Whacky December continues in the Rockies with folks mountain biking, even at upper elevations outside of Denver (Buffalo Creek). Rain continues in the Cascades. Canada remains cooler with moderate snow (4-8) likley for areas around Whistler. The issue is the temperatures. Even around Whistler, there will be rain initially this week below or near mid-mountain. Colder temps midweek will bring good news to the Pacific Northwest/Canada with moderate snow continuing in Canada, and heavy snow likely for the Cascades. The extended shows a positive pattern change in the Sierra.
Highlights:
* Moderate snow continues at upper elevations of BC in the next 2 days.
* Heavy snow is likley for the PNW midweek with cooler temperatures.
* Northern Rockies get into some decent action midweek (MT, WY)- Moderate totals.
* Snow continues in the PNW later this week with storm #2 filtering into the Rockies later this week and weekend.
* Model data shows low pressure over the CA coast later this weekend into XMAS week.
OUR GOLD SPONSORS
Chasing powder would bring us to the PNW for this storm; however, most ski areas are starting from scratch at lower elevations, and very strong winds will create issues in drifting, snowpack, and quality. I think that some ski areas in the PNW have decent snow above 6,000 feet (Crystal Summit, perhaps). While this week might not bring the perfect chase, it certainly will jump-start many ski areas in Washington and, to a lesser extent, Oregon. Many ski areas will be able to open after this storm.
Below: 4800 Foot temps Cool down below freezing Tuesday morning (Rain changes to snow) with another brief warm up on Tuesday night. You can see a longer duration of cold air settling into the PNW and northern Rockies on Wednesday morning. This cold stretch should continue into the end of the week with ample snowfall in the northern PNW and leftovers for the northern Rockies. Map: Tuesday-Thursday (Date and Day in upper right).
Below: Snow filling in from Tuesday morning into Thursday morning. The strongest influence is confined to BC and most of Washington, peaking on Wednesday-Thursday with the colder air. Leftovers trickle into northern Montana on Wednesday with heavy snow noted at the summits of Whitefish (Warm initially). Moderate totals are showing up in the Tetons from Wednesday mid-morning to Thursday. Scraps for the Wasatch and Colorado.
Below: Total Precipitation in the PNW and western Canada in the 2-3 inch range prior to the colder air moving in (Lower elevation rain). Rain changes to snow briefly Tuesday morning and again on Wednesday-Thursday.
Below: NAM 12 short-term models showing 2 feet of snow by Thursday morning in many Washington Resorts, the northern Cascade Ranges (Twisp), and the Mt Baker Ski area. Stevens Pass and Snowqualmie can do well in this pattern of cold air and brief periods of westerly flow (Convergence zones). Slightly lower totals (12-17) are noted for Crystal; however, White Pass shows higher amounts. Northern Oregon is favored for 12 plus inches and slightly lower totals further south. Note: The deterministic GFS and Euro show higher totals than the NAM listed below. We have high confidence in double digits by Thursday morning in the western Cascades of Washington, and perhaps a few spots in Oregon. Map: Ending Thursday AM.
Below: Upper-level winds (10K) in Washington State are very strong at the beginning of this loop on Tuesday night. The strong winds migrate to severe on Wednesday, calming a bit on Wednesday night before increasing again at the end of this loop on Thursday. These winds will create whiteout conditions at pass levels and drifting snow at many ski areas. You can see SW flow (Good for the northern Cascades), shifting west (Central Cascades, Snowqualmie, Stevens) before going SW again by Thursday.
Below: Decent totals mentioned above fall in the upper elevations near Whitefish (5-10) before dropping south over the Panhandle of Idaho and Wyoming.
Peak snowfall for the Tetons will be from Wednesday morning to Wednesday night (4-8 inches). Unfortunately, most of this snow falls before the cold front due late Wednesday night (low snow ratios). Cold air on Thursday might enhance snow showers in a few areas of the Tetons.
Utah and Colorado are on the lower end of the spectrum. Some higher totals are showing up closer to Summit County and the Front Range resorts closest to the Divide (3-7).
Below: Total snowfall on the GFS through Thursday morning. The PNW on the GFS is in the 40-inch range; however, much of this might be combined with the warmer periods earlier this week (Our forecast is 20-25 in the central and northern Cascades of WA). Decent totals also appear in the interior BC areas (Upper elevations initially) and coastal resorts. Northern Montana looks decent also, with lesser totals (Moderate) further south into the Panhandle of Idaho and the Teton Range. Utah and Colorado fall short.
Will Santa be able to chase powder? keep reading.
Extended Pow
The extended features another system moving into the PNW later this week. This system takes a similar track over the northern Rockies with colder air. A 3rd system might focus on the California Coast during Christmas week.
Below: 24-hour snow totals from Friday (12/19) to Sunday (12/21). Late week totals focus on western Canada and the PNW. Other notable winners might be in central Idaho, the southern Panhandle, central Montana, the Tetons, and the Wasatch.
At the end of this loop of 24-hour snow totals, you can see the Sierra possibly getting into the action on December 21 as moisture drops south by Sunday.
Below: Low pressure noted at the beginning of this loop, Friday (12/19), moving south over the Rockies by this weekend. Another low is noted at the end of this loop on the CA coast that lingers into XMAS week.
Below: 10K foot temperatures from Friday (12/19) to Wednesday (12/24- Xmas Eve). The pattern of very cold air up north continues with warmer air noted for the Sierra and central/southern Rockies. Warming might occur again on Christmas Eve for Santa's run (end of this loop warming).
XMAS WEEK
Below: 5-day snowfall ending Christmas Day (12/25). This is a low-confidence solution, being more than 10 days away! At least it is a signal of storms to drop further south into the Sierra and a wider area of the Rockies. Santa has a good chance of clear sailing here!
Forecaster: Powderchaser Steve @powderchasersteve
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