Super Ridge of High Pressure Will Bring Dry Conditions and Warmth

 Tired of the rain and cool temperatures?   A major change is about to occur:  the development of a "Super Ridge" of high pressure aloft over the northeastern Pacific.

This "Super Ridge" will bring a short period of spring-like warmth to some lucky folks in our region.

I am going to show you a series of forecast upper-level weather charts that describe the situation around 18,000 ft (heights of the 500 hPa pressure surface above sea level will be shown).   You can think of these figures as describing the pressure variation at 18,000 ft.  The colors indicate the difference from normal (red--above normal, blue--below normal).

Today, at  4 PM, the ridge of high pressure is found just inland from the West Coast, but with low pressure offshore.  Since sinking air and dry weather are found under and east of such high pressure aloft, we arestill  open to Pacific moisture that will push in later today and Thursday.

In fact, the latest weather radar image shows an approaching system lurking offshore.

But high pressure is not done with us!   By Tuesday at 4 PM, another high-pressure ridge builds over our region (see below).

This high pressure will be associated with warming air aloft and its surface reflection to the east will result in easterly flow over the Cascades, with downslope warming over the western slopes of the Cascades.  To show this, below is the predicted surface temperature map for 3 PM on Tuesday.  

Wow.  Temperatures will rise to around 60°F on the western slopes!

Even locations away from the slopes will be warmed...just not as much.  For example, the European Center model predicts a temperature of 59°F on Tuesday (see below).  That will feel very nice.

But this is only a taste of the upcoming Super Ridging.  By Friday morning, an absolutely extraordinary ridge/high-pressure area will form to our north (see below).  This pattern produces absolutely dry conditions over our region.

I have some confidence in this projection because all the major weather modeling systems are forecasting something like it.   

Want a sample?  

Here is the 72-hour total precipitation ending Sunday at 4 PM.  NO PRECIPITATION ANYWHERE.

I hope those pushing a drought narrative will wait before ringing the alarm bells.

Models forecast precipitation the following week, and the extended forecasts are for wetter than normal conditions over the next three months (see the European Center prediction below).

Even the Drought-loving U.S. Drought Monitor has backed off the drought alarms (see their latest graphic below), with drought gone over western Washington and "severe" drought only over the far southeastern side of the State.

Super Ridge

La Nina and Snow Expectations for this Winter

A number of you have asked about this coming winter and the status of La Niña.  

Will the snowpack continue to increase? Will those worried about flooding and drought get the answers they are looking for?   

The only useful meteorological tool for predicting more than a few weeks ahead is the correlation of our weather with El Nino and La Niña.

La Niña occurs when the central tropical Pacific sea surface temperatures are cooler than normal.  El Nino conditions occur when the water is warmer than normal (the area considered---called the Nino 3.4 area--is shown below)

We are now in a weak to moderate La Niña, as shown by the sea surface temperature differences from normal (called anomalies) below:

The Nino 3.4 temperatures over time are shown below.  Since August, they have been below normal, ranging from 0.5 to 0.9 °C below normal.  This is a weak to moderate La Niña.

Interestingly, such cold water periods have an impact on the weather in our region.

The latest predictions are that La Niña will remain in place through February and then weaken (see below).

During weak to moderate La Niña winters, we tend to be a bit cooler than normal, modestly wetter than normal, and the snowpack is modestly enhanced.

I know everyone is interested in the snow outlook, so let me get right to it.  For all La Niña years, our snowpack tends to be above normal in January through March (see below).

But what about weak La Niña years here in the Northwest?   The excellent folks at the Northwest Avalanche Center have examined this issue, with the results shown below.

For moderate and strong La Niña years, all the major ski areas have substantially above normal snowfall.  Weak La Niña years are a bit above normal at Mission Ridge and Timberline.  Near normal at Baker,  Paradise, and Snoqualmie.

Based on these and other statistics, a projection of slightly above normal snowpack in the Cascades is probably a decent prediction.

The European Center seasonal precipitation prediction for January through March is for wetter than normal conditions.

And the temperature prediction for the same period is near normal conditions for western WA and Oregon:

The official NOAA season forecast is for colder than normal and wetter than normal conditions:

At this point, there is little reason to expect to have low snowpack going into the summer.

Announcement

I will hold a special online Zoom session at 10 AM on Saturday for Patreon supporters.  Will answer questions and talk in detail about the outlook for the remainder of the winter, and perhaps cover some "controversial" topics.