547 FXUS65 KREV 221855 AFDREVArea Forecast Discussion National Weather Service Reno NV 1155 AM PDT Mon Sep 22 2025
.KEY MESSAGES...
* Near to slightly above average temperatures are expected through much of the upcoming week.
* Another weather system may bring shower and thunderstorm chances again late Wednesday through Thursday, mainly from I-80 southward.
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.DISCUSSION...
* High pressure ridge will set up over northern CA/NV through Tuesday night as a cut-off low pressure approaches the southern CA coast. This will keep the region dry with generally light east winds and warm daytime temperatures a few degrees above average for early fall season (80s for lower elevations, mid 70s-near 80 for Sierra valleys) through the next couple of days. Latest guidance is trending toward the ridge hanging on through much of Wednesday as well, resulting in a delayed arrival of precipitation associated with the low.
* With these latest timing adjustments, the upper low is now poised to move into south central CA with onset of showers reaching the eastern Sierra by late afternoon or evening on Wednesday. Bands of showers with possibly a few embedded t-storms could make a northward progression to the Tahoe basin and to near I-80 in far western NV overnight into Thursday morning. The best overall chances (30-50% except up to 60% near the Sierra crest) for showers and t-storms favor Alpine-Mono counties and southern portions of Douglas-Lyon- Mineral counties for much of Thursday with a marginal risk (5-15%) for locally heavy rainfall. Lesser precip chances (15-30%) continue Thursday afternoon-evening for the remainder of the eastern Sierra and western NV mainly from I-80 southward.
* From Friday through the upcoming weekend, the low is showing signs of retreating farther south again with a re-establishment of the high pressure ridge over northern CA/NV. This will lead to a generally drier weather pattern again with warmer than average conditions prevailing, although low-end shower chances may linger near the eastern Sierra. Longer range guidance hints at a modest cooling toward the end of September and slight chances of showers again, but a full blown blast of fall weather isn`t showing up even into the first few days of October. MJD
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.AVIATION...
* Main terminals through Wednesday: VFR conditions with mainly light winds (gusts below 20 kt) prevail. Only exception is patchy fog around KTRK between 10-16Z each morning through Wednesday with periods of MVFR to LIFR conditions. If enough east flow develops over the Sierra the next couple of nights, the extent/duration of this fog would decrease compared to recent days. MJD
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.REV Watches/Warnings/Advisories... NV...None. CA...None. &&
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NWS REV Office Area Forecast Discussion