Area Forecast Discussion
Issued by NWS Reno, NV

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FXUS65 KREV 232030

Area Forecast Discussion
National Weather Service Reno NV
130 PM PDT Wed Aug 23 2017


Isolated to scattered showers and thunderstorms are expected
through this evening with less coverage expected than yesterday.
Drier and hotter weather will return starting Thursday into this
weekend and potentially much of next week. Record highs will be



Through this evening, two areas of increased instability and
forcing with more favorable thunderstorm potential are showing up
on the latest guidance. The first area is over Mono-Alpine
counties and southern portions of Douglas-Lyon-Mineral counties,
in association with deformation zone north of the upper low
centered near the southern CA coast. The second area is north of
Gerlach to near the Oregon border, associated with a weak
shortwave passage across southern Oregon (where some cells
developed around midday and are ongoing). Elsewhere, thunderstorm
chances are less favorable, although a few pulse type cells have
developed recently in parts of northeast CA, with additional
isolated cells possible in western NV due to low level convergence
near the weak zephyr boundary setting up later this afternoon.
Outflow boundary interactions from the early afternoon activity
could also trigger new development through early this evening.
Compared to yesterday, coverage of thunderstorms is not expected
to be as widespread with less overall intensity, although some
storms may still produce small hail, gusts up to 40 mph and
locally heavy rainfall, especially for areas south of US-50 where
slower cell motion is more likely.

For Thursday and Friday, a drier southwest flow is expected to
develop across most of the region, which should prevent
thunderstorm development. The only possible exception is Thursday
near the Sierra crest in Mono County, where weaker flow and
slight instability lingering from the southern CA low could lead
to isolated storms during the mid-late afternoon. By Friday, the
low over southern CA is projected to dissipate with upper level
ridge building over the Four Corners region. Above average high
temperatures in the lower-mid 90s are expected each day in lower
elevations, with late day zephyr breezes producing gusts mainly
between 20-25 mph. MJD

.LONG TERM...Saturday through next week

For this weekend into early next week, very warm temperatures for
late August will be the primary weather headline, as high
pressure ridge expands over most of the Great Basin. Highs will
rise to the mid-upper 90s in lower elevations Saturday, with
triple digit heat possible especially from Sunday through Tuesday.
Near the Sierra, highs ranging from the upper 80s-near 90
degrees. There is a medium level of confidence that during the
upcoming week, Reno will set at least one daily record high, which
currently are either 99 or 100 degrees for the final week of

The location and orientation of the ridge is not favorable for
thunderstorm development especially through Monday, as warm
temperatures aloft will cap vertical growth of cumulus and there
are no significant sources of forcing evident over the Sierra or
western NV. There is a marginal potential for a bit of increased
moisture and weak forcing to creep into southern Mono County by
Tuesday, but at this time confidence is not sufficient to add a
mention of thunder. Winds will generally be light through Monday
with a possible slight increase in south to southwest winds by
Tuesday afternoon.

By the middle or later part of next week, a trough approaching
the Pacific Northwest will attempt to weaken the ridge. The main
effect of this transition would be an increase in west winds
along with a few degrees of cooling. However, some of the medium
range guidance sources keep the ridge largely intact, splitting or
weakening the trough as it moves inland. If this latter scenario
occurs, we could have highs near 100 degrees through the end of
August. In our current forecast we will only make a modest
downward trend in temperatures by Wednesday, with conditions
remaining unfavorable for thunderstorms. MJD



Through early this evening (until around 01Z at KRNO-KCXP and
until 03Z for west central NV south to KMMH), there is a small
chance for -SHRA or -TSRA affecting the region, but overall
conditions are likely to remain VFR at the main terminals unless a
thunderstorm moves directly overhead. These storms may produce
outflow gusts to 35 kt, small hail and brief heavy rainfall.

Otherwise, VFR conditions are expected to prevail for the upcoming
week with generally light winds other than typical late day
zephyr breezes with gusts mainly up to 20 kt through Friday. A
few sites could see slightly stronger gusts to 25 kt Thursday.
Patchy shallow fog may affect KTRK btwn 10-15Z early Thursday but
impacts on aviation will likely be limited. MJD


.REV Watches/Warnings/Advisories...


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