- The next storm is off the West Coast this morning. We will see light snow push in Saturday with heavier snow by evening and lasting through Sunday night, then tapering off Monday. Snow levels start to rise from below lake level Saturday afternoon up near lake level by Saturday night. Snow levels may rise to 6500-7500 feet Sunday into Sunday night. 2-3+ feet of snow is possible on the upper mountains above 7k, with several inches possible at lake level before a change to rain. Winds gusting 40-50 mph on the mountains. - We could see scattered snow showers Tuesday into Wednesday as the low off the coast moves inland. Snow level could remain around 7500-8000 feet. Highs in the 30s with lighter winds. - We may have a break on Thursday. Then the next storm looks like it could move in Friday into next weekend. This may be a warm to cold storm that could bring a decent snowfall to the mountains. - We may see a break after that to start the week of the 9th, but it may not last long.
WINTER HAS ARRIVED
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Short Term Forecast
Let's go over the recap of the 1st storm that ended yesterday, and then go into the forecast of the warmer/wetter storm that will move in by Saturday night. That storm is spinning up off the coast this morning...
We finished the 3.5-day storm on Friday evening. The snow showers on Friday were a little more consistent and heavier than expected, especially west of the lake along the crest. We were only expecting 1-3 inches of snow and the ski resorts are reporting 1-9 inches of final snowfall. It was enough to keep chain controls in place overnight and I-80 eastbound was closed most of the night due to accidents.
That ended the cold 3-day storm. With the storm starting Tuesday night we have 4 mornings of snowfall reports totaling 22-43 inches on the upper mountains. The bases and lake level did pretty well as well with reports of 10-20+ inches around the Tahoe Basin.
The season totals so far as of the end of November are only at 67% of average for the date. On average we see around 13% of the season totals by the end of November and we have only seen 9% so far. Still a world of a difference from the dirt on the ground 4 days ago!
For the first "keep me honest" scorecard of the season for the first storm, I didn't do too bad. The final forecast for the 3.5-day storm put out Tuesday morning was for 20-40 inches at 8k at the ski resorts. The final totals came in at 22-43 inches. 10 mountains came in right on the forecast with 4 coming in with more than forecast. The average variance is 1.6 inches, close to the 3-year average of 1.7 inches.
If you are new to the blog, I started tracking accuracy 3 seasons ago. Both for my own knowledge to fine-tune the forecasting process, and to avoid any conspiracy theories that I'm paid millions of dollars by the ski resorts to make fake forecasts. It's all recorded and posted for you to see now for 4 seasons. Every final forecast the day before a storm starts vs what actually fell at every ski resort reported the day after a storm.
I Hate Warm Storms:
Both as a forecasting headache with snow levels and as a skier that likes powder I do not enjoy these warm storms. But they are the norm here in CA. Our forecasters in the Rockies don't usually have to deal with snow levels as part of their forecasts. It must be nice, haha. We do need some thicker snow and the rain coming for lower elevations will condense and add water to the snowpack. Let's just hope it doesn't do too much melting.
We have low pressure spinning off the West Coast this morning as you can see above on the satellite loop. You can also see the AR (atmospheric river) of moisture coming in under the low and being drawn towards CA. This AR will take a direct aim at the northern Sierra and Tahoe tonight through Sunday night.
That will bring copious amounts of precipitation to the area. It will also bring a flow of warmer air and rising snow levels. We were hoping that the AR would stay aimed just to our south with SW flow through Sunday with a better chance of holding onto the colder air in place. But with a 2nd wave digging down the backside of the low it looks like the flow will tilt more southerly and stay aimed at Tahoe.
We have increasing clouds today. The winds aren't that strong, only gusting to 20+ mph on the upper mountains. The moisture will begin to push in this afternoon. We could see some light snow showers break out today, but the push of the heaviest precipitation should hold off until after 4 p.m. Snow levels starting well below lake level, but warmer air works in through the rest of the storm through Monday.
The question will be how long can the cold air in place hang on and how fast will the warmer air erode it. There is also still some discrepancy in the models with the European model still running freezing levels 1,000 feet higher than the GFS and the NAM model is in the middle of the two. We should see heavy precip last through Sunday night and then waning for Monday as the low off the coast shifts closer to the coast with the AR weakening and shifting south.
The latest model runs this morning have trended slightly wetter over yesterday morning, with the range of 3.3 - 4 inches of total precipitation near the crest, except for the GFS still way higher with up to 6 inches now... The 100 model average is up to 3.9 inches. Here is a look at the WPC blended model through Monday.
We know that plenty of precipitation is coming. Now the question is the snow levels. It's only in the teens this morning with highs in the 20's today. Snow levels this morning are down around 1,000 feet and are only around 4,000 feet by this evening. Then overnight warmer air works in. For the forecast, I'm taking the average of the GFS, NAM, and Euro models for snow levels. They could run 500' higher or lower.
Tonight snow levels may rise to around 6,500 feet by 4 a.m. on Sunday. I have snow changing to rain at lake level after midnight. Then for Sunday snow levels rise to around 7,000 feet and could sit there through most of the day. Then as the flow turns more southerly Sunday night we could see snow levels rise to around 7,500 feet. As things wind down on Monday snow levels could top out around 8,000 feet.
As always, rising and falling snow levels are a headache for snowfall forecasting. Both with the timing of snow changing to rain and with snow ratios changing. Both of which can greatly affect snowfall numbers. Assuming the snow levels used above, here is the final forecast for this storm through Monday.
You can see the big jumps in snowfall as you go up in elevation. Snow ratios on the upper mountains dropping down closer to 10:1 with heavy wet snow by Sunday night. Good base building snow. We could see 2-3+ feet above 8k on the upper mountains. Below that is where the forecast could vary depending on the timing of snow levels rising. We will be nowcasting during the storm tomorrow for snow levels.
The forecast models do not agree on the track of the low off of the coast Tuesday into Wednesday. Some of the GFS model runs have it close to the coast Tuesday and moving in Wednesday, bringing a chance for showers both days. The European model runs have the low tracking into southern CA mostly missing us and bringing mainly clouds.
Either way, the snow levels may stay near 8,000 feet into Tuesday and then maybe falling to 7,000 feet Wednesday. So any showers will be rain for the lower elevations with light snow possible for the upper mountains. The model average brings 1-3 inches of snow to the upper mountains over the 2 days. We will have to fine-tune this as we get a better idea of the track.
A lot to write about here in the 1-week window. The latest trend of the models is to slow the progress of the next storm. Thursday may end up being a dry day with highs in the 30s on the mountains.
The next storm could push in Friday into next Saturday.
This storm would likely be more typical, starting warmer with a cold front sweeping through and dropping snow levels. We will be tracking this system all week. It could bring another round of decent snowfall to the mountains.
The long-range models continue to come into better agreement that we may see a short break in the storms with a ridge building in over the West Coast to start the week of the 9th.
It still looks as if that won't last long. The models still show a stronger more consolidated jet stream extending across the Pacific and pushing into the West Coast later the 2nd week of December.
Possibly crushing any ridge and helping to push storms back into the West Coast, with a more zonal flow.
The European weeklies showed drier weather the 2nd week of December, and then wetter weather the last 2 weeks of December. Of course, this is also speculation out more than a week. Hopefully, any dry period is short-lived.
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If you are traveling through the Sierra please use the links below for travel advisories as we do not give our opinions for the "safest" or "best" travel times for liability reasons. You can also follow our I-80 Daily Snow forecast as well.
NWS Reno: https://www.weather.gov/rev/
NWS Sacramento: https://www.weather.gov/sto/
CA road conditions: http://www.dot.ca.gov/cgi-b... (and 1-800-427-7623)
NV road conditions: https://nvroads.com/
OSS weather share: http://oss.weathershare.org/#
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