Our ridiculous resilient ridge that you adore because of the lack of rain, or despise if you pray that the ski season will turn a quick 180° is about to go through some explosive growth.
Fog lovers and photographers have been in heaven the past few days, as a recent inversion has trapped moisture at the surface, and the clear, cool nights have provided ample time for radiation fog to form in the evenings.
For many, the ridge has overstayed it's welcome, and it's about to get worse before it gets better.
Hints way out in the Pacific are giving clues that our ridge is about to undergo some mega amplification.
First, I want to show you a very beautiful photo of the jet stream way out in the Pacific Ocean — It's kicking into overdrive.
But what does this have to do with your weather pattern for the Pacific Northwest?
Firstly, the jet stream is a high velocity air river in mid-latitudes that varies in height between 200-300 mb depending on the season. A couple features:
- Used as a marker for cold/warm air
- For meridional jet stream patterns, rising air is typically found to the north
- Jet streaks are the driving force behind the many troughs and ridges, and they ultimately drive our storm systems
- Jet streaks also cause an imbalance of forces as the parcel of air accelerates in and decelerates out of the streak
As our powerful jet streak exists to the left of a ridge, it's going to work to make the trough much more amplified; consequently, it will dig south. This in turn will enhance the massive ridge over us during the next 72 hours. So we can expect some low level warm air advection paired with the upper level forcing (-vorticity) we will be left with sinking/expanding airmass, increasing the height of the atmosphere (@ 500 hpa level).
Check out the resulting ridge in a few days:
How unusual is this extrodonarily amplified pattern for January, according to climatology...
It's showing over 3 standard deviations above normal for BC, up to 4 in northern BC, and 4 standard deviations below normal for parts of eastern Canada.
For those who need a quick little statistics refresher I've included this normalized distribution showing how much variation from the average that can exist:
As you can see, anything above 3 standard deviations from the norm is extremely rare and can be considered an extreme outlier, but the return periods are a little questionable due to the rarity of these events.
Forecast models are hinting at the return to a significant chance of rain (and mountain snow) in about 7 days time. The latest deterministic computer forecast model runs are showing fantastic hope (the Canadian and European models).
There's no point sharing a screenshot of a deterministic model run more than 7+ days out, because it will likely change. They're merely suggesting a major pattern change from the current regime, so that will be welcome news for skiers.
What would be responsible for me to show however is an ensemble prediction from NAEFS:
This pattern change is setting the stage which could be a much, much better ski month. One with normal mountain snows, with a more typical zonal flow
Current prediction by the European Centre for Medium-Range Weather Forecasting ensemble mean prediction for 500 hpa heights on February 1st:
It looks like someone sprayed a can of ridge-be-gone over western North America:
East Pacific Oscillation:
Although the EPO is forecast to remain negative, another important teleconnection is the PNA index which is forecasted to switch to a negative phase.
When the Pacific/North American teleconnection is negative what is typically found:
Surface Temperature Anomalies During Negative PNA:
500 MB Height Anomaly with Negative PNA
Again, like 10 days ago, this is giving a bit of confidence to local mountains such as Mt. Cain that STILL haven't opened for the 2013-2014 ski season.
There is hope. Hang in there, especially after some signs of improvement after our brief return to heavy precipitation about 10 days ago.
But, in the weather business...nothing is for certain.
By the way, if you missed my last post, catch it here, as I talk about how meteorologists can get a very poor reputation through how weather is portrayed through certain media organizations.