Area Forecast Discussion
Issued by NWS Reno, NV
FXUS65 KREV 232254
Area Forecast Discussion
National Weather Service Reno NV
254 PM PST Mon Jan 23 2017
Light snow showers with little additional accumulation may linger
into Tuesday but overall dry and cold weather is expected through
Wednesday. A weak disturbance may bring some light snow showers
to the region Thursday. Strong high pressure builds in for Friday
through next Monday, with valley inversions intensifying by next
Cold cyclonic flow will persist through Tuesday as a weakening
upper disturbance works its way down the California coast. This
could bring another round of scattered snow showers to eastern CA
tonight with accumulations generally less than 2 inches. Elsewhere,
isolated snow showers have been left in the forecast through
Tuesday morning with moisture hanging around. However, there is
really no focus so any showers would be brief and very light with
no accumulation expected.
A chilly airmass will remain over northeast CA and western NV
through Thursday, with a reinforcing shot of cold air arriving
Thursday night and Friday. During periods of substantial overnight
clearing (Tuesday night is best bet at this time), temperatures
will easily plummet to single digits or even below zero in areas
that hold onto a few inches or more of snow cover. With tonight
and Wednesday night expected to hold onto significant cloud cover
per current simulations, lows are not expected to be unusually
cold and any valley freezing fog or stratus may be limited in
As far as precipitation, the best shot after tonight will be on
Thursday as simulations persist in bringing a weak shearing
disturbance under a Pac NW/British Columbia ridge into northern
California and Nevada. How it interacts with broad cyclonic flow
over the Rockies and eastern Great Basin will determine how much
weather it produces (just clouds or snow showers?). The 18Z NAM
is the strongest versus the much weaker GFS/EC and would bring a
fast-moving band/burst of snow showers to the northern Sierra and
far western NV on Thursday, while the other simulations are much
more sheared out with the low and would probably just bring clouds
and a few flurries at best. Confidence is low, although even the
NAM would mean no more than a couple inches of snowfall. As a
heads up, I threw in low chances for snow showers for much of the
area until simulations can merge. Snyder
.Long Term (Friday Onward)...
* Main story will be the resurgence of cool air and "ear popping"
high pressure into the Great Basin Friday through the weekend.
Some very impressive MSLP anomalies showing up in the NAEFS
guidance. This will promote very strong valley inversions, with
limited mixing and tepid day-to-day warming for the lower
elevations including the W Nevada cities.
* We`re also eyeing a period of fairly strong E/NE ridge winds
Friday with the initial onset of that high pressure. Gusts over
100 mph are likely for the higher ridges around Tahoe
(especially near crest) and south into Mono Co and Mammoth.
Could be some tree damage and power issues given the unusual
wind direction and snow loading. Forecast soundings show a
fairly strong inversion below 700mb which will limit how much of
that wind mixes down into mountain and lower elevation valleys.
Will however increase gusts on Lake Tahoe some to indicate
potential for choppy water.
* Blocking upper ridge along the west coast looks to persist into
the middle of next week, per the GFS/EC ensemble guidance. This
will keep the risk of atmospheric river landfalls into California
low to zero. It does appear that ridge will break down mid/late
next week, with an upstream ridge building over the Aleutians.
This pattern typically favors storms into the west coast, and our
AR tools show increased probabilities of landfalls. However there
remains a lot of uncertainty of the latitude of landfalls,
anywhere from Big Sur, CA to Olympic National Park, WA. We have no
clue on potential intensity at this time, or precipitation type
rain vs snow.
Low pressure off the California coastline will keep moist and weak
upslope flow going into the overnight hours, with a few snow showers
possible. Overall probabilities are low enough to warrant VCSH at
most. Otherwise plenty of VFR-MVFR clouds expected into Tuesday with
mountain obscuration. With increased low level moisture from recent
snows, we could see some fog develop from low stratus building
downward around TRK but predictability is pretty low. -Chris
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