488
FXUS65 KREV 240958
AFDREV

Area Forecast Discussion
National Weather Service Reno NV
258 AM PDT Sun Aug 24 2025

.KEY MESSAGES...

* Afternoon shower and thunderstorm chances continue today through
  mid-week, bringing frequent lightning, small hail, gusty winds,
  and flooding potential.

* The greatest chances for flooding will take place today through
  Tuesday, with the highest risk for flash flooding over urban
  areas and burn scars such as the Davis and Connor.

* A cooling trend begins today and continues through this week,
  dropping temperatures by 10 to 15 degrees.

&&

.DISCUSSION...

Not too much has changed in the forecast since the last update.
Steady SW flow aloft continues to pull monsoonal moisture into the
region. Remarkably high PWATs around 0.90-1.10" will remain over our
CWA through at least Tuesday. This will create wet storms and will
be heavy rain producers. On Monday we`ll see a shortwave trough
quickly pass through, which is going to strengthen the t-storms that
afternoon. A larger trough sitting off the coast will slowly move
onshore mid-week and eventually lift and move east late-week. Precip
chances should subside as early as Thursday.

Today: Isolated showers are currently ongoing this morning over the
eastern Sierra and western NV. These should clear out by daybreak,
allowing the sun to heat up the surface for this afternoon`s storms.
Widespread shower and t-storm chances of 40-70% will continue today
with storms starting as early as 10 AM. Similar to yesterday, storms
will start along the Sierra and propagate east through the late
morning and early afternoon. Storm motions are looking similar to
yesterday`s (on the slower side), so flash flooding remains a risk
where stronger storms stall out, back build, or train. If you`re out
on a lake today or over in the Black Rock Desert, please be cautious
and have a way to receive weather alerts! Something we don`t see too
often here in our CWA that`s worth noting, the WPC has the eastern
Sierra over Mono County in a slight risk on their Excessive Rainfall
Outlook. The main takeaway from that is that there is a high
likelihood of seeing flash flooding in that area this afternoon. And
finally, in terms of storm progression, a similar scenario to
yesterday will likely pan out today where the storms start off
discrete and then as the afternoon goes on, the cloud cover
increases and the storms lose intensity and become more stratiform
in nature. Expect small hail with occasional hail that`s up to a
quarter in size, lightning, gusty outflow winds, heavy rain with
potential flash flooding, and possible blowing dust over the
playa.

Monday Onward: As noted earlier, a shortwave trough is expected to
pass through on Monday. This will likely exacerbate storm intensity
creating stronger winds, slightly larger hail, more frequent
lightning, and heavier rainfall. Precip chances will be similar
to today, such that western NV has a 60-70% chance, northeastern
CA 40-50% chance, Greater Lake Tahoe 60-80%, and eastern Sierra
70-90% chance. Storm motions Monday onward still appear slower
(less than 15kt), and it`s becoming increasingly likely that we
could see an even greater flash flood threat. If you`re on the
playa at the Black Rock Desert, you may very well be in for a
muddy mess Monday through Wednesday. Although, storm chances
decrease each afternoon from Tuesday through Thursday. The way
things are trending now, There may not be any showers on Thursday,
if even Wednesday. But we`ll have more details as time gets
closer to Wednesday.

Starting today and going through the rest of this week, we begin a
cooling trend each day and to cool down by 10-15 degrees by
Thursday. Synoptic scale winds won`t be a huge issue this week,
except over the playa in the Black Rock Desert. We`re only looking
at a background westerly wind of 10-15 mph, however that may very
well be enough to kick up some playa. In the vicinity of t-storms,
we may see gusts up to 50 mph, except Monday we could see gusts up
to 60 mph.

-Justin

&&

.AVIATION...

Update: No major changes in the forecast. The storms this
afternoon will have similar behavior and characteristics to
yesterday`s storms. There have only been slight storm probability
increases across the region this afternoon, and a greater chance
for heavy rainfall.

Previous Aviation Discussion:

A monsoon moisture push will provide widespread coverage of showers
and thunderstorms this afternoon. Main operational impacts with
these storms will include periods of IFR conditions due to storms
producing heavy rain and sudden reductions to visibility. Storms
are capable of producing 0.25-0.75" of rain in individual storm
cores, along with small hail, lightning, and outflow gusts up to
45 kts.

Precipitation chances are highest at KMMH (70-80% chance) with
60-70% chances for the other main terminals. Main window for
T-Storms across KMMH will be 18-00z, and 20-03z for Sierra and
W.Nevada terminals this afternoon.

Thunderstorm chances decrease northward of I-80 this afternoon but
still could see 40-50% chances after about 01z late this
afternoon. Outflow gusts will also be capable of producing
reduced visibility in blowing dust. An active thunderstorm pattern
is expected to continue through the middle of next week. Fuentes

&&

.REV Watches/Warnings/Advisories...
NV...Heat Advisory until 9 AM PDT this morning NVZ004-005.

     Flood Watch from 10 AM PDT this morning through this evening
     NVZ001.

CA...Heat Advisory until 9 AM PDT this morning CAZ071.

     Flood Watch from 10 AM PDT this morning through this evening
     CAZ073.

&&

$$