Tahoe Backcountry Snow

1500 wx. at 6350′ in Carnelian Bay: 31.3 deg. / 30.9 deg. dew point / 99% RH / occasionally gusty SW winds / 12″ new snowfall

Backcountry obs.:

I set out this morning for a tour around 0500, but never made it beyond the car due to whiteout conditions. At 0530 6-8″ of new snow had accumulated along Mt. Rose Highway at 8450′ with similar amounts lower down at a 7400′ TH.

Weather and forecast thoughts:

Today’s much anticipated storm arrived with gusto this morning and is still going strong as of Thurs. afternoon (2/13). Periods of heavy snow will continue through tonight and into tomorrow (2/14) before winding down to scattered convective snow showers tomorrow afternoon and evening. The weekend will be much quieter with a mix of clouds and sun, chances for light snow showers, and highs in the low to mid 30s for the backcountry.

Snow has been steadily heavy since early this morning. Temps. at 0400 hovered around 32.4 deg. in Carnelian Bay until late morning when they peaked at 34.7 deg. during a brief lull and burst of sunshine. Strong SW winds and renewed heavy snow followed the lull, along with a notable drop in temps. to below freezing. Since 1300 temps. have been below freezing with moderate to heavy snowfall rates. Somehow this location just barely kept its nose above the rain/snow line.

Reports from South Lake Tahoe and Truckee this indicated significant rain mixing in, if not dominating precip. since the start of the storm. If it hasn’t already, rain should transition to snow this afternoon near 6000′ for the balance of the storm.

In backcountry areas that have remained above snowline for the entire storm, expect density changes within the storm snow — lighter density to higher density to lighter density. These layers of various densities form during temperature swings in the storm and will likely promote storm slab instabilities within the new snow.

Now that the cold front has pushed through expect dropping snow levels and cooler temps with moderate to heavy snow continuing through the evening and overnight hours. Another 12-18″ is likely for locations below 7000′, especially west of the lake, with 1.5-3′ of additional accumulation above 7000′.

The airmass behind the cold front is moist, cold, and unstable. This airmass, combined with a flow nearly perpendicular to the Sierra, will promote orographic enhancement to snow squalls, creating particularly intense bursts of snow over the next 12 hours. Total storm accumulations by midday tomorrow should easily range from 2-4′ above 7000′, with many 6000′ locations near or at 2′ of total accumulation.

Showers will wane in intensity and coverage tomorrow afternoon as the storm finally moves out of the region. In its wake, expect clearing skies and cold temps on Fri. night. Lows should dip into the 10s and 20s for the backcountry.

The rest of the weekend will be rather quiet with chances of snow showers Sun. and Mon., especially north, and highs reaching the middle to upper 30s in the mountains. Lows will cool below freezing each night.

Next week kicks off another stretch of dry and mild weather. Chances of snow could return mid-late week, but models show weak storms, if any. Temps. also appear to moderate to near or slightly above average by the end of next week as high pressure returns, blocking any significant storms from reaching the Sierra.

For now, it’s here! Time to get out and enjoy it.

0400 wx. at 6350′ in Carnelian Bay: 18.9 deg. / 15.8 deg. dew point / 88% / calm winds / partly cloudy skies

0515 wx. At 8460’ Rose backcountry trailhead: 15 deg. / low broken overcast / light winds / flurries

Backcountry obs.:

Early morning tours in the Rose area on Sun. (2/9) and Tues. (2/11) revealed a substantially improved snowpack above 8000’, with cold snow surfaces throughout all sheltered NW-N-NE-E aspects. Below average temps over the past few days have largely preserved cold, soft snow. Solar aspects are the exception where cold, brittle sun crusts can quickly interrupt fluffy turns, should an unsuspecting skier drift awry of shadier aspects. Some wind sculpting has increased snow density on near treeline terrain and created a firm, yet edgeable surfaces above treeline into the alpine.

Aside from resort like tracks covering the most popular zones, the snow skis as fast, fun pow with a supportable, springy-firm base underfoot. Steeper exposed terrain is firm, but edgeable. Soft protected nooks and crannies hold wind-deposited fluff.

Weather and forecast obs.:

Today will be the last day to enjoy the calm reprieve before another storm arrives with heavy snow to close out the work week. By nightfall Friday, an additional 2-4 feet of new snow could fall above 7000 ft from Tahoe south through the Eastern Sierra. Lesser amounts between 1-2′ are possible at lake level.

Today, expect mostly sunny skies with cold temps. Highs will stay in the 20s above 7000’. A N-NW flow will increase by the afternoon, bringing an increase in cloud cover and chances for light snow showers as a weak, precursor system begins approaching the area. Winds may also tick up this afternoon.

Tonight temps will plummet under mostly clear skies. Colder valleys could drop below zero, while most locations will bottom out in the single digits to low teens.

Tomorrow (2/12) clouds and winds increase with the arrival of the weak slider from the NW, bringing chances for light snow showers throughout the day. Accumulations will be minimal at best. Highs tomorrow will remain in the 20s above 7000’, with low to mid 30s between 6000-7000’.

The main event starts in earnest overnight Wednesday (2/12) as a potent storm begins assailing the Sierra with heavy snow and high winds. Models are in good agreement that this could be the most potent storm of the season to date. Snow should begin falling late night on Weds., and pick up in intensity through the morning Thurs. During peak intensity Thurs. through Thurs. evening, snowfall rates could reach a few inches per hour. The storm will go strong into the early hours of Fri. (2/14), before waning around daybreak and transitioning to convective snow showers for most of Friday. Friday’s showers will produce additional accumulations, especially in higher terrain. By Fri. evening, the storm moves out, leaving clearing skies and cool temps. in its wake.

One bit of uncertainty with the coming storm is just how high snow levels reach on Thurs. The moisture arriving on Weds. PM will encounter a cold airmass and snow levels will start out around 4500-5000′. However, snow levels may begin flirting with 6000′ Thurs. afternoon, before falling again in the evening for the remainder of the event. Rain mixing in at lake level is a very real possibility, yet again. At higher elevations, the intrusion of warm air into the system will likely create a noticeable density change within the storm snow: lighter density snow at the start, followed by a layer of denser snow, finished off with lighter density snow at storm’s end.

Partly sunny skies and a few stray snow showers are possible on Sat. (2/15), but with light accumulations, if any. Highs Sat. look relatively mild for a post storm airmass midwinter, reaching the upper 20s to low 30s above 7000′.

Another weak system could impact the area on Sun. and Mon. (2/16-17), but with most impacts from Tahoe north. Milder air will also filter in on Sun. and Mon. bringing temps near to slightly above freezing in the backcountry.

A pattern change looks likely for next week bringing mild temps and dry weather for the foreseeable future.

Let’s hope it’s a good one.