Severe Thunderstorm Warning 29, NWS Reno, NV

Area Forecast Discussion
National Weather Service Reno NV
123 PM PDT Tue Aug 11 2020

.SYNOPSIS...

Thunderstorm coverage and intensity is expected to peak today,
especially in western and west-central Nevada, before drier air
brings an end to the thunderstorm threat for Wednesday and Thursday.
Breezy conditions Wednesday bring an increased threat for fire spread.
Isolated afternoon thunderstorms return Friday and persist into next
week. Temperatures rise to well above average this weekend.

&&

.SHORT TERM...

Not much change to the forecast thinking through Thursday.

Isolated thunderstorms have sprung up in the eastern Sierra, portions
of extreme western NV, and across northern Lassen County downwind
from Lassen Peak. Thunderstorms are expected to increase in coverage
and overall intensity (peak heating to maximize instability) while
spreading out into western and west-central Nevada this afternoon and
evening. Storms today have the potential to be strong with gusty outflow
winds in excess of 50 mph, especially given the meso-analysis from
the Storm Prediction Center indicating DCAPE values of ~1500 J/kg
already this afternoon. Given fairly modest storm motions, heavy
rain/localized flash flooding remains a concern, especially for burn
areas and for storms that get terrain-locked (already occurring in
the Pine Nut Range between the Carson and Smith valleys). Hail up
to around an inch in diameter and areas of low visibility due to
blowing dust (mainly Basin and Range) also remain a threat.

Drier weather returns for Wednesday and Thursday as a dry slot drives
into the region from the south and west as low pressure moves into the
Pacific Northwest. Thermal gradient increases due to the influence
of the low will bring back the afternoon and evening zephyr breezes,
with slightly elevated values expected (gusts 25-35 mph instead of
20-30 mph) on Wednesday. The wind and dry air will bring increased
danger for fire spread. Very dry vegetation conditions and the
winds and humidity could allow for a period of rapid fire spread
Wednesday afternoon and evening if a fire were to unfortunately
start. -Snyder

.LONG TERM...Friday through the middle of next week...

The main features for the extended will be a return to isolated
thunderstorms Friday, as well as building heat over the weekend into
early next week as strong high pressure develops over northeast CA
and western NV.

Friday is expected to feature more southerly flow with increasing
mid and high-level moisture as the Pac NW low exits into northern
Plains and an upper low off the California coast begins influencing
the region. The increasing moisture will combine with a weak zephyr
to bring a low chance for thunderstorms in the Sierra, generally
south of Hwy 50, with perhaps a 5-10% chance for a late day storm
near Truckee and in the Pine Nut Range east of Minden-Gardnerville.

Saturday, the aforementioned high pressure builds in earnest over
the region. It will persist through at least the middle of next
week, bringing above average heat along with rather typical zephyr
flows each afternoon and evening. As far as thunderstorms, isolated
ones cannot be ruled out any day...most likely in the typical eastern
Sierra and extreme western NV (south of Hwy 50) locales. -Snyder

&&

.AVIATION...

Isolated to scattered thunderstorms in northeast California, the
eastern Sierra (south of Hwy 50), and far western Nevada are expected
to spread out into west-central Nevada this afternoon and evening.
The potential remains for 40-50+ kt outflows, heavy rain obscuring
terrain, hail up to ~1 inch in diameter, and blowing dust (Basin
and Range including KLOL/KNFL/KHTH). Except for perhaps northern
Lassen County, storms are expected to mostly clear out of eastern
California by 5-6 PM.

Larger-scale breezy conditions return on Wednesday as low pressure
moves into the Pacific Northwest. Gusts of 25-30 kts (slightly
elevated from typical summer breezes) will be possible, especially
near and north of I-80 to the east of the Sierra.

There are wildfires, R-1 and Gold, located north of KSVE. They
could bring haze/smoke impacts to far northeast CA and northwestern
NV today and Wednesday (and a bit beyond possibly) depending on
how active the fires get. -Snyder

&&

.FIRE WEATHER...

We have dropped the fire watch for today; however, the fire weather
watch for winds and RH Wednesday has been upgraded to a red flag
warning.

Thunderstorms today look slow and strong enough with sufficient
atmospheric moisture (above average PWAT) in place to put down
rain (locally heavy) in a larger footprint than is typical on
drier days. Although it is hard to be sure how much lightning will
occur away from storm cores, the expected larger rain footprint
lowers the chance for large amounts of dry lightning strikes and
there just isn't the confidence for a red flag. Still, a few new
fires that spread readily in outflow winds for an hour or two
wouldn't be surprising given the state of fuels and with wind
gusts possibly in excess of 50 mph with stronger cells.

For Wednesday, a dry slot washes over the region as low pressure
moves into the Pac NW. This is expected to bring rapid drying by
afternoon as low-level moisture mixes out under the dry slot. The
gradients initiated by the low should bring slightly enhanced
afternoon breezes. We aren't looking at a big wind event but
30-35 mph gusts are expected for the northern Sierra Front,
northeast CA, and northern Washoe/Pershing Counties. This along
with the dry conditions is expected to bring critical fire
conditions...especially concerning following an active thunderstorm
day with possible yet-to-be-revealed fires. -Snyder

&&

.REV Watches/Warnings/Advisories...
NV...Lake Wind Advisory from noon to 9 PM PDT Wednesday NVZ004.

     Red Flag Warning from noon to 9 PM PDT Wednesday NVZ420-423-458.

     Lake Wind Advisory from noon to 9 PM PDT Wednesday for Washoe
     Lake in NVZ003.

CA...Red Flag Warning from noon to 9 PM PDT Wednesday CAZ270-271-278.

     Lake Wind Advisory from noon to 9 PM PDT Wednesday CAZ071.

&&

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

Special Weather Statement
National Weather Service RENO NV
1123 AM PDT Tue Aug 11 2020

CAZ070>073-NVZ001>005-120000-
Surprise Valley California-Lassen-Eastern Plumas-
Eastern Sierra Counties-Greater Lake Tahoe Area-Mono County-
Mineral and Southern Lyon Counties-Greater Reno-Carson City-
Minden Area-Western Nevada Basin and Range including Pyramid Lake-
Northern Washoe County-
Including the cities of Cedarville, Eagleville, Fort Bidwell,
Portola, Susanville, Westwood, Sierraville, Loyalton,
South Lake Tahoe, Tahoe City, Truckee, Markleeville, Bridgeport,
Coleville, Lee Vining, Mammoth Lakes, Hawthorne, Yerington,
Smith Valley, Mina, Schurz, Stateline, Glenbrook,
Incline Village, Sparks, Verdi, Gardnerville, Virginia City,
Fernley, Fallon, Lovelock, Silver Springs, Nixon, Imlay, Empire,
and Gerlach
1123 AM PDT Tue Aug 11 2020

...Thunderstorms to impact the region through 9 PM...

Showers and thunderstorms are building over the region and will
impact eastern California and western Nevada through 9 PM this
evening.

Strong to severe thunderstorms are possible with erratic outflow
winds over 50 mph, hail, periods of moderate to heavy rain and
dangerous lightning. Outflow winds may damage trees and utility
poles, and generate areas of blowing dust across western Nevada.
Heavy rain may lead to rock slides, debris flows on recently
burned slopes, and cause ponding of water on roads and poorly
drained urban areas.

Now is the time to consider alternate plans for outdoor
activities the remainder of today. Lightning poses an immediate
risk for all outdoor activities. If you have outdoor plans, make
sure you have quick and easy access to shelter inside a building
or vehicle.

http://weather.gov/reno