Not too many changes to the forecast this morning other than to move the start time of the rain up to Thursday morning. We have a weak system moving through Tuesday night with light snow, and then a warm storm with mostly rain moving in Thursday. Colder air works in through Saturday with rain showers changing to snow showers.

Tuesday - Wednesday:

We have nice weather on Tuesday morning. The winds right now are light and we have some inversions with temperatures in the 20s at lake level and 30s on the upper mountains. Highs into the 40s for Tuesday with winds and clouds increasing during the afternoon as the next storm approaches. Gusts to 30+ mph on the ridge tops this afternoon.

Tuesday night light snow showers should move through starting around 10 pm and ending Wednesday morning. This is a weakening system with not much moisture making it the Sierra. The models are slightly wetter this morning but not much. They are showing anything from less than a tenth of an inch of total precip on the east side of the lake up to a tenth or two on the west side. The wetter model run this morning is the NAM showing just over 2 tenths along the crest by Wednesday morning.

Snow levels drop quickly tonight, especially with the drier air in place to start and evaporational cooling. We should see mainly all snow down to lake level with snow levels around 6,000 feet or just below into Wednesday morning. So we could see a dusting of snow across the Tahoe Basin, with up to an inch or two on the mountains west of the lake and along the crest.

Wednesday we start to clear out but then the next storm is approaching. So we may hang onto clouds most of the day with maybe a brief break in the middle of the day. Highs slightly cooler, in the low 40s at lake level and 30s on the upper mountains. The winds continue to increase ahead of the next storm with ridgetop gusts to 40+ mph.

Thursday - Thursday Friday Rain Storm:

The jet stream is aimed at the Pacific NW Thursday into Friday with a weak AR into Northern CA. That will stream moisture towards the northern Sierra Thursday and Friday. This is a warm system with snow levels around 8500-9000 ft. Thursday into Thursday night, which is mostly rain on the ski areas except for the top of the highest peaks. A few mountains like Mt. Rose, Heavenly, and Kirkwood go above 9000 ft. at the top and could see wet snow accumulations up top.

Friday some colder air starts to work in. We could see snow levels drop to the 8000-8500 ft. range in the morning and 7500-8000 ft. during the afternoon. The winds continue to increase with ridgetop winds gusting to 50+ mph or stronger Thursday into Friday. So winds could affect lift operations on the upper mountains making it hard to access the highest peaks where any snow could be falling.

The latest model runs don't show a lot of precipitation in total with this storm. Thursday evening looks like the best chance to see heavier precipitation. Then lighter precipitation and showers Friday.Above 9000 ft. we could see 3-6 inches of snow and 1-2 inches down to 8000 ft. by Friday evening.

Friday Night - Saturday Night Snow Showers:

Some forecast models like the European show the moisture feed fading by Friday night with only a small chance for scattered showers into Saturday. Then a final weak system moving through Saturday night. Other forecast models like the GFS show the light precipitation continuing Friday night and becoming more showery Saturday. Then the weak system sweeping through Saturday night.

Colder air continues to work in from the north Friday night into Saturday night. Snow levels may drop into the 7000-7500 ft. range by Friday evening and down to 6500-7000 ft. overnight. Then dropping below lake level Saturday morning and below 5000 ft. by Saturday night. That would bring mainly snow showers for all elevations Saturday but very light precip is forecast. Then snow showers with the final wave Saturday night.

We could see a dusting up to couple inches of snow at lake level by Sunday morning, and a final 3-6 inches of snow on the mountains above 7000 ft. It's colder Saturday with highs in the 30s. The gusty winds continue on the mountain tops, with gusts to 30+ mph.

Total Precipitation:

The forecast models are in decent agreement this morning They are mostly showing a range of total precipitation near the crest of 1.1-1.6 inches through Saturday night. That is very little when spread out over 3 days. Like I mentioned above, the heaviest precipitation is expected during the warmer part of the storm Thursday into Thursday night. Then mostly lighter precipitation and showers Friday through Saturday night.

The GFS, as usual, is the outlier showing up to 2 inches of total precipitation. The total model average is around 1.4-1.5 inches near the crest with decent spillover to the east side of the lake.

Total Snowfall:

As always with warm storms, the snow levels make snowfall forecasting tricky. The timing of the snow levels rising and falling, and at what elevation the snow line is at during heavier and lighter precipitation, makes for big variations in snowfall amounts at different elevations. Based on the timing and precipitation amounts we went through above, here is the updated total snowfall potential through Saturday night.

The accumulations start at 8k Friday, at 7k Friday night, and 6k (lake level) on Saturday. Again, this is spread out over a few days and is very little snow per day. Mainly a rain event through Friday with a few inches of snow possible at the end Saturday/Saturday night. We will continue to fine-tune the details as we get closer. 

Sunday - Monday:

We clear out for Sunday into Monday with weak ridging. We should see some sun both days. The winds come down and highs remain in the 30s with overnight lows in the teens.

The long-range models continue to show a trough digging in over the West Coast by the middle of next week...

...and possibly continuing for at least a week.

That would keep the door open to storms moving in from the northwest. The deterministic models suggest a weak system by next Tuesday-Wednesday, with more behind that into the weekend of the 20th-22nd.

Stay tuned...BA

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