Area Forecast Discussion
Issued by NWS Reno, NV

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FXUS65 KREV 240904

Area Forecast Discussion
National Weather Service Reno NV
204 AM PDT SUN JUL 24 2016

Hot and dry conditions with mainly light late day breezes are
expected for the upcoming week as strong high pressure builds into
the Great Basin. By next weekend, some increase in moisture may
lead to a few thunderstorms forming south of Highway 50.



Very dry conditions will continue with humidity values in the
single digits during the day, and poor humidity recovery in mid
slope and ridge top locations for the next few nights. Model
soundings don`t indicate the extreme low 700 mb dew points
compared to recent nights, so ridge top sites appear less likely
to dip into the single digits during the overnight or early
morning hours.

A lingering north to northeast wind kept temps down a bit more than
expected in lower elevations Saturday, but the return of a weak
late day zephyr (wind gusts generally below 25 mph) will bring
better mixing starting today. Highs in warmer valleys should
reach triple digits, especially by Tuesday as the ridge expands
across more of the Great Basin. Near the Sierra, highs will mainly
range from the mid 80s to lower 90s. Little to no cloud cover is
expected through Tuesday, except for areas south of US-50 where a
modest amount of mid level moisture and weak convergent flow may
lead to flat cumulus development Monday-Tuesday afternoon. MJD

.LONG TERM...Wednesday through Saturday...

The early part of the extended has not changed this cycle as a ridge
of high pressure over the southwestern U.S. will be in place with
700 hPa temps in the 16-19 C range. This will produce surface
highs in the 100-106 degree range for the lower valleys with
Sierra valley highs in the upper 80s to lower 90s....about 6-10
degrees above average for late July. The warmest days should be
Wednesday and Thursday if the GFS solution verifies. If the ECMWF
solution wins out then Friday will be just as warm.

Now to issues with the model solutions. The deterministic models
start to diverge as early as late Thursday and this divergence is
amplified by Friday. The GFS produces a trough along the west coast
that would support drawing moisture north along the spine of the
Sierra while also shifting the ridge center east to near the Utah
border. The ECMWF holds the ridge in place through Friday before
starting to shift it east Saturday. The GEFS ensemble members have
little support for the GFS this cycle...but most members do develop
a bit of trough by Saturday.

So...the GFS would develop convection in southern Mono County as
early as Thursday...spread that convection north to near the Oregon
Border by Friday then redevelop convection Saturday. The ECMWF is
more consistent with its previous forecasts of only producing
convection over the far southern CWA by Saturday. Since the GFS
solution is a fairly significant departure from previous runs and
has little backing we will show some potential for convection as
early as Thursday with pops below 10 percent...mainly an increase
in afternoon cumulus...and only show slight chance of thunderstorms
for Saturday south of Highway 50. 20



Very light winds aloft will limit turbulence the next few days to
only that associated with daytime heating...especially near the
mountain slopes and ridge tops. Thermally induced low level winds
will develop in the afternoons east of the Sierra where gusts will
approach 20 knots. These Zephyr winds are likely to increase a bit
as thermal gradients strengthen into the middle of the week.

VFR conditions with few clouds as the air mass remains very dry each
day through mid-week. Some models hint at mid level moisture return
by late week that would produce high based thunderstorms with the
potential for gusty surface winds and turbulence by the
Friday/Saturday time frame. 20


.REV Watches/Warnings/Advisories...


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