There has been a lot of talk about warmth in the mountains, loss of snowpack, and inversion conditions.
The truth is a bit more complex.
The western side of the Cascades has been warmer than normal with significant loss of snow, but conditions have been MUCH cooler on the eastern slopes, helping to maintain snowpack on that side.
Let's explore the fascinating temperature variations of the past few days.
Below are the minimum temperatures on January 16th and 19th.
Forties on the western slopes of the Cascades, but below freezing east of the crest, with many locations in the teens.
As I have discussed in prior blogs, a pool of very cold air has been trapped in the Columbia Basin, with cold air associated with a low cloud deck of stratus and fog (see the satellite picture below).
The UW high-resolution modeling system accurately simulated this cold/warm pattern.
For example, the model forecast for the surface (2-m above surface) temperatures at 1 PM Saturday shows warmth (red colors) on the western Cascade slopes up to the crest level, but colder air right over the crest (blue and green colors).
Note the warm temperatures on the western slopes of the Olympics and coastal mountains as well.
In contrast, it was much cooler at Holden Village on the NE slopes of the Cascades. A short period of warmth followed by normal and colder than normal conditions.
The impacts on snow melt on both sides of the Cascades were noticeable.
The critical snowpack on the eastern side of the Cascades, so important for agriculture, is being protected by Columbia Basin cold!
Next, consider the temperatures at some locations on both sides of the Cascades.
At Paradise (Mt. Rainier) at 5000 ft on the western slopes, the temperatures (blue bars) were well above normal (brown band) during the past week..
The impacts on snow melt on both sides of the Cascades were noticeable.
On the west side of the North Cascades, the Upper Skagit snow water amounts are 89% of normal and have declined during the past week.
In contrast, the Methow drainage on the eastern Cascade slopes is a 124% of normal and holding steady!
North east looks good but upper Yakima (critical for irrigation) is at 42%, Naches 53%, Lower Yakima 62%, Central Columbia 76%.
ReplyDeleteA great analysis of the complexity of mountain snow and the wishes of Seattle skiers. Thanks for a great analysis of the confounding factors in forecasting.
ReplyDeleteMission Ridge has less than 12" at the base, 17" at the summit. Loup Loop is not open at all. Methow valley skiing is getting extremely thin. Lake Easton trails are bare. Leavenworth ski trails are barely hanging on, and there's virtually no snow in town. Snoqualmie has halted operation of nordic and east summit areas. SNOTEL has the Yakima slopes at 39% of normal. The upper Columbia basin in Okanogan is doing OK, but there is NOT evidence of a healthy eastern slope snowpack.
ReplyDeletereservoirs are in MUCH better shape. Too early to assume poor snowpack later in the season
DeleteThe comment I'm referring to is "The critical snowpack on the eastern side of the Cascades, so important for agriculture, is being protected by Columbia Basin cold!"
DeleteYour post was talking about snowpack, not reservoirs. I'm referencing the snowpack as it is NOW. Regardless of how well it's holding up, it's damn thin. Hopefully it recovers in time. But so far the forecasts look grim for the next 2 weeks.
While they are in relatively better shape than the catchments west of the Cascades crest, in fact, the basins along the eastern Cascades slopes which contribute to Central and Eastern Washington agriculture have very poor snowpack. The mean SWE for the 14 relevant contributing subbasins currently stands at just 54% of the normal median.
ReplyDeleteThe Methow basin, a rather minor contributor with a mean discharge of just ~1500 CFS (similar to the mean discharge of the Green River at Auburn), is a cherry-picked example. It is the only basin in the state that has managed to maintain comfortably above normal snowpack this season and this is only the case on paper due to one site (Hart's Pass) which has near record high SWE, skewing the basin average, and is also the highest elevation SNOTEL site in the state. The other SNOTEL stations which represent the Methow basin have much more modest SWE.
By comparison, the basins of the much larger and more important Wenatchee and Yakima Rivers, the combined mean discharges of which total nearly 5X that of the Methow, have much below normal snowpack at just 64% and 45% of their current normal median SWE, respectively.
The overall picture for snowpack statewide is currently quite bleak and nearly identical to what it was in late January of 2015. Even more disconcertingly, Central and Eastern Washington snowpack was actually better then than it currently is and, given the latest near term CPC outlooks for the PNW (high probability of above normal temperatures) this looks likely to only worsen during February.
reservoirs are in MUCH better shape than last year. Too early to assume poor snowpack in 3 months.
DeleteCliff - Aren’t we getting near the point where Feb-April needs to be well above normal precipitation to get back on track to keep filling the critical reservoirs? You’ve made it sound like it’s a matter of topping then off, when in reality, there’s still another 31% capacity left in the Yakima system before evaporation.
DeleteThe trend lines this season look like a roller coaster — quite a wild ride. I wouldn’t want to bet on ANY particular outcome at this point, based on how things have gone so far this season.
DeletePerhaps this pattern also helps explain why Mt. Si, at 4000 feet, often appears bare, when Snoqualmie Pass, at 3000 feet, has many feet of snow? (Besides exposure to afternoon sun.)
ReplyDeleteIts amazing how different conditions can be on the ground where the sun has been shining and where it hasn't been. Case in point, Hwy 109 between Hoquiam and Ocean Shores today. There is one patch of that highway near Hogan's Corner that almost never gets sunlight due to a large number of thick, lush trees that block it out. That stretch still had some ice on it early this afternoon (Sunday) while the rest of the highway had already melted out.
DeleteThe Methow Valley snow is thin yes, but had a hole lot of rain this fall prior to the snow sticking around. The upper mountain snow pack has been building since October.
ReplyDelete