Area Forecast Discussion
Issued by NWS Reno, NV

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FXUS65 KREV 280958
AFDREV

Area Forecast Discussion
National Weather Service Reno NV
258 AM PDT WED SEP 28 2016

.SYNOPSIS...

High pressure over northeast California and western Nevada will
slowly weaken through Thursday with a few showers possible over
southern Mono and western Mineral Counties. The ridge weakens
further late week as a trough of low pressure moves into the West
Coast. This will bring breezy and much cooler conditions for the
weekend, with increasing chances for precipitation by Sunday.

&&

.SHORT TERM...

The main changes to the short term forecast include adding a
slight chance of showers to Mono and western Mineral Counties for
Thursday and raising lows Friday night.

The upper low over southeast California will move north into
central and eastern Nevada tonight. The low will be shearing out
and weakening as it squeezes in between a ridge over the central
CONUS and a trough in the northeast Pacific, with the main moisture
intrusion over southern/eastern Nevada and Utah. For western
Nevada and eastern California (generally south of Tahoe), the
disturbance will mainly mean an increase in mid and high level
clouds tonight and Thursday. However, with well above average
temperatures and cooling aloft with the weakening ridge/divergence
in the mid levels, enough instability for some cumulus and a few
light showers is still possible over southern Mono County this
afternoon. Instability is quite weak, so thunderstorms are not
expected.

Thursday, NAM simulations show isolated convection over central
Nevada and near the Inyo/Mono County border in the late afternoon...
along with hints at convergence in Mono and Mineral Counties. While
the GFS/EC do not depict this, it is a reasonable possibility. In
fact, the better convergence in the lee of the Sierra could elevate
the chance for deeper convection and very isolated thunderstorms
on Thursday, especially with temperatures still well above average.

Friday, attention turns to a trough of low pressure nearing the
Pacific Northwest coast. This will bring an increase in winds by
afternoon, with gusts 30-40 mph especially north of highway 50.
This will increase fire weather concerns, although humidities will
be in some question as they may not fall enough on a widespread
basis for a major red flag event.

Friday night, increasing winds aloft ahead of the incoming trough
should keep the lower atmosphere mixed up enough to keep temperatures
up overnight into Saturday. With this in mind, I have raised lows
Friday night to above much of the guidance. Snyder

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

The trough that will be moving through for the weekend into early
next week will be the focus. Saturday still looks to be a breezy
day behind the initial cold front as well as cooler with highs
mainly in the 60s. It will be dry as we will be between short
waves at that point.

The focus then turns to Sunday afternoon and evening as the main
upper low and trough axis dive southeast towards Western Nevada.
Winds will be a bit breezy ahead of the system Sunday, but moisture
will be on the increase. It is beginning to look more likely that it
could bring a quick shot of lower elevation rain/mountain snow to
the region north of Highway 50. Snow levels will start near 7000
feet Sunday afternoon then could fall as low as 5-5500 feet behind
the front during the evening. Amounts still look relatively light. I
have increased the pops to chance in the Sierra north of 50 and near
the Oregon Border with slight chance elsewhere. There is still
enough spread in the models to not make a bigger jump at this time.
One thing is for sure though, it will be quite cool Sunday with
highs in the upper 40s to low 60s area-wide.

Behind the main trough Monday and Tuesday, a cool northwest flow
will continue. Some of the ensemble members keep some moisture and
weak short waves/warm air advection precip going into Tuesday
afternoon. Any precip at that point will be light so left the
slight chances in as it could be dry as well. One thing though is
that the temps will remain quite cool Monday before moderating
some on Tuesday. Winds will also be lighter those two days.

&&

.AVIATION...

VFR conditions with light winds today. Continued VFR Thursday and
Friday, but winds will begin to increase. A few gusts to 25 kts
north of I-80 Thursday afternoon with more widespread gusts 30-35
kts Friday afternoon. With the increasing winds Friday, some areas
of mtn wave turbulence are likely. Gusty winds to continue through
the weekend with mtn wave turbulence, with the next chance at precip
and lower CIGS Sunday afternoon/evening.

&&

.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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