829
FXUS65 KREV 052121
AFDREV

Area Forecast Discussion
National Weather Service Reno NV
221 PM PDT Sun May 5 2024

.SYNOPSIS...

A northwesterly flow increasing aloft will draw in cooler, and drier
air today into Monday. Shower chances return Monday mostly north of
the Lake Tahoe basin to the Nevada and Oregon border. Dry weather
remains for the rest of the week along with a slight warming trend
and lighter winds as higher pressure builds into the western US.

&&

.DISCUSSION...

Some impressive snowfall totals for the Sierra for the first weekend
of May. The Sierra overnight  received 1-2 feet of new snow across
higher terrain areas and areas around the west side of of the Tahoe
Basin received as much as a foot of the white cold stuff as well.
With the warming surface temperatures, and the colder air aloft, the
instability will bring increased shower chances (30-50%) over
northeast CA and northwest NV that swings into the Basin and Range
late this afternoon before dissipating an hour or two after sundown.
A short wave trough that will quickly swing over the region backdoor-
like Monday will bring another round of increased shower chances(up
to 30%)  late AM through the afternoon with showers holding closer
to the OR border areas of  NE-CA, and NW-NV.

Otherwise, the only notable impacts after today will be the colder
temperatures, breezy northwest winds, and patchy freezing fog
in some Sierra valleys Monday into Tuesday.

* As our post-winter Spring storm continues on it`s easterly
  track, a northwest flow aloft will not only bring drier
  conditions to the region but also will spread a colder air-mass
  across the Sierra into Mono County and the Great Basin as a
  whole for the next 36-48 hours. The daytime highs that struggled
  to break into the 40s over most mountain valleys, and into the
  lower 50s over western Nevada locales will ensure overnight
  lows followup on the below seasonal temperature trend as well.
  Look for overnights lows diving into the upper teens and 20s
  for Sierra valleys with a 60- 70% chance for lows dropping below
  freezing under clearer skies into the high 20`s to low 30`s for
  a few hours early Monday morning. Its advised to take
  precautions to protect sensitive plants, pets, people and pipes
  as overnight lows will fall into freezing territory through
  Monday morning. We`ll also see a repeat of these colder below
  average morning lows Tuesday morning with many locations across
  western NV dropping below the freezing mark once more.

* As high pressure struggles to build offshore the West Coast into
  western Canada, the Pacific Northwest, and into our region,
  opportunistic upper troughs will continue to swing into region.
  One such trough will bring enhanced west-northwest breezes into
  northeast CA, the Lake Tahoe basin, Mono County, and western NV
  Monday afternoon. Most areas will see west-northwest wind gusts
  peaking 30-40 mph during the afternoon, and then tapering off to
  less than 10 mph an hour or two after sundown. Tuesday will also
  be breezy to a lesser extent with most areas across western NV
  seeing gusts peaking to 30 mph from the north-northwest in the
  afternoon.

* There is up to a 25% chance for freezing fog developing in the
  Sierra and Martis valleys during the early morning hours Monday
  and Tuesday as well.

OUTLOOK: Through the later half of next week, the outlook does look
a bit murky with blended guidance still continuing to project a
gradual warming trend that includes continued dry conditions through
next week. That being said, daytime highs look to rise at least into
seasonal average by week`s end with current cluster ensemble
guidance is now favoring high pressure building strongly across the
Pacific Northwest midweek into next weekend. There still remains,
however, the uncertainty with placement of long-wave trough pattern
that now includes a cut-off low dropping south that then shifting
westward into the Great basin region by mid-week onward. At least
this setup favors a blocking pattern over the western US. Even with
the uncertainty, more Spring-like conditions may stay in place for
the long haul. -Amanda

&&

.AVIATION...

* An isolated snow shower may stray over Sierra terminals (KTRK-
  KTVL) through late this afternoon, and bring a brief period of
  MVFR conditions. Any remaining showers will dissipate shortly
  after sundown. VFR conditions will persist for Western NV
  terminals through the week.

* There will be an increased chance for patchy dense freezing fog
  forming around the Martis Valley after 08-10Z Monday and again
  Tuesday morning. Any fog will quickly dissipate by 15-17Z. There
  is a 10-20% for brief periods of IFR-LIFR ceilings and visibility
  conditions at KTRK during this period.

* West-northwest winds with gusts to 20-30 kts winds all area
  terminals will diminish to less that 10 kts after 03-06Z. Look for
  brief periods of mountain wave turbulence to continue till 06Z
  tonight. Breezy northwest winds return Monday late morning and
  afternoon with gusts to 25kt. After 15Z Monday, FL100 winds
  increasing from the west-northwest 25-35 kts bring a good chance
  for turbulence and LLWS east of the Sierra crest into far western
  NV. -Amanda

&&

.REV Watches/Warnings/Advisories...
NV...Lake Wind Advisory until 8 PM PDT this evening NVZ004.

CA...None.
&&

$$