textproduct: Reno

KEY MESSAGES

* Drying out today, ridge winds increasing tonight.

* A stronger storm will bring periods of heavier Sierra snow and valley rain late tonight through early Monday, with possible flooding concerns in northeast CA.

* Additional storms could bring more snow chances to the Sierra, with rain and snow in lower elevations by mid-late next week.

DISCUSSION

Our region is attracting system after system, with today being the lone break in the action. Ridge winds will begin to increase this evening into the overnight, when the next round of showers arrives.

Snow levels are hovering around 7500 feet near Colfax, CA this morning, and with winds out of the south, that is not surprising. Snow levels will be falling ahead of sunrise this morning to near 6500 feet, then increasing again this afternoon around 7000 feet, only to fall generally to around 6500 feet again tonight, or so the guidance indicates. That is when the southerly breezes advecting warmer air make things interesting for Saturday, as snow levels are projected to bounce to 7500 feet again during the early morning hours and into the afternoon. Then, as though we hadn't already done this, snow levels fall Saturday night to around 6000 feet. Temperatures will follow this trend, with a cool day today leading into a slight warm up on Saturday, followed by more cooling on Sunday. A caveat here is the recent guidance was struggling to accurately depict snow levels with the Christmas storm due to the influences of warmer sourced moisture interfacing with a cold air region sourced trough. Whether the modeling solutions will accurately reflect this system remains to be seen, but this forecaster is encouraging caution when interpreting the snow levels.

As for the showers, Saturday will see mostly rain with the higher snow levels, and since we have added to the snowpack recently, we are watching the rain on snow potential for the above mentioned snow levels on the specified days and timeframe. Areal flooding is possible, should the rain showers become heavier in nature. There is a bit of uncertainty on exactly when the snow levels will fall for Saturday, and timing will be critical. If the heaviest showers arrive as rain, there may be minor flooding on area streams such as the Susan and Feather rivers. However, should the heavier showers arrive when the snow levels fall, it may fall as wet snow, which would mitigate much of the flooding concern. This will be closely monitored as the system draws nearer. Snow levels addressed above will delineate who will receive snow, who will see mostly rain, and the in-betweeners that will see a mix of precipitation types through Saturday.

Sunday, the snow levels nudge closer to 5500 feet, and look to fall to valley floors for early Monday morning. The piece of the puzzle we will still need to solve will be where the moisture will be when these colder temperatures arrive. Many ensemble solutions hint that the bulk of the snow showers will be ongoing across the Sierra, with limited spillover into western Nevada valleys. So, while the Monday morning commute looks cold, we still need to work out where and if there will be moisture to go with the cold air that would produce snow on valley floors.

Beyond the beginning of the week, there exists more chances for new systems to approach the region. For now, eyes are trained on the horizon as a colder midweek system takes aim. HRICH

AVALANCHE

A winter storm will bring periods of potentially significant snow and windy conditions to all avalanche center terrain starting early Saturday morning through Monday morning.

* Snow Levels: Starting around 6500-7000 ft and fluctuating through the day Saturday only to settle at a similar elevation Saturday night. Snow levels have been shifting during this forecast period, lowering confidence on actual snow levels and timing. * Snow/SWE amounts: 1-3 feet with locally up to 4 feet for Mono County. SWE totals between 1.5" and 3", with a few sites receiving up to 4".

* Snow-Liquid Ratios (SLR): Higher density 7-10:1 Saturday, then becoming less dense with SLR's increasing to 10:1 and possibly up to 13:1 with colder air and lower snow levels from early Sunday morning through Monday.

* Snowfall Rates: Steady at 0.5-1"/hour with periodic bursts of up to 2-3"/hour through the weekend, particularly across higher peaks.

* Ridge top winds: Gusts 70-90 mph, with stronger gusts up to 100 mph for Sunday. HRICH

REV Watches/Warnings/Advisories

NV...Winter Storm Warning from midnight tonight to 10 AM PST Monday NVZ002.

Lake Wind Advisory from 4 AM Saturday to 1 PM PST Sunday NVZ004.

CA...Flood Watch from Saturday morning through Monday afternoon CAZ071.

Winter Storm Warning from midnight tonight to 10 AM PST Monday CAZ072-073.