Area Forecast Discussion
Issued by NWS Reno, NV

Home | Current Version | Previous Version | Text Only | Print | Product List | Glossary On
Versions: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20
000
FXUS65 KREV 241001
AFDREV

Area Forecast Discussion
National Weather Service Reno NV
301 AM PDT Sat Jun 24 2017

.SYNOPSIS...

Very warm temperatures continue this weekend with some cooling by
early next week. Isolated thunderstorms are possible near the
Sierra today, spreading into parts of western Nevada Sunday.
Critical fire weather conditions are possible Monday as very dry
air combines with gusty winds. Flooding will continue for the
creeks in Mono County and portions of the Walker River.

&&

.SHORT TERM...

Ridging will remain the predominant weather feature through the
weekend keeping conditions hot and generally dry, with triple
digit highs for Western NV valleys, and upper 80s to around 90 in
Sierra valleys both days. Reno`s current record highs of 103 for
today and 102 for Sunday will probably not be broken, but this
weekend`s highs should come within a degree or two of these
values. Winds will also remain light under the ridge axis through
Sunday afternoon.

As for thunderstorm chances, today looks to be similar to
yesterday with isolated cells possible mainly near the Sierra.
Due to increased heating producing a bit more instability, a few
cells could form farther north to near I-80 in eastern CA, and
into far western NV mainly south of a Minden-Hawthorne line. Late
tonight into Sunday morning, a weak upper level disturbance is
projected to track northward across the Tahoe basin into northeast
CA. For these areas, the potential for thunder looks slim, with
the more likely outcome being some increased mid level cloud cover
and sparse raindrops possibly reaching the ground.

For Sunday, the departing upper disturbance will leave most areas
in a less favorable convective environment through early afternoon,
although heating will reload convective cloud development by mid-late
afternoon. A weak late day zephyr may provide some low level
convergence across parts of western NV and eastern Lassen County,
but upper level forcing will be limited across most areas, leading
to more sparse pulse-type cells with redevelopment primarily due
to outflow boundary interactions and convergence along the zephyr.
Thunderstorm coverage may be a bit more cohesive north of
Susanville-Gerlach where some leftover upper level forcing could
come into play during the late afternoon-early evening hours. Even
though we aren`t expecting a significant convective event, a few
stronger cells could produce brief heavy rainfall, small hail and
gusty outflow winds, with weaker showers and thunderstorms
possible into the late evening.

By Monday, upper level trough is still on track to shift inland
increasing the surface pressure gradient across the region. As a
result, winds will become breezy Monday afternoon with
temperatures trending downward especially west of US-95, although
a few valleys near and east of US-95 may still touch 100 degrees.
These increasing winds coupled with very low humidity will likely
produce critical fire weather conditions for western Nevada.
Areas affected by lightning this weekend will need to be monitored
closely for possible fire starts and holdovers which could spread
quickly when winds pick up Monday. For more details, see the Fire
Weather segment below. MJD

.LONG TERM...Tuesday through Friday...

A trough will be over the region Tue-Wed with temperatures edging
closer to normal both days. Relaxing thermal gradients in the post
frontal environment and decreasing winds aloft will result in winds
Tuesday that will be less than those expected Monday. Gusts will
stay mostly in the 25-30 mph range Tuesday afternoon/early evening.
As trough axis swings southeast through the northern Great Basin
late Tuesday, a few light showers cannot be ruled out along the
Oregon border. For now we have introduced some very low pops but
will leave the mention out of the forecast unless models become more
aggressive.

For the balance of next week, heights begin to rise again although
ridge axis will remain west and south of the region. This will mean
a warming trend and generally light winds. There are indications
that instability will begin to slowly build along the Sierra next
Fri-Sat and isolated thunderstorms may need to be introduced at some
point. Hohmann

&&

.AVIATION...

Towering cumulus and a few storms built along the Sierra in Alpine
and Mono Counties Friday and will likely develop in these same areas
again today, spreading a bit farther north into the Tahoe Basin by
early this evening. Otherwise, expect VFR conditions to prevail
today with light northeast to east flow.

A shortwave will lift northward across the area tonight and early
Sunday. This will result in some mid level cloud development and
possibly isolated showers/virga. Clouds should break sufficiently to
allow for daytime heating/initiation of storms Sunday afternoon
along the eastern Sierra northward into Lassen County. Storms will
generally be isolated as they push off the Sierra in response to the
zephyr although a few could be strong. As the Lassen convergence
increases, coverage of storms could be a bit more over northeast CA
and northwest NV by late afternoon/evening.

Gusty southwest flow will bring a more stable airmass Monday but
increase the chance for low level turbulence. Hohmann

&&

.FIRE WEATHER...

Afternoon temperatures will soar into the mid 90s to low 100s once
again this weekend. In addition to the low afternoon humidity,
recoveries will remain poor to moderate. A few storms are possible
today near the Sierra and like yesterday they will be slow moving.
Any wetting rains will be very localized with most areas receiving
little or no rain.

Sunday, an upper disturbance will move over northern California in
the morning. Due to the weakness of the impulse, the wave is NOT
expected to initiate any elevated thunderstorms. The main impact
from the disturbance will be the Sunday afternoon zephyr as thermal
gradients increase between the Sacramento Valley and west-central
NV. This is expected to encourage the development of mainly isolated
thunderstorms along the leading edge of the zephyr, as well as north
of Susanville and Gerlach in the typical convergence zone there.
With inverted-V profiles and storm motions in the 10-15 mph range
(based on cloud-level flow from simulations), there is definitely
the threat for dry lightning strikes. However, with the wave timing
in the morning, the coverage should remain isolated. Still, winds
gusts over 50 mph could affect a few areas for an hour or so near
any storms.

Turning to Monday, the upper ridge bringing the hot temperatures
will break down. This will bring a cooling trend lasting into mid-
week, with stabilizing southwest flow aloft ending the threat for
thunderstorms. Unfortunately, it will also bring increasing winds
for Monday as thermal gradients are maximized across the region.
Monday afternoon and evening, sustained winds could reach around 20
mph with gusts up to 35 mph. This could threaten to bring renewed
vigor to any fires started by Sunday`s convection or to any new
fires. Also, some simulations show a dry slot moving in Monday night
for a possible continuation of poor recoveries on midslopes. With
all this in mind, a Fire Weather Watch remains in effect for fire
zones 450 and 453. Other areas will have winds and low
humidities, but they have not yet been cleared for red flags by
the GACC. Snyder/Hohmann

&&

.HYDROLOGY...

Rapid snowmelt from the remaining deep high elevation snowpackwill
bedrivenbyhot days and warm nights.Expect continuedvery high
flows at least throughSundaynight on creeks and streams draining
high elevation terrain near the Sierra Crest, as well as creeks
draining the eastern and northeastern flanks of Mt. Rose. This
includes the forks of the Walker River, other creeks and streams in
Mono County, Galena Creek, and neighboring creeks in the Mt. Rose
area.

Peak nighttime flows throughSundaynight are likely to be similar
to observed peaks over the last three nights. A combination of
slightly cooler temperatures and depleting snow covered
contributing area should lead to gradually decreasing flows
starting early next week.

Preliminary measurements of snowmelt flows on the West Walker above
and below Topaz reservoir have exceeded the previous snowmelt peak
flow of 1995 and that water is slowly moving into and through the
Mason Valley. Fortunately this year at this time, the East
Walker is contributing significantly less water than it was during
the peak of 1995. The combination should lead to flows and
impacts in the Mason Valley and downstream similar to or slightly
less than from the peak flows of mid-July 1995.

&&

.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



USA.gov is the U.S. government's official web portal to all federal, state and local government web resources and services.