textproduct: Reno

KEY MESSAGES

* A downward temperature trend starts today with seasonal temperatures expected by early next week.

* Increasing westerly gusts today and Saturday lead to elevated to near critical fire conditions for northeast CA and northwest NV.

* Isolated shower and thunderstorm potential returns for the NV Basin and Range, and south of US-50 this afternoon into the weekend.

DISCUSSION

The broad upper-level ridge over the Four Corners region will continue to influence the weather pattern, maintaining a southerly flow of monsoonal moisture into the region. A weak upper-level trough will move across northern California and Oregon today through Saturday, bringing increased winds and slightly modifying the airmass, though temperatures remain above seasonal averages. Temperatures will be slowly decreasing this weekend with afternoon highs in the 90s for western NV/NE CA, and upper 70s to mid 80s for Sierra communities.

West to southwest winds will increase across the region this afternoon and peaking on Saturday. Afternoon gusts of 25-35 mph are expected, particularly for northeastern California and northern Washoe County, with isolated gusts up to 40 mph possible in exposed areas. These conditions, coupled with low relative humidity, will lead to elevated to critical fire weather conditions, especially on Saturday.

Monsoonal moisture will continue to advect northward into the region, with PWAT values around 0.6-0.8 inches. This moisture, combined with daytime heating, will lead to isolated showers and thunderstorms. Chances are low (1-10%) today and confined to the eastern Sierra and western Nevada Basin and Range. By Saturday, chances increase to 10-40% and become more widespread, especially for the eastern Sierra and the Nevada Basin and Range. Instability remains with marginal MUCAPE 100-500 J/kg, but strong DCAPE to 1000 J/kg, suggesting that any storms could produce gusty outflow winds up to 40 mph, brief heavy rain, small hail and frequent lightning. On Sunday, conditions begin to dry out slightly, with lower chances for convection 10-20% across the NV Basin and Range.

The pattern next week remains dominated by a persistent upper-level ridge over the Southwest and a longwave trough in the PacNW. This will continue to support seasonal temperatures. Highs will generally remain in the low to mid-90s for western NV and northeast CA valleys, and in the upper 70s to mid-80s for Sierra communities. Monsoonal moisture will continue to stream northward around the western flank of the ridge, leading to very low chances (~5%) of isolated, diurnally-driven showers and thunderstorms, primarily over the higher terrain and NV Basin and Range.

-HC

AVIATION

VFR conditions continue with mid to high level clouds through the forecast period. SHRA/TSRA has a 5-10% chance to develop near KMMH/KHTH/KBAN this afternoon, increasing to 10-20% for Saturday. Winds increase this afternoon with westerly gusts to around 25 kts. Then on Saturday gusts potentially increase to 30-35 kts in the afternoon.

-HC

FIRE WEATHER

* Elevated fire risk today with an increase of west to southwest winds of 20-30 mph and min RH of 10-20% for eastern Lassen, the Surprise Valley, northern Washoe, the Sierra Front, and portions of Mono counties. Conditions deteriorate to critical by Saturday over northeast CA and northwest NV with gusts to 30-35 mph with a 10-60% chance of exceeding 40 mph in isolated locations including the Surprise Valley, and similar min RH compared to Friday. Critical conditions are expected to last for 3-6 hours between Saturday afternoon and early evening. For these reasons, we issued a Fire Weather Watch from 11 AM through 11 PM Saturday for northern Washoe and eastern Lassen counties, and Surprise Valley in Modoc County. Other areas in western NV and Mono County will see gusts of 25-30 mph on Saturday, creating elevated fire weather conditions in the afternoon.

-HC/HRICH

REV Watches/Warnings/Advisories

NV...Fire Weather Watch from Saturday morning through Saturday evening NVZ458.

CA...Fire Weather Watch from Saturday morning through Saturday evening CAZ270-278.