249
FXUS65 KREV 092004
AFDREV

Area Forecast Discussion
National Weather Service Reno NV
104 PM PDT Thu May 9 2024


.SYNOPSIS...

A warming trend finally settles in across the Sierra and western
Nevada with above average temperatures expected by this weekend. The
potential for showers and thunderstorms also return to the Sierra by
Friday afternoon with ongoing low chances each day through early
next week.

&&

.DISCUSSION...

Plan on at least a couple more days of the pesky northeast to
easterly flow for the Sierra and western Nevada. The easterly flow
has limited the warming potential and also kept the region fairly
dry for much of the week. The broad upper level low centered over
the Four-Corners Region is projected to retrograde westward
slightly, resulting in one last push of easterly winds from the
Tahoe basin southward. This wave will also bring low chances (10-
15%) for light showers (light snow for highest mountain peaks) for
areas from Mono Lake southward in Mono county and Mineral county too
this evening through early Friday morning. Residual moisture from
the exiting upper level wave along with afternoon heating may be
enough to kick off a handful of showers and storms along the Sierra,
but with easterly steering flow anything that pops up will meander
toward interior CA.

The broad upper low finally migrates eastward as weak high pressure
builds across CA and NV in its wake. The fly in the ointment for a
true ridge pattern (warmer/drier conditions) appears to be a weak
trough in the vicinity of the West Coast Saturday into Sunday.
Surface temperatures will still warm through the weekend, but the
low will introduce varying chances for showers and thunderstorms as
it nears the region. For now, simulations highlight a 10-15% chance
for isolated showers and thunderstorms for the Sierra on Sunday
afternoon with less than a 10% chance on Saturday. The potential
will continue through early next week as the weak trough sags
through the SoCal.

Beyond Wednesday, ensemble clusters are showing hints of a stronger
ridge signal to wrap up the latter half of the week. There may be a
bit of a weather pattern shift battle between the building Eastern
Pacific Ridge and the upper level trough deepening across the
Rockies. Warming trend should remain on track through the early half
of next week, but the blended guidance is showing a bit more spread
in the forecast highs by Thursday, which would line up with the
pattern shift indecision by mother nature.

-Edan

&&

.AVIATION...

* VFR conditions will persist at all TAF sites to end the week. KMMH
  will be the exception overnight where some mid to high level cloud
  cover arrives between 0z-6z Friday.

* Winds: Breezy easterly afternoon winds will develop today and
  Friday afternoon before shifting to lighter flow on Saturday. The
  more typical west winds are slated to return on Sunday afternoon.
  Breezes will remain in the 20-25 kt range each afternoon through
  the weekend, with the lightest winds on Saturday.

* Precipitation: A few cumulus buildups will develop late this
  afternoon, but less than a 5% chance for showers or thunderstorms
  through 0z Fri. Between 0-6z KMMH may have a few showers develop
  as the upper low retrogrades westward towards the Sierra. Light
  showers, and even very high elevation snow, may continue through
  Friday 18z. Any additional showers or thunderstorms potential will
  form along the crest with the easterly steering flow pushing them
  toward interior CA.

-Edan

&&


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

$$