Area Forecast Discussion
Issued by NWS Reno, NV

Current Version | Previous Version | Graphics & Text | Print | Product List | Glossary Off
Versions: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22

000
FXUS65 KREV 200146
AFDREV

Area Forecast Discussion
National Weather Service Reno NV
646 PM PDT Wed Jul 19 2017

.UPDATE...
Have issued a dense smoke advisory for the Tahoe Basin, eastern
Sierra and portions of western Nevada due to smoke from the
Detwiler Fire.

For the latest air quality readings refer to www.airnow.gov

Smoke from the Detwiler fire isn`t going to dissipate this
evening despite the zephyr winds. If anything the zephyr winds are
helping to push the smoke into the region. The fire has burned
very active today and this has launched a large and dense smoke
plume along Sierra Crest. Reported visibilities from automated
sensors around the Tahoe Basin, eastern Sierra and far western
Nevada are in the 2-6 mile range. However there are likely areas
where the visibility is at one mile or less. Needless to say air
quality around the region is unhealthy, so outdoor activities are
discouraged, especially strenuous ones.

Note about the dense smoke advisory: The "expiration time" is set
for 5 pm Thursday afternoon with winds in the models showing a
favorable pattern for smoke to continue to move into the region
over the next day or two if the Detwiler Fire continues to burn
actively. At this point, I`m leaning to yes we will be dealing
with rather thick smoke and unhealthy air quality the next 24-48
hours. Brong

&&

.SYNOPSIS...

Areas of smoke and unhealthy air quality will continue across the
region the next day or two days as a result of the Detwiler Fire
in Mariposa County. Dry conditions continue with temperatures
warming a few degrees the next few days. The next chance for
showers and storms may occur by late weekend and into early next
week.

&&

.PREVIOUS DISCUSSION... /Issued 251 PM PDT Wed Jul 19 2017/


SHORT TERM...

A persistent pattern will be in store into the start of the
weekend as we remain in a dry southwesterly flow aloft.
Unfortunately this means no real change in our prevailing wind
direction over the next few days which could mean continued smoke
transport from the Detwiler Wildfire in Mariposa County. Assuming
continued active burning of the fire, south to southwest flow
aloft will transport smoke across the northern Mono County and the
Tahoe Basin with smoke settling into valley locations across
western Nevada overnight.

Air quality issues could continue for the next few days
particularly in the morning hours when light winds will help keep
smoke trapped in the valleys. We do expect our typical afternoon
breezes to develop each afternoon (2-3pm) with gusts in the 20-25
mph range which will help mix and lessen the concentration of
smoke particulates through the evening hours. For the latest AQI
readings please refer to Airnow.gov.

Otherwise the weather will remain dry and temperatures will warm
into the mid 90s each afternoon. The pronounced dry slot aloft
will keep chances for precipitation out of the forecast until the
end of the weekend where we could see some moisture transport
increasing across the region. Fuentes

LONG TERM...Sunday through Wednesday

An expansive ridge across the central Plains will begin to build
westward by the end of the weekend and into early next week. This
will help increase our temperatures into the upper 90s across
western Nevada with upper 80s for Sierra valleys.

As the ridge builds westward, winds become more southerly and
will help usher in more moisture along its periphery. How much
moisture we transport into our region is the main point of
uncertainty as the GFS and EC have shown some better signs for
this occurring by forming a shortwave trough off the northern
California coastline. This would strengthen the southerly
transport and also provide some dynamic forcing to help trigger
showers and thunderstorms.

These small shortwave lows can be lower confidence to forecast a
few days out but most ensemble members do show some type of trough
developing offshore. As such have included chances for
thunderstorms next week Monday and Tuesday afternoon. Fuentes

AVIATION...

The main aviation impact will come from reduced visibility as a
result of wildfire smoke and haze from the Detwiler Fire in
Mariposa county.

Prevailing winds will transport smoke across the Sierra from KMMH
through KTVL, KTRK. Visibilities for western Nevada valleys,
particularly KMEV, KCXP, and KRNO could see vis lowered to 1-3
miles again overnight and into Thursday morning as smoke settles
back into the valleys. Do expect afternoon breezes of around 20-25
mph to help mix out and improve visibility again Thursday
afternoon after about 21z. Fuentes

&&

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

$$

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



USA.gov is the U.S. government's official web portal to all federal, state and local government web resources and services.