Area Forecast Discussion
Issued by NWS Reno, NV

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000
FXUS65 KREV 141054
AFDREV

Area Forecast Discussion
National Weather Service Reno NV
354 AM PDT Sat Apr 14 2018

.SYNOPSIS...

After a dry and warm day today, a storm system will bring windy
conditions Sunday with rain and snow late Sunday through Monday.
Slick road conditions are possible for the early Monday morning
commute. A weaker storm may bring lighter precipitation
Wednesday night through Thursday. Below average temperatures are
expected for next week.

&&

.SHORT TERM...

The main item of interest in the short term continues to be the
Sunday-Monday storm, as we will issue Wind and Winter Weather
Advisories for this event.

Before this storm arrives, today will be the preferred day for
most outdoor activity as temperatures warm to near 70 degrees in
the western Nevada valleys and mid 50s-near 60 for Sierra valleys.
A late day zephyr-type breeze is expected with gusts 25-30 mph.

For Sunday, the thermal and pressure gradients will tighten up
during the day with most locations seeing windy conditions ahead
of the cold front. Wind gusts 45-55 mph are likely Sunday
afternoon and evening, with stronger gusts up to 70 mph possible
in wind prone areas along I-580, US-395 from Susanville to Mono
County, and US-95 through Mineral County. Sierra ridge gusts of
80+ mph are also likely. Areas of blowing dust are also possible
Sunday afternoon-evening, especially in west central NV including
Fallon-Lovelock-Yerington-Hawthorne. These stronger winds could
extend into the late night hours for Mono-Mineral-southern Lyon
counties.

As the storm and cold front move inland, rain and snow will
quickly develop across northeast CA by mid-late Sunday afternoon,
with the heaviest precip then pushing south into the Tahoe basin
and Alpine County Sunday evening. A short period of spillover rain
and snow will likely spread into the Reno-Carson vicinity Sunday
evening, with most activity tapering to snow showers after
midnight. Model guidance continues to favor a faster progression
of this front, and we have trended precip/snow amounts higher
prior to midnight and a bit lower after midnight.

At this time, confidence in snow accumulations is highest for the
Tahoe region, where we have issued a Winter Weather Advisory.
Snowfall rates up to 2"/hour with possible whiteout conditions are
anticipated due to strong forcing associated with the cold front
passage, leading to projected totals of 3-6" at lake level, with
locally higher amounts west of Highway 89 and up to 1 foot along
the Sierra crest above 7000 feet. For travel over the Sierra
passes on Sunday, it is strongly advised to complete the trip
during the afternoon before conditions quickly become hazardous
toward sunset and through much of the night.

For northeast CA, much of the heavier precip looks to arrive
prior to sunset, limiting snowfall accumulations. Farther south
into Mono County, the moisture band and forcing loses some of its
punch, also leading to lesser snow amounts. With snow levels
falling to valley floors by late Sunday night, we could
potentially see a bit of snow (generally less than 1") down to the
valley floors of far western Nevada and northeast California.
Foothill areas around Reno-Carson City including Virginia City
could see a couple inches of snowfall. Even though it is mid-
April, plan for slick road conditions around the urban areas for
the early Monday AM commute, with conditions improving by mid-
morning as snow on roads will melt more quickly due to higher
springtime sun angles.

For Monday afternoon and evening, a secondary shortwave will keep
snow shower chances going, especially for northeast CA-far
northwest NV and areas near the Sierra. Unstable conditions with a
cold pool aloft could produce isolated thunder and snow
pellets/graupel especially for northeast CA and areas north of
US-50 in western NV. While snow accumulations will be limited
especially prior to sunset, the main hazard to watch for will be
rapid drops in visibility when heavier showers move through. Snow
showers could continue into Monday night, with isolated light
accumulations possible on roads especially above 5000 feet. MJD

.LONG TERM...Tuesday through Friday...

Not much in the way of changes were made to the extended forecast
this cycle. The model simulations are in fair agreement with the
trough sliding east Tuesday and a ridge developing to the west. That
may result in lingering showers early Tuesday in central Nevada.
Below normal temperatures should warm to near normal by Wednesday as
the ridge axis slides east.

There is still disagreement between the GFS and ECMWF for Wednesday
night through Thursday night. The ECMWF remains faster moving the
next trough into and out of the region and keeps it farther north...
impacting our area earlier Wednesday evening. On the other hand...
the GFS is slower and is now back to favoring a more split solution
taking the main low a bit farther south by midday Thursday. The GEFS
ensembles are leaning a little more toward the GFS solution.

The differences between the model solutions leave us to use a more
broad-brushed general forecast for Wednesday night through Thursday
that leans toward at least slight chance POPs for the entire
forecast area with chance to likely POPs in the Sierra. Whatever
solution comes to fruition...this appears to be a fast moving system
with limited QPF. Snow accumulations will be limited to mainly above
6500 feet in the daylight hours due to the higher sun angle for the
middle of April.

A short wave ridge briefly dries the region out Friday before the
models suggest another fast moving system for either Saturday or
Sunday. Spring storms can be hard to pin down this far in advance
as the model solutions have a difficult time during the transition
seasons.

&&

.AVIATION...

VFR conditions will prevail today with late day west breezes to
20-25 kts (especially north of Highway 50). However, there is a
40% chance for patchy FZFG at/near KTRK through 15Z this morning.

The next storm will bring strong southwest winds Sunday
afternoon-evening (mainly from 18z-06z) with peak gusts to 45 kt
in most areas, except about 5-10 kt lower for the Tahoe
terminals. Widespread turbulence is likely, with pockets of LLWS
in terrain-channeled flow and near wind rotors also possible.

Accumulating snow and IFR conditions are expected at the Sierra
terminals Sunday night, especially prior to midnight for KTRK-KTVL.
The chances for snow accumulation on paved areas look minimal for
western Nevada terminals, with a slightly higher chance for KRTS-
KMEV than at other terminals. MJD

&&

.REV Watches/Warnings/Advisories...
NV...Wind Advisory from 11 AM to 11 PM PDT Sunday NVZ003>005.

     Wind Advisory from 2 PM Sunday to 2 AM PDT Monday NVZ001.

     Lake Wind Advisory from 8 AM to 5 PM PDT Sunday for Lake Tahoe
     in NVZ002.

     Winter Weather Advisory from 5 PM Sunday to 8 AM PDT Monday
     NVZ002.

CA...Wind Advisory from 11 AM to 11 PM PDT Sunday CAZ070-071.

     Wind Advisory from 2 PM Sunday to 2 AM PDT Monday CAZ073.

     Lake Wind Advisory from 8 AM to 5 PM PDT Sunday for Lake Tahoe
     in CAZ072.

     Winter Weather Advisory from 5 PM Sunday to 8 AM PDT Monday
     CAZ072.

&&

$$

For more information from the National Weather Service visit...
http://weather.gov/reno



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