THIS AVALANCHE FORECAST EXPIRED ON February 2, 2020 @ 6:40 am
Avalanche Forecast published on February 1, 2020 @ 6:40 am
Issued by Brandon Schwartz - Tahoe National Forest

Snow surface melt leading to loose wet avalanche problems is expected again today at all elevations, mainly in areas of direct sun exposure. Most avalanches will be fairly small, but avalanches large enough to bury a person could occur. MODERATE avalanche danger exists at all elevations.

2. Moderate

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Above Treeline
Heightened avalanche conditions on specific terrain features. Evaluate snow and terrain carefully; identify features of concern.

2. Moderate

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Near Treeline
Heightened avalanche conditions on specific terrain features. Evaluate snow and terrain carefully; identify features of concern.

2. Moderate

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Below Treeline
Heightened avalanche conditions on specific terrain features. Evaluate snow and terrain carefully; identify features of concern.
    Heightened avalanche conditions on specific terrain features. Evaluate snow and terrain carefully; identify features of concern.
Avalanche Problem 1: Loose Wet
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The situation remains largely unchanged. Snow surface refreeze is expected to have occurred again last night due to radiational cooling under clear skies despite above freezing air temperatures. These same clear skies and well above freezing air temperatures at sunrise today will allow snow surface melt to occur quickly on E-SE-S-SW-W aspects. Fairly widespread loose wet avalanche problems are expected again today with avalanche size mostly at D1 with up to D2 possible. The still fairly low sun angle and shorter length of daylight hours this time of year are expected to keep problematic amounts of surface wet snow from forming today on NW-N-NE aspects. While increasing winds and some cloud cover this afternoon will slow the rate of late day melt on sunny slopes, unstable conditions will have already formed quickly during the morning hours.

Areas around exposed rocks in direct sun is where the greatest amount of incoming solar radiation and snow surface heating will occur. Rollerballs are an indication that instability associated with loose wet avalanches is forming. Choose terrain wisely considering how consequences from otherwise small avalanches can be greatly exacerbated by involvement with trees, rocks, cliffs or terrain traps below.

Photo: Recent loose wet avalanche debris. A normally inconsequential avalanche until you hit the trees. Cloud deck associated with the air temp inversion layer - colder air below, warm air above.

recent observations
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* Well above freezing air temperatures and surface wet snow in sun exposed areas was observed around the forecast area yesterday at elevations above the lower atmosphere inversion.

* Numerous small loose wet avalanches (size D1) have occurred around the forecast area over the past two days.

* The upper snowpack remains transitional in most areas with a thin surface melt-freeze layer on top of cold snow yet to be affected by melt. This structure transitions from frozen to wet and unstable quicker than a well established spring time melt-freeze snowpack.

Weather and CURRENT CONDITIONS
weather summary

High pressure will hold on over the forecast area today for another round of well above freezing air temperatures. Air temperature inversion conditions are in place again this morning with the coldest air down on the mountain valley floors and well above freezing air temperatures overnight at the mid and upper elevations. Maximum daytime air temperatures today will once again climb well above freezing at all elevations. Cloud cover is expected to increase this afternoon. Ridgetop winds out of SW will also begin to increase this afternoon, reaching gale force tonight. A strong cold front will move through the region tomorrow bringing dramatic air temperature cooling and a 1 to 2 hour period of high intensity snowfall in the afternoon.

CONDITIONS ALONG THE SIERRA CREST BETWEEN 8200 FT. AND 9200 FT. IN THE LAST 24 HOURS
Weather Station Map
Weather Station Table
6am temperature: 43 to 48 deg. F.
Max. temperature: 50 to 56 deg. F.
Average ridgetop wind direction: SW
Average ridgetop wind speed: 12 mph
Maximum ridgetop wind gust: 29 mph
New snowfall: 0 inches
Total snow depth: 43 to 52 inches
Two-Day Mountain Weather Forecast Produced in partnership with the Reno NWS
For 7000 ft. to 8000 ft.
Saturday Saturday Night Sunday
Weather: Sunny then becoming partly cloudy. Snow levels 7000 feet increasing to 8000 feet in the afternoon. Chance of precipitation is 0%. Partly cloudy. Snow levels 7500 feet decreasing to below 7000 feet after midnight. Chance of precipitation is 0%. Mostly cloudy. Slight chance of snow showers in the morning, then snow likely in the afternoon. Snow levels below 7000 feet. Chance of precipitation is 75%.
Temperatures: 52 to 58. deg. F. 28 to 33. deg. F. 34 to 39. deg. F.
Mid Slope Winds: Light winds becoming southwest around 15 mph with gusts to 25 mph in the afternoon. Southwest 15 to 20 mph. Gusts up to 35 mph increasing to 60 mph after midnight. Southwest 20 to 35 mph with gusts to 55 mph.
Expected snowfall: No accumulation. | SWE = none. No accumulation. | SWE = none. 70% probability of 1 to 2 inches. 30% probability of 2 to 4 inches. | SWE = up to 0.15 inch.
For 8000 ft. to 9000 ft.
Saturday Saturday Night Sunday
Weather: Sunny then becoming partly cloudy. Snow levels 7000 feet increasing to 8000 feet in the afternoon. Chance of precipitation is 0%. Partly cloudy. Snow levels 7500 feet decreasing to below 7000 feet after midnight. Chance of precipitation is 0%. Mostly cloudy. Slight chance of snow showers in the morning, then snow likely in the afternoon. Snow levels below 7000 feet. Chance of precipitation is 75%.
Temperatures: 48 to 54. deg. F. 25 to 30. deg. F. 30 to 35. deg. F.
Ridge Top Winds: Southwest 15 to 25 mph. Gusts up to 25 mph increasing to 45 mph in the afternoon. Southwest 25 to 35 mph with gusts to 60 mph increasing to 35 to 55 mph with gusts to 85 mph after midnight. Southwest 40 to 60 mph with gusts to 80 mph.
Expected snowfall: No accumulation. | SWE = none. No accumulation. | SWE = none. 70% probability of 1 to 2 inches. 30% probability of 2 to 4 inches. | SWE = up to 0.15 inch.
Disclaimer

This avalanche forecast is provided through a partnership between the Tahoe National Forest and the Sierra Avalanche Center. This forecast covers the Central Sierra Nevada Mountains between Yuba Pass on the north and Ebbetts Pass on the south. Click here for a map of the forecast area. This forecast applies only to backcountry areas outside established ski area boundaries. This forecast describes general avalanche conditions and local variations always occur. This forecast expires 24 hours after the posted time unless otherwise noted. The information in this forecast is provided by the USDA Forest Service who is solely responsible for its content.

For a recorded version of the avalanche forecast call (530) 587-3558 x258