Area Forecast Discussion
Issued by NWS Reno, NV

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FXUS65 KREV 190951

Area Forecast Discussion
National Weather Service Reno NV
251 AM PDT Thu Apr 19 2018


Chilly weather with periods of brisk winds will continue through
Thursday. A weak storm system will bring light rain and snow
showers later today through Thursday evening. Much warmer
temperatures will quickly return for the upcoming weekend through
early next week, with dry conditions prevailing.



An upper low will move through the region today bringing isolated
to scattered showers through the day. Some snow showers this
morning may cause rapid reductions in visibility and brief slick
driving conditions. While most showers will transition to mostly
rain after sunrise, instability and temperatures aloft are
sufficient to allow for some pellet showers across western Nevada.
Again, the main concern would be brief slick driving conditions
during heavier showers. Some light snow accumulations are possible
for higher elevations of west-central Nevada and portions of Mono

The main forecast changes were primarily to increase precipitation
chances across western Nevada as upper flow switches out of the
north. This flow regime favors banking of moisture along the
Sierra Front increasing precipitation chances along the eastern
Sierra, Carson Range, and Sierra Front. In general, conditions
will be quite cloudy with scattered showers through the day.

Otherwise, it will feel quite cool today due to brisk northerly
flow across the region. Gusts will top out around 35 mph with
highs in the low/mid 50s for western Nevada. A Lake Wind Advisory
has been issued for Pyramid Lake for the afternoon and early
evening hours. Those with plans to go onto Pyramid Lake may want
to consider the breezy conditions and rough lake water before
heading out. Gusts will be lower in the Sierra, but temperatures
will be about 10 degrees cooler as highs only reach the low/mid

The upper low circulation exits into Utah overnight tonight with
high pressure building across the region by Friday. Winds will
drop off as the pressure gradient weakens. Temperatures will begin
to rebound into the mid/upper 60s for western Nevada and low 60s
in Sierra valleys. Boyd

.LONG TERM...Saturday through Wednesday...

The only significant changes made to the extended forecast this
morning involved adding some slight chance showers and thunderstorms
over the far northern part of the forecast area near the Oregon
border for Sunday. Otherwise...the forecast was pretty much left as

After a dry and mild Saturday...the models solutions start to become
a bit more aggressive with a short wave trough Sunday. Earlier runs
showed this mainly in the ECMWF...but with limited convection. The
GFS is now taking up the mantle as well and driving a short wave
east along the Oregon border. While the confidence in this solution
falls squarely in the medium range...we have opted to include slight
chance showers and thunderstorms north of a line from Susanville to
Gerlach Sunday afternoon...with a little left over convection north
of Gerlach Sunday evening.

Weak short wave ridging for early Monday is the last vestige of any
agreement in the model confidence beyond early Monday
is quite low in the extended period. The ECMWF carves an upper level
low into the base of a short wave trough and drops it south well off
the coast for the Monday through Wednesday time frame. This low is
seen as far west as 135W Tuesday before opening as a wave and moving
into the west coast Thursday. Proximity to upper level
divergence could trigger a few showers as early as Wednesday.

The GFS shows the upper low moving inland Tuesday and then diving
south through central California into Arizona by late Wednesday; a
very different solution...indeed. The GEFS ensemble members are not
much help as they show those solutions...and more.

For now we will maintain a middle of the road forecast with no POPs
Monday and slight chances north of a Susanville to Gerlach line
Tuesday and Tuesday evening. For Wednesday we spread the POPs south
along the Sierra and show some slight chances in the higher
elevations of eastern Churchill and Pershing counties. High
temperatures generally stay above normal so low- to mid-level
instability may be enough both Tuesday and Wednesday for isolated

This is a fairly typical forecast challenge for the spring as the
models do not tend to handle potential cut off lows very well. The
forecast may change drastically as we get into the weekend and early
next week.



An upper level circulation will provide forcing for isolated to
scattered showers today. These showers will bring periods of
mainly MVFR conditions to area terminals. Intermittent lower
ceilings will be the primary concern after sunrise, but lower
visibility with light snow showers can be expected before sunrise.
There will be enough instability this afternoon to produce some
pellet showers along the Sierra Front as well. Ridge level winds
will support light to moderate turbulence in and around the Sierra
while surface gusts peak around 30kts today. The upper low will
exit the region by Thursday evening allowing for winds to slow as
high pressure builds across the region.

Flying conditions should be VFR from Friday morning through the
weekend with the exception of morning fog around KTRK. Boyd


.REV Watches/Warnings/Advisories...
NV...Lake Wind Advisory from noon today to 8 PM PDT this evening for
     Pyramid Lake in NVZ004.



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