textproduct: Reno

KEY MESSAGES

* A heatwave will impact outdoor activities each afternoon through the weekend, but a cooling trend mitigates heat impacts next week. * Showers and storms return each afternoon in the E. Sierra and far W Nevada, with increasing chances and coverage next week.

* Increased breezes elevate fire and recreation concerns Sunday and Monday afternoons.

DISCUSSION

Our ongoing heatwave is expected to last through the weekend as daytime highs reach the 90s and triple digits each afternoon away from higher Sierra elevations. The most dangerous heat continues to reside across lower W Nevada valleys where nighttime lows in the upper 60s to low 70s provide little to no relief from the 100-105F daytime heat. Moreover, cloud debris from afternoon convection may lead to slightly warmer nighttime lows, further compounding heat impacts. Fortunately, a much-needed cooling trend next week will lower temperatures to seasonal averages and mitigate heat impacts.

Strong surface heating beneath deep mid-level moisture will renew a low probability (10-30% chance) of showers and isolated t-storms this afternoon, once again favoring the Sierra from Tahoe southward and far W Nevada. However, stronger W/SW breezes should increase low- level convergence from Lassen Co into N Washoe Co today, which when combined with shallow instability aloft, warrants at least a 15% chance of showers this afternoon in this area. A deep, well-mixed subcloud layer with steep lapse rates favor strong outflow gusts as the primary hazard with both showers and t-storms. Given that a similar environment supported 45-55 mph outflow gusts yesterday afternoon, the expectation is for outflow gusts to be in this range this afternoon. Other potential hazards include occasional lightning and brief heavy rainfall (mainly in Mono County).

Shower and thunderstorm coverage will focus across Mono-S.Lyon- Mineral counties Sunday afternoon, with probabilities increasing to 20-40%. Farther north, chances decrease to 10% or less as drier air filters in. Strong outflow gusts remain the primary hazard, but there is a very low chance (5% or less) of localized flash flooding in the Mono-S.Lyon-E.Mineral Co vicinity where antecedent rainfall, abundant moisture, and slower storm motions overlap. After Sunday, chances decrease and remain confined to areas south of US-50.

As alluded to above, W/SW breezes will increase each afternoon this weekend before peaking on Monday in response to a deepening eastern Pacific trough. These increased breezes will heighten fire concerns Sunday and Monday afternoons from the OR border south along the Sierra Front, as well as make more more choppy lake waters. Winds shift to N/NW during the overnight hours, directing smoke from PacNW wildfires into the region and potentially degrading air quality north of Reno. Late next week, the weather pattern becomes more favorable for daily showers and thunderstorms, but exact details are uncertain at this point.

-Salas

AVIATION

Showers and thunderstorms remain the primary weather concern today, particularly at KMMH-KBAN where chances (20-30%) are greatest in the 20-03Z timeframe. Elsewhere, chances reduce to 10-20% at KTVL-KTRK and KRNO-KCXP-KMEV. Sudden and erratic outflow gusts up to 45 kts, brief heavy rain/MVFR conditions, and occasional lightning are among potential hazards with showers and storms. Additional showers and storms are expected Sunday afternoon, once again favoring KMMH-KBAN where odds increase to 20-40%.

Otherwise, widespread VFR conditions and typical afternoon breezes prevail this weekend with continued heat posing density altitude concerns.

-Salas

REV Watches/Warnings/Advisories

NV...Heat Advisory until 8 AM PDT Monday NVZ001-003-005.

Extreme Heat Warning until 8 AM PDT Monday NVZ004.

CA...Heat Advisory until 8 AM PDT Monday CAZ070-071.