Area Forecast Discussion
Issued by NWS Reno, NV

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FXUS65 KREV 211135
AFDREV

Area Forecast Discussion
National Weather Service Reno NV
335 AM PST Sun Jan 21 2018

.SYNOPSIS...

Dry and cool conditions will prevail today with increasing clouds.
A weak disturbance may bring very light snow for parts of eastern
California tonight and Monday. A stronger and colder storm is
expected late Wednesday into Thursday, bringing more snow to the
Sierra and possibly to lower elevations.

&&

.SHORT TERM...

Flat ridge today will give way to a weak upper disturbance moving
across the Pacific Northwest, with a shallow feed of Pacific
moisture pushing into northern CA tonight into Monday. The main
feature will be increasing amounts of cloud cover today through
Monday. Model guidance continues to indicate limited amounts of
precip pushing beyond the Sierra crest, with most valley locations
of western NV and eastern CA unlikely to receive measurable
amounts of snow or rain.

Snowfall projections with this system continue to be sparse, with
only a couple inches or so near the Sierra crest west of Tahoe and
northward into far western Lassen County, and 1 inch or less for
northeast CA and the Tahoe basin below 7000 feet. Still, with this
light snow occurring overnight into Monday morning, there could
be a few slick spots so some caution is warranted for those
heading into and over the Sierra.

Winds will also increase this afternoon and evening but this will
not be a significant wind event. Gusts could reach 35 mph north
of a Susanville to Gerlach line where valleys are more efficient
in channeling southerly flow, with peak gusts up to 65 mph
possible for Sierra ridges. Elsewhere, wind gusts should generally
be 30 mph or less.

Most of the region should be dry Tuesday-Tuesday night and model
guidance has trended toward more ridging and backed off on warm
advection precip potential. This has been a steady trend so we
removed the precip chances except for retaining some slight
chances late Tuesday night north of Susanville-Gerlach ahead of
the next storm system. Cloud cover will be most widespread north
of I-80 while temperatures edge upward into the lower 50s for
most valleys along and south of I-80. MJD

.LONG TERM...Wednesday through next weekend...

Attention continues to point to a cold winter storm that has had
decent model agreement the last several nights (only some minor
variation in timing and QPF). The storm is relatively cold and
more like a typical winter storm with snow levels starting around
lake level and then falling to valley floors as a strong cold
front moves across the area. The front and associated
precipitation will reach northeast CA and maybe the Tahoe Basin
Wednesday afternoon although the brunt of the storm is expected
Wednesday night, progressing quickly through the area by Thursday
morning. So the fast movement of the initial storm will limit
snowfall but it still looks like a decent amount with 12 to 18
inches along the Sierra crest from western Lassen County down to
Mono County and 6 to 12 inches down into the Tahoe Basin. Lesser
amounts are expected down in lower elevations due to the fast
frontal movement, but some accumulation is possible behind the
front. The morning commute Thursday will be hazardous through the
Sierra and possibly for lower elevations as well.

Ahead of this front, strong gusty winds are expected as 700MB flow
increases to 50+ kts and surface gradients tighten. Ridge level
winds will likely hit 100+ mph with gusts across valleys 40-55 mph
(stronger in wind prone areas). High profile vehicles and aircraft
will likely experience significant impacts Wednesday afternoon
through Wednesday evening. Good mixing will help push temperatures
well into the 50s across western NV with a few spots possibly
exceeding 60 degrees.

Cold and unstable conditions will persist Thursday through Friday
with isolated to scattered snow showers gradually waning. Some
model solutions bring a secondary wave through the flow late
Thursday which could being some enhanced snow shower activity and
possible slick road conditions. Temperatures will be below normal
with 30s and low 40s most locations. High pressure is progged to
build over the weekend for slowly warming temperatures and dry
conditions. Hohmann

&&

.AVIATION...

VFR today as high pressure dominates aloft. Very dry air has
allowed for KTRK to remain fog free so far this morning although
some patchy freezing fog will be possible through 17Z.

There will be considerable high clouds today ahead of a weak
system that will move across northern CA and northern NV tonight
and Monday. Precipitation will be sparse although a few snow
showers mainly north of I-80 could reach the Tahoe Basin and bring
brief periods of MVFR cigs/vsby in light snow 00Z to 18Z Monday.
Accumulation on runways at KTRK/KTVL will be an inch or less.
While a few flurries are possible at KRNO/KCXP, accumulation is
very unlikely.

Winds will increase across the ridges later today through early
Monday with gusts around 50-55 kts. Surface winds will generally
remain light although the gradient will be a bit stronger across
northeast CA and northwest NV, generally north of KSVE-KWMC where
some gusts this afternoon/evening could reach 35 mph. Hohmann

&&


.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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