070
FXUS65 KREV 012226
AFDREV

Area Forecast Discussion
National Weather Service Reno NV
326 PM PDT Wed May 1 2024

.SYNOPSIS...

Cooler daytime temperatures continue today behind the passage of a
cold front earlier in the day. Following a brief warmup on Thursday
and Friday, temperatures expect to cool down once again over the
weekend with chances for valley rain and mountain snow returning
along with some stronger winds on Saturday. The latest forecast
beyond the weekend going into the beginning of next week calls for a
warming trend across the region along with some lower precipitation
chances.

&&

.DISCUSSION...

At the beginning of the forecast period, the latest RAP analysis
shows the CWA currently with a mostly northwesterly flow aloft being
west of the axis of an upper air trough this afternoon with ridge
trailing the trough over the Pacific Ocean. The current satellite
imagery along with surface observations show dry conditions along
with mostly light and variable winds with the exception of southern
portions of Mineral and Mono Counties as they are experiencing some
breezy north-northwesterly winds. Models show the trough moving
eastward as the Pacific ridge advances toward the CWA on Thursday.
By Friday afternoon, the axis of the upper air ridge is projected to
move over the CWA as an upper air low moves into the Pacific
Northwest. At the surface, the dry conditions look to continue
through the rest of today. While most of the region looks to stay
dry on Thursday, northern portions of Washoe County as well eastern
Modoc and northern Lassen Counties may see chances for light snow
showers in the early morning that transition to light rain as it
warms during the afternoon due to a surface low in OR projected to
move eastward into ID during the day. Minimal amounts of rain and
snow are anticipated with models showing a few hundredths of QPF at
most in the locations that see the precipitation. By Thursday
evening, these precipitation chances depart to the east with the
passing system leaving dry conditions through the remainder of
Thursday as well as on Friday. Warmer daytime temperatures compared
to today`s are expected on Thursday and especially Friday with
models showing a possible warm front beginning to pass through the
southern half of NV and northern CA by the late Friday afternoon
hours. A good portion of the region may warm up to the middle 60s
to the lower 70s during the day on Friday with higher elevations
in the Sierra Mountains being slightly cooler.

On Friday night, model guidance shows the CWA starting to take a
more southwesterly upper air flow as the upper air low moves toward
the OR coast. By Saturday afternoon, models are in pretty good
agreement with the low moving through onto the OR shore and towards
the CWA. On Sunday morning, forecast guidance has the low passing
over the northern portion of the CWA before departing to the east in
the afternoon causing a northwesterly flow over the CWA for the
remainder of the day. With this upper air pattern, models have a
surface low in the northeastern CONUS pushing cold front across the
region on Saturday. This cold front will allow chances for light
rain to move into the northwestern portions of the CWA on Friday
night and then spread through the remainder of the CWA during
Saturday. Snow levels continue to be near or above 7000 feet on
Saturday afternoon. By the evening hours, the snow levels look to
drop to around 5000 feet in northeastern CA and around 6000 feet in
the Tahoe Basin which will allow for a bit more areas to see the P-
type transition to snow. By Sunday morning, the colder temperatures
and lower snow levels will allow for most of the area to see light
snowfall if precipitation occurs. By Sunday evening, the
precipitation chances are anticipated to depart out of the CWA to
the northeast. When looking at the NBM snowfall probabilities from
Friday night through Sunday, portions of Lassen County have less
than a 10% chance of four inches of snow. Higher elevations in the
Tahoe Basin as well as Mono and Alpine Counties see a 20-60%
probability of four inches of snow. Will continue to monitor this
as this may cause hazardous traveling conditions over the weekend
for people going through mountain passes with roads becoming slick
with some potential slushy snow. As for the latest QPF values for
this event, it looks to range between around a tenth of an inch
to around a little over an inch in western portions of the region.
Another concern during this event is the potential for some
stronger southwesterly to west winds with the cold front passage
on Saturday afternoon. The latest probabilities of 55 mph wind
gusts within the southern half of the CWA ranges between 50-90%.
Will monitor this going forward as well in case a high wind
product is needed this weekend.

Going through the beginning of next week, the northwesterly upper
air flow continues with ensemble guidance showing the low opening up
into a negatively tilted trough on Monday and Tuesday over the Rocky
Mountains. As a result, warmer daytime temperatures are seen to
begin the work week with a 10-20% chance for afternoon and evening
isolated showers each day mostly for the northern half of the CWA.

-078

&&

.AVIATION...

VFR conditions are anticipated across the region at the REV
terminals through the remainder of today and going into Thursday.
While most terminals may see light and variable winds, KMMH and KMEV
see northwesterly winds around 10 kts through around 03-05Z when
they begin to decrease. By Thursday afternoon, wind gusts up 25-30
kts are possible for the western NV terminals southward to KMMH
while KTVL and KTRK may see gusts up to around 20 kts.

A cold front passing through the area is anticipated to produce
increased aviation impacts Saturday-Saturday night due to gusty
winds with areas of potential LLWS, increased precipitation chances
with periods of lower CIGS/reduced VIS, and even some light snow for
the Tahoe and Eastern Sierra terminals.

-078

&&

.REV Watches/Warnings/Advisories...
NV...None.
CA...None.
&&

$$