Area Forecast Discussion
Issued by NWS Reno, NV

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FXUS65 KREV 161506 AAA
AFDREV

Area Forecast Discussion...UPDATED
National Weather Service Reno NV
806 AM PDT Mon Apr 16 2018

.UPDATE...
Quick update to extend the Winter Weather Advisory for the Tahoe
Basin thorugh 11 am. Many roads are still snow covered and snow
showers will continue through the day. At this point, I believe
the showers will become a little more scattered by the afternoon
which will allow the roads to clear by late morning. There will
still be issues in the heavier snow showers where a quick inch of
snow could accumulate in 20 to 30 minutes.

Snow showers are also expected west of Highway 395 in Mono County
as the short wave with the trough axis moves through. Elsewhere
scattered snow/pellet showers are expected with a few
thunderstorms possible as well. The cold pool aloft with stronger
insolation during mid-April will create enough instability.

The other changes were to increase the showers chances in the
Sierra as they will occur off and on all day. X

&&

.PREVIOUS DISCUSSION... /Issued 226 AM PDT Mon Apr 16 2018/

SYNOPSIS...

Brisk and chilly conditions with snow showers are expected today,
with a few thunderstorms possible this afternoon. 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...

Winds have diminished overnight and all wind-related advisories
were allowed to expire at their scheduled times.

The main area of snow over the Sierra has transitioned since
midnight to bands of snow showers, which should continue through
mid-morning. We will continue the Winter Weather Advisory for
now, although additional accumulations will be more limited due to
the reduced areal coverage of the heavier snow bands. For western
NV, the AM commute does not appear to face significant travel
impacts as snow did not fall at a sufficient rate to produce much
accumulation, although patchy slick road surfaces could be
encountered above 5000 feet.

For this afternoon and evening, chilly conditions and brisk winds
(gusts mainly 30-35 mph) will prevail while bands of snow showers
redevelop due to unstable conditions and secondary shortwave
passages. The stronger wave is projected 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.

Later tonight, 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. For Tuesday,
dry conditions with lighter winds will prevail with some warming
into the 50s for lower elevations and 40s near the Sierra (still
about 10 degrees below average), while on Tuesday night cloud
cover increases ahead of the next storm system. MJD

LONG TERM...Wednesday through Sunday...

Adjustments were made to the Wednesday/Thursday time frame to
account for shifts in the model solutions this cycle. The primary
deterministic models have come into good alignment in the early
part of the extended...but they do start to diverge toward the end
of the forecast. The GEFS ensemble members are mainly trending
toward the EC/GFS solutions early on as well. This lends more
confidence to the forecast of the next system...but given this is
spring...there could still be shifts in the track of any upper low
that moves into the region.

This is typically the time of year we see upper level lows start to
split and dive a bit farther south as they make their way into the
coast...and that is what is happening with the system for Wednesday
and Thursday. Even with this southern deviation in the track versus
24 hours ago...it is still close enough for precipitation to develop
Wednesday afternoon in eastern California...spreading into western
Nevada by early evening. But the evolution of this track farther
south means a little less QPF for the bulk of the area...and the
best chances for snow accumulations in the Sierra with the highest
amounts south of Highway 50...and also in the Sweetwater Range in
Mono and Lyon counties...the Wassuk Range in Mineral County...and
the White Mountains in Mono County. Still...only a few inches look
likely except at the very highest elevations where up to 6 inches
are possible above 9000 feet. If the low tracks farther
south...there will be even less snow potential.

The upper low moves east Thursday afternoon and evening. Gusty
northwest winds are likely behind this low in Mineral County. Below
normal temperatures are likely through Thursday. Short wave ridging
builds for Friday with highs warming to near normal.

The model solutions break down over the weekend...so only very minor
changes were made to the forecast then. The primary change was to
bump high temperatures above normal for the weekend. The GFS does
hint at convection near the Sierra Saturday as a weak short wave
trough passes through...but the ECMWF does not show this feature.
There is also a stronger hint at a wave impacting the northern part
of the forecast area after Sunday night into next week...but it is a
little early to glean any details from the guidance this far out for
that potential. XX

AVIATION...

For today, unsettled conditions continue with -SHSN mainly 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 Sunday, brisk west to northwest winds with
gusts generally 25-30 kt along with the showers (and a slight
chance for PM thunder) will keep turbulent conditions for flights
into and out of the region.

From tonight through Tuesday night, VFR conditions will prevail
with lighter winds. There could be some FZFG formation at KTRK
early Tuesday morning between 10-15Z if cloud cover breaks up
prior to this time frame. MJD

&&

.REV Watches/Warnings/Advisories...
NV...Winter Weather Advisory until 11 AM PDT this morning NVZ002.

CA...Winter Weather Advisory until 11 AM PDT this morning CAZ072.

&&

$$

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



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