452
FXUS65 KREV 301020
AFDREV

Area Forecast Discussion
National Weather Service Reno NV
220 AM PST Mon Dec 30 2024

..SYNOPSIS...

* Dry and milder conditions will return through the upcoming week
  with valley inversions forming by mid week under clearing skies.

* A slight chance of light showers across northeast California on
  New Years Day will be followed by another winter storm by
  weeks end that brings more Sierra snow, valley rain showers,
  and strong winds.

&&

.DISCUSSION

A dry northwest flow aloft over the region will usher in a period of
clearing skies, and lighter winds as high pressure works its way
over the western US. A weak, but dry upper short wave will swing
southeast over the Sierra and western NV on Tuesday, but go
largely unnoticed except or a few extra wisps of cirrus or a
scattered layer of mid-level clouds. This upper feature will be
followed on Wednesday by the trailing end of a cold front that
lifts east-northeast over northeast CA. It is projected to bring
an increased chance of perhaps 15-30% for a few showers close to
the Lake Tahoe Basin northward towards the Oregon border. Any
precipitation that falls will be light, and only a few hundredths
of an inch of liquid equivalent. Any snowfall will be light and
confined to the highest elevations around Mount Lassen, and
Warner mountains close to the northeast corner of Lassen County.

The clearing skies and lighter winds mean the formation of strong
overnight inversions in most valley areas. The stable and stagnate
conditions could trap pollutants and smoke near the surface that
may bring about air quality issues, especially in the more
urbanized areas around Reno-Carson City. To get the latest air
quality information, it can be found at www.airnow.gov. The clear
skies and stable conditions will increase the chances for
formation of patchy/dense freezing fog around most Sierra valleys
during the early morning hours before daybreak. Any freezing fog
that does form will dissipate by mid-morning.

Although high pressure will influence conditions for much of this
week, a brief change in the current quiet pattern may still occur
late in the week. A low pressure system looking to lift into the
Pacific Northwest will swing a cold front into the region that
brings more Sierra snow, valley rain showers, and gusty winds
into the Sierra and western NV. Timing and precipitation
uncertainties still need to be ironed out as the week progresses.
Therefore, any projections will most certainly be of a low
confidence nature as well. Stand-by for more news to come. -Amanda

&&

.AVIATION...

.Until 12Z Tuesday...

High pressure ridging into the region through the forecast period
will bring mostly VFR conditions to main terminals. The only
exception will be Sierra valleys like the Martis valley (KTRK),
where patchy dense early morning freezing fog could bring IFR/LIFR
conditions that dissipates by mid-morning. Clearing skies and
lighter winds will also mean the formation of valley inversions
that may bring hazy conditions and reductions in slant-range
visibility to those areas. Winds will be predominately light from
the north-northeast less than 10 kts. -Amanda

&&

.AVALANCHE...

No significant snowfall is projected for the Sierra through mid-
week. Also, winds will remain light from the north-northeast less
than 10 mph through mid-week as well. Skies will remain mostly
clear while temperatures near 7000 feet will remain below freezing
through this evening. -Amanda

&&

.HYDROLOGY...

Precipitation has ceased and snow melt will be minimal due to
decreasing temperatures, only minor rises below action stage are
anticipated on the Susan and Pit Rivers through today. Therefore,
no significant flooding is anticipated at this time on the Susan
River at Susanville, CA, or the Pit River at Canby, CA. -Amanda

&&

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

$$