Pattern Change Busts in the West, and a Major Blizzard Back East

The big weather news is not currently about winter storms impacting the West. Rather, news headlines are focused on a Nor'easter (blizzard) forecast to slam the Mid-Atlantic and New England states. Given the storm's potentially high impact, I will discuss more details about this event in a moment. 

First, I don't have good news for those expecting a weather pattern change in the West. For weeks, extended range models were generally indicating a retrograding long wave pattern toward the end of January. I hoped a consolidated ridge would amplify further west over the Pacific, allowing for an active storm pattern over the Western states. Unfortunately, it now appears likely the ridge will remain too close to the West Coast, blocking moist Pacific storms. Here's the latest GEFS forecast upper height anomaly average for the first 10 days of February: 

There's broad consensus among the extended models that this pattern will dominate, even moving into the second week of February. Not good at all. Now, there is some westward shift in the major features expected, just not enough. Notice the ridge height anomalies offshore now extending inland to the Great Basin. Lower height anomalies are confined to the north/central part of the country. This pattern often leads to "clipper" systems tracking across the Northern Plains and upper Mid-West regions (minor snowfalls). 

The flow aloft over Utah and interior West, will come from a drier and colder northerly direction. Don't expect much warming here in Utah, but rather seasonable temperatures. A weak upper trough will move through from the north on Wednesday. Coming from an over land trajectory, this system will be moisture starved. Some models show a chance of minor snow accumulations, likely under 1". The NBM (model blend) forecast snow amounts on Wednesday look reasonable:

Not impressed? You shouldn't be. We need a lot more mountain snow if we want to end the season with just average snowpack. If the pattern doesn't improve in the coming weeks, our reservoirs are likely to end up in worse shape this summer than last year. 

Could the pattern become favorable for snow later in February? Short answer: I don't know. Extended range models are demonstrating poor consistency, and signal weak anomalies that don't point to a particular pattern later next month. 

Given the lack of weather in the West, let me discuss the Nor'easter that is forecast to slam parts of the East with blizzard conditions this weekend. Here is the water vapor satellite view of the storm, in the early phase of developing Friday afternoon:

The surface pressure is forecast to drop sharply tonight through midday Saturday, as the system rapidly intensifies. This storm fits the definition of a "bomb cyclone" (sea level pressure falling 24 mb in 24 hours). Some models show a sub 970 mb surface low just to the southeast of Boston, MA Saturday afternoon:

If pressures deepen anywhere near this low, there will be coastal flooding, and high winds coinciding with the heavy snow band shown above (blues/purples). Blizzard conditions are almost certain for near coastal areas of the Mid-Atlantic states to New England. The National Weather Service has blizzard warnings and numerous other hazard statements in effect for the region:

Northeasterly wind gusts will peak in the Mid-Atlantic states late tonight and in New England on Saturday. Here are the expected wind gusts near the peak of the storm's strength on Saturday, 60-70+ mph from Long Island to New England. High winds combined with heavy snow will lead to widespread power outages from New Jersey to Maine.

Snow amounts are forecast to be rather extreme, but not unprecedented. The heaviest snowfall across the region in years, for sure. There will be a tight snowfall gradient from lighter amounts to the highest amounts, possibly exceeding 2 feet. Greatest uncertainty of forecast snow amounts are from near Dover, Delaware to New York City (up to a foot possible). A slight shift in the track of the low could bring higher or much lower snow amounts within that corridor. Highest confidence in snow amounts are from Long Island to the coastal New England states. Here are the potential snow totals through the weekend:

Yes, you're reading that right. Portland, Boston, Providence, New Haven, and Montauk/Hamptons in Long Island could all see 2 feet of snow. Local amounts up to 30 inches are possible, especially at hill top locations like Worcester, MA. Snow of this magnitude has occurred in the past, but amounts over 30 inches are rare. This may not be a record-breaking storm, but certainly memorable (or historic) given the combination of hazards causing damage, travel impacts, and outages.

A Quick Update on Next Week's Weather Change

I still see the potential for a storm early next week, with snow in the valleys and mountains of Utah. As mentioned in the previous post, this could usher in a change to more active wintry weather. But, uncertainty has grown today in both the details and even the evolution of large scale features next week. A system is still expected to affect Utah next Monday and Tuesday. Details are still up in the air, so I can't yet offer specifics on potential snow amounts. Not yet! 

There was a shift in nearly all the latest models today, trending toward a stronger ridge closer to the U.S./B.C. Coasts next week. This is not good news for getting decent snowfall into Utah. Here is what the GFS 500 mb height anomaly looks like for the first 10 days of February:

 

Notice the ridge anomalies (yellows) reach the West Coast of North America and the long wave trough is centered further inland. This implies storms could arrive from a northerly land trajectory, southward through BC. These nearly always lack moisture, and disappoint with snowfall. The only positive, is that precipitation would likely fall as all snow in the valleys. Amounts are likely to be on the low-side...If the large scale pattern evolves in this manner.  

A different model, the Euro EPS ensemble (50 runs of the same model, "tweaked" for different potential outcomes) is also pessimistic. Reading along the bottom, from left to right, you see the average daily precipitation value through the 10th of February. Not impressive, not at all-- right!  These amounts are much lower than what models showed the past couple days. I would not put too much faith in this particular run.

So, let's wrap this up on a positive note! Models continue to be quite volitile. A lot of variability and poor run to run consistency simply screams the message-- Uncertainty is very high! I do believe models will come into better agreement over the next couple days. Enough so, for another update toward the weekend. Check back!

I will end with the GFS ensemble of 30 runs. It still shows snow accumulation early next week. Not much, but there's potential. Fewer members indicate snow beyond a week, but you can see the chance is still there.

A Potential Return to Winter Weather Next Week

We finally have the makings of a weather pattern change in the West, starting early next week. The past few weeks, I have discussed the potential for a retrograding long wave pattern toward the end January into early February. Indeed, it appears this shift will soon be underway. In the world of weather forecasting, nothing is ever simple. Hence, the accurately coined phrase "weather is an imperfect science". While I believe changes are on the way, aspects of the extended outlook are still rather merky. I will get to that in a moment. 

Let's first check up on mountain snowpack as we near the end of a relatively dry month. Good news first. Thanks to blockbuster mountain snowfall in December, snow water equilvalent (SWE) values are still in decent shape. Although storms were lacking much of January, SWE values are still close to normal in most regions, as of January 25th. Southern Utah, and Southern Nevada are well above average. While, Colorado and Wyoming are not faring as well.  

It's best to measure progress using the water year calendar, which runs from October 1st to the end of September the following year. This allows us to visualize the seasonal data. Let's take a closer look, starting with the Alta Resort measurent site. They maintain good records. How has the snowpack progressed since Oct 1st 2021? Here's the data:

The brown line is average snowfall from October 1st to current date. Green is accumulated snowfall. Alta has had 192.9" so far, not far below the average of 218.2". Highest on record is blue, and red is lowest. 1983-1984 had some crazy extreme snow up to this point! What does average yearly snowfall (by month) look like for Alta: 

The bar graph shows the best snow months are Dec-Jan-Feb, with March not far behind, in 4th place. Point being, we still have a couple of the best months for mountain snow to come. What about the valleys? Here's the liquid precipitation and snowfall at the Salt Lake Airport for the water year to date:

Surprisingly, the airport still has above average precipitation, for the water year to date. However, SLC snowfall only stands at 22.1" to date, almost all of which fell in December. A normal year would have 30" of snowfall by this point in the year. 

Let's see if we can do some catch up, alright! Here is the Climate Prediction Center's 6-10 day outlook. For the interior West, near to above average precipitation and colder than average temperatures. They also believe a pattern shift will occur by early February! 

This season has featured some huge monthly flip-flopping extremes in temperatures and precipitation.  It just so happens, the storm-blocking high pressure ridge near the West Coast, will begin a westward shift.  I hope this will open the door to storms arriving from the northwest. Look at the 500 mb trough anomaly for the first week of February:

This particular GFS model develops a long wave trough over the West. Think of the upper height anomalies (deep blues) as a region where storms are likely to be active. Looks interesting! 

I have a word of caution here, listen up! Not all models agree on the strength and location of the big weather influencers come early February.  Uncertainty is quite high!  We could get a short window of active weather, or set up a pattern favorable for a series storms. Hopefully, the latter. 

That said, I am watching one storm of interest, expected to reach Utah early next week. It arrives from a cold trajectory, so I would expect mostly snow in the valleys (except far south). In fact, much of the state could get some decent snow including the mountains-- you're welcome skiers!  It's way too early for further details. Just know there could be appreciable snowfall around Monday-Tuesday next week. 

Below is projected precipitation accumulation through the 10th of February at the SLC Airport. There is minimal skill that far out, so only focus on the trend. Notice the green line (mean of 30 model runs) trends upward around next Monday-Tuesday through the first 10 days of February. A potentially wet/snowy period in Salt Lake City, and possibly much of the state and surrounding region.