Atmospheric River Aimed At The West | 4-6 FEET For The Sierra + Extended Forecast [Powderchasers]

Atmospheric River Aimed At The West | 4-6 FEET For The Sierra + Extended Forecast [Powderchasers]

Weather

Atmospheric River Aimed At The West | 4-6 FEET For The Sierra + Extended Forecast [Powderchasers]

Forecast radar for 3/23/18 | Image: NOAA | Cover Image: 

ATMOSPHERIC RIVER HEADS TO THE WEST, WARMING TEMPS SOUTH OF THE CASCADES. HEAVY SNOW IS LIKLEY IN OREGON WITH 4-6 FEET OF CREAM CHEESE FOR THE SIERRA

Summary. 3/21/18 AM report

Significant moisture is once again aimed at the Sierra with perhaps even more moisture than last weeks monster 100 inch storm. Warming will degrade conditions in many areas before colder air moves in for the weekend. Colorado may offer a surprise for Friday.

Short Term Forecast:

In our last forecast for Monday morning, I highlighted 9-15 inches for areas north of I-70 and included Vail and Beaver Creek in the upper limits. The short term models indicated these amounts even over I-70. Winter Park and Steamboat both reported double digits Monday morning with most other areas falling short. We were wrong on areas to the south. The GFS and Euro were still in the 5-10 inch range for many areas. We chased to Steamboat and was rewarded with 14-16 inches at the summit and much less at lower mountain. This forecast was overstated for the areas south of Winter Park. One theory on Steamboat is westerly winds and colder temps helped orographic enhancement. We have always liked westerly winds for Steamboat where most disagree with us stating NW is better.

The Sierra can expect significant warming and snow above 8000 feet (that’s the top of the KT chair at Squaw). 2-4 feet will fall in the northern Sierra at the summits with 4-6 feet likely in the southern zones near Mammoth. Rain will be falling at most bases with the exception of mixed rain/snow at Mammoth. Consider resorts with the highest summits like Mt Rose (Base elevation above 8,000 feet), Heavenly (Summit is above 10K) and Mammoth (11K). Winds may impact lifts at upper elevations and its a given that Mammoth will keep the upper mountain closed until perhaps Friday when temps cool and a dry slot kicks in. Perhaps this is when ski areas conduct upper mountain AVY mitigation (AVY danger will be rising significantly this week).

In the Pacific Northwest, cold air and continuous periods of snow showers will persist through Friday. Expect a cooling trend on Thursday (2-5 inches of wet snow in the morning) with an additional 4-9 inches through Friday. Snow levels are plummeting to 1,000 feet (We would love that in the Rockies and Sierra) with snow likely in the foothills east of Seattle towards the ski areas. Mt Baker Ski Area may see higher amounts with SW wind direction (wildcard). There is no single deep event (continues light or moderate snow showers). Oregon should score some decent amounts with up to 12-15 inches for Timberline by late Thursday and a a foot or more for Mt Bachelor by Friday. I may give Oregon the chase pick of the week! Heavy snow Thursday for most areas develops a dry slot late. Snow returns to the Oregon Cascades on Friday. Some areas may see 12-20 inches by Saturday morning.

Decent snowfall totals through late Friday over the Cascades extending into the higher elevations of the Sawtooth’s (5-10) | Image: WXBell

The Rockies will grab decent snow above 8,000 feet but I am not sure it’s worth any long term chases. Sun Valley will see 2-6 inches by mid day Thursday above 7,000 feet and higher amounts towards the summit. A warming trend will occur on Thursday (Rain at the base). Additional high mountain snow is likely into Thursday night (Wet cream).

The Tetons grab a tease of 2-4 inches of medium density up top tonight with 5-10 inches of cream Thursday/Friday (Rain at the bases by early or mid morning Thursday). You could stay at the summit of JHMR and most likely ride all snow through the event.

Utah has good potential Thursday night and Friday for 9-12 inches above 9500 feet (It may be raining at the base of Snowbird). Big Cottonwood is favored with SW wind direction and should see the higher totals at the summit. Its not worth a long term chase in my eyes but the cream could be deep in spots.

In Colorado models point to a light or moderate event for Friday morning. Expect a wide area of 2-4 inches for spots along or north of I-70 with higher amounts in the south. Aspen may score 3-7 inches by late Friday (storm ski) at the summit. Snow levels Thursday into the evening will be a dreaded 10K. Snow levels drop to near 7500 briefly with showers Friday morning before climbing slightly during the day. Expect the southern or central mountains to fare best for the Friday system (Crested Butte, Aspen, Silverton, Wolf Creek). Most snow will fall after midnight Thursday through late Friday. Warmer temps will limit amounts especially lower elevations. Upper elevations may offer some surprise amounts.

Snowfall by late Friday favoring Aspen and areas south (Upper elevations) | Image: WXBell

Extended Forecast:

Finally, some cold air works into the Sierra for the weekend. Expect a final round of snowfall (12″ +) for Saturday morning through Sunday. Quality will be improving. Leftovers head to the Tetons for Saturday (Storm ski light or moderate amounts) and into the Wasatch for Sunday afternoon (Moderate amounts). Colorado will nab snow early next week (Monday night or Tuesday) with a possible Front Range system. Its too far out for details but colder temps by the weekend in many areas of the Rockies will help to improve conditions.

-Powderchaser Steve

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