ForecastHeavy Snow Expected In Western Colorado From Saturday PM to MondayMost of Colorado's mountains should pick up accumulating snow, and the longer term forecast looks colder and snowier than this week.
- Winter storm will impact Colorado from Saturday PM to Monday (with some weaker impacts possible into Tuesday AM)
- Model guidance still has significant disagreement, but is slowly converging.
- Models have consistently shown an impactful event for the western Colorado mountains in the initial phase of the storm (10-20" in spots) during the initial phase of the storm (Saturday night through Sunday).
- Colorado's eastern ranges (Summit County, RMNP, etc.) are not favored by most of the setups shown in models, but a decent event is not out of the question.
- These ranges would pick up snow in the Sunday to Monday timeframe.
- The I-25 corridor is unlikely to pick up accumulating snow, but parts of the foothills may see some flakes.
- Temperatures next week look markedly colder across the state, and with the fresh snow, ski areas should start opening, and lower elevations that haven't seen their first freeze yet may finally do so.
- Ensembles have a decent signal for a weaker wave next Thursday to Friday, and the pattern looks unsettled and fairly cold after that.
Enjoy the warmth and sun this week because the first real taste of winter is on the way.
The Front Range is looking at highs in the 70s through Thursday (10-20 degrees above average):
In the mountains, temperatures are also pretty warm, and wet bulb temperatures in the 20s will hamper snowmaking efforts.
Earlier this week we discussed the large amount of uncertainty in weather model guidance and the various disparate scenarios that were on the table. There has been some convergence in the forecast the past couple days but overall the models are still leaning towards the solutions they were showing a couple days ago -- the Euro with an open trough, the Canadian with a closed low over the desert southwest, and the GFS somewhere in between.
The good news is that none of these models have backed off from showing considerable snow accumulations for the western Colorado mountains, and some of the drier solutions that we've seen in ensemble guidance have started to disappear. It's become quite certain that the higher elevations of some Colorado mountain ranges will pick up double digit snow totals by Tuesday morning.
For the San Juan mountains, most model guidance is quite favorable for heavy snow, despite the differences in how this system evolves. If we look at the Euro ensemble, we can see that the initial salvo of snow from Saturday PM to Sunday comes as a result of divergence in the jet left exit region, likely juiced up a little by a bit of split flow pattern.
That should be good for at least 10-20" of snow in favored spots (such as Red Mountain Pass), and we'll be able to bump that number up as model guidance continues to converge. Further east (Wolf creek), dynamics don't look quite as good and we would expect a few inches less of snow.
For the San Juans, the biggest limitation seems to be that the best moisture could end up to the north and south -- some dry air entrainment could spoil a bit of the nice dynamics in play over this mountain range.
Thus, as far as the Euro ensemble is concerned, the west Elks, Elk Mountains, and Flat Tops could get those same potent dynamics. but better moisture, with the Flat Tops actually favored as the mountain range to receive the heftiest snow accumulations. However, if the system ends up impacting Colorado more like the GFS and Canadian models are expecting, these areas further north in Colorado may not do quite as well.
This initial wave of snow with westerly to southwesterly flow from Saturday PM to Sunday should be the main event of the storm, so it's no surprise that the western mountain ranges are heavily favored for considerable snow totals.
Behind the main axis of the system come the best chances of snow for the eastern Colorado mountains (Summit County, RMNP, the Sangres) -- Sunday to Tuesday AM (depending on how fast the system is tracking). This drier northwesterly flow will have to deal with mild subsidence in the jet left entrance region, so accumulations likely wont be nearly as exciting as what the Elk Mountains, San Juans, Flat Tops, and possibly even the Park Range saw earlier on the storm.
Still, the low end is looking like 2-3" for most of these less favored mountain ranges, and a 5-10" event is certainly not out of the question at this point. It's highly unlikely that the mountains will see any less snow than shown on this map:
The 75th percentile map (high end) is currently looking pretty decent as well:
As certainty over the impacts of this storm increase over the course of this week, we expect both of those percentiles to bump up by a several inches, at least in the favored mountain ranges.
The deterministic Blend is somewhere in the middle, and will also bump up snow totals in western Colorado we get closer to this event:
If we consider that the above products are pretty conservative this far out from a storm, it's safe to say that this is looking like a pretty exciting start to the season for southern and central Colorado. Elsewhere -- perhaps not so much, but we have to start somewhere, and it the fresh snow plus colder temperatures should let a few ski areas open next week.
It's continuing to look like the I-25 corridor will largely miss out on any significant snowfall, with Denver only looking at a 20% chance of a dusting. The Palmer Divide does have a 50% chance of at least a dusting, with maybe Trace to 2" in the foothills if the storm does impact Colorado as expected.
After Sunday, freezing overnight temperatures on the table for lower elevations, even if conditions remain dry.
Storm Next Thursday to Friday
After a bit of a break behind this first system, most ensembles are showing another weaker wave which would bring another round of snow to the mountains somewhere in the Thursday to Friday timeframe.
Models have some even weaker waves behind that which at the very least will keep high temperatures in the northern and central mountains near freezing even if they only bring light snow.
We'll continue to update you on Saturday night's storm as we approach it!
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