Area Forecast Discussion
Issued by NWS Reno, NV

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FXUS65 KREV 221008
AFDREV

Area Forecast Discussion
National Weather Service Reno NV
308 AM PDT Mon Jul 22 2019

.SYNOPSIS...
Mid-summer heat will persist across the Sierra and western Nevada
for the upcoming week. The threat for mainly afternoon and evening
showers and thunderstorms continues for the next few days, with
some storms possibly strong with locally heavy rainfall, gusty
winds and small hail. Lightning could also occur late tonight into
early Tuesday for parts of western Nevada.

&&

.SHORT TERM...

Yesterday`s convective activity featured isolated but strong
persistent storms moving quickly north across parts of northwest
NV. Instability was quite impressive for western NV, and some of
the cells remained active for a few hours. A few lightning fires
also were ignited by these storms.

For this afternoon-evening, a similar setup looks likely,
although conditions appear to favor a greater coverage of showers
and thunderstorms, but less overall intensity. Still, we can`t
rule out some cells producing heavy rainfall, frequent lightning,
small hail and outflow gusts of 40+ mph, especially where the late
day zephyr provides enhanced convergence. The most favored areas
for these late day storms include Lyon County, eastern Storey
County, and from Pyramid Lake-Gerlach eastward to western parts of
Churchill and Pershing counties.

For tonight into Tuesday morning, an upper level disturbance
moving northward across the region will provide elevated
instability, which could lead to some thunderstorms redeveloping
across parts of western NV, mainly west of US-95.

For Tuesday afternoon-evening, another round of thunderstorms is
expected, with the best potential shifting eastward to west
central NV. A few cells could still pop up near Pyramid Lake and
Fernley along the initial convergence set up by the zephyr,
otherwise the increased west winds will reduce the threat for
storms north of I-80, with Tahoe and northeast CA also unlikely to
receive any storms.

For Wednesday, drier and more stable air sets up across more of
the region as the high pressure ridge becomes suppressed farther
to the south, pushing the thunderstorm threat to areas south of
US-50. For more details/impacts related to the next few days of
thunderstorm activity, please see the Fire Weather section below.

Temperatures today look to be similar to yesterday, with a few
locations along the US-95 corridor having the best shot at triple
digit heat. Portions of the heat advisory areas will start on the
warm side this morning (near or above 70 degrees) due to an
extensive area of mid-high level cloud cover. Another round of
cloud cover could keep tonight relatively warm as well. A bit of
cooling is expected Tuesday due to the weak trough passage across
the Pacific Northwest, while Tuesday night isn`t likely to remain
as warm due to some drying and less overnight cloud cover.
However, daytime temperatures are projected to remain above
average for at least the next week. MJD

.LONG TERM...Thursday onward...

Biggest change for the end of the week is the ridge displacement
to the southeast due to troughs moving into the Pacific
Northwest. Ensemble guidance has been hinting at this possibility
for several days now, and operational runs are leaning in this
direction as well. This will bring the potential for increased
winds across northeast CA and extreme northwest NV and shift
deeper moisture south and east. The question at this point is if
we could see an increase in thunderstorms Thursday night into
Friday across northeast CA and northern Washoe County due to
forcing from a jet streak between these two features. This is a
similar set-up to what we are seeing currently, but the trough is
not elongated quite as far south.

As we progress into the weekend, a drier airmass results over much
of northern CA/NV in the wake of the trough passage. This should
bring a decrease in storm activity for a couple of days, so have
reduced chances outside of the Mono/Mineral convergence zone. The
ridge simultaneously retrogrades and strengthens, leading to warmer
temperatures next weekend into the early part of next week. -Dawn

&&

.AVIATION...

Seasonably hot temperatures will continue to bring density altitude
concerns during the day. Winds will generally be light with peak
afternoon gusts of around 15 kts. Slightly stronger winds are
possible near the Oregon border today and Tuesday afternoon with
gusts to 25 kts.

Thunderstorms are possible once again today from approximately
21z-06z, with isolated storms possibly continuing overnight.
Storms will most likely initiate in Mono/Mineral/Southern Lyon
counties, expanding north and east across western Nevada by late
afternoon and early evening. These same areas have chances for
nocturnal storms tonight, though coverage will be more isolated.
Greatest threat will be strong outflow winds which could also kick
up dust and reduce visibility. Discrete supercells are possible,
bringing a hail and localized heavy rain threat as well.

Additional thunderstorms are possible this week. -Dawn

&&

.FIRE WEATHER...

Thunderstorms Sunday initiated a few new fires and storms today
are likely to do the same. While storms are putting down decent
rainfall within the core, lightning strikes outside of the core
can easily ignite new starts. Storms today have the potential to
bring gusty and erratic outflow winds in excess of 40 mph in
addition to hail. Widespread wetting rains are unlikely due to
fast storm motions.

Nocturnal storms are still possible tonight from approximately the
Sierra Front eastward. Coverage is anticipated to be isolated, so
no watches or warnings are in effect at this time. Just be aware,
the nocturnal storms will be fast moving, limiting how much rain
will reach the surface in any one spot. Even a few storms can lead
to additional fire starts.

Generally, afternoon winds will be lighter than usual, with the
one exception being northeast California to northern Washoe
County where afternoon gusts could reach 25-30 mph Monday and
Tuesday afternoons.

Additional storms are possible through the week, though there will
be a sharp moisture boundary setting up somewhere between I-80 and
US-50, with a drier and more stable airmass to the north, and
wetter thunderstorms more likely to the south. Storms may make it
farther north again by the end of the week. -Dawn

&&

.REV Watches/Warnings/Advisories...
NV...Heat Advisory until 11 PM PDT this evening NVZ001-003-004.

CA...None.
&&

$$

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


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