Tracy-Clark, Nevada Weather Forecast Discussion

278
FXUS65 KREV 182015
AFDREV
Area Forecast Discussion
National Weather Service Reno NV
115 PM 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...
Current radar imagery shows light rain showers just starting to
creep into Mono county. As the day progresses, showers from former
Tropical Cyclone Mario will push north. These showers will be
relatively slow moving and will hug the Sierra and Sierra front
communities; we`re expecting little to no shower activity for the
Basin and Range today. Hi-res guidance has improved its agreement
for spatial coverage of showers today but remains a bit misaligned
on timing of this first wave of showers. For locations south of
I-80, including the Tahoe Basin, showers will arrive by 5pm and
will be light. Locations north of I-80 up towards Susanville can
expect light showers by midnight.
While showers along the Sierra (Tahoe Basin and southward) don`t
necessarily stop today in the pure sense of the word, they will
ramp up in intensity overnight tonight around midnight. This will
continue through around sunrise. QPF values will range between
0.3-0.5" overnight while some high-end scenarios hint at over an
inch possible.
Chances for thunder today are less than 10% but increase to
20-25% tomorrow afternoon. HREF CAM guidance is highlighting the
best chance for convection to be out in the Basin and Range
tomorrow afternoon. However, PWAT values look to exceed 1", which
could be too much moisture for thunderstorms. If the cloud cover
today sticks around as well, it will be challenging to get
instability from surface heating.
Saturday afternoon has been trending drier with the past two
forecast packages but it`s warranted to note that the PWATs will
still be above the 75th percentile. Clear skies in the morning may
allow for cumulus buildups, and the EFI continues to hint at
higher CAPE. Model soundings for Reno currently show 200-400 J/kg
of MUCAPE that afternoon with 600-800 J/kg of DCAPE. For
thunderstorms that develop Friday and Saturday, the main threats
will include brief heavy rainfall, gusty outflow winds, frequent
lightning, and small hail.
Further drying is expected Sunday and Monday before another surge
of tropical moisture gets entered into the equation on Tuesday.
The low pressure that is bringing our showers this weekend looks
to pivot west off the southern California coast before tracking
more inland again Tuesday.
-Giralte
&&
.AVIATION...
VFR conditions continue through the majority of today despite the
increase in cloud cover. KMMH will see showers first today (by
20-22Z) but they will be light. Showers with the occasional
embedded thunderstorm are expected to move north to impact
terminals along the Sierra Front and the Tahoe Basin by 00-03Z
this evening. Reductions to VIS/CIGS down to MVFR are expected,
but showers are expected to increase in intensity (for
KTVL/KTRK/KMMH) late tonight (after 06Z). Chances for showers and
isolated thunderstorms return Friday for all main terminals.
-Giralte/Justin
&&
.REV Watches/Warnings/Advisories...
NV...None.
CA...None.
&&
$$

NWS REV Office Area Forecast Discussion