textproduct: Reno

KEY MESSAGES

* Widespread strong winds today and possibly again on Sunday. Likely impacts for both road and air travel. Localized fire weather concerns in the Eastern Sierra.

* Showers including mountain snow showers this afternoon and evening. Heavier rains likely Saturday night through Sunday that could lead to localized flooding concerns.

* Another storm or two could bring significant rain and snow Tuesday into Christmas Day, but confidence remains mixed.

DISCUSSION

* Welp, it's still looking rather busy weather-wise over the coming 7 days with a series of Pacific storms including atmospheric rivers. Anyone with holiday travel plans by road and by air should keep an eye on the forecast and adjust accordingly.

* Wind: Today & Sunday are the windiest days in what will be a breezy period through most of next week. Rather impressive zonal jet moving though the Pac NW & N Calif coupled with increasing pre-frontal gradient will yield widespread strong winds today. Given W/SW flow orientation and 700mb speeds 50-60 knots, wave breaking and downslope enhancement is possible today along Hwy 395 from Susanville-Reno-Mammoth where we have wind advisories posted. Low humidity could create fire weather concerns, and it won't be a pretty day for flying either. For Sunday another plume of high speed air aloft comes in with an moderate atmospheric river. RRFS showing 700mb winds over 70 knots. Wow. So if we end up being more shadowed on Sunday (more T than V from the AR IVT) we could have another round of rather strong, impactful winds regionwide.

* Rain: While today will generally be dry, high-res models show showers moving in post-front this afternoon into the evening. Should be mostly rain except the Sierra peaks, however NBM and HREF are showing potential for snow p-type at passes if we see heavier precip rates. Rapid p-type changes can catch travelers off- guard. Saturday night through Sunday is still the main show for heavy rain with pronounced atmospheric river signal and high rain- snow lines (8000'+). QPF in the mountains is similar to guidance 24 hours ago but a little less in lee-side areas of W Nevada (more periods of shadowing/wind perhaps?). Highest risk of heavy rains and potential flooding remains the Tahoe Basin into NE Calif where models stall/pivot the main AR band for the longest time. If there were an area to underperform it would be the Eastern Sierra/Mono Co based on further north trajectories of the AR plume.

* Snow: Precip never totally shuts off in the mountains but does lessen in intensity Monday into early Tuesday. Starting Monday night the snow lines drop enough were we could start seeing more regular impacts to travel over the passes. Simulations showing one or two additional notable and cooler storms moving in Tuesday evening through Christmas Day. Lots of variables here with models digging troughs off the coast which sometimes can result in a southward shift of the heaviest precip, wide boom/bust scenarios, and an increased airing of grievances next week. That all being said, QPF and snowfall in the NBM 50th percentiles has gone up quite a bit vs 24 hours ago for Wednesday-Thursday. Potentially good news for the snowpack and local "white Christmas" stats, but not so good news for those trying to get someplace at the last minute before Christmas.

-Chris

AVIATION

* Buckle up, it's not exactly going to be a smooth day for flying with strong winds, mountain waves, rotors, and low level wind shear all on the table today into this evening.

* Strong W/SW flow with RRFS 700mb winds to 60 knots forecast today and tonight, associated with an upper jet and approaching cold front. 80% chance of seeing peak gusts at least 35 knots at most airfields including RNO/CXP/MEV, TRK/TVL, MMH with 40-60% at NFL/SVE/HTH. High-end gusts over 50 knots cannot be ruled out in more wind prone areas along Hwy 395. NBM has 40-60% chances of 50 knot peak gusts at RNO and MMH for example. Another round of strong winds is looking likely on Sunday as well.

* With that front today, we will have showers develop this afternoon and evening. Mainly in the mountains from SVE to TRK/TVL with potential for MVFR-IFR conditions in rain. Can't rule out a rain/snow mix but low confidence. For RNO/CXP/MEV, light showers are possible (40% chance) but visibility/ceilings look to remain VFR. MMH misses out on this one, just wind for them.

* Additional showers possible Saturday but mainly light intensity. Winds should be less robust as well.

-Chris

FIRE WEATHER

* There is concern over areas of critical wind and low humidity in the Eastern Sierra today, specifically fire weather zones CA274 and NV421.

* Latest NBM and HREF guidance suggest 1-3 hours of critical conditions especially along Hwys 395 & 6 where W/SW winds could gust over 50 MPH this afternoon (see Wind Advisory). Humidity values already in the teens as of this writing and it's been rather dry lately with well above normal ERC levels.

* No Red Flag Warning at this time due to limited spatial extent and duration of critical conditions however we will highlight the risk in the FWF and our morning briefing email.

-Chris

HYDROLOGY

Repost of yesterdays hydro section. This will be updated with the daytime discussion.

* Moderate to heavy rains will lead to significant rises on rivers and streams Sunday into Monday most notably from the Tahoe Basin north through Lassen County, but no mainstem river flooding is currently expected.

* Minor flooding of urban and poor drainage areas and rockfall are possible during any prolonged periods of high intensity rainfall. Watch for additional rises near Christmas Eve and possible flooding concerns especially in drainages with large mountain drainages below about 6,000 feet, like the Susan River for example.

* You can find river forecasts updated twice daily at: www.cnrfc.noaa.gov

-Tim

REV Watches/Warnings/Advisories

NV...Wind Advisory until 4 AM PST Saturday NVZ002-003-005.

Lake Wind Advisory until 4 AM PST early this morning NVZ002.

Lake Wind Advisory until 4 AM PST Saturday NVZ004.

CA...Wind Advisory until 4 AM PST Saturday CAZ070>072.

Lake Wind Advisory until 4 AM PST early this morning CAZ072.