textproduct: Reno

KEY MESSAGES

* Dry and mild conditions continue through Thursday, with a gradual cooling trend this weekend.

* Isolated and light rain and snow showers Thursday evening across the Sierra, lingering through Friday.

* Upper level trough on Saturday and Sunday brings wetter conditions with valley rain, and mountain snow above 7000 feet.

DISCUSSION

Mild and dry conditions along with lighter winds continue today and tomorrow as weak ridging slowly develops over the area. Afternoon highs will be in the upper 50s and low 60s for western NV, northeast CA and southern Mono valleys; with low to mid 50s in Sierra communities. However, weather conditions deteriorate as we get closer to the weekend.

On Thursday evening through Friday afternoon, a closed-low off the PacNW will send a weak shortwave trough towards northern CA/NV. This will lead to the start of our cooling trend, an increase in cloud cover, and low (10-30%) chances of rain and snow in the Sierra. Temperatures will drop a few degrees compared to Thursday. HREF and REFS members show these showers, although it appears that most of the activity will be blocked by the Sierra crest, so spillover will be minimal. Therefore, expect light amounts of rain in Sierra valleys and light snow above 6500-7000 ft. Rain amounts will be below 0.05" and snow amounts up to 0.5" (10-20% chance of exceeding 0.5"). A few stray showers may make it to western NV valleys with chances below 5%.

As we get into the weekend, a developing trough from the Eastern Pacific merges with the aforementioned trough over the PacNW as they move inland towards the Great Basin and Central Rockies. So, our precipitation chances increase from Saturday through Sunday morning. POPs are around 20-35% for the Sierra Front, NE CA and eastern Mono, and 30-70% for the Sierra including the Tahoe Basin, and for eastern Mineral/Churchill/Pershing counties.

There is plenty of uncertainty about the details with this system as the forecast has changed every single day this week with its evolution. As of this writing, the trough to our north is pulling into the low pressure system in the Eastern Pacific potentially leading to snow levels somewhere between 6500-8500 ft, trending higher early on Saturday and then lowering by Sunday morning as the moisture starts to exit the region. This, of course, affects how much snow we are going to get. There is a 10-40% chance of snow amounts greater than one inch between 6500-8500 feet, and 30-50% chance of snow greater than 2 inches above 8000 feet. Liquid equivalents appear to be below 0.1 inches for most of the area, and 0.1-0.2 inches for the higher elevations of the Sierra and eastern Churchill/Pershing.

Another ridge appears to develop Sunday through mid-week next week until the next low pressure system arrives sometime late next week. Thus, drier and warmer conditions should return briefly. However, the guidance has been unreliable in the extended period. So, keep an eye out for changes over the next few days.

-HC

AVIATION

VFR conditions prevail through the next 36 hours. Winds remain the main concern with periods of LLWS and minor turbulence over the Sierra through 15Z Wed, and again after 09Z Thurs with FL100 winds around 25-30 kts. Surface winds will be generally light and VRB with a few afternoon gusts to around 15 kts from the east for KCXP and from the west for KTRK/KTVL.

-HC

REV Watches/Warnings/Advisories

NV...None. CA...None.