The pattern over the west has been pretty tame over the last couple of days. The only locations that have seen some decent snows this weekend are in the Washington Cascades and the Northern Rockies near Idaho and Montana.
A quick check of Western Snowpack shows that the Northern States (ID, WA, OR, MT) are doing decently in terms of their snowpack. The Sierra Nevada is running well above-normal thanks to that last storm that completely wallopped them. Colorado, Wyoming and Utah are getting better but they still need some appreciable moisture to bring them back to an okay spot. Arizona and New Mexico are struggling. This just hasn’t be the year for them thus far.
The incoming parade of storms and overall troughiness is supposed to benefit just about every area in the west between now and the New Year. Let’s start out with right now. Moisture is being pushed north from the subtropics and hitting the Cascades and further downstream, the northern Rockies. Here is what the future radar looks like between now and Tuesday:
Notice how the moisture is moving south to north – this means that warm air is doing the same. This is a relatively mild storm so snow levels will be a bit higher than they have been recently. Snow levels across all of the PNW and N. Rockies should be about 5,000 feet and above.
Ultimately, there should be some big winners here in the Northern Oregon Cascades and the Southern Washington Cascades. SW facing mountains will squeeze out the most moisture. Again, snow levels will be above 5-6,000 feet. The biggest totals will be found on the highest peaks. Idaho and Montana should do well with this storm with some SW facing mountains getting over a foot of snow.
The rest of the west from Cali to Colorado will have some nice sunny and mild days ahead.
Here’s where it starts to get interesting.
A rather substantial trough is expected to carved down the coast from Canada by Tuesday/Wednesday. This will bring moisture initially to the Washington Cascades first then further south to the Sierra Nevada. Since this storm is coming from the north, colder temperatures can be expected thus lower snowfall levels. Moisture will also be hitting the Northern Rockies at this time bringing them rather continuous snow during this period of time.
From Wednesday to Thursday, this trough is expected to dig more across the intermountain west bringing many mountain locations favorable winds for orographic snow. This storm is expected to have sufficient moisture with it across all of the west since the main flow is coming off the Pacific. Due to the strength of this trough, that Pacific moisture should make it inland to Colorado, Utah and Wyoming. At times, snow could be very heavy since there will be additional forcing mechanisms in place to enhance snowfall rates as well.
This stormy pattern has the possibility of just hanging around until after Christmas. That means, once it starts snowing for once given area, it may not stop for several days. There will be pulses of energy and moisture that will cause heavier snowfall rates at times but generally, consistent light snow is possible for days on end with this pattern.
Here’s another way to visualize what is happening. A GIF of this trough digging down and then just setting up shop. Think of this as a swirl of water in a river that just keeps spinning in the same spot somehow. That’s what is happening in the atmosphere. These little swirls are the troughs we watch for and when one sets up shop – it usually means good things for snow.
So, what this means is that the snow will be staking up for many areas between now and the New Year.
The precip outlooks issued by NOAA show above-normal precipitation expected between December 24 – January 1. That is good news for the western snowpack which should see a beneficial rise because of this pattern.
So what about snow totals? Of course, there are details that need to be watched. If this trough doesn’t dig as far south as expected, if it’s not as strong as expected and if there isn’t as good of moisture as expected, totals could change.
Again, this could turn out slightly different but a wetter, more stormy pattern is definitely forecast so skiing and riding should be superb around the Holidays. Enjoy!