182
FXUS65 KREV 220923
AFDREV

Area Forecast Discussion
National Weather Service Reno NV
223 AM PDT Tue Apr 22 2025

.KEY MESSAGES...

* Warm and dry through midweek with highs 5 to 10 degrees above
  average will enhanced snowmelt that keep streams cold and swift.

* Pattern changes late week with increasing chances for rain showers
  and high elevation snow starting Friday

* Gusty Sierra winds and colder temperatures may lead to light snow
  accumulations over mountain passes and subfreezing lows in Sierra
  valleys through this weekend.

&&

.DISCUSSION...

Weak high pressure aloft will allow mild spring-like conditions to
persist today through Wednesday for the Sierra and western NV.
Afternoon highs are not expected to deviate much from the 5-10
degree above average trend. Sierra valleys will still see daytime
temperatures rising into the 60s this afternoon with western
Nevada locations seeing mostly 70s this afternoon and again
Wednesday afternoon. A weak upper short wave trough approaching
the West Coast will pass across northern CA later this afternoon
and continue across northern NV this evening. Tightening pressure
gradients ahead of the incoming trough will give afternoon winds a
boost with gusts peaking at 20-25 mph that then dissipate an hour
or two after sunset. A follow up short wave ridge will build over
the region overnight Wednesday, and extend the mild and slightly
cooler conditions into Thursday. This rather warm and mild period
will also enhance spring snowmelt that will keep mountain creeks
and rivers running fast and cold. Any flooding concerns should
remain minimal as well.

An approaching pattern change to more active weather looks to still
initiate later Thursday and persist into the weekend. A rather broad
upper trough with a closed low tracking into northern CA overnight
Friday into Saturday, that continues east by Sunday morning. This
low pressure system will bring periods of valley rain showers, high
elevation mountain snowfall, and breezy southwest winds by Friday
that continues through the weekend. Blended guidance is also showing
for Friday afternoon a 10-15% for isolated thunder across NE-CA to
include Mono into Mineral counties. This is what blended simulations
also project:

* Snow levels Thursday starting around 7500- 8500 dropping to
  6500- 7000 by Friday which eventually fall by Saturday morning
  to 5000- 5500 across NE-CA, and 5500`- 6000` across western
  NV, the eastern Sierra, to include Mono County. Blended
  simulations show snow levels across western NV dropping further
  to around 5000`- 5500` through the overnight hours Saturday into
  Sunday.

* Ensemble simulations are now showing better agreement as to
  liquid precipitation amounts based on current storm timing and
  trajectory. Still, early precipitation amounts are not
  particularly impressive at this time. Blended guidance is at
  present showing up to a 40% chance of a very slushy inch or two
  of accumulated snow over higher mountain passes. Blended
  guidance also indicates at least a 10-20% chance for up to 4
  inches of accumulating snow falling on mountain passes. This may
  still bring travel impacts over higher mountain passes
  especially overnight Friday into Saturday.

* Breezy west-southwest winds over the Sierra ridgetops peaking at
  50-60 mph with gusty conditions mixing down into western NV with
  gusts to 30-40 mph. Look for choppy surface conditions across
  larger area lakes especially friday afternoon for Pyramid Lake,
  and periods of moderate mountain wave turbulence and low level
  wind shear for aviation concerns.

Unseasonably colder temperatures will filter into Sierra valleys
from northeast CA, south to the Lake Tahoe basin, and Mono County
with overnight lows still projected to drop below freezing into the
mid-high 20s for a brief few hours before day break early Saturday,
Sunday, and Monday mornings. If you have already started a garden,
it is advise to take precautionary steps to protect your plants
sooner than later.

ECMWF-Ens multi-model ensemble simulations are now showing a closer
solution with GFS-Ens simulations that projects less uncertainty
with similar timing for this incoming spring storm. Stay tuned for
updates for any changes to forecast details. -Amanda

&&

.AVIATION...

VFR conditions will prevail across all terminals today. Surface
winds will strengthen from the west-southwest between 21Z-02Z this
afternoon with gusts 20-25 kts for Sierra terminals, and 25-30
kts for western NV terminals. These breezy conditions coupled with
FL100 winds from the southwest increasing to 20-30kt will allow
for periods mountain wave turbulence and low-level wind shear.
Although surface winds will dissipate this evening shortly after
sunset, turbulence will continue overnight to 12Z-15Z Wed. -Amanda

&&

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

$$