textproduct: Reno

KEY MESSAGES

* Strong southwest winds will develop today and peak Saturday, leading to critical fire weather conditions and hazardous lake conditions.

* A potent cold front will bring a drastic pattern change with significant cooling, widespread rain, and mountain snow showers Sunday into early next week.

* Remnant moisture from Tropical Storm Rachel will enhance precipitation chances, especially south of I-80.

DISCUSSION

Today will be the last day of well above average temperatures. Highs are expected to reach the mid-80s to low-90s in western Nevada and northeast California valleys, with eastern Sierra communities seeing mid-70s to near 80 degrees. As an upper level trough approaches, southwest winds will increase by early afternoon. Gusts of 25-35 mph are likely along the Sierra Front, northwest NV, and northeast CA. These winds, combined with very dry antecedent conditions and minimum relative humidity values of 12-18%, will lead to critical fire weather conditions. Red Flag Warnings are in effect for portions of northeast CA and northwest NV this afternoon and evening.

The cold front will move through the area on Saturday, bringing widespread strong southwest winds. Gusts of 35-45 mph are likely across much of the region, with eastern Sierra ridgetops and western NV peaks experiencing gusts between 70-80 mph. These strong winds, coupled with continued dry conditions in many areas (though RH will begin to increase in NE CA/far NW NV), will maintain critical fire weather concerns, especially in the inner basin and range, Sierra Front, and Mono County. Hazardous boating conditions are expected on area lakes, including Lake Tahoe and Pyramid Lake, with Lake Wind Advisories in effect. Temperatures will begin to drop, with highs in the low-70s for western NV and low-60s for eastern Sierra.

A significant cool down is expected behind the front. High temperatures will drop by as much as 20-25 degrees from Friday to Sunday, settling 10-15 degrees below average. Western NV valleys will see highs in the low 60s, while eastern Sierra communities will only reach the low 50s. The main upper low will dig into the Great Basin, drawing significant moisture northward from the remnants of Tropical Storm Rachel. This will lead to widespread precipitation chances (50-80%), primarily south of I-80. Snow levels are expected to range from 7500-8500'. Showers are likely to begin Sunday morning in the Sierra, spreading eastward into western NV through the day and night.

The upper low will continue to influence the region on Monday, maintaining widespread precipitation chances (50-80%) across the forecast area, with the highest totals expected in the Sierra and western NV south of I-80. Snow levels will remain variable, generally in the 6500-8000' range, leading to accumulating snow in the higher elevations. Temperatures will remain well below average, with overnight lows dropping below freezing in many Sierra valleys (20s-30s) and a 50-60% chance of subfreezing temperatures in northeast CA and western NV valleys.

By Tuesday, the upper low is forecast to slowly lift northeastward, with precipitation chances gradually decreasing. A gradual warming trend will begin as ridging starts to build in from the west. For Wednesday onward, we return to drier and warmer conditions. Temperatures will steadily climb back to near- average values by the end of the week. Overnight lows will still be chilly, especially in the Sierra, but the widespread precipitation threat will diminish significantly.

-Justin

AVIATION

VFR prevails today. SW-W winds increase this afternoon with gusts of 20-30 kt, producing mountain wave turbulence along and east of the Sierra. Surface winds ease this evening, but SW winds of 35-45 kt at FL100 favor LLWS overnight into Saturday morning. Looking ahead to Saturday, expect sfc winds to increase out of the SW with gusts up to 25-40 kt for Sierra and Sierra Front terminals. These winds will bring another round of LLWS and mountain wave turbulence, especially Saturday morning.

-Justin

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 conditions may produce periods of critical fire weather conditions both days.

TODAY: Afternoon gusts will reach 25-35 mph as minimum RH falls to 12-18%. 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 increasing confidence in the strong winds and low RH, we have upgraded our Fire Weather Watches to Red Flag Warnings 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 upper 50s/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.

-McKellar/Justin

REV Watches/Warnings/Advisories

NV...Red Flag Warning until 9 PM PDT this evening NVZ458.

Red Flag Warning from 11 AM to 9 PM PDT Saturday NVZ420-421-423- 429.

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

Lake Wind Advisory from 9 PM to 11 PM PDT Saturday NVZ001>004.

CA...Red Flag Warning until 9 PM PDT this evening CAZ270-278.

Red Flag Warning from 11 AM to 9 PM PDT Saturday CAZ274.

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

Lake Wind Advisory from 9 PM to 11 PM PDT Saturday CAZ072-073.