Area Forecast Discussion
Issued by NWS Reno, NV

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FXUS65 KREV 141011

Area Forecast Discussion
National Weather Service Reno NV
311 AM PDT Wed Mar 14 2018


After a brief lull in snow activity, another round of light to
moderate snow is expected in the Sierra this afternoon and
evening. A stronger and colder storm moves into the region by
Thursday evening and continues through Saturday morning. This
storm will produce additional periods of heavy snow in the Sierra
with some snow accumulation also possible for lower elevations.
Showers continue through Sunday, then conditions become much
drier through Tuesday morning ahead of the next storm system.


.SHORT TERM...This morning through Thursday Morning...

Snow and shower activity has decreased early this morning behind
the initial wave. Upstream Radar and observations show the
precipitation field expanding again in the upslope area east of
Sacramento as water vapor outlines the next wave moving into
towards the California coast at the time of writing this.

Expect snow levels to continue to fall through this morning as the
cold-core of the low moves over the region. Currently, snow levels
are around 5000-5500 feet and should be 4000-4500 feet through
the morning and early afternoon hours today. The next front will
drop them further this evening to pretty much all valley floors.

Light to moderate showers will continue as instability increases
due to steepening lapse rates. Some isolated convection is
possible again this afternoon as the wave moves into the
California interior increasing surface instability. Some showers
associated with thunderstorms could be quite heavy resulting in
rapid reductions to visibility. More widespread Sierra snow is
expected by early afternoon. This wave is more focused towards
the Tahoe Basin through Mono County, and should move rapidly
through western Nevada by late this evening with showers tapering

Additional accumulations from this morning through Thursday
morning are expected to be up to another foot along the Sierra
Crest down to another 3 to 6 inches around Lake Tahoe level. Up to
4 inches will be possible around Mammoth while only up to an inch
for western Nevada. Accumulations for lower valleys during the
daytime hours will be difficult due to the higher sun angle. The
"best" chances for slick conditions today in western Nevada would
follow brief, more-intense shower activity. Finally, convection
will complicate snow totals. There could be areas where convective
cloud elements train over one location resulting in heavier snow
accumulations; mainly a very isolated threat for the Sierra. Boyd

.LONG TERM...Thursday Afternoon through Tuesday...

Minor changes were made to the portion of the forecast that
encompasses the next part of this broader storm system...Thursday
night into early reflect a few small changes that
models are now producing.

The operational models have shown a slight decrease in QPF over the
northern half of the forecast area starting Friday as the primary
jet...and its forcing...drops farther south and puts the
spotlight on the Mono County area for heavy snowfall Friday and
Friday night.

There remains some troubling sings with this system...however.
The decrease in QPF is the overriding one...but the shift to
better forcing over the far southern areas and to the south of the
forecast area is also starting to cause some consternation. As
such...we will leave the current configuration of the
watches/warnings/advisories and not plan any upgrades at this

The decrease in QPF is tied to the lack of a deep moisture tap with
this part of the overall storm system. Looking at some tools we have
for deep moisture plumes...that plume gets shunted more to south
into southern California with this part of the system. But...there
is still a good amount of precipitation that develops thanks to the
instability and highly dynamic nature of this low. The instability
continues to point toward a likelihood of isolated thunderstorms
over much of western Nevada and parts of northeast California both
Thursday and Friday.

Instead of noting snow totals here...check the latest winter weather
products as these totals will change as we move closer to this part
of the storm.

Showers linger Saturday as the low opens into the trough and
progresses slowly east. There are likely to be some lingering
showers in the higher elevations Sunday as well...but drying in the

A weak short wave ridge tries to develop Monday. This should make
for a dry day...but still below normal temperatures...ahead of the
next developing storm.

The ECMWF and GFS differ on the location of the next storm...and
thus the timing of the start of precipitation...but both do try to
bring at least some light precipitation into the Sierra by early
Tuesday. This spreads into the entire forecast area by late
Tuesday...but the chances remain highest in the Sierra and northeast
California. This system starts a little warmer as it is coming more
from the west than the northwest. Given we are seven days away...
these solutions are likely to change quite a bit before next week.



After a lull this morning, another wave will move through the
region this afternoon and evening. Expect hit-or-miss shower
activity for Sierra Front and western Nevada terminals with more
consistent precipitation in the Sierra.

The threat of an isolated thunderstorm has been expanded to cover
the whole central and southern Sierra as well as western Nevada.
Concerns for convective precipitation rates have increased with
brief, intense snow possible in stronger cells; IFR or worse
conditions will be possible in these showers. More general shower
cells will have brief MVFR restrictions. These shower periods
could result in slick runways even for western Nevada terminals
where snow levels are around or above valley surfaces.

The heaviest precipitation will start by early afternoon for the
Sierra with widespread snow for Sierra terminals. Accumulations
will be lighter than the previous round, but there is potential
for another 3-6 inches. Other aviation concerns will be
widespread mountain obscurations. Snow and shower chances diminish
this evening as the wave moves into eastern Nevada.

Another round of snow is expected later Thursday through early
Saturday morning with heavy accumulations likely in the Sierra. A
few to several inches will also be possible for western Nevada
terminals during this time frame as well. Winds will become more
of an issue as a stronger jet moves over the Sierra. Expect
turbulent conditions and mountain waves. Boyd


.REV Watches/Warnings/Advisories...
NV...Winter Storm Watch from Thursday afternoon through late Friday
     night NVZ003.

     Winter Storm Warning until 11 AM PDT this morning NVZ002.

     Winter Storm Warning from 5 PM Thursday to 5 AM PDT Saturday

CA...Winter Weather Advisory until 11 AM PDT this morning CAZ071.

     Winter Storm Warning from 2 PM Thursday to 11 PM PDT Friday

     Winter Weather Advisory until 1 AM PDT Thursday CAZ073.

     Winter Storm Watch from Thursday afternoon through late Friday
     night CAZ073.

     Winter Storm Warning until 11 AM PDT this morning CAZ072.

     Winter Storm Warning from 5 PM Thursday to 5 AM PDT Saturday



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