Graeagle, CA Weather

Key messages

* Dry and mild conditions with light winds continue through much of today across the area.

* Low chances of light rain and mountain snow return this evening through Friday for the Sierra.

* A storm system on Saturday and Sunday brings colder temperatures along with valley rain and mountain snow above 7000 ft.

Discussion

High clouds are here to stay for the next few days as upper level low pressure systems approach the region. We are still expecting that shortwave trough to push through this evening and overnight. Therefore, expect one more mild and mostly dry day. However, light rain and light mountain snow chances return after 4 PM this afternoon. The probabilities are low for the Tahoe Basin with a 10-20% this evening, and up to 30% overnight. South of US-50 the chances of precipitation are higher at 20-50%. HREF and REFS members still show minimal spillover to the eastern slopes of the Sierra, resulting in light accumulations. The best chances for snow remain near the Sierra crest and passes, where 1-3 inches of snow are likely with a 10-40% of exceeding 3 inches above 8000 ft through Friday afternoon. Isolated higher amounts are likely above 10 kft. Liquid equivalents at the crest will be around 0.1-0.3 inches. Rainfall amounts in elevations below 6500 ft will be very light from a trace to 0.05 inches at the most. I wouldn't be surprised if there was a light and brief snow burst below 6500 ft due to saturation of the air, in the Tahoe Basin and portions of US-395 in Mono County.

As we have been advertising the past few days, the forecast continues to be very dynamic with changes every day with this complex system. Some models are hinting at another smaller shortwave embedded in the flow on Friday afternoon and evening that may lead to more lingering snow showers near the Sierra crest. Plus the merger of the split flow that was expected in central and eastern NV is now closer to western NV and the Sierra. Thus, our chances for higher accumulations of rain and snow have increased. Furthermore, the ECMWF ensemble members are slowing down the progression of this system through Sunday night. So, uncertainty for timing, and precipitation amounts persists for the weekend system.

At least snow levels have held around 6500-8500 ft depending on the type of moisture dominating the scenario as we have two different airmasses (warm vs. cold) clashing over the Sierra and the Great Basin. However, thinking for snow accumulations above 8000 ft in the Sierra we could observe 1-4 inches in the Carson Range and areas north of US-50, while south of US-50 amounts of 3-6 inches are likely with 30-70% chance of exceeding 6 inches above 9-10 kft, potentially up to 9 inches in isolated areas near the crest. The main concerns will be for mountain passes - keep an eye out if you have travel plans across the Sierra this weekend. Check your road maps with CalTrans and NDOT (for Mt. Rose Highway). Snow amounts between 6500-8000 ft will be around a trace up to 2 inches. The higher amounts in this range may be mostly due to brief snow bursts in isolated locations.

By Monday, most of the moisture associated to the upper level system should be east of our area. A high amplitude upper ridge will take its place through at least mid-week. Models are still hinting at another system late week into the weekend again, but we'll wait to be done with this weekend's system before looking closer at that one.

-HC

Aviation

VFR conditions prevail through this afternoon at all sites. VFR conditions continue for western NV sites through Friday. Periods of MVFR conditions are likely for Sierra sites including KTRK, KTVL and KMMH due to periods of light snow resulting in reductions of CIGs and VIS. KTRK and KTVL have a 10-25% chance of snow, while KMMH has a 25-40% chance of snow. Accumulations will be very light. Mountain obscurations are expected starting this evening.

Winds will be generally below 10 kts with gusts to around 15 kts in the afternoon. Periods of LLWS and turbulence begin after 00Z this afternoon.

-HC

.REV Watches/Warnings/Advisories: NV: None. CA: None.