Area Forecast Discussion
Issued by NWS Reno, NV

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638
FXUS65 KREV 162118
AFDREV

Area Forecast Discussion
National Weather Service Reno NV
218 PM PDT Fri Jun 16 2017

.SYNOPSIS...
High pressure will bring very warm temperatures for the upcoming
week, with the best chance for highs at least 100 degrees next
Monday through Wednesday. Most areas will remain dry, except for
low chances of showers and thunderstorms mainly near the Sierra
for the next few afternoons. Snowmelt runoff will increase flows
especially in the Walker River basin and creeks in Mono County.

&&

.SHORT TERM...

Flat upper level ridge will keep dry air mass in place through the
rest of today. We left in a mention of brief isolated
thunderstorms for Mono and western Mineral counties, however this
potential looks rather slim due to the absence of any significant
forcing, while the east-west oriented ridge axis remaining south
of Mineral-Mono counties keeps these areas in a less favorable
zone for thunderstorm development. We are expecting zephyr-type
breezes (gusts 25-30 mph) east of the Sierra into western NV
through this evening, with gusts up to 35 mph in northwest NV as
weak shortwave brushes across the Pacific Northwest.

On Saturday, we scaled back the thunderstorm potential, leaving in
a mention only near the Sierra crest in Mono County where a few
cells could form due to terrain driven convergence combined with
daytime heating. However, even if any cells do manage to form,
they are likely to push west of the crest due to north or northeast
mid level steering flow.

By Sunday and Monday as the ridge axis lifts northward, potential
for thunderstorms does improve a bit compared to today and
Saturday. A weak disturbance moving north across central CA could
provide better forcing across the Sierra mainly south of Lake
Tahoe on Sunday. Most cells are likely to travel relatively
parallel to the Sierra as mid level steering flow becomes
southeast. By Monday, a few cells are also possible into portions
of Lassen County due to improved low level convergence. Elsewhere,
warm mid level temperatures are likely to cap cumulus development
during each afternoon, although on Monday there is a very slight
possibility (about 10% chance) for a couple of brief cells over
far western NV, given better heating and possible local or
terrain-enhanced convergence in the late afternoon.

Temperatures this weekend will rise into the 90s across most of
western NV with 80s near the Sierra. By Monday, some valleys
especially near and east of US-95 have a decent chance of
reaching 100 degrees for the first time this year. While this
isn`t a heat event approaching historic levels, basic precautions
to protect against heat-related illness should be taken: drink
plenty of water, limit strenuous outdoor activity during the
afternoon, and never leave children or pets in your car unattended
for even short periods of time. More information on heat safety
can be found at www.weather.gov/heat. MJD

.LONG TERM...Tuesday through Friday.

The hottest day overall is still most likely to be Tuesday,
closely followed by Wednesday, with highs near or above 100
degrees across most western NV valleys. Later next week, the most
recent guidance has trended toward a more modest cooling, only
edging temps down by few degrees (mainly the 90s for valleys and
80s near the Sierra) by Friday.

Isolated thunderstorms remain possible Tuesday mainly due to
daytime heating and local convergence zones, but limited forcing
will reduce the potential for stronger or more organized
convection. The main threats would be gusty outflow winds and
brief heavy rainfall. A few brief cells are also possible
Wednesday mainly south of US-50, but confidence is not sufficient
to add a mention to the forecast, as moisture and instability
will be less compared to Tuesday. Later next week, with the
flatter ridge and dry west flow over the Sierra, conditions become
unfavorable for any thunderstorm formation, despite the continued
very warm temperatures. MJD

&&

.AVIATION...
VFR conditions will prevail through this weekend with mainly
clear skies except for scattered afternoon cumulus. There is a
very slight possibility of isolated thunderstorms between 23z-04z
today in Mono/western Mineral counties, then limited to Mono
County near the Sierra crest Saturday, with less than a 15%
probability of impacting any of the Sierra terminals either day.
By Sunday, the potential for thunder near the Sierra increases,
up to 20-25% from KTVL-KMMH.

Afternoon zephyr-type breezes will prevail today with gusts
generally 20-25 kt along the I-80 and US-50 corridors, with
locally higher gusts near 30 kt north of Gerlach, and less than
20 kt south of US-50. For this weekend, lighter winds are expected
except for stronger erratic gusts near thunderstorms. MJD

&&

.HYDROLOGY...

Persistent heat and mild overnight temperatures will lead to
progressively higher snowmelt rates in the remaining deep, high-
elevation snowpack. In many basins, these higher melt rates will
have limited impacts due to the relatively small remaining snow
covered area. In contrast, areas draining from high elevation
terrain near the Sierra Crest generally do have adequate remaining
deep snowpack to sustain high flows for area rivers.

The areas of highest concern are the Walker River system and
other creeks and streams draining from the Eastern Sierra into
Mono County. Flows are expected to increase daily with peak flows
occurring overnight or in the early morning hours from the middle
to the end of next week. These flows are expected to match, or
exceed, previous high flows that occurred earlier this season.
High flows are likely mid to late next week farther downstream on
the Walker River in Mason Valley and beyond, but the magnitude is
highly uncertain due to reservoir management decisions and the
timing of area reservoirs reaching their capacities. While
impactful flooding is not expected on the Tahoe Basin creeks or
the forks of the Carson River, very high flows are expected which
could cause minor issues and could be a risk to people recreating
in the mountains. Bardsley

&&

.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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