Area Forecast Discussion
Issued by NWS Reno, NV

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FXUS65 KREV 221010
AFDREV

Area Forecast Discussion
National Weather Service Reno NV
310 AM PDT Tue Aug 22 2017

.SYNOPSIS...

Increased thunderstorm coverage is expected this afternoon and
evening along with an elevated risk for flash flooding. Heavy
rainfall, small hail, and gusty outflow winds will be possible with
these storms. Drier weather returns late week as high pressure
strengthens and provides high temperatures reaching back into the
mid to upper 90s across western Nevada.

&&

.SHORT TERM...

Shower and thunderstorm coverage will be at its peak today as an
upper level low draws ample moisture in the region and provides
enough instability and forcing to enhance the threat for flash
flooding through this evening.

Currently, a band of light to moderate showers is working its way
across Mineral county to just south of the Tahoe Basin in
association with deformation along the northeast quadrant of the
low. This forcing will work with daytime heating to help trigger
thunderstorms in the eastern Sierra and for western Nevada by early
to mid afternoon.

The heavy rain and flashing flooding threat will be enhanced today
as column moisture increases to 0.75"+ and storms embed within
unidirectional and light steering flow. This will allow for slow
moving storms and longer duration rainfalls today. Precipitation
efficiency will also be improved as the increased moisture allows
LCLs to dip about 5,000` lower than yesterday afternoon (lower 25th
percentile) and instability exhibits a "long/skinny" CAPE profile.

Favored areas for flash flooding include areas of steep terrain and
burn scars in the Sierra from northern Mono County into the southern
Tahoe Basin, the Pine Nut Range through the Virgina and Pah Rah
ranges across western Nevada. Areas such as the Farad burn scar
are particularly vulnerable and may produce areas of mud of debris
flows which could impact portions of Intestate 80. The potential
for flash flooding is lower confidence in northern Lassen,
northern Washoe, and Pershing counties as this activity will
largely be forced by the low`s deformation in an area of weaker
instability.

Outflow winds and small hail will also be possible with today`s
storms but max outflow speeds should be somewhat muted with the
increased moisture. Generally looking for gusts up to 40-45 mph
with pea to dime sized hail possible.

Wednesday will feature one more day of isolated to scattered
showers and thunderstorms with localized heavy rainfall before
drier, more stable southwest flow aloft arrives late Wednesday
night and Thursday. Fuentes

.LONG TERM...Friday and beyond...

A strong area of high pressure sets up over the west Friday, lasting
through the weekend. This will bring warming temperatures and dry
conditions to the eastern Sierra and western Nevada. High
temperatures are likely to be in the mid to upper 90s in western
Nevada valleys with 90s in Sierra valleys. Winds will generally be
light through the period with some afternoon breezes.

The ridge begins to weaken around the middle of next week in
response to a trough approaching the northwest coast. This, along
with increasing moisture, may allow for some thunderstorms to return
to the region midweek. -Dawn

&&

.AVIATION...

A few showers with isolated embedded thunderstorms are possible
this morning moving southeast to northwest from KHTH- KBLU. Most
of this activity will have waned by 16z, but then more widespread
shower and thunderstorm activity will develop between 17-19z,
lasting through 03-06z this evening. The greatest risk for
aviators today will be locally heavy rainfall and reduced CIGS/VIS
along with terrain obscuration. Gusty and erratic thunderstorm
outflow winds and small hail are also a concern with gusts
generally 40-45 mph or less unless a storm gets particularly
strong. Storms will overall be slow moving with storm motions
generally from a southerly direction, becoming more south
southwest by tonight.

Thunderstorm chances continue overnight for areas mainly north of I-
80, with some lingering rain showers possible south of there.
Additional showers and thunderstorms are possible on Wednesday.

Storm chances will wane Thursday into the weekend with typical
westerly afternoon breezes. Conditions will be VFR outside of
thunderstorms. Early morning patchy fog remains possible around KTRK
if the airfield receives rainfall. -Dawn

&&

.REV Watches/Warnings/Advisories...
NV...None.
CA...None.

&&

$$

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



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