An atmospheric river is setting up in the Pacific with up to 6 feet forecasted for localized areas of the Sierra by week’s end reports NOAA.
“A period of light valley rain and higher elevation snow is expected Tuesday evening and Tuesday night. A much stronger system pushes into the region Wednesday night through early Friday morning. This will bring periods of valley rain and heavy Sierra snow along with gusty winds. The weekend will be colder with snow showers possible down to all valley floors.” – NWS Reno
Tahoe should still see decent accumulations in the 2-3 foot range albeit a little rainy until Friday. The best days for skiing will be Friday-Sunday as a cold front brings snow down to lake levels before spring like weather returns on Sunday.
LET IT SNOW!
Forecast Discussion [NOAA]
A period of light valley rain and higher elevation snow is expected this evening and tonight. A much stronger atmospheric river type storm pushes into the region Wednesday night through early Friday morning. This will bring periods of heavy valley rain and heavy Sierra snow along with gusty winds. The weekend will be colder with snow showers possible down to all valley floors.
SHORT TERM FORECAST:
Clouds will be on the increase today as a period of light valley rain and higher elevation snow begins this evening and tonight.
However, the main focus in the short-term forecast is the incoming Atmospheric River (AR) storm poised to provide multiple feet of high elevation snowfall (Sierra cement) and periods of heavy rain to lower valleys in the Sierra and western Nevada. Main change in the forecast was to continue to increase expected precipitation totals Wed-Thu.
TIMING: Initial light to moderate precipitation with this storm begins on Wednesday in the Sierra but expecting the main period of heaviest precipitation to begin Wednesday night into early Thursday morning. Moderate to heavy precipitation continues Thursday afternoon before quickly diminishing Thursday night as a pronounced dry slot cuts off precipitation.
SNOW LEVELS: AR storms are inherently warm systems as their moisture has tropical origins. As such, snow levels on Wednesday into Thursday morning will begin in the 7,500-8,500` range from the Tahoe Basin extending southward into Mono County. Snow levels will begin to drop in the late Thursday afternoon into evening time frame as the cold front nears. There is still some timing uncertainty on how quickly the front arrives but nonetheless, late Thursday afternoon-evening looks to be the period where
travel deteriorates across most passes and snow will be possible at Lake Tahoe level and along portions of Hwy 395 through Mono County.
RAIN/SNOW/HYDROLOGIC CONCERNS: This AR storm will provide heavy rains and high elevation snowfall Wed-Thu with most precipitation occurring Thursday. Overall, the main moisture plume will be concentrated through the Sierra in Mono County where 2-4 feet of snow will be possible above mainly 8,000` with localized areas up to 6 feet along the crest in southern Mono County. The Tahoe Basin will see up to 2-3 feet mainly above 7,500` with localized areas up to 4 feet along the crest. Snow amounts below 7,500` are much lower confidence but generally 6-12″ are possible down to 7,000` feet with a few inches possible down to lake level by Thursday night.
This will be a rain event for western Nevada with moderate to heavy rain expected on Thursday. 0.50-0.75″ are possible across western Nevada valleys. Rises on small creeks and streams can be expected with some minor flooding possible in urban and poor drainage areas.
Minor flooding is also possible through the Sierra where snow has not been removed to allow for drainage. There could also be rises on small streams below 7000 feet that drain into the Tahoe basin and on the east side of the Sierra. Although, main stem rivers do not look like an issue, rises are expected on all rivers. The current forecast takes the Middle Fork of the Feather River in Portola to monitor stage, but at this point all other rivers are forecast to remain below the point of concern. Fuentes
LONG TERM Forecast:
Friday onward… The break in the precipitation between the warmer and colder portions of the storms Friday morning is even more defined in latest model guidance. Colder air moves into the region Friday as an upper trough digs into northern CA/NV with a secondary cold frontal boundary shifting through the region Friday night. This boundary will provide the forcing to develop snow across the area with the best chances in the Sierra, northeast California, and in western Nevada mainly north of Highway 50. This is a fast moving feature and there will only be a short period where the moisture and forcing align, so am not expecting significant snow accumulations. However, with snow levels at all valley floors, even light accumulations may bring travel impacts across the region. A final passing shortwave could bring one more chance for light snow showers Saturday night. Considering we are getting into the latter part of March, most road impacts from these lighter snows will be limited to the overnight and early morning hours.
A warming and drying trend looks likely for next week, however springtime is notorious for poor long range model guidance, so nothing is a lock just yet. -Dawn
Find the entire discussion here: Area Forecast Discussion