Area Forecast Discussion
Issued by NWS Reno, NV

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FXUS65 KREV 280955
AFDREV

Area Forecast Discussion
National Weather Service Reno NV
255 AM PDT THU JUL 28 2016

.SYNOPSIS...

Hot and dry conditions will prevail this week in eastern California
and western Nevada with a few record highs possible. A slow
increase in moisture will lead to a few afternoon and evening
thunderstorms, especially by Friday. High temperatures will ease
downward over the weekend and early next week as a trough moves
through the Pacific Northwest.

&&

.SHORT TERM...

Minimal changes to the short term forecast this morning. Temperatures
will remain 10 or more degrees above average through Friday, with
a few records likely, before some cooling ensues over the weekend.
Take precautions to avoid overheating if you must do anything strenuous
outside during the heat of the day.

Convection-wise, a few showers and very isolated thunderstorms
were noted late Wednesday afternoon and evening in southern Mono
County. With similar atmospheric conditions again today, another
round of isolated to scattered (near crest) showers and thunderstorms
are expected between about 2 PM and 9 PM in and near the Sierra
south of highway 50. Also, a stray cumulus buildup is possible a
bit farther north, with the 06Z NAM hinting at some in the Carson
Range near Mount Rose late in the day. On Friday, instability and
moisture continues to slowly build with another hot day on tap.
Model simulations continue to show the possibility that convection
will reach up into Lassen and northern Washoe Counties by Friday
afternoon, especially as a bit stronger westerly/zephyr flow kicks
in to aid low level convergence. As far as coverage, there is no
large-scale forcing to bring more widespread organized convection
so it is expected to remain isolated to locally scattered through
Friday.

As far as impacts from any thunderstorms through Friday, due to
high bases and limited moisture/narrow cores the primary threats
will be lightning and strong outflow winds to 50+ mph, especially
with storms that move out over the lower and hotter valley floors.

On Saturday, the ridge flattens out some as low pressure moves
into British Columbia and the Pacific Northwest. This will bring
increased southwest to west flow aloft, with the focus for afternoon
and evening thunderstorms being pushed out mainly into the Basin
and Range well south and east of Reno. In Mono County, simulations
seem to indicate that the threat for isolated storms would be east
of highway 395 near the CA-NV border so the slight chance we have
back to the crest may need to be pulled eastward in the next
couple model runs. Farther north, there could be a storm or two
north of Susanville and Gerlach although flow may keep most
convective buildups out in northwest NV. -Snyder

.Long Term (Sunday onward)...

Main theme of the long term is the (slow) ridge breakdown or shift
eastward with more of an off-shore trough influence by the mid-end
of next week. Guidance is in fairly good agreement.

Impact-wise the main stories next week will be cooler but still
seasonably warm temperatures and periods of increased winds. Right
now Tuesday looks to be the breeziest day especially if the more
amplified GFS pans out with trough swinging through the Pac NW. This
could result in some fire weather concerns for areas along/north of
Hwy 50.

A few afternoon-evening thunderstorms remain possible mainly south
of this line Sun-Wed as moisture building up over the next few days
never gets completely scoured out. GEFS plume diagrams for precip
water bear this out, however they are showing wide variability so
forecast confidence in thunderstorm coverage is fairly low for next
week. Instability is also a limiting factor keeping coverage
isolated at best based on latest guidance. -Chris

&&

.Aviation...

Isolated thunderstorms and hot temperatures will be the main weather
impacts for aviation Thursday and Friday. Outside of this, mainly
weak-moderate westerly zephyr winds will affect the region.

High resolution guidance shows isolated storms developing over the
high terrain from roughly TVL-BIH this afternoon. Cells will be slow
moving but high-based so strong outflow winds and lightning will be
the primary hazards, with brief periods of MVFR in rain showers.
Friday afternoon coverage of storms is likely to be further north,
also impacting CXP-RNO-SVE along the zephyr convergence zone.
Similar impacts with strong winds, lighting with increased storm
motions.

Record heat today and tomorrow will contribute to enhanced thermals
and turbulence into and out of area airports including RNO, MMH.
Also the heat will raise density altitude levels possibility
impacting aircraft performance during peak afternoon heating. Max
temp of 105 projected at RNO both days would yield DA of about 7900-
8100 ft MSL during the 22z-00z timeframe. -Chris

&&


.REV Watches/Warnings/Advisories...
NV...Fire Weather Watch from Friday afternoon through Friday evening
     NVZ450-458-459.

     Heat Advisory until 11 PM PDT Friday NVZ001-004.

CA...Fire Weather Watch from Friday afternoon through Friday evening
     CAZ270-271-273-278.

&&

$$

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


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