Area Forecast Discussion
Issued by NWS Reno, NV

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FXUS65 KREV 152149
AFDREV

Area Forecast Discussion
National Weather Service Reno NV
249 PM PDT Thu Jun 15 2017

.SYNOPSIS...

Warming and drying trend will continue through the weekend.
Temperatures will be hot for the weekend and start of next week
with a low chance of showers and thunderstorms. Expect an increase
in water flow on the Carson and Walker River systems by the end  of
this week.

&&

.SHORT TERM...

Hot conditions are still expected this weekend and into next week
with daily highs running 10-15 degrees above seasonal averages. High
pressure continues to build over the weekend with a central 500mb
height expected to reach 598dm by Monday- an anomalously strong
ridge for the end of June. Temperatures jump from the low 90s on
Friday to around 100 degrees by Monday. Heat illness will be a
concern and people should plan accordingly. Know the signs of heat
illness, carry plenty of water, 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.

Correspondingly, high temperatures for elevations above 9000 feet
will be very warm as well. This will result in rapid melting of
the remnants of the Sierra snowpack. Concerns are increasing for
flooding mainly for the Walker River system and for creeks and
streams in Mono County late this weekend into next week. However,
flows will be high elsewhere posing a risk to those recreating
near streams and creeks as far north of the Tahoe Basin. For more
details, see the hydrology section below.

Otherwise, conditions will be a little breezy, gusts 20 to 30 mph,
this afternoon and Friday afternoon as a weak wave strafes the
region. Winds then become light over the weekend as the pressure
gradient weakens.

Another consequence of heat building under the ridge will be the
potential for convection each afternoon starting Saturday as
instability increases along convergence zones. Initially,
convection will occur in Mono/Inyo Counties before spreading
northward to the southern reach of the Tahoe Basin Sunday through
Tuesday. Also, Sunday`s chances will be the most expansive and may
extend into the Sierra Front from the Pine Nuts southward as a
wave passes over. Given elevated precipitable water values from a
confined stream of Pacific moisture and weak steering level flow,
some cells may be capable of producing localized heavy rain
totals. Wind gusts could also be rather strong based on the
strongly inverted V soundings and extremely dry surface
conditions. It is still unclear how severe these storms may be,
but it is something to watch out for especially if you will be
outside. Boyd

.LONG TERM...Wednesday through the end of the week...

Chances of convection diminish somewhat as upper flow becomes
northwesterly and as ridging deflects southward. This shift will
also herald "cooler" conditions by the end of the week as highs
begin to drop back into the low/mid 90s. Boyd

&&

.AVIATION...

VFR conditions and generally pleasant flight conditions are
expected as high pressure builds over the region. A passing wave
this afternoon through Friday will increase afternoon breezes up
to 25kts along the Sierra Front. Otherwise, winds will be light.

As heat builds under the ridge, density altitudes will increase.
This could be an issue for Sierra terminals like KTVL and KTRK as
highs exceed 80 degrees. Temperatures will be pushing the upper
90s and 100 degrees for Nevada terminals also resulting in higher
than usual density altitudes.

Also, instability increases this weekend with low chances of
afternoon convection possible from Saturday through Tuesday
mainly over the higher Sierra from South Lake Tahoe through Inyo
County. Atmospheric parameters suggests slow moving cells, but
outflows would be rather strong considering thermal differences
from downdraft origination heights and surface temperatures.
Terminals most likely to be impacts by TS include KMMH and KTVL.
Boyd

&&

.HYDROLOGY...

Persistent heat and high overnight temperatures will lead to
progressively higher snowmelt rates in the remaining deep, high-
elevation snowpack. This time of year there is a competing balance
between the snowmelt rates and contributing area of snow
coverage. Lengthy days and very warm temperatures will create
conditions necessary for very high snowmelt rates. In many
basins, these high rates will have no or 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 of headwater creeks and streams 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 stream 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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