Area Forecast Discussion
Issued by NWS Reno, NV

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FXUS65 KREV 290955

Area Forecast Discussion
National Weather Service Reno NV
255 AM PDT Wed Mar 29 2017

Dry conditions, light winds and warm temperatures stick
around for one last day before a storm pushes into the region late
tonight into Thursday. The storm on Thursday will bring a strong
cold front through western Nevada with gusty winds as well as
rain, snow, and pellet showers. Cooler temperatures will stick
around through the end of the week behind this cold front.


Main changes to the short term forecast were to upgrade the High
Wind Watches in Mono/Mineral counties to High Wind Warnings and to
increase wind speeds for those areas for Thursday afternoon. Forecaster
confidence is high for strong winds to impact much of the Sierra
and western Nevada all day Thursday.

Last day of high pressure will bring the warmest of the
temperatures this week with highs near 70 for western Nevada
valleys this afternoon and upper 50s to lower 60s for the Sierra
valleys. Enjoy today while it lasts, but be sure to secure any
loose outdoor items before the winds come into the region early
Thursday morning.

Forecast simulations have trended faster with the timing of the
cold front on Thursday morning, so we could be seeing wind gusts
40 to 50 mph between 7-9AM. The strength of the cold front is
evident in the very tight packing of surface pressure and
temperature gradients on the latest forecast models, and they have
shown this over the past few model runs. Although the cold front
is forecast to move through fast, the surface winds don`t appear
to drop off rapidly behind frontal passage. In fact, the winds
appear to stay up for several hours after the cold front moves
through the area. As the cold front accelerates south towards
Highway 50 and Mono/Mineral counties, the surface winds accelerate
into the 35 to 45 knot range at 30AGL as well. Travel restrictions
for high profile vehicles will be likely, especially for Highway
95 and Highway 395 in Mono/Mineral counties. Hazardous boating
conditions are also likely for lakes in the region, along with
areas of aviation turbulence and wind shear. Winds should begin to
drop off after 8pm on Thursday.

The precipitation aspect with this storm isn`t looking quite as
favorable as in previous simulations. The moisture and dynamics
appear to be a bit farther east with much of the precipitation
impacting far northeastern Nevada. Even though the precipitation
amounts look relatively light, the dynamic nature of the cold
front will allow for some showers to develop along the cold
frontal passage. Showers will begin early Thursday morning in
northeastern California and then spread south with the cold front
down towards the Highway 50 corridor around 11am-noon. Snow levels
will quickly drop behind the cold front to near 6,000-6,500 feet,
so we could see some accumulating snow pellet showers along with
some chances for lightning/thunder. Once the forcing with the
front drops southward, the chances for lightning/thunder largely
disappear although we could still some rain/snow showers through
the day.

By early Friday morning, most of the showers will be diminished
along with the strongest winds. Cold air advection into the Basin
and Range will keep east flow across the Sierra and western
Nevada through early Saturday morning. Gusty east ridge winds will
likely also be a concern through Saturday morning along with the
potential for some breezy conditions on the west slopes of the
Sierra. -Edan

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

Medium range models continue to struggle with the evolution of the
next system slated to affect the region late in the weekend and
early next week. Thus...few significant changes were made to the
going forecast.

In the wake of ridging Saturday that allows temperatures to
warm...the operational models are pushing the ridge axis east
Saturday night...flattening the flow aloft early Sunday...then
dropping a short wave trough into the region late Sunday afternoon
and Sunday evening. The differences in the solutions revolve around
timing and strength of the wave. The GFS...which had been far less
aggressive...has now become the primary aggressor with this
system...digging the trough and moving it through by late Sunday
night. This dynamic wave and surface front would usher in showers
and cooler temperatures Sunday evening into Monday morning. The
ECMWF is slower with the trough...but about as deep as the GFS. It
is also not as cool as the GFS by Monday morning. This is a
departure from prior ECMWF runs up to 24 hours ago when it was the
aggressor. The GEFS ensemble members support a trough over the
region...but vary widely in its strength and speed. We have
increased pops slightly for Sunday evening and overnight across
the far northern CWA...but given inconsistencies between the
models and run-to-run inconsistencies within each model
family...we have opted not to go too strongly toward one solution.
While forecast confidence is increasing in a trough solution for
Sunday/Monday...the vagaries of model forecasts in the transition
seasons necessarily keeps confidence in any one forecast cycle
from reaching higher than moderate.

The trough moves east late Monday with lingering showers during the
day. Then northwest flow develops as another weak short wave ridge
tries to take hold. This ridge slides east beyond the forecast time
frame as another trough starts to impinge on the west coast late


Ridging persists today before a fast moving system approaches the
region late tonight into early Thursday. The fast moving front
will bring rain and snow pellet showers to the Sierra and western
Nevada, but the main impact for western Nevada terminals will
likely be from strong gradient winds with the frontal passage.
Widespread wind gusts of 30-40 kts are possible Thursday, with
wind gusts around 50 kts for Mono and Mineral counties.

Although we are expecting rain and snow pellet showers along the
cold frontal passage, little in the way of accumulation is
expected. Any quick snow pellet accumulations should quickly melt
off during the day. -Edan


.REV Watches/Warnings/Advisories...
NV...Wind Advisory from 7 AM to 11 PM PDT Thursday NVZ004-005.

     High Wind Warning from 8 AM to 8 PM PDT Thursday NVZ001.

     Wind Advisory from 5 AM to 8 PM PDT Thursday NVZ002.

     Wind Advisory from 7 AM to 8 PM PDT Thursday NVZ003.

CA...Wind Advisory from 7 AM to 11 PM PDT Thursday CAZ070.

     High Wind Warning from 8 AM to 8 PM PDT Thursday CAZ073.

     Wind Advisory from 5 AM to 8 PM PDT Thursday CAZ072.



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