textproduct: Reno

KEY MESSAGES

* Increased breezes elevate fire and recreation concerns this afternoon, with areas of smoke continuing over parts of northeast CA, northwest and far western NV from ongoing fires.

* Isolated showers and thunderstorms return this afternoon south of Highway 50, with increasing storm chances and coverage by midweek.

* Heat eases up but lingers through Tuesday for west central NV, followed by a more notable cooling for the rest of this week.

DISCUSSION

The multi-day heat wave is winding down with the high pressure ridge retreating from the Great Basin to the Four Corners region, and losing some of its strength. Some valleys in west central NV could still see highs edge above 100 degrees today with isolated Major HeatRisk, but overall impacts will decrease so all heat- related warnings and advisories have ended. Temperatures take a more notable downward trend from Tuesday through the end of this week, with Thursday-Friday expected to be the coolest days when highs settle to the 80s for most lower elevations and 70s for Sierra communities.

This afternoon a weak trough near the Pacific NW coast will bring increased breezes and continued dry conditions, leading to elevated fire weather concerns as highlighted in the Fire Weather section below. Isolated shower and t-storm activity this afternoon remains limited to Mono, Mineral and southern Lyon counties, with a few cells pushing into southern and eastern Churchill County into the early evening.

Smoke and haze will continue over northeast CA-northwest NV today, with the most widespread impacts near the OR border through this morning. Areas near and north of Reno-Sparks and extending east to Fernley and Fallon will also be affected by haze and smoke from the Bug and Fred Mountain fires this morning, with additional smoke production likely this afternoon as temperatures warm up and humidity decreases.

From Tuesday through Thursday, deeper moisture (PW values 0.6-0.9", with some areas near or above 1.0" for Wed-Thurs) advances northward across western NV and eastern CA, increasing the risk for mainly afternoon-evening showers and t-storms. An area of low pressure forming near the CA coast is projected to provide additional forcing, leading to stronger storms with a heavy rainfall/flash flood threat especially Wednesday-Thursday. The presence of this low could keep shower activity and isolated lightning going through the overnight/morning periods from late Tuesday into Thursday.

By the end of this week, shower and storm activity starts to decrease, with lower chances overall by next weekend. The medium range guidance shows a wider spread of scenarios so confidence is lower on how quickly the storm chances or coverage decreases. Residual moisture and weak upper level disturbances appear to be in play to prevent a definite end to shower or t-storm chances next weekend. MJD

AVIATION

Drier SW-W breezes with gusts 20-25 kt will shift the risk of PM showers and t-storms away from the main terminals today, except for KMMH which has about a 15% chance of isolated showers/thunder affecting the terminal mainly between 21-01Z with brief light rain and occasional gusts 25-30 kt being the main effects. For Tuesday, the shower and t-storm chances increase to around 25% at KMMH, near 15% for KRNO-KCXP-KMEV but remain less than 10% for KTRK-KTVL. Again, brief rain and gusty winds to 30 kt remain the primary threats with Tuesday's storms, mainly between 20-02Z. More widespread showers and storms are likely to bring more significant impacts to all the main terminals by Wednesday afternoon.

Smoke filtering into northwest NV and northeast CA from wildfires in Oregon continues to reduce slantwise visibilities across those areas through at least Tuesday. The peak smoke concentration favors the overnight/morning hours with some improvement each afternoon when breezes increase. Elsewhere, the ongoing fires north of Reno will produce areas of reduced slantwise visibility in this area, although at KRNO itself VFR conditions are expected to prevail. MJD

FIRE WEATHER

Westerly gusts of 25-35 mph will and RH reductions to 7-15% will promote a 2-5 hour period of near-critical conditions this afternoon from far NE California and NW Nevada -- including ongoing wildfires in Washoe and Douglas counties. Winds become breezy again Tuesday afternoon, but will be weaker than today's winds. Nighttime recoveries remain poor for most areas in NE California and W Nevada as RH struggles to exceed 30-40%, extending burn periods into the overnight hours.

Low probabilities (10-20%) of showers and isolated thunderstorms return to Mono, S.Lyon, Mineral, and S.Churchill counties this afternoon. Attendant hazards include occasional lightning and new fire starts, and strong outflow gusts of 50+ mph. Elsewhere, drier air aloft and increased breezes should limit vertical plume growth and attendant hazards this afternoon despite an unstable airmass. However, increasing moisture aloft and slightly weaker mixed-layer winds will increase the potential for more impactful plume activity (i.e., locally strong near-fire winds, sudden/erratic downdraft gusts from plume collapses) with the more intense wildfires Tuesday afternoon.

An ongoing ridge breakdown sequence culminates in much cooler temperatures, higher daytime humidity, and improved nighttime recoveries from Wednesday onward. However, this pattern change also directs deeper moisture into the region, increasing the potential and coverage of showers and a mix of wet and dry thunderstorms from Tuesday to Friday. One benefit of abundant moisture is a higher likelihood of wetting rains on new/existing wildfires, but it also encourages heavy rain and flash flooding impacts to operations. Isolated dry lightning and new fire starts will also be possible with thunderstorm activity this week. -Salas

REV Watches/Warnings/Advisories

NV...None. CA...None.