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KEY MESSAGES

* Light freezing rain could produce slick roads for valleys of eastern CA including I-80 around Truckee, with snow in higher elevations this evening into Thursday morning.

* Stronger storm brings heavy mountain snow, strong ridge winds, and valley rain showers Friday night through the weekend. Some flooding concerns for the Susan and Feather Rivers.

* Additional storms could keep valley rain and mountain snow chances going through early to mid next week.

DISCUSSION

As we flip the calendar from 2025 to 2026, our weather pattern will also be transitioning to a more active regime with several storm systems in the pipeline through the first week of the new year.

The first storm is spreading light precip into the Sierra and thick cloud cover over the remainder of eastern CA-western NV. Normally this wouldn't be very impactful as snow levels are high with precip rates generally on the light side. However, more protected valleys across eastern CA will see temperatures in the lower-mid 30s tonight-Thursday morning with little or no wind scouring out the inversions in areas still snow-covered from the storms around Christmas. As a result, some of the light rain tonight could freeze on contact with some surfaces, so we have issued a Winter Weather Advisory for northeast CA, the Tahoe Basin, and Mono County. While this freezing rain risk is likely to be isolated, the impacts of even small patches of ice on roads would be magnified due to expected heavier traffic with New Year's Eve events.

As for snow, that will be limited to elevations near and above 8500 feet and may include the Mt. Rose Summit and the higher terrain around Mammoth Lakes--again with potential magnified impacts due to heavier traffic tonight. Overall, snow totals are expected to be 4" or less, but a burst of heavier snow Thursday morning may bring localized higher amounts of 6-10" near the crest in Mono County before this storm winds down. Elsewhere in western NV, light rain showers may dampen some of tonight's festivities a bit but rainfall amounts will generally be 0.05" or less with temperatures mainly in the upper 30s-near 40 degrees as the clocks strike midnight.

From late Thursday through Friday afternoon, we'll see a break in storm activity apart from a few leftover light rain or snow showers mainly near the Sierra. Then a more potent storm takes aim on the region from Friday night through the remainder of the holiday weekend, although the onset may be delayed until Saturday morning based on latest high resolution guidance trends. This storm is expected to bring lower snow levels, initially near 7000 feet but may drop to near or even a bit below 6000 feet at times. A Winter Storm Watch remains in effect for the Sierra for this event, with medium to high risk for travel impacts over all main passes and eventually down to lake level by late Saturday through Sunday. For lower elevations, this continues to be primarily a rain event. In northeast CA, waves of rain falling on existing snow cover could bring flooding impacts near the Susan River and poor drainage areas this weekend and early next week, and also notable rises on the Middle Fork Feather River. For western NV, this storm will be primarily a rain event, with precip totals generally between 0.20-0.50" across the main urban areas, locally up to 1" for foothills (snow may mix in at times near and above 5500 ft), with lighter amounts across west central NV.

For early next week, yet another storm could push across the Sierra and western NV, although there is more spread in the track. Some of the more aggressive scenarios show little break between the weekend event and this subsequent storm, while the drier scenarios only brush this system across northeast CA with light precip amounts. The unsettled weather pattern could continue through the reminder of next week, although overall trends show weaker storm systems after Tuesday. MJD

AVIATION

VFR conditions expected through Friday for western NV terminals, although -SHRA may produce brief MVFR conditions with higher terrain obscured. For Sierra terminals, periods of MVFR CIGS/VIS are expected from late this afternoon thru late Thursday morning.

While precip is mainly expected to fall as -SHRA for the Sierra terminals, the risk for patchy -FZRA continues for KMMH tonight and into Thursday morning and also possible (20-30% chance) for KTRK at times, especially tonight between 03-08Z, leaving surfaces slick. Winds will continue to be relatively light today through Thursday, although increasing ridge top winds could produce minor LLWS near the Sierra terminals by Thursday morning. MJD

AVALANCHE

Two storm systems will impact all avalanche center terrain starting today through at least Sunday.

* First storm--Tonight through Midday Thursday: Warm with snow levels generally 8500-9000 feet. Snowfall amounts of 6-10" isolated to higher peaks above 9000 ft in Mono County. Higher elevations around the Tahoe Basin may see up to 4". SLRs are low (6-9:1) with SWE 0.30-0.60", except up to 1" along the Mono County crest. Snowfall rates generally 0.5"/hour or less, except up to 1" for Mono County Thursday AM.

* Second storm--Late Friday Night-Sunday Night: Colder with snow levels starting around 7000 ft at storm's onset, then dropping to 6000-6500 feet Saturday night-Sunday, although some spread in snow levels remains. Snowfall amounts generally 1-2 feet along the crest, with locally higher amounts for higher peaks. SLR's mainly 8-11:1 with SWE 1-2" and locally up to 3" along the highest peaks for the Tahoe Basin, and 1-1.5" with up to 2" along highest peaks for Mono County. Snowfall rates near 1"/hour at times Saturday, then a period of 1-2"/hour snowfall rates may occur Sunday afternoon or evening, but confidence is lower. Expect southwest ridge winds of 60-80 mph, with gusts near 100 mph.

-Giralte/MJD

REV Watches/Warnings/Advisories

NV...Winter Storm Watch from Friday afternoon through Sunday morning NVZ002.

CA...Winter Storm Watch from Friday afternoon through Sunday morning CAZ072-073.