The Morning Intel | Tahoe Sector Watch

Location: #HippieHaus | South Lake Tahoe, CA

Date: Thursday, December 18, 2025

Time: 0628 PST

¡Buenos días my friends, Cup'O'Joe in hand, #StokeLevelRising, on a #TheologianThursday. Rain, top to bottom, yesterday at KirkwoodMtn and Regionally, not a flake was seen in the Tahoe Region. Now, let's brush all that aside and prep up for the next round that we've been talking about for a week now.

The second #Pineapple Express, or AR (Atmospheric River) pipeline, is taking shape off the coast as I type. #MotherNature looks like she is going to be dropping the JET, Feeder, and Pump right across the Sierra Crest starting late Friday afternoon, and it’s #GameOn Saturday through Monday.

The "Fatty Caveat" & The Science: The Storm doors are wide open, and we have the three ingredients needed to build a better base and get our regional resorts up and running for the holiday. We have a Water Source, a deep moisture tap reaching far into the Pacific. At the same time, model guidance has us looking at cold air dropping in with a deepening trough, and the engine is in place.

All good news, but—and here is the reality check—all things in the snow science world can and do change. One concern from NWS Reno this morning is that even next week (Wednesday & Thursday), it’s never really "all-snow." Probabilistic guidance shows a 55-65% chance of snow p-type, but still a 15-30% chance of rain mixing in. NWS guidance references: "25th and 50th percentile snowfalls for mountain communities are zero, but 90th is 7-15" each day Wednesday-Thursday." Boom or bust, my friends.

The Mtn Ops Shout-Out: Let's give our Mtn Ops teams the room and space needed to keep up with the snow if and when it falls. YES, the resorts are ready; YES, they want to open more terrain; AND YES, they are just as frustrated with the last 19 days of warm temps and lack of WetBulb windows. So R.E.S.P.E.C.T. and give 'em a high five, a box of bagels, a hug, or just be kind!

Stay'nThirsty, and stay tuned. The next five days are going to be a wild ride. For more info, tune into 101.5 Truckee Tahoe Radio from 4-7pm today as I drop in on the Afternoon Show, pinch-hitting for Tarrin to discuss all this magic, and the wild ride we are all on.

Current Tahoe Sector Data

Regional Temperatures:

• South Lake Tahoe (KTLV) at 6,308': 46ºF (Warm start)

• Truckee (KTRK) at 5,899': 36ºF

• Mammoth Mtn Race (MTH03) at 11,034': 32ºF (Freezing line is high)

• Chair 6 Ridge (9,100'): 41ºF

Regional Winds:

• HippieHaus: 220º (SW) 9mph

• Truckee: 214º (SW) 8mph

• Donner Pass: 184º (W) 5-9mph

• Carson Pass: 237º (WSW) 13-24mph (Winds ramping up)

Roads (CalTrans @ 0432):

• Sierra Sector: ALL CLEAR (SR88, Hwy 50, I-80).

• Trucker Alert: All westbound trucks on I-80 must stop at the brake check area 0.5 mi west of Nyack.

Forecast Update: The Pineapple Pipeline: Comparing today's data against yesterday, the "Lull" is here for Thursday, but the signal for the weekend AR event and the Christmas week cooling trend has strengthened.

1. The Immediate "Lull" (Thursday):

• Update: Today is dry with gusty winds. A "break" in the precip before the main event.

• NWS Reno: Notes that 700mb flow is already near 50 knots, so while valleys are calm, ridges will be breezy today.

2. The Wind Event (Friday - Saturday):

• Change: Wind potential has "ticked up" for Friday and especially Sunday.

• Data: We are looking at 700 mb (Ridge-level) winds projected near 60 knots. This translates to 100+ MPH gusts for the higher terrain on Friday and again on Sunday.

• Impact: Expect lift holds. If you are skiing on Friday, get it while you can before the winds potentially close or wind-hold the upper mountains.

3. The Sunday Soak (Atmospheric River):

• New Data: QPF (Quantitative Precipitation Forecast) amounts have trended UP for Sunday-Monday.

• The Risk: There is a 30-60% chance of "moderate atmospheric river conditions." This means heavy rain is likely for the Tahoe Basin and Mammoth Lakes on Sunday, with rises on creeks and rivers.

• Snow Levels: Still high for the weekend (start >8,000'), but NWS Sacramento notes snow levels dropping Monday to 6,000-7,000', then 5,500-6,500' by Tuesday.

4. The Christmas Eve "Wildcard":

• The Hope: NWS Sacramento is watching a trend for Major Impacts to mountain travel due to Heavy Snow on Wednesday (Christmas Eve). This is the "Engine" (Cold Trough) arriving.

• NWS Reno Nuance: The snowpack is currently at or near record lows. We need this system to convert to snow mid-week to save the holiday season.

✈️ Aviation

Current Status:

• VFR conditions generally prevail today, but the atmosphere is turbulent aloft.

Forecast & Hazards:

• Wind Shear (LLWS): This is the primary concern for the next 36 hours. Strong W/SW flow aloft (50-60 knots at FL100) will create significant shear for all Sierra airfields, including KTRK, KTVL, and KRNO.

• Turbulence: Expect Moderate to Severe Mountain Wave Turbulence Thursday and Friday east of the Sierra crest.

• Surface Winds: Gusts over 30 knots are 30-50% likely today (21z-03z), increasing to 70-90% likelihood on Friday.

• Ceilings: VFR today drops to MVFR-IFR in rain/mountain obscuration by Friday during the day.

⚓ Mariners Forecast

Lake Tahoe:

• ⚠️ LAKE WIND ADVISORY: In effect from 4 PM This Afternoon to 4 AM Saturday.

• Today: Southwest winds 10-15 mph, gusts increasing to 30 mph in the afternoon. Waves 1-2 feet.

• Tonight: The energy arrives. Winds increasing to 15-25 mph with gusts up to 40 mph. Wave heights building to 1 to 4 feet.

• Friday: Rough. Gusts to 40 mph. Waves 2-4 feet. Rain and snow likely in the afternoon.

• Coop's Note: If you didn't secure the vessel yesterday, do it before 4 PM today. A 4-foot toss’r on Tahoe is unforgiving.

Sierra Avalanche Centers

Central Sierra (Tahoe/Carson):

• Status: Early Season Conditions.

• Hazard: Wet Loose / Rain on Snow.

• Update: "Very high elevation rain on snow could create wet snow avalanches this week." The shallow snowpack means obstacles (rocks, stumps, sharks) are the primary danger.

Eastside Region (Mammoth):

• Status: Low Tide.

• Hazard: Shallow coverage and variable surfaces. Isolated wind slabs may exist where drifts have formed above weak, sugary snow.

The Bottom Line: We are in the gap between systems. Use today to prep. The moisture tap is primed, the winds are cranking up to 100mph+ on the ridges, and the "Will it / Won't it" game for Christmas snow is on.

Tune in to 101.5 Truckee Tahoe Radio tonight (4-7pm)—we'll break it all down live.

Stay'nThirsty for POW,

Coop | RS#69