Let Us Pray:
Lord, bless those small storms, the ‘tweeners, the wafters, breezers and clippers – bless all that they do for the winter recreationalist’s fragile psyche. God bless those dancing, randomly falling flakes, instantly melting on 60-degree pavement. May God bless unnecessarily-intense snow squalls, enthralling and grinding life to a halt – only to last for 3 minutes. God bless the “chance” for snow, and God bless the “slight chance” for snow. May God bless the lonesome shepherd (meteorologist), bringing the good news to his flock – unbiased and utterly perfect. For that matter, let God also bless the “botched” forecast, the “no-cast,” the obnoxious “bar-cast” and late night “beer-cast.”
Lord, bless the lifty in his first season out west, mindlessly swinging chairs and shoveling slush for weeks on end – have mercy, for this is certainly not what he signed up for. Let us not forget the lonesome plow driver rising before dawn, eagerly scraping a fresh 2cm off the pavement so he can put something on his timecard this week – if he can’t get to it before it melts, it doesn’t count… Bless this poor soul and the forgotten dreams of financial security during the off-season.
God bless, says the non-religious weatherman. Yet, the dismal state of mountain snowpacks throughout parts of the west can lead one to question, has God forsaken us?
I’m not here to dwell on the past or the winter that wasn’t. There’s nothing we can say or do at this point to change how much snow is on the ground. Yet at this point in February – some are actually having a pretty decent winter (portions of the northern and central Rockies). While for others, hope is slowly slipping away with each passing day above freezing and subsequent rain storms (Cascades).
And let us not forget the lost-souls of the Sierra. Of those few that remain, even fewer exist in plain-sight. Liquor sales are up, yet morale and optimism are at a season’s low. For many, the depression dates back to last winter. It runs deep in their veins and is now very much a part of their inner-being. The typical coping-mechanisms are no longer cutting it – they’ve switched over to the hard stuff some time ago. Those with the ability to jump ship have done so already, while others dream of powder days long-gone – utterly delirious and half-mad in their plight.
Well, The Barlometer is here to change all that. So let’s get started. Time to set the table.
Below, I have our first product of the day. 500mb constant height analysis (green contours), along with the infrared (IR) satellite channel – courtesy of the GOES-West satellite. I’ve also highlighted a few key features at the surface and aloft, along with the general storm-track in yellow. It’s hard to miss the high-amplitude western Ridge (capital “R”), and the long-wave trough over the eastern United States. Different evolutions of this same persistent pattern have been in place since early November.
Slight wobbles in the ridge-axis have allowed weak disturbances and cold air to ride down the ridge recently, bringing snow to portions of Montana, Wyoming, and Colorado. Yet the west remains cut-off from the deepest Pacific moisture, a trend that will continue this week.
I get quite a few questions on my website like “why is the ridge so persistent this winter?”, “when will it break?”, or “why isn’t it moving?” Well, I don’t have a concrete answer for any of these, but let’s look closer at what these features actually are.
Concerning meteorological scale analysis, the western ridge and eastern trough fall into the synoptic category – and at times, even into the global category (the largest spatially). The dominant wave pattern at the upper-levels (troughs, ridges) are known as Rossby Waves. At the very core, they are what drives our sensible weather on earth. Due to a surplus of radiation and thermal energy at the equator and a deficit at the poles, these waves efficiently transport moisture and energy meridionally (north to south) in an effort to restore balance. This is essentially why we have weather. The earth is constantly in a state of flux, never quite able to restore balance, as it pushes warm and cold air around to try and compensate.
Embedded within these Rossby Waves may be smaller features like shortwave troughs/ridges, center’s of low pressure etc. For example in the image above, the large-scale trough over the eastern CONUS is actually composed of (2) different vortices of low pressure. Yet the feature as a whole spans hundreds of miles – from the Rockies to Greenland. Larger features like these are much less progressive than smaller-scale waves, meaning they move much more slowly. Blocking patterns can set up as well, as outflow from high pressure reinforces low pressure downstream. In terms of physics, the (2) features are getting just enough of what they need not to move. The result is a static, stationery pattern that can last for weeks. (2) blocking patterns we’ve seen this winter include The Omega Block and The Rex Block – which we were under this past weekend.
Next product, let’s have a look at the upper-level pattern through next Tuesday 2/24. 12z GFS model, 500mb geopotential height.
Rossby Waves are easily identified in this loop, as is the general global circulation in the northern hemisphere. Also, the jet stream track generally follows the yellow-shaded contours – cold air to the north, warm to the south. Rather than looking at the finer details of this loop (which can make you dizzy…), un-focus your eyes a bit and just visualize the troughs and ridges. As you can see, the western Ridge + eastern trough remain generally in place through the end of the run. Ho-hum.
As we zone-in on regional analysis, I can only target a few areas per discussion where significant snow is forecast for the next 5-6 days. Regardless of how well I’m understanding the large-scale pattern, it takes an incredible amount of time and energy to analyze and write-up a professional forecast. For example, I spend 3-4 hours per discussion on my own site, just to target Colorado alone. If you do not see your area mentioned, don’t fret, I’ll get you next time. It’s unlikely I’ll make mention of highly-localized snowfall events, snow over “flat” terrain, or 2cm dumps for the guy in Tahoe to plow. Forecast zones include: Cascades, Sierra, Wasatch/Uinta , Northern Rockies and Central/Southern Rockies. I should also note that this “plan” is subject to change… so the format may continue to evolve. This first run-through tonight is just a sample, until I get my recipe right for Unofficial Networks.
Below, the latest GFS output for total snowfall through noon next Tuesday 02/24. Remember, this only (1) model’s interpretation, and it’s 192hrs out.
It’s only fitting to start with nature’s stepchild, though, I have some good news (perhaps). Forecast-confidence is very low for prospective snowfall, as it would come at the tail-end of the period. Anything (5) or more days out is highly suspect, but I see at least a little bit of snow on a few of the models right now. This would otherwise fall into the “do not forecast for” category mentioned above, but, you guys need all the help you can get.
Troughing over the central US looks to pinch the western ridge by the end of the week amplifying it further, but pushing the axis offshore. This puts the Sierra under northwest flow aloft, perhaps opening the door for a few shortwave disturbances this weekend. At the very least, temperatures look to cool under this regime.
The American GFS and Canadian GEM models are the most bullish right now, beginning snowfall sometime on Saturday. The GEM favors the Northern Sierra in the 6-10″ range, with lesser amounts towards the central portions of the range, including Tahoe. On the contrary, the GFS puts the bulls-eye over the Tahoe, with similar amounts in the 6-10″ range. Southern and northern portions of the range would also receive a decent pulse under this solution.
The UKMET and European ECMWF models do not support this unfortunately. It looks like tr-2″ (at best), as high pressure steers these disturbances further east. Regardless, these are not the type of storms that favor this area. For now, we’ll need to wait for a big maritime heater off the Pacific for a higher-impact event.
Below, I’ve got 700mb analysis of relative humidity on Sunday morning. This is slightly above the mountain-top level. In short, good moisture at this level is a requirement for snow production. I’m getting RH values in the 70%-80% range, as the tongue of better moisture is pushed west into the Sierra. It’s not as deep as I’d like to see… but, it could do the job.
I should note, I look at at least (5) different weather models regularly to incorporate into my forecasts. Several of them are paid, licensed products that cannot be displayed online. They all have their own unique personalities, biases, and inherent flaws. One of the most well-known is the GFS’s inclination to over-do things at the end of the forecast period. The larger global models ingest data at the time of initialization (today), and then run an interpretation 240hrs out. By the end of the run, models can be delusional and create unrealistic solutions. Pick your metaphor – it’s hungry for more data, low blood sugar, relationship status w/ the atmosphere “is complicated,” the model is on crack etc… In short, anything beyond 4-5 days should be taken with a grain of salt.
Wasatch & Uinta
Model spread here is similar to the Sierra, and very much contingent on the placement of the ridge-axis and evolution of features riding down from the north. A further east orientation, as the GFS and GEM support, brings a healthy dose of snowfall beginning Friday through at least Monday. Snowfall would not be continuous, but likely distributed throughout 2-3 pulses. It would end up being heavy for both ranges. Models also show an active portion of the southern jet stream (subtropical), which could advect some deeper moisture into NE Utah. Still, not all models are on-board, and the European ECMWF is the driest.
Forecast confidence is once again low, mainly because the pattern is, well, really weird. The GFS has a shortwave trough diving out of the Pacific Northwest on Friday, eventually retrograding west into the weekend. This is very unusual! – storms typically move from west to east, at least in some sort of fashion. Yet, this is the result of the nearly-stationery western ridge (once again), pinching and wobbling, but still remaining dominant.
Prospective snowfall for next weekend is still too-far out to pinpoint amounts and distribution. But I’d like to talk about jet stream dynamics a little bit. Utah snowfall for Friday/Saturday could receive some enhancement from a well-placed northern jet stream. Certain areas of maximum winds (known as a jet streak), are conducive to lift in the atmosphere. These would be the left-exit region and right-entrance region of the jet streak. We’ll certainly discuss this further throughout the next few months, as it plays an important role in mountain snowfall.
Below, I’ve got the GFS’s interpretation of jet stream placement on Friday. We’re looking at the 300mb level (~30,000ft). I see the Wasatch and Uinta under the favorable right-entrance region of the jet streak, which could enhance snowfall over this region.
Well, that’s really all I got for tonight – I’m spent! Though this was just a sample.
Going forward, I’m seeing an active pattern evolution beginning next week to close out February. This means there will be much to talk about in my next discussion. Concerning global model output and long-term ocean teleconnection/oscillations, I’m seeing favorable signs for a large-scale pattern change – perhaps beginning next week. Though, models can sometimes jump the gun on things like this, signaling a change a week or two premature. We’ll see…
I hope you enjoyed it, and at least learned a little bit that you can take with you tonight.
Along with a dedicated Colorado-specific forecast on Barlometer.com (3-4 times a week), there’s some supporting pages with information about myself, the forecast process, credibility and my vision. Check it out if you’ve got the time!