Area Forecast Discussion
Issued by NWS Reno, NV

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000
FXUS65 KREV 122145
AFDREV

Area Forecast Discussion
National Weather Service Reno NV
145 PM PST Mon Feb 12 2018

.SYNOPSIS...

Snow showers will diminish over most areas, but continue over
parts of Mono County tonight into Tuesday morning, producing slick
travel conditions. Another weak weather system could bring light
showers Wednesday and Wednesday night. Near average temperatures
are expected through Thursday, then become warmer through
Saturday. A colder storm may bring more snow Sunday and Monday.

&&

.SHORT TERM...

Light snow showers continue across parts of western NV primarily
due to upslope flow and some enhancement off Pyramid Lake. Current
travel impacts are minimal due to low snowfall rates and moderate
north to northeast winds allowing road surfaces to dry.

As we transition into this evening and tonight, the focus for
additional snow shifts south into Mono County as the upper low
center moves southwest from the San Joaquin valley to the central
CA coast. Additional snow accumulations across most of the county
should be 2 inches or less. There is one possible exception:
Upslope flow combined with enhancement from Mono Lake, and a small
deformation zone associated with the upper low could produce a
localized area of much heavier snowfall overnight (6 or more
inches) around the June Lake-Lee Vining-Conway Summit vicinity.
The main uncertainty is the location of the deformation zone--if
it sets up farther west or south, snowfall amounts would be more
mid-range (local areas of 2-6 inches) in this part of the county.
We are not planning any winter headlines due to the smaller scale
and lower probability of this heavier snow potential, but anyone
planning travel tonight into early Tuesday across central Mono
County may experience rapid drops in visibility and snow covered
roads. Conditions will improve during the day Tuesday as these
show showers diminish.

Otherwise, increasing mid level east flow will bring stronger
ridge wind gusts (60+ mph) for the Sierra crest late tonight into
Tuesday morning, with locally choppy conditions possible along the
west shores of Lake Tahoe. Aside from isolated snow showers in
parts of Mono County during the morning, dry and cool conditions
will prevail across the region Tuesday and Tuesday night, with
highs Tuesday mainly in the 40s (slightly below mid-February
averages).

For Wednesday-Wednesday night, another upper low is projected to
drop southeast from the Pacific Northwest to the central and
eastern Great Basin. Winds will increase during the afternoon,
with gusts to 30 mph mainly from I-80 northward. The best
moisture and dynamics are projected to remain farther north and
east compared to this morning`s system, resulting in the best
chances for light snow accumulations (up to 1") limited to areas
near the Oregon border and into the NV Basin and Range north and
east of Lovelock. Elsewhere, we can`t rule out a few very light
non-accumulating snow showers Wednesday night into early Thursday
as this trough passes through, followed by dry and cool conditions
(highs mainly in the 40s) for the remainder of Thursday. MJD

.LONG TERM...Friday through Monday...

There have been no surprising changes today as models continue to
hold onto the idea that east Pacific ridging will retrograde
westward. This will allow for the storm track to shift over the west
coast and interior basins. However, storm trajectories will remain
inland keeping moisture more limited by largely separating moisture
transport mechanisms from tapping into oceanic moisture. Therefore,
the next series of passing systems will be cold, but will tend
towards being drier. At this point, though, we`ll take what we can
get.

After a pleasant Friday, Saturday appears to be a breezy-to-gusty,
warm day with highs around 60 for western Nevada and in the 50s
for Sierra Valleys. Looking at the thermal gradient, Sunday will
also be breezy to gusty as a strong cold front drops out of
Oregon; temperatures will begin to drop. Winds will likely
continue to be breezy to gusty behind the front as well.

There are some discrepancies between the GFS and ECMWF model suites
concerning the next low pressure system dropping out of the Pacific
Northwest this weekend. The GFS has a colder and drier tendency
while the ECMWF starts warmer and is the wetter solution. The
difference in moisture is fairly large with the GFS producing 0.25-
0.4" inches of QPF in the Sierra while the EC produces around 1" of
liquid equivalent. Current forecaster wisdom is that precipitation
amounts are far too uncertain this far out, but both models
present reasonable amounts of moisture. These totals will be
refined over the next few days.

Temperatures are more certain; it is going to get colder behind the
strong front. Temperatures will likely dip below seasonal averages
as the cold core of the upper trough settles over the western United
States. Highs may struggle to get out of the 30s early next week for
western Nevada with overnight lows possibly dipping into the teens.
Keep an eye on the forecast through the week...there will be some
variations in exact numbers as the low`s track and upper trough
placement become more apparent. Boyd

&&

.AVIATION...

For the western NV and Tahoe area terminals, prevailing
conditions are likely to be VFR with mountain obscurations through
tonight. Snow showers remain possible until around 03Z this
evening, bringing short periods of lower ceilings and visibility
but accumulations on runways are unlikely.

Farther south at KMMH, a better chance for snow showers continues
through tonight, with IFR conditions possible at times especially
from 04z-10z, and snow accumulations of up to 2 inches.

Northeast wind gusts of 15-20 kt continue into this evening, with
winds diminishing by 05Z. Stronger east winds then develop across
the Sierra crest overnight into Tuesday morning with peak gusts
50+ kt. This will lead to turbulence along and downwind of the
Sierra from a little east of the crest towards the central valley
of California.

For Tuesday-Wednesday VFR conditions are expected. Winds will be
lighter on Tuesday, followed by increasing southwest winds
Wednesday afternoon with gusts around 20 kt from KTVL-KCXP
northward. MJD

&&

.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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