990 FXUS65 KREV 241951 AFDREV Area Forecast Discussion National Weather Service Reno NV 1251 PM PDT Thu Jul 24 2025 .KEY MESSAGES... * Thunderstorm activity increases this afternoon, continuing each day through Sunday. Potential impacts include heavy downpours and flooding, strong outflows, small hail, and lightning. * Cooler than normal temperatures expected for the rest of the week and the weekend. * A gradual warming and drying trend returns early next week, bringing highs up to near or slightly above normal. && .DISCUSSION... An Aleutian low has taken residence, keeping a troughing pattern just off the Pacific coast. This is going to be a factor in our weather through the weekend, but the main feature for today is a separate low tracking into the central coast of California for today. The influence of the larger Aleutian low will help to determine the steering on the California coastal low, which will be absorbed into the troughing pattern as it migrates northeast over the Central Valley. What does this mean for the end of the week into the weekend, and beyond? Let`s dig in! The central California low`s position will allow for upper level flow from the southeast toward the northwest. This upper flow will allow for slower storm motions(10-25 kts) today, which could produce slow-moving and training showers that can produce heavy rainfall. If these showers and storms produce heavy rainfall (0.6-0.9 inches of PWAT can do that here), we could see localized flooding issues. Main concerns for storm hazard include heavy rainfall, flooding (especially if storms set up near burn scars), small hail, gusty outflow winds and frequent lightning. The lightning threat today could include lightning strikes outside of wet cores that have potential to spark new fire starts. Showers and some storms also have a bit of staying power into tonight according to CAMs, although the hazards of lightning and small hail will taper as we lose daytime heating. Areas of focus will include northeastern California where chances range 35-65%. Further south, near the Tahoe Basin and into the US-395 corridor, chances will be around 25-40%. South of the Tahoe Basin, basically along and south of US-50 and southward into Mono County, chances will range 35-50%. For the US-95 corridor through Fallon and Yerington, chances today around 10-15%. For Friday, similar areas will see increasing chances as the low tracks inland and has a closer proximity to the Sierra. Chances for the Reno-Carson City-Minden and Tahoe areas will range 55-65%. The Sierra will see chances 55-60%, while the Basin and Range will see shower chances along the US-95 corridor reaching 40-45%. We will have a better tap into the moisture source, so the potential for heavy rains and flooding increases likewise. Particularly if showers produce heavier rains today, antecedent soil moisture could increase the likelihood of localized areas of saturated soils that would be more productive in regards to flood potential. The threat for dry lightning strikes will be more limited in spatial extent for Friday, primarily found along the southern Sierra and then the leeside valleys along the Sierra Front, and northeastward through the Basin and Range up to the Oregon border. Saturday the threat lingers for showers and storms that can produce heavy rains, with chances and areas similar to Friday. The difference here will be the shower activity is beginning to shift eastward as the main trough begins to pick the inland low up into the flow. Monday, the trough lingers, but shower chances dwindle as the main forcing of the low becomes removed from the area. That pesky, persistent Aleutian low will keep things interesting as we look to the close of July. Showers are possible along the Oregon border and also to the east toward the Utah/Nevada border. Temperatures look to nudge slightly upward, but still hanging around seasonal averages to close out the month. HRICH && .AVIATION... * Clouds will continue to build this afternoon as showers and storms arrive for today. All terminals will have a 30-50% chance for a shower or storm in the vicinity. Chances increase for Friday and Saturday, with 40-60% chances for most terminals. Lower chances for KNFL of around 10-20% through the weekend. Some showers may linger into the overnight tonight, but the threat will shift from thunder to mostly rain. Hazards today into the weekend may include erratic and gusty outflow winds, frequent lightning, and heavy rainfall that may reduce visibility, especially for mountain terrain. HRICH && .FIRE WEATHER... * Thunderstorm chances are expected each day through the weekend, with widespread coverage today through Saturday. Minimum relative humidity appears to increase from 30-40% today to 50-75% by Saturday. The best chances for dry lightning will be Sunday once humidity starts to erode over the leeside valleys and Basin and Range. Frequent lightning can be expected each day through Saturday. However, with heavy rain expected, this could hinder the development of new fires. Regardless, new ignitions due to lightning are possible away from rain cores. HRICH/Giralte && .REV Watches/Warnings/Advisories... NV...None. CA...None. && $$