textproduct: Reno

KEY MESSAGES

* One last day of well above average temperatures. * 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

We'll get one more day of well above average temperatures before a strong pacific trough and cold front brings a drastic change to our pattern. High temperatures will range from the 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 near 80s, with mid 50s to mid 60s in the higher elevations.

As this system approaches the region today, southwest winds will increase by the early afternoon. Gusts between 25-35 mph are likely along the Sierra Front, northwest NV, and northeast CA. These increased winds along with the dry antecedent conditions will bring critical fire weather conditions to northeast CA and northwest NV this afternoon and evening. The Fire Weather Watch was upgraded to a Red Flag Warning.

As the cold front moves through the area on Saturday, widespread southwest wind gusts between 35-45 mph are likely throughout the region. Additionally, ridgetops in the eastern Sierra and western NV will have gusts between 70-80 mph. Once again, these winds combined with the dry conditions in place will lead to critical fire weather conditions in the inner basin and range, the Sierra Front, and Mono County. Fire Weather Watches are in place for those areas Saturday afternoon and evening. See the Fire Weather Discussion for details. In addition to the fire weather concerns, these strong winds will lead to dangerous boating conditions on all area lakes, including Lake Tahoe and Pyramid Lake. We could also see travel impacts along wind-prone areas of US-395 in western NV, eastern Lassen, and Mono County.

Temperatures will drop upwards of 25 degrees from today to Sunday. By Sunday, high temperatures will only reach the low 60s in western NV and low 50s for eastern Sierra communities. These readings are between 10-15 degrees below average. Low temperatures on Sunday through Wednesday will be well below freezing in Sierra valleys. Western NV valleys are still looking at a 20-30% chance of reaching freezing, with a 50-60% chance of subfreezing temperatures in more rural areas.

As has been the case for several days, ensembles and models are still showing differences in the timing, location, and intensity of the upper low. There is also high uncertainty on how the upper low interacts with the remnants of Tropical Storm Rachel. However, given the broad area of upper level divergence shown by each model and ensemble, widespread precipitation is likely (50-80%) on Sunday and Monday. Current guidance still favors the Sierra from Tahoe Basin into Mono County and western NV south of I-80, with a 20-50% chance of at least 0.50 inches of liquid. Snow levels are variable, right now ranging from 7,500-8,500 feet. Current guidance is showing a 50-90% likelihood for at least 2 inches of snowfall from the Tahoe Basin south into Mono County on Sunday into Monday. After Tuesday into the end the week, we return to a ridge pattern with temperatures warming back to average. -McKellar

AVIATION

Through Saturday morning:

* VFR prevails through tonight. SW-W winds increase this afternoon with gusts of 20-30 kt, producing mechanical turbulence near terrain. Mountain wave turbulence is expected along and east of the Sierra. Surface winds ease Friday evening, but SW winds of 35- 45 kt at FL100 favor LLWS overnight into Saturday morning.

Outlook for Saturday afternoon through Sunday night:

* Stronger winds Saturday bring gusts of 25-35 kt, locally near 40 kt, with the strongest winds at KRNO-KCXP-KMEV expected from 18Z Saturday to 00Z Sunday. Gusty winds at Sierra terminals and mountain wave turbulence continue into Saturday night, with LLWS possible as valley winds ease. VFR continues through Saturday, then showers increase Sunday after 12Z and expand through Sunday night. Mountain obscuration and localized MVFR conditions are possible across the Sierra and western NV, mainly Sunday afternoon and night; confidence is lower in timing and duration at individual terminals. Winds generally decrease Sunday, although KMMH may gust 25-35 kt during the afternoon.

-Johnston

FIRE WEATHER

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

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. Red Flag Warnings are in effect this afternoon and evening for portions of NE CA and NW NV, including fire weather zones 270, 278, and 458.

SATURDAY: Winds peak Saturday afternoon and evening, with widespread gusts of 35-45 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. Due to recent record warmth combined with prolonged dry conditions, additional Fire Weather Watches have been issued for portions of W.Nevada including the Sierra Front and the E.Sierra from E.Alpine County into Mono County.

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 Tropical Storm 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...Red Flag Warning from 1 PM to 9 PM PDT Friday NVZ458.

Fire Weather Watch from Saturday morning through Saturday evening NVZ420-421-423-429.

Lake Wind Advisory from 5 AM to 11 PM PDT Saturday NVZ002>004.

Lake Wind Advisory from 11 AM to 11 PM PDT Saturday NVZ001.

CA...Red Flag Warning from 1 PM to 9 PM PDT Friday CAZ270-278.

Fire Weather Watch from Saturday morning through Saturday evening CAZ274.

Lake Wind Advisory from 5 AM to 11 PM PDT Saturday CAZ072.

Lake Wind Advisory from 11 AM to 11 PM PDT Saturday CAZ073.