Area Forecast Discussion
Issued by NWS Reno, NV

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000
FXUS65 KREV 240925
AFDREV

Area Forecast Discussion
National Weather Service Reno NV
225 AM PDT Tue Apr 24 2018

.SYNOPSIS...

Warm afternoon temperatures are expected through Thursday, with a
cool down to near or possibly below average temperatures by next
weekend. Areas for showers and a few thunderstorms increase each
afternoon through Friday. Conditions become breezy for Friday and
Saturday with more widespread showers over the weekend as low
pressure moves into the region.

&&

.SHORT TERM...

No major shifts in the forecast were made this cycle. The main
message is that there will be at least isolated thunderstorms
each afternoon through Thursday. Outdoor plans should include a
method of getting to safety if thunderstorms begin to form - When
thunder roars, go indoors. Forecast details follow.

Ridge axis placement favors increased convergence along the
eastern Sierra today and the onset of a light afternoon zephyr.
While conditions will generally be dry, expect some cumulus
build-ups along the Sierra crest mainly south of Highway 50, but
including the Sierra along the west side of Lake Tahoe.

Coverage of isolated thunderstorms expands Wednesday as the ridge
amplifies in central/eastern Nevada. Temperature discontinuities
from the Sacramento Valley across the Sierra to the Great Basin
increase resulting in increased convergence along known
convergence zones. Expect zephyr winds to increase and push
isolated cells into western Nevada as well as along terrain
features like the Pah Rahs, Virginia, and Pine Nut ranges. As far
as thunderstorm threat characteristics go, surface wind gusts and
lightning will be the primary threats; gusts around 40-45 mph will
be possible. Small hail around 1/4 inch is also possible, but
generally will be less of a threat than lightning strikes or wind.

Forcing dynamics begin to change for Thursday. Upper level lapse
rates begin to increase as a cut-off low is projected to meander
into northern California. A weak wave is also projected to
progress around the low coincident with lowest surface instability
from heating in the afternoon. Isolated coverage is likely to
increase to scattered with the additional forcing associated with
the upper low. While forcing parameters are not overly impressive,
surface gusts in the 40-50 mph will be possible; strongest gusts
would be over western Nevada valleys along the Sierra Front. Any
hail may also be slightly larger than Wednesday`s storms, but
still generally less than 1/2 inch. The threat for fire starts is
not zero, but not too concerning considering we are still in a
green-up period; storms will not be moving too quickly either
allowing for wetting rains to reach the ground. Boyd


.LONG TERM...Friday onward...

While there are still forecast differences going into the weekend,
finally the larger scale pattern is showing better agreement in
operational and ensemble models through the weekend. Confidence is
increasing in cooler temperatures along with chances for showers and
some thunderstorms Friday through Sunday. However, it remains lower
in the smaller scale details such as exactly where these showers and
storms have the best chance of forming in addition to what will
happen for the early part of next week.

The closed low looks to move inland across northern CA/NV and
southern Oregon Friday into early Saturday. This will lead to
increasing winds Friday afternoon and evening with peak valley
gusts in the 30 to 40 mph range. Now for the differences...The EC
keeps the low closed longer than the GFS and stays centered over
northern CA/NV through the weekend. The GFS opens the low and
lifts the wave north and east as a secondary wave digs south and
carves out a trough over the west. The EC keeps a general trough
over the west, but it`s not as deep or defined as the GFS for the
early part of next week.

The main takeaway at this time is expect a much cooler weekend
compared to the warmth of this week with high temperatures dropping
below normal. There will be chances for rain and mountain snow
showers above 6500-7500 feet. Thunderstorms are also a possibility
which may bring gusty and erratic winds along with small hail. If
you have outdoor plans, pay close attention to the forecast and
ongoing weather so you aren`t caught off guard in inclement
conditions. -Dawn


&&

.AVIATION...

VFR conditions to continue much of this week outside of a 30% chance
for morning fog at KTRK. There are chances for isolated afternoon
thunderstorms along the Sierra crest the next several days with
coverage increasing Wednesday through Friday as an area of low
pressure approaches the west coast. Storms may bring brief periods
of reduced ceilings and visibility, gusty and erratic outflow winds,
and small hail. It is too soon to say if storms will directly impact
any of the terminal sites, however, thunderstorm debris clouds are
likely in the late afternoon and early evening. -Dawn

&&

.REV Watches/Warnings/Advisories...
NV...None.
CA...None.
&&

$$

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



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