textproduct: Reno

KEY MESSAGES

* Well above average temperatures will persist through Friday, with daily record highs possible throughout the area. * A potent cold front is expected to produce gusty winds with enhanced fire weather concerns Friday and Saturday.

* Significant cooling is expected behind the front with below average temperatures returning, along with 50-70% chances for rain and mountain snow showers by Sunday into early next week.

DISCUSSION

Temperatures throughout the region will remain upwards of 10-15 degrees above average today and Friday. We'll see mostly mid to upper 80s in western NV, northeast CA, and the lower elevations of Mono County. Meanwhile, temperatures for a majority of our eastern Sierra communities will range from the mid 70s to mid 80s, with mid 50s to mid 60s in the higher elevations.

After over a week of summer-like temperatures and dry weather, we're in store for a drastic pattern change arriving Friday into next week. A potent system dropping in from the north is poised to bring strong gusty winds Friday and Saturday, producing fire weather concerns and impacts to recreation, travel, and aviation. We are also going to have significant cooling, as well as valley rain and mountain snow Sunday into Tuesday.

For Friday, southwest winds will start to increase ahead of the approaching system as pressure gradients tighten. Gusts during the afternoon will range between 25-35 mph along the Sierra Front, NW Nevada, and NE California. When we combined these winds with the persistent dry weather, critical fire weather conditions are possible Friday afternoon in those aforementioned areas. Fire Weather Watches have been issued across NE California and NW Nevada Friday. See the Fire Weather Discussion below for details.

Winds increase further on Saturday with the arrival of the cold front. Gusts between 30-40 mph will be common for a majority of the area. Depending on humidity values, additional fire weather watches may be needed for Saturday for portions of the inner basin and ranges. Meanwhile, ridgetop winds by Saturday morning into Sunday morning will range from 60-80 mph. Bottom line, winds on Friday and Saturday may create dangerous recreational activities on area lakes, and possible travel impacts along wind prone areas in W Nevada, E Lassen, and Mono County.

By Sunday into Tuesday, the models and ensembles are coming into slightly better agreement with the evolution of the larger scale pattern. A broad upper level low pressure will drop south into the region, pulling in additional remnant moisture from now Hurricane Rachel into the region. Precipitation is likely (50-70%) on Sunday and Monday for areas south of I-80 in W Nevada, as well as from southern Lassen County south into Mono County in the eastern Sierra. Areas north of I-80 in W Nevada and NE California have a 20-50% chance of precipitation during this time frame. We retain a cool, showery pattern on Monday and Tuesday. For now, blended guidance shows the highest liquid totals in the Sierra from southern Lassen into Mono County, and areas south of I-80 in W Nevada. These areas have a 20-50% chance for at least 0.50 inches of liquid. Snow above 8,000 to 9,000 feet is becoming likely Sunday into Monday. As of now, there is a 20-50% chance for at least 3 inches of snowfall for higher elevations in the Tahoe Basin south into Mono County. Finally, this system will bring a drastic cooldown Sunday into next week. High and low temperatures will be around 10-15 degrees below average. Sierra valleys will be well below freezing while W Nevada valleys may drop as low as upper 20s to low 30s. -McKellar

AVIATION

VFR conditions will predominate. Light, terrain-driven winds continue today, with afternoon gusts below 20 kts.

Southwest flow strengthens Friday into Saturday, with Sierra ridge gusts increasing to 50-70 kts late Friday night. Mountain wave turbulence potential increases along and east of the Sierra crest, with periods of LLWS possible where valley winds remain lighter. Regional surface wind impacts peak with Saturday's cold frontal passage.

Shower chances become more widespread across the Sierra and western Nevada Sunday into Sunday night, with the highest precipitation probabilities Sunday evening. Mountain obscuration and periods of MVFR conditions are possible, particularly at Sierra terminals.

KRNO...Westerly winds increase around 21Z Friday, with gusts of 25- 30 kts continuing into the evening. Stronger gusts of 30-35 kts are favored Saturday afternoon and evening, increasing crosswind concerns. LLWS is possible Friday night into Saturday morning if terminal winds diminish beneath strengthening flow aloft.

-Johnston

FIRE WEATHER

The seasons first potent cold front will bring increasing southwest winds Friday afternoon, peaking Saturday as it moves through NE California and W.Nevada. Winds combined with low humidity may produce periods of critical fire weather conditions both days.

FRIDAY: Friday afternoon gusts will reach 25-35 mph as minimum RH falls to 10-17%. The strongest winds will favor areas near the Oregon border, though elevated fire weather concerns may extend along the Sierra Front. As such, Fire Weather Watches have been issued for Friday afternoon and evening for portions of NE California and NW Nevada, including fire weather zones 270, 278, and 458.

SATURDAY: Winds peak Saturday afternoon and evening, with widespread gusts of 30-40 mph mainly south of I-80. Humidity will increase across NE California and far NW Nevada, while areas south of I-80 may see continued elevated concerns with a more marginal minimum RH of 15-20% on Saturday afternoon. Areas south of I-80 may need additional fire weather products Saturday.

SUNDAY ONWARD: Behind the front, highs will drop 20-25 degrees from Friday to Sunday, reaching the low 60s across W.Nevada and low 50s in E.Sierra communities. Wetting rain potential increases Sunday- Monday, mainly south of I-80, as remnant moisture from Hurricane Rachel moves northward. The moistures track and precipitation totals still show higher uncertainty, but the overall trend has been wetter. Areas south of I-80 have a 20-50% chance of receiving at least 0.50 inches of rainfall through early next week, with the highest chances farther south. Fuentes/McKellar

REV Watches/Warnings/Advisories

NV...Fire Weather Watch from Friday afternoon through Friday evening NVZ458.

CA...Fire Weather Watch from Friday afternoon through Friday evening CAZ270-278.