vapor (lighter shades) direct from the big island to the Northwest.

And as this moisture moves into us, it will be lifted by two mechanisms that will convert the water vapor into precipitation.    

The first is obvious: our substantial terrain, which forces air in the lower atmosphere to be pushed upwards, cooling as it rises, and thus converting the water vapor into rain and snow (cool air can "hold" less water vapor than warm air and thus some of the moisture condenses out).   The second source of upward motion is a potent upper level disturbance that is moving it (see 500 hPa upper level (about 18,000 ft) map below for tomorrow morning at 7 AM). The low just offshore is what I am talking about.

The precipitation will be bountiful for us.  Here is the forecast for the next 48 h.  Up to about 5 inches in the higher reaches of the Olympics, with nearly comparable amounts in the north Cascades and mountains of Vancouver Island.

And a close up view of western Washington for the same period really illustrates the HUGE precipitation contrasts of our region, with roughly 5 inches on the upper, west-facing slopes of the Olympics, but only about a tenth of an inch around Port Townsend and Sequim.  A factor of FIFTY.

There is plenty more where this is coming from, with an active period expected over the next week.  In fact, the total precipitation over the next week may reach 10 inches in places on the upper slopes of some of our region terrain.

A number of our local rivers will rise to near bank-full (yellow colors, see forecast from the NOAA/NWS River Forecast Center below) over the next few days, but at this point no major flooding is expected.

Snowfall?   There will be plenty, particularly with a series of cool/wet systems expected to hit us during the next week (see below).  At least three feet in the higher terrain of the Cascades and BC Coast Mountains.  Lots of snow over eastern WA.

Just good news for water resources.  It is what we depend on for all our water needs in the region.

The January Snow Outlook

As we pass the holiday period, we naturally think about snow.... in the mountains and near the surface....particularly considering this is a La Nina year, which tends to arc cold and wet after January 1st here in the Northwest.

The current snowpack over our region is very much near normal (see below), so ski areas and water resources are in decent shape at this point.

But as I noted in earlier blogs, we are now in a moderate La Nina, with the tropical Pacific cooler than normal (see plot of temperature anomaly from normal below).  Blue indicates cooler than normal.

Turning to the most skillful extended forecasting system--the European Center weekly predictions, it is going for cooler than normal conditions during the next 46 days (through 8 February) over the region.  Good for snow.

And the precipitation prediction (again, difference from normal) for the same period shows wetter than normal conditions over Washington and Oregon (see below).    That, again, is good for our snowpack.  

An issue of concern, and one quite typical of La Nina years, is that California will be drier than normal.  Is certainly an issue for wildfires over the Golden State next summer/fall if it verifies.   

Turning to the the one-week snow totals from the UW system--- close enough in time that we have some confidence in the predictions-- there are huge amounts in southern BC and the north Cascades, with a decent snowfall down into Oregon.  But not California.

At this point, there is no suggestion of the type of situation that would bring lowland snow to western Washington, and certainly nothing like the crazy superfront snow of past week.  That event was extraordinary is so many ways:  snow on a a day with a high temperature record, record daily rainfall, huge temperature drops, eastern WA windstorms, and so much more.

But it was extraordinary in another way.  Our numerical weather prediction models nailed it.  Several (un-named) forecasters dismissed the predictions (not this blog!) and did not communicate them to the public. 

We simply could not have provided such forecasts a decade ago.