Scientific Forecaster Discussion

Return to Local Conditions & Forecast

Without Abbreviations
With Abbreviations

fxus65 krev 251108 
afdrev

Area forecast discussion
National Weather Service Reno Nevada
408 am PDT Mon Mar 25 2019

Synopsis...

A series of weak to moderate late season storms will impact the
region this week with heavy mountain Snow, Valley rain showers,
and widespread strong gusty winds. Drier and warmer conditions
will likely return by the weekend.

&&

Discussion...

The changes this morning revolve around a slower timing of
precipitation with the first wave today-tonight and a more
definitive break in the intensity of precipitation late Wednesday
night into Thursday morning between the main storm and a third
final wave due to roll through the region Thursday afternoon.
Snow levels and snow amounts were mostly unchanged with the
heaviest and most adverse period expected during the day
Wednesday.

Impacts from the first wave will be confined mainly to the higher
passes from echo/Donner Summit north to fredonyer/Yuba during the
nighttime hours tonight into Tuesday morning. Models have
continued to slow the timing of this wave today as southerly low-
mid level flow keeps most of the precipitation confined to the
crest and points west as the north-south band advances to the
northern Sierra. Few impacts are anticipated for the daytime today
as precipitation may not even reach the Tahoe basin/western
Lassen County until this evening. Given the warm Road temperatures
and the relatively light precipitation accompanying this first
storm, it will not be until after Sundown that snow will begin to
impact mainly the passes around the Tahoe basin and areas above
5000 feet across western parts of Lassen County as well as
Plumas/Sierra counties. We tapered pops more quickly for areas to
the east and south with little snow making it past the crest into
Mono County and only some very light quantitative precipitation forecast for western Nevada. Snowfall
amounts tonight will generally be only a few inches at lake level
with 3 to 6 inches near the passes. We upgraded the Winter Storm
Watch to a Winter Weather Advisory for western parts of the
northern Sierra but did not include the Tahoe basin where these
amounts will be limited to mainly areas west of Highway 89. Bigger
snowfall totals are likely on the west side of the Sierra where
precipitation will be a bit heavier. So travel across the Sierra
will still be hazardous tonight into Tuesday morning.

The main wave will arrive Tuesday night and really ramp up during
the day Wednesday. Colder and more unstable air will result in a
period of moderate to heavy valley rain and mountain snow with the
peak intensity occurring during the day Wednesday. We could even
see a few thunderstorms from I-80 south as the main jet and cold
front punch into the region. Most model scenarios show snow levels
falling through the day with snow amounts of 5 to 10 inches
possible at lake level by the time the snow winds down Wednesday
evening and up to 1-2 feet for areas above 7000 feet. Locally
heavier amounts are possible in convective bands Wednesday
afternoon. This will be a rain event for lower valleys as snow
levels do not fall to valley floors until the precipitation is
winding down. Right now it looks like there will be a general
break in the precipitation late Wednesday night and Thursday
morning with snow showers confined mainly to the crest and west
slopes. So we have fine tuned the Winter Storm Watch to highlight
the main impact period from overnight Tuesday night through the
evening Wednesday.

Finally, a third wave will roll through the area Thursday
afternoon and bring scattered showers. Given the timing of day,
impacts will be confined to elevations mainly above 6000 feet even
though snow may fall as low as western Nevada valleys. Accumulations
will be more spotty as the nature of the snow will be quite
showery.

Winds will be breezy through Thursday with the strongest winds
this afternoon. Gusts this afternoon will approach 45 mph with
rough and choppy lake waters and turbulence/low level wind shear for aviators.
Temperatures will warm well into the 50s and 60s today under good
mixing conditions, then cool to below normal mid week with brisk
conditions Wed-Thu. Heights rise by the weekend with generally
drier and warmer conditions returning. There are some indications
of a weak system bringing a few showers late Sunday into Monday.
Temperatures this weekend should return to the 50s and 60s.
Hohmann

&&

Aviation...

A series of weather systems will impact the region beginning
today lasting through Thursday. Expect mountain snow and valley
rain along with strong gusty winds and mountain wave turbulence.

Winds have begun to strengthen aloft, which will result in increased
turbulence and possible low level wind shear at area terminals
especially this afternoon. Gusty S/SW winds are expected to increase
across the Sierra, which will affect tvl/trk before 18z and spread
into rno/cxp/mmh valleys after 18z today. Gusts will likely be on
the order of 30-40 kts for most areas. Breezy/turbulent conditions
will continue Tuesday through Thursday

Precipitation will spread into northeastern California early this afternoon
and will not reach trk/tvl until after 03z tues. IFR/MVFR conditions
and mountain obscurations are likely in the Sierra tonight through
Tuesday. Flight conditions will degrade further Wednesday morning
as a second wave of heavier precipitation moves into the region.
Moderate to heavy snow can be expected at tvl/trk/mmh and mostly
rain can be expected at rno/cxp through Thursday morning.

-Cj/Chris

&&

Rev watches/warnings/advisories...
Nevada...Lake Wind Advisory until 8 PM PDT this evening for Lake Tahoe in
nvz002.

Winter Storm Watch from Tuesday evening through Wednesday
evening nvz002.

Lake Wind Advisory from 8 am this morning to 8 PM PDT this
evening for Pyramid Lake in nvz004.

California...Winter Weather Advisory from 8 PM this evening to 11 am PDT
Tuesday above 5000 feet in caz071.

Winter Storm Watch from Tuesday evening through Wednesday
evening above 5000 feet in caz071.

Winter Storm Watch from Tuesday evening through Wednesday
evening caz073.

Lake Wind Advisory until 8 PM PDT this evening for Lake Tahoe in
caz072.

Winter Storm Watch from Tuesday evening through Wednesday
evening caz072.

&&

National Weather Service Glossary of Abbreviations