Special Weather Statement, NWS Reno, NV

Area Forecast Discussion
National Weather Service Reno NV
259 PM PDT Tue Aug 8 2017

.SYNOPSIS...

Low pressure stalled over northern California will produce
isolated to scattered thunderstorms through Thursday. Storms
could bring heavy rainfall with a few severe thunderstorms
possible. Thunderstorm chances will diminish late week with dry
conditions for the weekend. Temperatures will remain near or
slightly below average through the week.

&&

.SHORT TERM...

Modest cumulus buildups have developed over areas of higher terrain
this afternoon; however, thunderstorms have been fairly slow to get
going today as we await better focus in the form of westerly wind
convergence in the northern Sierra. This is starting to occur
based on SSW to SW winds on the west slopes of the northern Sierra,
so deep convection should begin to initiate across northeast
California in the next couple hours. Storms today are expected to
feature similar traits to yesterday with wind gusts up to 30-40
mph, brief heavy rain, and a few lightning strikes possible from
any storms. A few stronger storms cannot be ruled out due to
unpredictable boundary interactions, with heavier more persistent
rainfall and hail to 1/2" in diameter possible.

As far as flash flooding today, with limited coverage of
thunderstorms overall the main threat is expected to be restricted
to burn scars in steep terrain such as the Farad (I-80 near NV/CA
line) and Tule Peak/Long Valley Fire (west of Pyramid Lake) areas.
With only localized concern for flash flooding, will cancel watch
with the package.

After daytime convection dies out, a residual threat for isolated
thunderstorms exists late tonight and Wednesday morning, mainly
north of I-80, as some divergence aloft and a weak jet streak move
over northwest NV and northeast CA.

Wednesday afternoon and evening, the potential for strong to severe
thunderstorms is expected to increase as the upper low near the coast
begins to eject into northern California. The approaching low will
bring strengthening wind shear (both speed and directional) in the
storm-bearing layer which, when combined with afternoon zephyr
convergence, will increase the risk for organized, longer-lived
thunderstorms. The strongest storms could contain hail to an inch
or so in diameter, very heavy rain, and wind gusts over 50 mph
(especially in western and west-central NV).

Late Wednesday night and Thursday morning, the upper low moves into
northern CA in a negative-tilt fashion per current simulations.
Good divergence aloft will provide the environment for isolated to
scattered showers with some embedded thunderstorms, mainly north
of I-80. For Thursday afternoon, the negative-tilt upper low will
provide the focus for more thunderstorms along with a continued
threat for severe thunderstorms. With the low over northern CA, a
dry slot could invade areas south of Highway 50 and near the
Sierra crest from Tahoe south by late afternoon Thursday...
bringing the best potential for thunderstorms over northeast CA
and northwest NV. Precipitation chances may need to be increased
in those areas given the fairly stout forcing.

On Friday, drier and more stable flow finally invades northeast CA
and western NV in the wake of Thursday's low. With this in mind, I
have removed all thunderstorms on Friday. -Snyder

.LONG TERM...Saturday through Tuesday...

Over the weekend, dry and more stable southwest flow is expected
to remain over the region with high temperatures near or slightly
above average (80s Sierra valleys, 90s lower valleys). Early next
week, a trough is shown to break off of a northeast Pacific low
and drop south along the West Coast. While there are varying
solutions, at this time it looks like the trough will keep highs
at least near average (GFS)...but possibly below average (ECMWF
with highs in the upper 70s to upper 80s for lower valleys).
-Snyder

&&

.AVIATION...

Isolated to scattered thunderstorms are expected today and
Wednesday. Threats will be gusts to 30-40 kts and localized heavy
rain (decreasing terrain visibility). Storms on Wednesday are
expected to be stronger with an increased threat for large hail
(to around 1 to 1.25" in diameter) and damaging outflow winds over
50 kts.

A few overnight thunderstorms are possible, generally north of
I-80, tonight and again Wednesday night. Local, sudden gusts to
30 kts and isolated lightning strikes could accompany storms.

Thursday will see one more round of strong to possibly severe
thunderstorms, but they will generally be from I-80 northward. It
is finally expected to be dry all areas Friday and over the
weekend as drier, more stable southwest flow aloft ensues.
-Snyder

&&

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

CA...None.

&&

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

Special Weather Statement
National Weather Service RENO NV
139 PM PDT Tue Aug 8 2017

CAZ070>072-NVZ002-005-082200-
Surprise Valley California-Lassen-Eastern Plumas-
Eastern Sierra Counties-Greater Lake Tahoe Area-
Northern Washoe County-
Including the cities of Cedarville, Eagleville, Fort Bidwell,
Portola, Susanville, Westwood, Sierraville, Loyalton,
South Lake Tahoe, Tahoe City, Truckee, Markleeville, Stateline,
Glenbrook, Incline Village, Empire, and Gerlach
139 PM PDT Tue Aug 8 2017

...Thunderstorms Developing over the Sierra and Northeast
California...

As of 130 PM, isolated storms were beginning to develop over the
far northern Sierra from Tahoe north to Lassen County and far
northern Washoe County. This trend will continue through the
afternoon.

While widespread severe storms are not expected today, a few
storms could become strong with copious lightning, heavy rain and
flooding, small hail, and strong outflow winds.

If you're on a lake or trail in Lassen or Plumas Counties, now is
the time to head toward a safe shelter before lightning becomes a
hazard. This includes areas near Lassen National Park, Eagle Lake,
and Lake Davis.

Chris

http://weather.gov/reno

Special Weather Statement
National Weather Service Reno NV
530 PM PDT TUE AUG 8 2017

CAZ071-090115-
Lassen-Eastern Plumas-Eastern Sierra Counties CA-
530 PM PDT TUE AUG 8 2017

...GUSTY OUTFLOW WINDS MAY AFFECT FRENCHMAN LAKE THROUGH 630 PM...

At 528 PM PDT, Doppler radar was tracking a rapidly developing
thunderstorm near Frenchman Lake, or 8 miles northeast of
Beckwourth, moving northeast at 10 mph.

Half inch hail and gusty outflow winds in excess of 40 mph will be
possible with this storm. The storm could also produce brief periods
of moderate rain.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

If on or near Frenchman Lake, get out of the water and move indoors
or inside a vehicle now. Don't be caught on the water in a
thunderstorm. Strong wind gusts and lightning pose an immediate
danger to boaters. Gusty winds will cause a rapid increase in wave
heights which may capsize small boats.

&&

LAT...LON 3987 12028 3992 12037 4010 12030 3998 12009
TIME...MOT...LOC 0028Z 208DEG 8KT 3992 12029