Upper Sardine Lake, California Weather Forecast Discussion

800
FXUS65 KREV 180912
AFDREV
Area Forecast Discussion
National Weather Service Reno NV
212 AM PDT Thu Sep 18 2025
.KEY MESSAGES...
* Tropical moisture moves into the region today, increasing
  chances for showers and thunderstorms through Saturday.
* Relatively dry start to early next week with another weather
  system possible as early as Tuesday.
&&
.DISCUSSION...
Taking a look this early morning at IR satellite we can see the
remnants of Post-Tropical Cyclone Mario headed our way. Outer cirrus
bands have started to move into our area, with showers following
behind. On water vapor imagery we can see an extensive moisture
plume headed our way from SoCal.
Diving into it, showers will start in southern Mono County near
Mammoth Lakes around noon today, give or take an hour or two.
Showers will spread north throughout the afternoon and reach the
Tahoe basin around 5-8 PM and then into the Susanville area shortly
after midnight. Chances for showers on Thursday range from 20-40%,
with a 10% chance of lightning embedded within the showers. I
mentioned the plume of moisture headed our way, well, PWAT values
will skyrocket throughout the day today starting off around the
usual 0.30-0.40" in the morning to 0.80-1.00" by the evening. There
really isn`t too much instability left with this system as it moves
over our area. MUCAPE values only make it up to 200 J/kg at the
peak today, leading to that 10% chance of lightning. The areal
extent of the showers is where we run into some uncertainty still.
Some hi-res models are showing the showers kept mainly to the
Sierra with a little spillover into western NV, while others move
the QPF further east over Fallon and Lovelock. However, the
majority of models, including NBM guidance, do have Churchill and
Pershing counties dry, so I`d lean a little heavier on that
outcome. QPF totals through Thursday night will be 0.10-0.30"
along the Sierra and eastern Sierra up to the Tahoe Basin, and
spillover into the Reno area will be limited to 0.05-0.15".
Showers will continue overnight for the same areas along the Sierra.
In the afternoon, showers will be more convective in nature with the
help of a little more instability thanks to the center of the low
passing by. Because of this, we`re going to see an increase in
lightning potential to about 20%. QPF for Friday will increase as
well, to 0.30-0.40" in the Sierra with locally higher amounts of
0.60", and 0.10-0.20" spillover into Mono County and western Nevada.
By Friday night the showers will slowly subside with the last
lingering showers hanging around Susanville and northern Washoe
County.
Saturday looks like a much drier day, though isolated showers and
thunderstorms are back in the forecast for Lassen/N. Washoe/Mono
counties. After Saturday the pattern has us in a holding pattern
where another round of tropical moisture awaits us. More remnants
from a storm down off the Baja California coast will follow a
similar track and impact our area Tuesday - Wednesday next week.
-Justin
&&
.AVIATION...
VFR conditions continue through this morning. Expect cloud cover to
increase throughout the afternoon. Showers and isolated
thunderstorms are expected to move into the vicinity of KMMH late
this morning (18-20Z), then move north to KTVL/KTRK/KMEV/KCXP/KRNO
around 00-03Z this evening. Reductions to VIS/CIGS down to MVFR are
expected, although there`s a 10% chance of lightning and heavier
showers which could reduce VIS to IFR. Expect wind gusts out of the
south gusting up to 20kt this afternoon. Chances for showers and
isolated thunderstorms return Friday for all main terminals.
-Justin
&&
.REV Watches/Warnings/Advisories...
NV...None.
CA...None.
&&
$$

NWS REV Office Area Forecast Discussion