Red Flag Warning 5, NWS Reno, NV

Area Forecast Discussion
National Weather Service Reno NV
321 AM PDT Tue Sep 27 2022

.SYNOPSIS...

Warm Fall days and cool nights to continue this week. Today and
Wednesday will see enhanced afternoon breezes with the strongest
breezes Wednesday afternoon. A few isolated light showers will again
form this afternoon from the eastern Sierra front into portions of
western Nevada, mainly south of I-80.

&&

.DISCUSSION..

Today will mark the last day for the more summer-like above normal
temperatures as the high pressure continues to influence much of the
western US.  Daytime highs will again peak in the mid-upper 80's for
northeast CA and western NV. Sierra valleys will once again enjoy
these warmer temperatures highs peaking in the low 80s this
afternoon. Blended guidance continues to boost today’s high close
to 90 in lower valley areas of Churchill and Pershing counties as
well.

High pressure which up to now has been the major influence for the
warmer autumn weather across the region will recede east with the
ridge axis shifting more over the Rockies. Therefore, the upper
flow over the the Sierra and western NV will increase more from
the southwest today shunting the northward flow of mid-level
moisture into the region. Also, a weak embedded short wave lifting
over the central CA into western NV will enhance afternoon
breezes with winds gusting to 20-30 mph.

* Although European (ECS) and GEFS simulations show PWAT values
  dropping into the more modest 0.3”-0.5” range over the region,
  enough moisture coupled will the warmer daytime temperatures
  should be enough to once again form a few light showers and/or
  virga this afternoon over the eastern Sierra that will push into
  parts of western NV mostly south of I-80. Steeper lapse rates
  and warmer temperatures south of US-50 may better initiate
  convection and bring a slight risk (5-10%) of an isolated
  afternoon storm or two mostly over Mono-SRN Lyon-Mineral
  counties, as well as southern Churchill County.

* A stronger upper trough driving into the western US through
  Wednesday will further tighten pressure and thermal gradients
  over parts of northeast CA into western NV and bring enhanced
  afternoon breezes again on Wednesday. The increased magnitude of
  winds over the region will bring a few hours of elevated fire
  weather conditions to northeast CA and northwest NV. Blended
  guidance, along with European (ECS) and GEFS ensemble model
  guidance suggests afternoon peak wind gusts reaching more into
  the 30-40 mph range for many areas north of US-50. Higher Sierra
  peaks could see wind gusts to 60+ mph before tapering off later
  during the overnight hours.

Following passage of the trough overnight Wednesday into Thursday,
a more northwest flow will spread cooler air into the Sierra and
western NV and bring a slight pause to the rather warm autumn
temperatures into a more seasonable range through the remainder of
the work week. High pressure will once again build weakly over the
west coast through the weekend and bring slightly warmer
temperatures to the region.

-Amanda

&&

..AVIATION...

* An increasing southwest upper flow will ensure for the most part
  that dry-stable conditions continue through this forecast period.
  Therefore, VFR conditions will continue for regional terminals
  today through Wednesday.  Afternoon breezes for Sierra and far
  western NV terminal will see a slight enhancement with gusts 15-25
  kts between 21-03Z.

* A few afternoon light showers and /or virga will again develop
  this afternoon over the eastern Sierra, north across Lake Tahoe,
  and into northeast CA.  These showers will push off east-north
  with the afternoon breezes into far western NV. There is a slight
  risk (5-10%) for the development of an isolated afternoon
  thunderstorm or two mostly over Mono, SRN Lyon, Mineral, and
  Churchill Counties between between 21-03Z.

* An upper trough pushing across the Sierra and western NV Wednesday
  will bring enhanced afternoon breezes with gusts ranging 25-35 kts
  for all terminals.  Sierra and far western NV terminals (KTRK-KTVL-
  KMEV-CXP-KRNO) will see periods of increased turbulence and
  moderate chop below FL180 as mid-level winds  increase to 35-40
  kts. -Amanda

&&

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