Area Forecast Discussion
Issued by NWS Reno, NV

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FXUS65 KREV 291610 AAA

Area Forecast Discussion...UPDATED
National Weather Service Reno NV
910 AM PDT WED JUN 29 2016

A quick update to add thunderstorms to Eastern Churchill County
this afternoon and evening. Given the trend of the past couple
days of the convection being slightly further north than models
have shown (except the NCAR high res ensemble), thought it would
be prudent to add here. It will be right on the edge, but given
the Horseshoe fire in that area any potential would be a concern
to firefighters. The chance is only around 10%. Otherwise, no
other changes planned or anticipated this morning. Wallmann


Highs around 100 degrees are expected for lower elevations of
western Nevada through Friday as high pressure remains over the
Great Basin. A few thunderstorms are possible today and Thursday
mainly south of Highway 50, with the threat of isolated storms
expanding farther north on Friday. For the holiday weekend, dry
conditions are expected with temperatures remaining above average.




The most notable change to the current forecast was expanding the
slight chance of thunder on Friday afternoon-evening to include
more of eastern CA-western NV.

Otherwise, the majority of the ongoing forecast remains intact.
For today, thunderstorm chances will again be highest for Mono
County, with more isolated coverage northward into portions of
western NV from the Pine Nut mountains eastward across Mineral and
Lyon Counties. Fewer cells are expected Thursday as the ridge
retreats southward into the Desert Southwest region, which will
weaken the moisture feed for the Sierra and western NV south of

For Friday, short range guidance is in better agreement with
placing a weak upper low/trough over central CA, which would
spread better instability and increased mid-upper level moisture
farther north across eastern CA-western NV. Although there are
still uncertainties with the location of the low, the general idea
favors eastern CA-far northwest NV for initial isolated
thunderstorm development in the afternoon, then spreading east
across much of western NV by early evening. We are not expecting
a widespread convective event with significant impacts, although
slow cell movement may produce localized heavy rainfall which
could lead to possible flooding or debris flows in recent burn
scars, especially in steeper terrain.

Daytime temperatures will continue to run about 10 degrees above
average through Friday. Highs will remain near or above 100
degrees for most lower elevations, with mid to upper 80s for the
Sierra valleys.

One other item of note is the possibility of smoke and haze
from the Trailhead wildfire spreading across eastern CA-far
western NV later today. For now, we will just mention some haze in
eastern CA north of I-80 and south of Susanville, and far western
NV just north of Reno. For more details, see the Aviation segment
below. MJD

Long Term (Saturday Onward)...

Messaging focus will be on continued warm temperatures and drier
flow for the holiday weekend into early next week. Pretty typical
stuff for the beginning of July. No big changes made to the forecast.

Simulations have come into somewhat better agreement showing a weak
upper trough along the west coast persisting into the middle of
next week with a dry southwest flow aloft over the region. As a
result thunderstorm chances are minimal, except perhaps some
isolated cells in favored convergence zones. Predictability of
these are too low this far out to include in the forecast.
Temperatures will be slightly cooler compared to this week, but
not by much with 500 mb heights remaining near to above normal.

Weak-moderate daily winds are expected through the period. One thing
to watch is both GFS, ECMWF bring a more potent trough through the
Pac NW next Tuesday-Wednesday which would increase the winds
around our region, perhaps into critical fire weather levels. GEFS
precipitable water plumes show the area drying out quite a bit too
so some poor humidity levels are possible with the winds. -Chris


Generally VFR with typical weak-moderate late afternoon westerly
winds through Friday. However as moisture aloft has increased we do
expect isolated-scattered thunderstorms to develop each afternoon,
early evening. These storms will produce MVFR ceilings and
visibility, lightning, strong outflow winds, and possible blowing
dust. Areas south of Highway 50 have the best chances of seeing
impacts from thunderstorms.

For today, based on the latest NCAR convective resolving ensemble,
we`ll likely see storms initiate near MMH as early as 19-20z, with
development further east and north, perhaps extending up along the
Pine Nuts east of MEV, CXP by 22-00z. This simulation did quite well
on thunderstorm coverage yesterday. I can`t completely rule out
cells near RNO but simulations keep activity over the Pine Nuts,
Virginia Range well SE of the field. Note that our primary radar
KRGX is out of service until likely early afternoon today.

Another item to mention is potential for smoke from the Trailhead
wildfire east of Auburn to impact our region. If the fire
continues to be active today, HYSPLIT simulations show light to
moderate levels of smoke working into the Tahoe, Reno areas with
the zephyr westerly wind, after 22z. While I won`t put
restrictions in the TAFs due to uncertainty, degraded flight
visibility is possible between Reno and Sacramento over the Sierra
with terrain obscuration. That is, again, assuming the fire
remains active today. -Chris


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