Area Forecast Discussion
Issued by NWS Reno, NV

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FXUS65 KREV 140457
AFDREV

Area Forecast Discussion
National Weather Service Reno NV
957 PM PDT Tue Apr 13 2021

.UPDATE...

This spring storm continues to overperform across the Reno-Tahoe
area this evening. The highly convective nature of the storm has
produced some areas around north Tahoe and Truckee with 4-8 inches
of snow. There has even been some in-cloud lightning west of
Tahoe, creating areas of thundersnow near the Sierra Crest.

Roads have remained fairly warm with melting snow and wet
conditions, except over the higher passes with snow sticking to
the roads. Expect to see an additional 2-4 inches tonight for some
areas around Lake Tahoe, with potential for up to 4-8 inches
above 7000ft. There is a convective band west of Tahoe that is
expected to move over the area producing heavier snow amounts.

It`s possible that we could even see some light snow down to the
valley floors around Carson City and Minden tonight. Be prepared
for a slick morning commute on Wednesday for the Tahoe-Carson-
Minden areas. -Hoon

&&

.PREVIOUS DISCUSSION... /Issued 253 PM PDT Tue Apr 13 2021/

SYNOPSIS...

A colder system will affect the region today through Wednesday
night. Winds have increased today area-wide with strongest winds
south of US-50. There will be scattered rain, high elevation snow,
and pellet showers today through Wednesday along with low end
chances for thunderstorms. It will be much colder through
Wednesday before warmer and drier conditions return for the end of
the week and through the weekend.

DISCUSSION...

The main forecast concern continues to be critical fire weather
conditions for southern Mono County related to strong, gusty winds
and low RH. Gusts have been running quite high, especially along
the Highway 395 corridor and at canyon openings. For more
information, please see the Fire Weather discussion below.

Low pressure has moved over the region bringing showers and gusty
winds. At the time of this writing, Radar shows that shower
coverage is increasing over the northern Sierra with a swath of
showers extending northeast into northeast Nevada. Biggest changes
to the forecast were to increase precipitation chances over the
northern Sierra and adjacent foothills on the Sierra Front as well
as extend coverage of isolated thunderstorms/dust along the Sierra
Front of Nevada through this evening.

Winds: Gustiest winds are occurring along the Sierra Front of Mono
County, 30-50 mph, with higher gusts to 70 mph reported at canyon
openings. High profile vehicles are encouraged to avoid this area
if possible. Elsewhere, gusts have been more tame in the 25-35 mph
range with up to 40 mph for wind prone spots. There is a sharp
boundary draped across northern Mono County that separates
northerly flow north of the boundary and southwest through west
flow south of the boundary. Expect flow to switch northerly
through the evening for the remainder of Mono County. While color
enhanced satellite shows limited blowing dust, blowing dust could
still be an issue for the evening given its low threshold for
lofting. Winds taper down sharply late Wednesday morning with
lighter northerly breezes holding into Thursday.

Precipitation: Precipitation chances were increased across the
northern Sierra with showers evident, and filling in, on Radar.
Model trends have continued to moisten with potentials sliding
slightly towards higher QPF in the high Sierra, but static at
lower elevations. The character of precipitation over the Sierra
has trended to more consistent precipitation with potential for
1-2 inches of snow accumulation tonight around Lake Tahoe level
and 2-6 inches 7000ft and above. There`s about a 25% chance that
the higher elevations could see 6-12 inches which is only a
marginal increase over the previous forecast. Lower elevations and
western Nevada will continue to have more hit/miss variety of
precipitation with any given location capable of seeing up to 0.25
inches of rain should a heavier shower pass over. Otherwise,
precipitation chances were lingered along the Sierra Front and
higher Sierra of Mono County longer than the previous forecasts;
owing mainly to continued upslope flow and a slightly slower exit
of the upper low.

Thunderstorms: Isolated thunderstorms will remain possible this
afternoon and evening over the Sierra and along the Sierra Front
of Nevada. Steep lapse rates and diurnal warming will be
sufficient to trigger a cell or two. These low chances extend from
late morning through the afternoon on Wednesday as well.

Temperatures: Running below average through Thursday morning with
potential for freezing conditions. Thursday morning will be the
colder of the two days and a better chance to have freezing
morning temperatures in urban centers. Best advice would be to
cover exposed irrigation systems and any early season plants.

Friday onward...
Temperatures will be on the rise with much drier conditions for
the region. However, there will still be some lingering moisture
associated with today/Wednesday`s precipitation that could result
in clouds and a few sprinkles over higher terrain Friday/Saturday
afternoons. Outside of cloud cover, temperatures will warm above
seasonal averages, and will increase 10-15 degrees above averages
by Sunday/Monday. We`re looking at the potential for our first 80
degree day for the calendar year. It`s a good time to remind
ourselves to "Look before you lock." and ensure no one is left
inside a sealed vehicle as temperatures climb above 80 degrees.
Boyd

AVIATION...

Low pressure is bringing chances of showers to Sierra terminals
today through Wednesday night. KTVL/KTRK could see an inch or so
of snow accumulation with periods of IFR/MVFR tonight. Other
terminals should stay VFR, but a stronger shower could brings
conditions briefly to MVFR. Instability associated with this low
is also sufficient to kick off some isolated thunderstorms along
the Sierra Front of Nevada and for the northern Sierra.

Winds will result in turbulent conditions across the region with
surface gusts 20-30kts for most terminals. LLWS continues to be a
concern for TVL where southerly channeled surface winds are at
least 90 degrees out of phase with ridge level winds resulting in
strong directional shear. Gusty winds for MMH have been reported
to 45kts today and will decrease over tonight with winds shifting
more northerly by Wednesday morning.

FIRE WEATHER...

Incoming cold front continues to produce gusty W-SW winds with the
strongest gusts occurring as expected across Mono County. Peak wind
gusts observed so far this afternoon in Mono County have mostly been
in the 40-50 mph range with wind prone canyons along US-395 reaching
into the upper 60s near Lundy Canyon and Virginia Creek.

Relatively humidity below 15% continues across the US-395 corridor
through Mono County with single digit RH being reported from Benton,
Hammill, and Chalfant Valleys. As of this writing, it appears we
have reaching our minimum RH values for the afternoon with multiple
sites showing an steady increasing trend in RH. Nonetheless, with wind
gusts reaching a magnitude of 50+ mph, critical fire weather
conditions will continue through the early evening across southern
Mono County. A Fire Weather Watch will remain in place through 8pm
this evening where we should see RH increase appreciably as the cold
front moves through. Winds will begin to subside as well behind the
front with gusts 20-25 mph through the early evening.

Showers are likely along and behind the front tonight into Wednesday
morning. Chances for wetting rains are about 60% around the Tahoe
Basin, northern Mono County, and portions of western Nevada.
However, chances for wetting rain remain below 20% through the US-
395 corridor across southern Mono County and 0% through the Chalfant
valley where the highest fire weather concerns exist. Fuentes

&&

.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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