Area Forecast Discussion
Issued by NWS Reno, NV
Issued by NWS Reno, NV
939 FXUS65 KREV 010834 AFDREV Area Forecast Discussion National Weather Service Reno NV 134 AM PDT Mon Sep 1 2025 .KEY MESSAGES... * Above average temperatures with dry conditions for Labor Day. * Areas of smoke and haze may locally impact visibility and air quality the next several days due to fires in the southern Sierra. * Thunderstorm chances return Tuesday through the end of the week. && .DISCUSSION... * A building ridge overhead will allow for above normal temperatures for Labor Day. Afternoon highs will end up around 5 degrees above average. There are minimal chances for showers or storms this afternoon in the eastern Sierra (< 10%). We`re lacking significant moisture as well as any forcing mechanism. But a few Cu buildups are possible along the ridges. * High-resolution HRRR depicts haze areawide with higher chances for heavier surface smoke for Mono, Alpine, Mineral, and Lyon counties this morning due to the Garnet Fire. Smoke later this afternoon and Monday night will depend on how much smoke is produced today on the Garnet Fire. As a side note, the HRRR assumes a constant source of smoke which is not always the case. * Storm chances increase Tuesday through the end of the week, with the best chances for convection on Tuesday (more on that below). But first, Wednesday through next weekend looks to have 10-25% chance for showers and storms each afternoon. However, the model ensembles start to diverge by Wednesday onward in how much moisture remains over the area. For now, we`ll keep current blended guidance given the uncertainty three plus days out. As for the end of the week into next week, there are hints by the ensembles for a Pacific low to impact the area, which would bring increasing winds. * As for Tuesday, we have a combination of increasing moisture from the south (PWATs >90th percentile) and a negatively tilted trough moving through central California. This setup is more of a concern for fire weather (see Fire Weather Section below); given the upper air support, dry lightning, and faster storm motions. But another thing to consider is that these storms maybe more of a hybrid variety because of the moisture in place. Storms will be capable of strong outflows, small hail, locally heavy rain, and dry lightning. -McKellar && .AVIATION... * Smoke filtering in from the Garnet Fire may bring periods of visibility reduction at terminal KMMH. Any other restrictions to visibility will be primarily slantwise due to haze aloft. Otherwise, VFR conditions will prevail with light winds. * Mostly dry conditions today across the region today. Storm chances increase Tuesday through the remainder of the week. * High density altitudes may become a problem in western NV today. -McKellar && .FIRE WEATHER... Warm and dry conditions along with generally poor overnight recoveries persist today. There is a very low chance less than 10% for showers and thunderstorms over Mono, Alpine and Mineral counties this afternoon. A wetter pattern returns on Tuesday, but with a twist. Another plume of monsoonal moisture slips into the region with PWs generally over 0.75 inches, which matches with the 90th percentile for this time of the year. However, an upper negatively tilted trough to our west moving onshore into northern California will enhance the speed of storms to the north. Surface-based instability aligns with a mid to upper level jet streak resulting in high confidence in the development of storms across the Sierra, NE CA and western NV. Also seen in the agreement of hi-res models. The main hazards will be dry lightning, small hail, gusty outflow winds greater than 45 mph and brief periods of moderate to heavy rain. The gusty outflow winds could exacerbate any new fire ignitions from lightning, especially over western NV, where there is a 20-40% of wind gusts exceeding 35 mph per NBM guidance. The potential for dry lightning remains for much of the week as we don`t totally dry out, but the probabilities drop to 10-25%. However, this weekend we may have another upper trough, drier, but with potential for wind gusts exceeding 30 mph, especially for mountain areas, northwestern NV and northeast CA. -HC && .REV Watches/Warnings/Advisories... NV...None. CA...None. && $$