Portola, California 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

958
FXUS65 KREV 231052
AFDREV

Area Forecast Discussion
National Weather Service Reno NV
Issued by National Weather Service Elko NV
352 AM PDT Wed Apr 23 2025

.KEY MESSAGES...

* Warm and dry through Thursday with slight chance of isolated
  thunder continuing into this afternoon to the north.

* Light mountain snow and valley rain, thunderstorms, breezy
  winds, and cooler weather projected by Friday into the weekend.

* Lower shower chances on Sunday with warmer and drier conditions
  starting early next week.

&&

.DISCUSSION...

Little change from the continued warm Spring conditions through
Thursday. Daytime temperatures will rise a few degrees above
seasonal normal with breezy westerly winds gusting to 20-25 mph
each afternoon through Thursday. Daytime highs will stay pleasant
in the 70s across western NV valleys, and upper 50s and 60s across
Sierra locations down to Mono County. The one weather item worth
noting is some showers and isolated thunderstorms firing up across
portions of northeast CA and northwest NV into southeastern OR.
This convection is the result of an upper short wave lifting
northeast over the region. This activity will gradually dissipate
around sundown.

Ensemble simulations continue to show an approaching pattern change
and more active weather starting early Friday. A broad upper trough
and upper closed low are still on track to track into northern and
central CA Friday into Saturday, that exit east by Sunday afternoon.
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. Most recent blended
guidance is showing for Friday afternoon a 15-20% for isolated
thunder across NE-CA to include Mono into southern Lyon and Mineral
counties.

ECMWF-Ens multi-model ensemble simulations as well as
  GFS-Ens simulations are also trending a slightly wetter solution
  with this incoming system. ECMWF ensemble shift of tails
  simulations show higher snowfall anomalies from Lassen County
  south into southern Washoe County that continues west of Highway
  395 from Carson City to Mono/Mineral Counties. Although snowfall
  will be confined above 5000-5500, surrounding foothill areas to
  include the Virginia City could see something just short of an
  inch of accumulation.

Latest simulations still project limited available moisture from
  this system with liquid amounts based on current storm timing
  and trajectory ranging 0.10" to 0.35". Blended guidance is at
  present showing up to a 40-50% chance of a very slushy 1-2
  inches of accumulated snow over higher mountain passes with
  slightly higher snowfall totals across the Sierra crest. This
  will still bring impacts for mountain travel especially
  overnight Friday into Saturday.

Breezy west-southwest winds over the Sierra ridgetops peaking at
  40-50 mph with breezy southwest winds mixing down into western
  NV with gusts to 30-35 as well as 40 mph across higher foothill
  areas both Fri and Sat. Look for choppy surface conditions
  across larger area lakes, and period of moderate mountain wave
  turbulence and LLWS for aviation concerns to continue Fri and
  Sat as well.

Unseasonably colder temperatures around 10-15 degrees below
  seasonal averages with Sierra valleys from NE-CA, south to the
  Lake Tahoe basin, and Mono County seeing overnight lows dropping
  below freezing into the mid-high 20s for a brief few hours before
  day break early Saturday and Sunday morning.

Even though the upper low is exiting into the eastern part of NV
Sunday, any drying will be limited with a slight chance for a few
lingering light showers holding out across the high Sierra. It will
stay relatively cool as well. Blended simulations still projects
daytime highs topping out 5-10 degrees below seasonal normal. By
early next week, a more robust warming trend will complement the
drier conditions as high pressure builds into the Western US. Stay
tuned for updates for any changes to forecast details in the
coming days.

-Amanda

&&

.AVIATION...

VFR conditions will largely prevail through Thursday with lighter
winds in the morning that give way to breezy west-southwest winds by
early afternoon. Wind gusts for main terminal will range 20-25 kts
with brief periods of light to moderate turbulence persisting
through the afternoon. Look for increasing shower chances and winds
by Friday for all main terminal that continues into the weekend.

-Amanda

&&

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

$$