Area Forecast Discussion
Issued by NWS Reno, NV

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000
FXUS65 KREV 151006
AFDREV

Area Forecast Discussion
National Weather Service Reno NV
306 AM PDT Sun Apr 15 2018

.SYNOPSIS...

A fast moving storm will bring strong winds today, with rain and
snow this evening through Monday. Slick road conditions are likely
tonight and Monday morning especially near the Sierra. A weaker
storm could bring light rain and snow showers Wednesday through
Thursday. Below average temperatures are expected Monday through
Thursday with warmer conditions returning by next weekend.

&&

.SHORT TERM...Through Monday night...

All Wind and Winter Weather Advisories will remain in place for
the upcoming storm today through early Monday, with no notable
change in overall wind speed and snowfall projections.

For today, winds will strengthen as thermal and pressure
gradients increase ahead of the approaching shortwave and cold
front. Wind gusts of 45-55 mph are likely early this afternoon and
through the evening. Stronger gusts up to 70 mph are possible
along wind prone areas of I-580, US-395 from Susanville to Mono
County, and US-95 through Mineral County. Even outside these wind
prone areas, a brief burst of 60+ mph wind gusts, capable of
producing isolated fence/tree damage, could occur this evening
along the leading edge of the main precip band as the cold front
pushes through. Sierra ridge top wind gusts of 80+ mph are likely.
Areas of blowing dust are also possible this afternoon and
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 shortwave and associated cold front move inland, rain and
snow will quickly develop across northeast CA by mid-late
afternoon, with the heaviest precip then pushing south into the
Tahoe basin and Alpine County this evening. A short period of
spillover rain and snow will likely spread into the Reno-Carson
vicinity during the evening, with most activity tapering to bands
of snow showers after midnight.

Total snow accumulations of 3-6" are likely at lake level in the
Tahoe region, with locally higher amounts west of Highway 89 and
up to a foot possible above 7000 feet, especially near the Sierra
crest. Farther south into Mono County, the precip band will lose
some of its intensity but a couple inches could accumulate on
portions of US-395 above 6500 feet, with up to 6" near the Sierra
crest. For travel over the main Sierra passes today, it is
strongly advised to complete the trip by mid-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, although a few inches
can`t be ruled out for higher elevation roads such as Highways
36 and 44 west of Susanville, Highway 49 over Yuba Pass and
portions of Highway 89. With snow levels falling to valley floors
by late tonight, 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, brisk and chilly conditions
prevail while snow shower chances continue due to unstable
conditions and secondary shortwave passages. The stronger wave now
looks to swing into Mono County, with potential for heavier snow
shower bands extending east of the crest (originating from
thunderstorms forming west of the Sierra). Portions of western
Mono County could receive a few inches of snowfall from these
bands, especially if they hold together near and after sunset.
Isolated thunder and snow pellets/graupel are also possible for
northeast CA and areas north of a Hawthorne-Carson City line in
western NV. The main hazards to watch for will be rapid drops in
visibility and short periods of slick road conditions when heavier
showers move through Monday afternoon and evening.

Later Monday night, the snow showers are expected to diminish,
with chilly conditions prevailing as temperatures drop into the
20s for most lower elevations and teens for Sierra valleys. MJD

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

The weather picture for the middle of the week has become a bit
clearer as model solutions are starting to converge in the
Wednesday/Thursday time frame. Thus...we had made some changes to
the forecast for mainly the Wednesday evening through Thursday
morning part of the forecast, and confidence is starting to
increase.

A short wave ridge Tuesday pushes east of the region by early
Wednesday. A few residual showers are possible early Tuesday in
central Nevada...but overall Tuesday through midday Wednesday should
be dry.

The big change has the operational GFS starting to come more in line
with the ECMWF and bringing the possibility of precipitation into
the region faster Wednesday. The main upper low is not showing as
much of a tendency to split and dive toward central California
before getting to our forecast area. Many of the GEFS ensemble
members now support this solution as well. This has a number of
implications on the forecast and adjustments have been made to
address these.

First...the faster movement means precipitation starts earlier for
Wednesday...starting in the afternoon instead of the evening.
Second...there is a better chance of seeing stronger winds in
western Nevada ahead of the storm as the pressure and thermal
gradients tighten faster in the morning and afternoon. Winds were
increased for Wednesday afternoon/evening. Third...with increased
winds comes better mixing and slightly higher temperatures for
Wednesday. But the faster moving system also means that cold air
comes in quicker in the evening...so snow levels were dropped a
little faster. Lastly...the more progressive nature of the low
means that precipitation will generally end Thursday morning...but
this system is dynamic enough that QPF amounts have been raised.

With the falling snow levels and increased QPF there is a better
chance of accumulating snows in the mountains with up to 6 inches
possible in the higher elevations. The focus by Thursday morning
shifts to Mono County where the greatest snow amounts may occur.
The cold core aloft early Thursday means a likelihood of
convection through the day with graupel. The lower valleys should
see little in the way of accumulation in the showers due to the
time of year.

Short wave ridging develops by Friday with temperatures rebounding
to near normal. This ridge may flatten by Saturday with a weak brush-
by system near the Oregon border. Highs climb above normal by
Saturday. There are some hints at another storm system for
Sunday...but the details are not very clear this time. XX

&&

.AVIATION...

Flying conditions will be quite rough today and tonight, with
potential for flight delays, cancellations or diversions. Strong
winds will arrive this 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 mountain wave turbulence is
likely, with lee side breaking waves also possible. Pockets of
LLWS are most likely this morning and in proximity to wind rotors
or terrain-channeled flow.

Accumulating snow and IFR conditions are expected at the Sierra
terminals tonight, especially prior to midnight for KTRK-KTVL and
after midnight for KMMH. A shorter period of snow could produce
brief IFR conditions late this evening for KRNO-KCXP. 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.

For Monday, unsettled conditions continue with -SHSN especially in
the afternoon and early evening, producing quick periods of
MVFR/IFR conditions especially for the Sierra terminals. Although
winds won`t be as strong as today, brisk west to northwest winds
along with the showers (and a slight chance for PM thunder) will
keep turbulent conditions for flights into and out of the region.
MJD

&&

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

     Wind Advisory from 2 PM this afternoon to 2 AM PDT Monday NVZ001.

     Lake Wind Advisory from 8 AM this morning to 5 PM PDT this
     afternoon for Lake Tahoe in NVZ002.

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

CA...Wind Advisory from 11 AM this morning to 11 PM PDT this evening
     CAZ070-071.

     Wind Advisory from 2 PM this afternoon to 2 AM PDT Monday CAZ073.

     Lake Wind Advisory from 8 AM this morning to 5 PM PDT this
     afternoon for Lake Tahoe in CAZ072.

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

&&

$$

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



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