749
FXUS65 KREV 042146
AFDREV

Area Forecast Discussion
National Weather Service Reno NV
146 PM PST Wed Dec 4 2024

.SYNOPSIS...

* Strong valley inversions continue at least into the start of the
  weekend with areas of freezing fog redeveloping each night.

* Expect near seasonable temperatures outside of valley areas
  impacted by fog and low clouds.

* No significant storms are on the horizon through mid-month, but a
  slider system could help erode the inversions by late weekend.

&&

.DISCUSSION...

Hi-res ensemble guidance, as well as blended guidance, continue to
generate simulations that show little change to the current status
quo weather-wise as the current upper level blocking pattern
persists across the western CONUS, and splits the westerlies.
GOES-West derived infrared imagery confirms this current forecast
assessment as well. Looks like this continuing period of stagnant
conditions under a cold dome of high pressure will continue
through the remainder of the week into Saturday as well.

Therefore, look for little deviation from the current forecast the
next few days. This includes a continuation of cold overnight lows
under clear skies, lighter winds, strengthening overnight
inversions, and a continuance of air quality issues, especially in
the more urbanized areas between Reno and Carson City. Also, denser
patches of freezing fog will continue overnight across the Honey
Lake Valley corridor of Highway 395 from the NV/CA state line to
Susanville, that includes portions of Highway 36 and 44. This
freezing fog projection also includes areas along highway 447 from
Wadsworth to Gerlach, which includes areas around Pyramid Lake,
and portions of the I-80 corridor from Fernley to Trinity Junction.

Later this weekend starting overnight Saturday into Sunday morning,
the trailing west edge of a weak cold front will become embedded in
the upper ridge aloft, and sneak across the Sierra into the Great
Basin backdoor-like. Areas north along the CA-NV-OR border will also
have a 15-20% chance for precipitation late Saturday into Sunday as
well. Following close behind, a deeper short wave system will take
advantage of the now opened synoptic door, and push southeast
"Inside slider-like" through northeast CA into Nevada later Sunday
into Monday. The combination of these two features with the second
system producing greater upper forcing, and stronger northwest
breezes, will allow for better mixing into western Nevada valleys
that mixes-out the stagnant conditions and enables dissipation of
persistent freezing fog across the region. All other areas across
the Sierra into western NV will remain dry, but a few degrees colder
the first part of next week and colder air briefly filters into the
region. Blended guidance also projects a slight upward trend in
temperatures by mid-week that remains mostly seasonal through the
remainder of next week.

On a side note, extended ensemble simulations show a low confidence
projection for an impending pattern change starting later next week.
Although this projection carries a decent amount of uncertainty,
it is something that will be tracked. More on this to come! -Amanda

&&

.AVIATION...

* Strong valley inversions will persist at least through Saturday
  morning. There is a good chance for areas of haze and minor
  reductions to slantwise visibility continuing for area terminals
  during the afternoon hours. Otherwise, western NV terminals
  outside of known areas of freezing fog will remain VFR with light
  winds continuing through the week.

* Look for areas of morning freezing fog and low stratus to persist
  across the Honey Lake Basin, and the area around Pyramid Lake
  which stretches north through the Black Rock/Smoke Creek Deserts,
  and south to Fernley during the overnight hours. The freezing fog
  potential will still be high for KSVE and KTRK from 10Z to 17Z
  with periods of IFR/LIFR conditions in reduced visibility. There
  is also a less than 10% chance of KRNO and KRTS seeing some
  visibility reductions due to morning freezing fog as well.

* Look for an end to stagnate conditions, and areas of freezing
  fog Sunday and Monday. Weak systems aloft will work their way
  across northeast CA into western NV, and bring an increased
  chance for W- NW breezes into the region. -Amanda

&&

.REV Watches/Warnings/Advisories...
NV...Freezing Fog Advisory from 8 PM this evening to 11 AM PST
     Thursday NVZ004-005.

CA...Freezing Fog Advisory from 8 PM this evening to 11 AM PST
     Thursday CAZ071.

&&

$$