textproduct: Reno

KEY MESSAGES

* Shower and thunderstorm chances (15-30%) return Friday with slick mountain roads.

* Showers and thunderstorms continue this weekend with more persistent mountain snow for the Tahoe area and eastern Sierra Saturday night into Sunday.

* An active pattern remains in place for next week though the chances for significant rain and mountain snow are less than 10%.

DISCUSSION

Blocking high pressure ridge over the eastern Pacific, and two areas of low pressure over the northern Rockies and off the central/southern California coast. Pieces of energy from both systems will maintain a showery pattern for the Sierra and western NV into early next week.

Showers and thunderstorms (15-30% chance) return for Lassen County, Tahoe area, eastern Sierra and into western NV Friday afternoon with a little instability boost from surface heating. Not looking at any major precipitation totals, but a mix of rain, snow and snow pellet showers in the Sierra could lead to slick/wet mountain roads.

Simulations are showing a more steady period of rain and mountain snow arriving late Saturday into Sunday as low off the California coast is absorbed into the northern Rockies low. Two areas of precipitation may develop (60%+ chance) from this interaction. As with any late April storm, snow is more apt to sticking to roads and paved surfaces during the overnight hours.

* The first over northern portions of Lassen and Washoe Counties early Saturday morning with rain/snow lines falling to near 5000 ft. Snow total remain light with only a 40-50% chance of exceeding 2 inches.

* Simulations show the second area of precipitation south of US-50 in Alpine, Mono, Douglas, Lyon and Mineral Counties. Rain/snow are forecast to fall from 7000-8000 feet to 6000 feet with a 40-50% chance of exceeding 6 inches. High end scenarios (10% chance) show up to 12 inches of snow in Mono County along the Sierra Crest and in the White Mountains. Below the snow line, there is 20-30% chance for more than 0.50 inch of rainfall.

Looking ahead to next week the pattern doesn't change much. The low off the California coast redevelops along with additional energy from the northern Rockies low maintains a 10-20% chance of showers through most of the week. Brong

AVIATION

* Mostly clear skies and light winds tonight. 70% confidence in areas of shallow IFR-LIFR fog after 6z around TRK and Sierra valleys that saw precipitation earlier this week.

* Increased W/NW winds Friday afternoon-evening ahead of approaching upper trough. Isolated showers and t-storms possible (20-30% odds) which would produce temporary MVFR-IFR conditions, erratic wind gusts, lightning, and pellet showers.

* Potential for more widespread showers and isolated t-storms Saturday afternoon into Saturday night. Snowfall possible for mountain airfields, MMH in particular.

-Chris

REV Watches/Warnings/Advisories

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