textproduct: Reno

KEY MESSAGES

* Critical fire weather and hazardous lake conditions continue through this evening due to strong southwest winds.

* Much colder temperatures along with rain and mountain snow shower chances begin next week in the wake of a cold front passage.

* Moisture associated with Tropical Storm Rachel will boost shower chances Sunday and Monday.

DISCUSSION

According to the latest surface observations, a cold front, associated with an upper trough over the western CONUS, has crossed into NE California and far NW Nevada this afternoon. Ahead of this frontal passage, winds through this evening will gust up to around 35-45 mph in the lower valleys while the Sierra ridges will gust up to around 70-80 mph going through the overnight hours. These winds in conjunction with low relative humidity values (~15-25%) will allow for critical fire weather concerns through this evening in portions of the Eastern Sierra as well as W.Nevada (see the Red Flag Warning currently in effect and the Fire Weather section for more details). These increased winds will cause choppy conditions on area lakes today (refer to the ongoing Lake Wind Advisory for more details), so please keep this in mind if you have outdoor recreational plans. Blowing dust is also possible near desert sinks and playas today. Be prepared for a colder night as the forecast calls for overnight lows around the 40 degree mark in W.Nevada with Sierra communities near or slightly below the freezing mark.

For Sunday, forecast guidance shows the upper trough progressing eastward and continuing the trend toward cooler temperatures behind the cold front passage. W.Nevada valleys will have highs in the low to mid-60s with Sierra communities in the mid-50s to around the 60 degree mark. Forecast guidance also shows Tropical Storm Rachel making its way across SE California early Sunday, which will allow for 15-25% shower chances within the region in the morning that increase up to 30-50% by Sunday afternoon. By late Sunday and going through Monday, shower chances increase to 60-80% especially for areas along and south of I-80 as the core of the system passes well off to east. The latest QPF values through Sunday and Monday range from a trace to around 0.5 inches in S.Mono and SE Mineral Counties. Snow levels are forecast to start around 8.5-9.5 kft on Sunday, fall to around 6-7 kft by Monday morning, and then rise up to around 7-7.5 kft on Monday afternoon. The latest NBM run shows a 60-80% probability of the highest peaks of the Sierra with 4+ inches of snowfall by Tuesday morning. There's also a 10-25% for around 1 inch of snow at lake level in the Tahoe region. While severe weather is not anticipated, there around a 10% or less chance for isolated thunderstorms on both days south of I-80. The latest WPC Excessive Rainfall Outlook shows a marginal (5%) risk for heavy rainfall that could lead to localized flash flooding on Monday in portions of W.Nevada south of I-80. There's still some uncertainty with this upcoming wetter and colder system, so please continue to watch for forecast updates especially if you have holiday plans.

The cooling trend does continue through Monday with the system allowing for colder air to flow in from the north. Daytime temperatures are forecast to be around 15-20 degrees below seasonal normals on Monday. Monday night into early Tuesday will be extra chilly for mid-October with overnight lows in the low to mid-30s for W.Nevada valleys and in the upper teens to mid-20s range for the Sierra communities. Please prepare yourself and your property now for this upcoming cold over the next few nights. On Tuesday, the moisture with the system moves eastward as forecast guidance begins to trend warmer and drier through the rest of the week. -078

AVIATION

VFR conditions are expected across all area TAF sites today and tonight. Ahead of an approaching cold front, southwest winds gusting up to between 30-40 kts are expected through 11/03Z at Sierra Front terminals and through 11/09Z at Sierra terminals. Sierra ridge top winds gusting up to 60-70 kts are forecast through 11/12Z, so expect mountain wave turbulence and LLWS.

Cloud cover and shower chances increase on Sunday in the wake of the cold front passage. By Sunday night into Monday, moisture from Tropical Storm Rachel allows shower and high elevation snow chances to increase even further. -078

FIRE WEATHER

The seasons first potent cold front brings increasing southwest winds today as it moves through NE California and W.Nevada. Winds combined with low humidity and dry conditions will allow periods of critical fire weather conditions.

TODAY: Winds peak this 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% this afternoon. Red Flag Warnings remain in effect through this evening due to strong winds and low RH 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, temperatures cool down drastically going into next week. High temperatures on Monday are forecast to be in the 50s for W. Nevada and in the 40s for the 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 good uncertainty at this time, but the overall trend has been wetter. -HRICH/078

REV Watches/Warnings/Advisories

NV...Red Flag Warning until 9 PM PDT this evening NVZ420-421-423-429.

Lake Wind Advisory until 11 PM PDT this evening NVZ001>004.

CA...Red Flag Warning until 9 PM PDT this evening CAZ274.

Lake Wind Advisory until 11 PM PDT this evening CAZ072-073.