Chase Powder Daily Snow
By Powderchaser Steve, Forecaster Posted 3 months ago November 28, 2023
Atmospheric river approaches the NW late this week overspreading the Rockies this weekend into next week. While AR events are usually associated with warm temps, there is a cold front that will keep snow levels very low during the initial phases. Deep snow is likely for the PNW and areas of the Rockies. Warm temps will raise snow levels late this weekend in the PNW and eventually the Rockies.
Compared to yesterday's models, I am down-trending the snow totals for the southern San Juan Range for Thursday/Friday. The initial phase of energy unrelated to the larger storm over the PNW will impact southern areas of Colorado on Thursday/Friday. SW flow will bring 3-8 inches to the southern San Juan Range including the central mountains near Crested Butte. The European and American models are in disagreement. Amounts are going to be very variable with models showing upside and downside.
Main Course-Western summary-AR Event
The main energy associated with an Atmospheric River and very cold temps in the PNW will arrive late this week. Currently, the main focus will be later Thursday to Sunday with steady snow and low snow levels (3000) on the initial phase through Saturday. This will be a game-changing storm for the PNW with some models showing upwards of 20-28 inches, especially in Oregon.
Winds are SW initially veering more westerly during the peak of this storm on Friday/Saturday. Westerly winds will provide equal chances of many resorts picking up significant totals. The models show a bit of emphasis for Oregon (2 feet plus) with 12-18 inches likely for many western Washington Resorts. Less snow is noted in Canada with moderate amounts for Whistler and interior BC. Most resorts in Oregon and Washington are still closed. This will allow resorts to open after this storm. The Good: Cold temps and decent snow totals through Saturday afternoon. The Bad: Strong winds, warming by Sunday with rain likely at some base locations. Warming continues into next week. Bottom Line: Game-changing storm. The new snow will stick around even with the warm temps into next week.
Below: U.U ensembles using multiple models showing wide lines (Less confidence) for a range of 15-30 inches for Mt Bachelor through Sunday. I think 15-20 inches is a reasonable estimate for many Oregon resorts. Peak snowfall is Friday, December 1 to early Sunday, December 3. Snow changes to rain at lower elevations later this weekend. Temps warm considerably next week.
The take-home message for the Rockies is several small to medium waves of snowfall. There are moderate events on Saturday/Sunday and again on Monday mainly impacting Idaho, western Montana, Wyoming, Utah, and Colorado. Decent totals are very likely for the Mcall area mountains (Tam and Brundage) in western Idaho, Central Panhandle (Lookout Pass), extending north to CDA or Sandpoint (Schweitzer is on the cusp being a bit north). Kalispell to Whitefish will likely see some moderate totals. Timing: Friday to Sunday. Amounts: 9-15
For the Tetons high confidence exists for 3 waves (Friday/Saturday/Late Sunday-Monday). While each event might not hit double digits, the sum totals are likely going to be in the 15-20-inch range or higher. I think each day this weekend including Friday will have new snow on the reports. No blockbuster single event, but an upside exists on totals for the week. Conditions currently are marginal in many areas, so this storm will really help us build our bases (Unfortunately it comes in cold and ends warm).
Below: U.U ensembles for JHMR showing decent confidence (Tight lines) for a gradual ramp of snowfall from Friday to Monday in the 20-plus inch range. This will be a combo of 3 moderate waves with a warming trend late Sunday/Monday.
Below: U.of U snow ratio chart (JHMR) showing the initial phases Friday-Sunday with colder temps (18:1 snow ratios or 18 inches of snow for every inch of water). Warming on Monday will reduce ratios and bring denser snow, likely increasing avalanche danger in the Tetons (Chart at 10:1 or less=wet snow).
Utah sees similar waves of energy starting on Friday and ending on Monday. The models are trending higher totals possible for the northern Wasatch Range (Beaver, Snowbasin, Cherry Peak, Snowbasin) with SW flow turning westerly through most of the weekend. I am bullish for the Ogden and Logan area mountains, with decent confidence for the Cottonwoods also. PCMR might end up on the moderate side of totals (9-15).
The westerly flow will turn NW on Sunday/Monday with a slight warming trend (Denser snow). Grand totals for many mountain locations in Utah will likely be in the 14-20 inch range through Monday with the higher amounts at the peaks of the Ogden Area mountains or Cottonwoods. PCMR is likely going to land in the 9-15 inch range by Monday. NW flow Sunday night will likely favor the southern Wasatch (Cottonwoods).
Below: You can see the roller coaster of snowfall totals gradually increasing for Alta with 3 distinct moderate waves. The stronger wave is likely on Saturday and again on Sunday night. Overnight snow might be highest Sunday night into Monday with a warming trend (Denser snow). Totals on this chart are in excess of 20 inches. but only rely on 1 operational model. Conditions will improve each day with the warmer Monday finale landing some good base-building layers (Less punch through to the bottom layers). Avy danger is likely to rise with the snow levels by Sunday night. Winds are strong with these storms this weekend.
Colorado grabs leftovers Saturday/Sunday (Light to moderate totals) with a boost noted for Sunday to Monday. This phase of the storm has NW flow and will provide a good shot of some decent totals for Steamboat, Vail Pass, and Summit County. Areas south towards Snowmass and even Telluride can often benefit from this pattern. An early guess on totals for Colorado is 5-10 inches (Saturday-Monday) with perhaps higher amounts for Steamboat.
Below: Total snowfall for the west with 10:1 snow rations (Actual ratios are higher early this weekend). The deepest totals are likely in the PNW, central Idaho including the panhandle, Tetons, and Northern Utah. Northern Colorado sneaks in late this weekend into early next week after several teasers beginning on Thursday.
As far as chases, most resorts are still closed in the PNW, and the conditions in the Rockies are still marginal at lower elevations. Conditions will improve each day with new openings likely. Perhaps stick to the higher elevation resorts in the Tetons (Targhee can often improve quickly with lower angle riding), Upper Cottonwoods, or grassy areas at Steamboat. This will be a storm that comes in pieces rather than a single overnight blockbuster but conditions are going to get better each day. I have no idea where I am going to chase yet.
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