.Another warm atmospheric river is expected to push into the Sierra
and western Nevada beginning on Friday. High snow levels and
prolonged heavy rainfall will allow for significant rises on both
mainstem and smaller rivers/streams. This may result in minor to
moderate flooding on some area rivers and streams. Rock falls will
be possible, especially in steep terrain and where soils are already
saturated. Some urban flooding is likely, particularly in low-lying
areas or poor drainage.
...FLOOD WATCH IN EFFECT FROM FRIDAY MORNING THROUGH SATURDAY
* WHAT...River and urban flooding caused by excessive rainfall is
* WHERE...Portions of California and Nevada, including the following
areas, in California, Greater Lake Tahoe Area, Lassen-Eastern
Plumas-Eastern Sierra Counties, Mono County and Surprise Valley
California. In Nevada, Greater Lake Tahoe Area, Greater
Reno-Carson City-Minden Area and Northern Washoe County.
* WHEN...From Friday morning through Saturday evening.
* IMPACTS...Excessive runoff may result in flooding of mainstem
rivers, creeks, streams, and other low-lying and flood-prone
locations. Creeks and streams may rise out of their banks.
Flooding is possible in urban areas and locations with poor
drainage. Low water crossings may be flooded.
Mainstem river flooding is most likely to occur on the East Fork of
the Carson near Gardnerville and the Susan River at Susanville.
Other streams draining significant terrain under approximately 6,500
feet will also be prone to flooding. Out-of-bank flows could result
in road closures, causing travel impacts.
* ADDITIONAL DETAILS...
- High snow levels along with prolonged heavy rainfall on
recently saturated ground and snow pack. Storm total liquid
accumulations of 4 to 7 inches along the Sierra crest, 3 to 5
inches in the Tahoe Basin, and 1.5 to 3.5 inches elsewhere in
the Flood Watch, including the Reno/Carson/Minden area.
- Visit CNRFC.noaa.gov and http://www.weather.gov/safety/flood.
You should monitor later forecasts and be alert for possible Flood
Warnings. Those living in areas prone to flooding should be prepared
to take action should flooding develop.
...Quick Hitting Storm Thursday Followed By A Significant Storm
Expected New Year's Eve Weekend...
A cooler system will bring minor impacts to the area on Thursday.
Snow levels will start out below valley floors during the morning
hours before gradually rising ahead of the next system which will
push into the region Friday. Between 4 to 8 inches of snowfall is
possible along the Sierra Crest with 2 to 4 inches near Lake
Tahoe level. Up to 2 inches of accumulation is possible across
western Nevada foothills with little to no accumulation expected
in the valleys. Nevertheless, some morning commute impacts are
certainly possible. Sierra ridge gusts of 50 to 70 mph is
possible but lower elevation winds should not be a concern.
----------------Details For Next Storm---------------------------
A significant atmospheric river storm will bring another round of
impacts to the region Friday through early Sunday morning. Some
minor flooding will be possible, especially Friday into Saturday.
* Rain and snow: Heavy rain and high elevation snow is anticipated
with this storm with peak rates Saturday and Saturday night.
Liquid totals in the Sierra could reach 5 to 7 inches over a
2-day period, with 2 to 4 inches in the foothills, and 1 to 2
inches across western Nevada.
* Snow levels and character: Snow levels are expected to rise to
8000-8500 feet for around 24 hours during the heaviest
precipitation. Snow levels then begin to fall Saturday afternoon
bringing impacts to most Sierra passes by evening and to Lake
Tahoe and foothill elevations by early Sunday morning. With snow
levels to valley floors by Sunday morning, any lingering showers
will be snow and light accumulations in the valleys cannot be
ruled out. The snow character will be a heavy and wet Sierra
* Hydrology: Significant rises occurred on small streams and a few
mainstem rivers with the atmospheric moisture push on early
Tuesday. The next warm system will lead to additional rises in
rivers and streams Friday and Saturday. Rivers and streams may
respond more quickly then they did Tuesday due to the priming
nature of Monday night into Tuesday's rains. Expect additional
flood impacts in urban and poor drainage areas similar to, or
somewhat worse than those experienced today. Small Creeks and
streams will have major rises on Friday, especially those
draining large areas below ~6500 feet. Currently no mainstem
river flooding is anticipated, but can't be entirely ruled out,
especially if the incoming systems come in wetter and warmer
than currently expected. Stay tuned for forecast updates. River
Forecasts are available at CNRFC.noaa.gov and are updated at
~9am and 3pm.
* Winds: Another round of gusty southwest winds are expected with
this storm, but winds do not look as strong as what we
experienced this morning.