Area Forecast Discussion
Issued by NWS Reno, NV

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FXUS65 KREV 251019
AFDREV

Area Forecast Discussion
National Weather Service Reno NV
319 AM PDT Sun Jun 25 2017

.SYNOPSIS...
Very warm temperatures continue today along with isolated
thunderstorms this afternoon and evening. Critical fire weather
conditions are possible Monday as very dry air combines with
gusty winds. Temperatures will cool down to near seasonal
averages through midweek, then slowly warm up again late in the
week with dry weather prevailing.

.SHORT TERM...

We are expecting one more day of much above average temperatures,
with highs today near or above 100 degrees in some western NV
valleys and upper 80s near the Sierra.

Weak upper level disturbance moving northward across central CA
is spreading mid and high level clouds over much of northern CA
and most of NV, which should continue moving north through this
morning. While a few brief very light showers/sprinkles can`t be
ruled out, the potential for any measurable rainfall or thunder is
too slim to justify a mention in the forecast for this morning.

By this afternoon, most of the morning cloud cover will have
departed to the north, with warm and unstable conditions leading
to convective buildups. Initial cell development is most likely to
occur in eastern CA and far western NV between the Sierra crest
and US-395. As a modest late day zephyr sets up and outflow
boundaries interact, additional cells could develop across
western NV mainly between US-395 and US-95 from late afternoon
through this evening. Upper level support is not very strong and
cell coverage should be isolated across most areas, although
north of Susanville-Gerlach, cells may be a bit more concentrated
as an upper level wave brings slightly more favorable thunderstorm
conditions there. The stronger storms will be capable of producing
brief heavy rainfall with small hail, outflow gusts 40+ mph, while
moderate cell motion (around 15 mph) increases the potential for
new lightning fire starts in areas where dried out grass and
brush is prevalent. The continued interactions with outflows and
warm evening temperatures could allow a few showers and weak
thunderstorms to linger past midnight in far northwest NV and
southern Mineral-Mono counties.

For Monday and Tuesday, upper level trough passage across the
Pacific Northwest will flatten the ridge which gave us our recent
days of triple digit heat. Temperatures will begin to drop on
Monday with highs mainly in the 90s across western NV valleys,
then fall further on Tuesday to the upper 80s-lower 90s with dry
air mass leading to more typical cooler nights for our high desert
climate (lows mainly in the 40s and 50s). More stable air mass
will prevent thunderstorm formation both days, although there is a
slight possibility of a shower or two near the Oregon border early
Monday evening as the southern edge of the main trough passes
through.

The more pressing concern will be increased winds Monday afternoon-
evening with potential gusts of 35-40 mph mainly from US-50
northward. Additional details and impacts are highlighted in the
Fire Weather segment below. MJD

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

Upper trough will be pulling away from the area Wednesday as a
shortwave ridge approaches the northern CA coast. This will result
in seasonal temperatures Wednesday before readings climb back above
normal for Thu-Fri. Winds will generally be light with mostly clear
conditions.

A shortwave trough will move across the area for late Friday into
Saturday although models differ in the details. Some scenarios split
this trough and keep the more dynamic portion north of Nevada
while cutting off a weak low off the CA coast. Others are more
consolidated and farther south which would bring a period of gusty
winds, slightly cooler temperatures and possibly some shower/storm
chances across northern and eastern areas. At this point we have
maintained a middle of the road approach with low pops/no mention
of weather for the Sierra Fri-Sat (although most of the model
data have trended more stable and drier). Hohmann

&&

.AVIATION...

Upper level wave will be lifting northward across the northern
Sierra and northwest NV this morning with mainly some mid level
clouds. A few showers and even a lightning strike or two are still
possible through 18Z but the chances are really low.

Otherwise, clearing behind this wave should help the atmosphere
destabilize this afternoon for isolated storms along the eastern
Sierra and across northeast CA. An afternoon zephyr and increasing
southwest flow aloft will help push activity off the Sierra into far
western NV this evening. At this time coverage is expected to remain
isolated except for northeast CA and northwest NV where some
dynamics and better convergence may bring a little more coverage.
The chance of a storm at area TAF sites is only around 10%.

The trough moves inland for Monday which will stabilize the airmass
and bring an end to storm chances. However, gusty southwest to west
winds will result in an increasing potential for turbulence. Surface
wind gusts will be around 30 kts while gusts across ridges will be
40-45 kts. Hohmann

&&

.FIRE WEATHER...

A period of critical fire weather conditions is still possible for
Monday as a trough moves into the region. For today, isolated
thunderstorms are expected to develop along the eastern Sierra and
northeast CA and push into far western NV ahead of this trough.
Storm motions are going to be a bit faster today as winds aloft
increase. This will make storms more capable of starting fires. The
mitigating factor may be the isolated nature of storms as a weak
shortwave lifting across the area this morning initially helps
stabilize the atmosphere. LAL 2 looks reasonable except for maybe
far northeast CA and far northwest NV where forcing will be a little
bit stronger and push LAL to 3 (generally north of a Susanville to
Gerlach line).

As the trough moves inland, much drier air will spread into the
northern Sierra and western NV tonight and Monday with increasing
southwest winds by Monday afternoon. Humidity recoveries will likely
be poor to moderate to start the day on Monday with levels falling
to around 10 percent Monday afternoon. Low humidity and wind gusts
30-40 mph will enhance the push of existing fires or new starts
from today`s lightning. Hohmann

&&


.REV Watches/Warnings/Advisories...
NV...Fire Weather Watch from Monday afternoon through Monday evening
     NVZ450-453.

CA...None.
&&

$$

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



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