Area Forecast Discussion
Issued by NWS Reno, NV

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823
FXUS65 KREV 201007
AFDREV

Area Forecast Discussion
National Weather Service Reno NV
307 AM PDT Mon Aug 20 2018

.SYNOPSIS...

Above average temperatures today will ease down closer to average
for the rest of the week as low pressure slides into northern
California and far northwest Nevada. Typical afternoon and evening
breezes are expected for the next few days. Dry weather will
prevail this week, except a few thunderstorms will be possible
north of Susanville and Gerlach on Tuesday.

&&

.SHORT TERM...

Weak low pressure near the Oregon coast will slide south into
northern California and extreme northwest Nevada tonight and
Tuesday, then kick out to the northeast by Wednesday. The main
effect of this low will be typical afternoon and evening breezes
(gusts 20-25 mph) for the next few days, except for some gusts
around 30 mph today. Winds over northeast CA-northwest NV will
become lighter and could shift to a northerly component Tuesday-
Tuesday night. This low will finally end the triple digit heat
for a while, with highs trending a few degrees cooler today, then
dropping further to the lower 90s for western NV valleys by
Tuesday and Wednesday. Cooler nights are also expected (lows
mainly 40s-50s except 30s for Sierra valleys).

The projected location of this low will bring a small area of
instability and forcing on Tuesday north of Susanville-Gerlach,
with showers in these areas possible during the morning and
isolated thunderstorms during the afternoon and evening.

Smoke and haze will be less widespread for the next few days,
based on current fire activity across Oregon and northern CA. We
reduced the haze and smoke extent for most areas north of I-80
starting Tuesday, with northern Lassen County most likely to be
affected by smoke primarily from the Stone fire in Modoc County.
Otherwise, narrower but more concentrated smoke plumes remain
likely downwind of the Donnell and Lions fires in parts of Alpine,
Douglas, Lyon, Mineral and Mono counties. MJD

.LONG TERM...Thursday through next weekend...

The main storm track will remain north of the region while high
pressure aloft will continue to extend across the southern tier of
the U.S. Thu-Sat. This leaves the Sierra and western NV in a dry
southwest to west flow with temperatures running only a few degrees
above normal. Highs will be in the low-mid 90s lower valleys and
upper 70s-lower 80s Sierra valleys. Typical afternoon zephyr breezes
will persist with gusts around 25 mph.

There continue to be signals of a pattern change next week as a
large scale trough over the Pacific Northwest drops southward in
the vicinity of the west coast. This would bring increasing winds
and a modest cool down to near or slightly below normal. Some
solutions including the ECMWF show much cooler weather with
chances for showers and thunderstorms as it drops the upper low a
bit inland of the coast. Hohmann

&&

.AVIATION...

With continual southwesterly flow expected through Wednesday, smoke
will likely stay clear of the Tahoe basin and much of western
Nevada. However, slant-wise and flight level visibility may continue
to be reduced for areas north of Susanville and Gerlach, in addition
to areas immediately downwind of the Lions and Donnell fires in
Alpine/Mono/Mineral Counties. Expect dry conditions with enhanced
wind gusts up to 25 kts this afternoon and evening. Isolated
thunderstorms will be possible across far northeast CA and northwest
NV Tuesday afternoon and evening. Hohmann

&&

.FIRE WEATHER...

Winds along the Sierra Front approached critical conditions Sunday
afternoon as the upper jet dropped south toward northern NV and
ridge winds increased to 25-35 mph. Wind gusts were 30-35 mph along
the foothills as minimum humidity values dropped to around 10%. For
today, model data continue to indicate ridge winds not as strong as
Sunday, although currently speeds remain around 25-35 mph.
Localized critical conditions may once again occur mainly along
the Sierra Front from about 2 pm through 8 pm today where gusts
will approach 30 mph with RH again around 10%. We will continue to
headline the fire weather forecast for now and assess the upper
air sounding and ridge wind trends early this morning to determine
if a red flag warning will be necessary. Regardless, the fire
community should be aware that any new fire starts will still
spread quickly as the afternoon zephyr will be enhanced.

Humidity recoveries will worsen tonight and Tuesday night as very
dry air pushes into the region on the south side of the upper
trough. This dry air will push into the Tahoe Basin and Sierra Front
today and then southward into Mono County late Tuesday. Despite the
slightly cooler temperatures, humidity levels could fall as low as
10% in some higher elevations while recoveries may only be in the 20-
35% range.

The final concern is the potential for thunderstorms near the Oregon
border Tuesday. These storms would tend toward dry with gusty
outflow winds and a few dry lightning strikes. Coverage is expected
be on the low isolated end. Hohmann

&&


.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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