Area Forecast Discussion
Issued by NWS Reno, NV

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FXUS65 KREV 110949

Area Forecast Discussion
National Weather Service Reno NV
149 AM PST Sun Mar 11 2018


Drier conditions are expected today into Monday. A stronger
system will bring gusty winds, rain, and snow Tuesday and
Wednesday with unsettled conditions into the weekend. Temperatures
will be near, or slightly above, average through the early
portion of this week before falling below average late in the



Areas of fog and dense stratus formed over the Saturday evening
hours in Sierra valleys from South Lake Tahoe northward into
Lassen County. Expect this fog and stratus to linger into the late
morning hours today with lower potential for another round
tonight as clouds build aloft. It`s still feasible to get another
round of stratus and fog over Lake Tahoe given the relatively warm
conditions and presence of the snowpack. Outside of the Sierra,
stratus is more sparse tonight and can be seen on area web
cameras mainly around Verdi. Some of this more ragged stratus
could encroach on Sierra Front terminals like KRNO this morning.
Chances of recurrence tonight are small along the Sierra Front,
but there could be some shallow ground fog just east of KRNO
closer to Steamboat Creek by Monday morning.

Otherwise, no major changes were made through Monday night other
than to trim back precipitation chances for the Sierra. The next
system is showing signs of a slower approach and necessitated
cutting precipitation chances back more towards early Tuesday
morning. As such, snow levels are expected to rise to near 7500
feet with weak warm air advection associated with a transient
short-wave ridge and general southwesterly upper level flow.
Winds will still begin to increase Monday with gusts in the 20-30
mph range and ridge gusts increasing above 50 mph by Monday
night. Boyd

.LONG TERM...Tuesday through Saturday...

The extended remains problematic as model solutions from the
operational GFS and ECMWF remain at odds with each other while the
solutions from the GEFS ensemble members show a significant spread
in how they deal with an upper low during much of the period.

One thing we have relative high confidence in is the upcoming week
will be characterized by an extended period of unsettled weather
with accumulating snows in the Sierra and the higher elevations of
northeast California while in the lower valleys a mix of rain and
snow is likely with little accumulation.

The first wave approaches Tuesday morning with snow in the Sierra
and breezy conditions across western Nevada. By the late afternoon
and evening there should be some light precipitation in western
Nevada...but it may be tempered by continued southerly flow ahead of
the low. Snow levels start fairly high as well...but then fall
through the evening.

Snow levels are a point of contention throughout the week due to the
varying model solutions. The GFS would support slightly higher snow
levels...falling by the end of the week...while the ECMWF brings
them down faster with better chances for accumulating snows in the

After the initial wave Tuesday/Tuesday night...the GFS keeps the
main upper low offshore while the ECMWF spreads it into northern
California. This is the crux of the entire variation in the model
solutions. The GFS wants to try to split the system...or at least
slow it down...while the ECMWF is more aggressive bringing the main
low and its colder air close to the forecast area. The GEFS
ensembles support both solutions...and a few others.

Another thing that is becoming more clear is that the better chances
for significant QPF are shifting to the Thursday/Friday time frame.
QPF was raised slightly for those periods along with POPs and snow
levels were lowered a little as the GFS is trying to bring cooler
air closer to the forecast area. It can be folly to latch on to one
or two forecast runs...but this is a trend that has been ongoing.

We could still see a split system roll down the coast and produce
far less QPF east of the this forecast has a fairly high
bust potential. We are fairly confident the Sierra will pick up
significant snow over the extended period...but no one part of the
overall storm system will be a big snow maker. There is far lower
confidence in any solution for areas from northeast California
southeast into the valleys of western Nevada. Hopefully the models
will start to converge on a solution...but that has not been the
case thus far.



Sierra fog and stratus will keep IFR/MVFR conditions in place for
Sierra terminals through about 17/18Z. There is lower potential
for a repeat tonight as clouds increase aloft. KTVL could still
see stratus formation tonight though if the layer forms prior to
higher clouds advecting into the region; chance of occurrence is
about 50%.

Elsewhere, KRNO stands the best chance to see a small amount of
ragged stratus this morning with much more limited impacts than
Sierra terminals. This is not anticipated to return for Monday
morning, but there could be some shallow ground fog encroaching
from the east off of Steamboat Creek.

Otherwise, conditions will be VFR with light winds today. Winds
begin to increase Monday with gusts 20-25 kts. Ridge winds
increase further Monday night above 40-45 kts likely resulting in
light to moderate turbulence associated with mountain waves along
the Sierra Front. Conditions further deteriorate by Tuesday as a
stronger storm moves into the region. Boyd


.REV Watches/Warnings/Advisories...


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