Red Flag Warning 10, NWS Reno, NV

Area Forecast Discussion
National Weather Service Reno NV
252 AM PDT Wed Aug 21 2024

.SYNOPSIS...

* Seasonable temperatures with typical afternoon breezes will
  prevail today.

* Areas of critical fire weather conditions will be possible
  Thursday and Friday due to gusty winds and dry conditions.

* An early season cold front will provide gusty winds, chances for
  precipitation, and much cooler temperatures on Friday and Saturday.

* A warming trend along with dry conditions are in the forecast to
  begin next week.

&&

.DISCUSSION...

The latest RAP analysis shows the CWA with a southwesterly upper air
flow this morning being just east of the axis of an upper air
trough. Current surface observations and satellite imagery report
light winds with some cloud cover developing over northern Washoe
County. Model guidance shows the axis of the trough passing over the
CWA later this morning as a strong upper air low moves down the
coast in the Pacific Northwest through the day. At the surface, the
region expects to see typical afternoon breezes and dry conditions
to continue throughout today underneath mostly sunny skies with the
exception of Lassen and Northern Washoe Counties as areas near the
OR border may see some afternoon cloud development. Daytime high
temperatures look to be generally in the lower to upper 80s in
the valley areas while the Sierra Mountain communities expect to
range between the upper 50s and the middle 70s. Overnight low
temperatures look to cool to between the middle 40s and the middle
50s with higher elevations in the Sierra Mountains seeing
temperatures close to the freezing mark.

On Thursday, forecast guidance projects an upper air low moving
down the coast in the Pacific Northwest before making its way over
the CA/OR border late Thursday/early Friday morning. During late
Friday, the upper air low opens up into a trough and then passes
over the CWA on Saturday before progressing to the northeast later
in the day. With this new system making its appearance, increased
winds continue to be in the forecast on Thursday and Friday with
a cold front passing through the area. Southwesterly winds gusting
up to around 40 mph are in the forecast for the region causing
some fire weather concerns (see Fire Weather section), potential
blowing dust in desert areas, and even possible choppy lake
conditions. Those with outdoor plans may want to stay weather
aware over the next few days as these conditions may impact your
activities. While the far northeastern portions of CA may see
10-15% chances of precipitation, better chances and coverage of
precipitation are expected on Friday that last into Saturday.
Currently, the forecast calls for precipitation chances ranging
from 10% in Mono County up to around 50% in Lassen County. The
latest QPF values look to range from a trace in the eastern half
of the region to just under 0.40 inches in western Lassen County.
While thunder may accompany these precipitation chances for areas
closer to the OR border, severe weather is not anticipated at this
time, but will continue to monitor the situation in case this
changes. With this system bringing cooler temperatures, some
higher elevation areas may see light snow mixed into the
precipitation on Friday night. The colder air mass may also bring
a 30-50% chance for a hard freeze in some of the Sierra Valleys
while chances for a light freeze in the lower valley look to be
20-40% on Friday and Saturday nights. Please consider preparing
yourself and your property for these chilly temperatures today!

By Sunday, the CWA looks to take a northwesterly flow aloft in the
wake of the passing trough that becomes more zonal on Monday and
Tuesday. With this upper air pattern allowing for a surface high to
setup in the region, dry conditions and a warming trend is in the
forecast for the region to begin next week. Some areas may see the
return of daytime highs in the 90s by Tuesday and Wednesday of next
week. -078

&&

.AVIATION...

VFR conditions are expected today for all REV TAF sites with
afternoon gusts peaking between 21/18Z and 22/04Z up to 25 kts.
Along the Sierra, expect increased low-level turbulence.

Thursday-Saturday: A mid-level trough with an accompanying cold
front will affect the Sierra and western NV starting Thursday and
through the weekend. This brings higher wind speeds, more low-level
wind shear, turbulence, and chances for precipitation. Latest forecast
max wind gusts (kts) for Thursday/Friday: KRNO: 30/31; KCXP: 30/34;
KMEV: 25/31; KTRK: 26/29; KTVL: 24/29; KMMH: 28/35. -078

&&

.FIRE WEATHER...

* An early season cold front will provide increasing southwesterly
  winds for Thursday and Friday. A Fire Weather Watch has been
  issued for portions of far northeastern CA and northwestern NV on
  Thursday with areas of the Western NV Basin and Range seeing
  critical conditions by Friday due to these expected winds combined
  with marginally dry conditions.

* Winds on Thursday will begin to increase after 21z with gusts
  generally in the 25-35 mph range with minimum humidity around 15%.
  The favored areas to see 3-5 hours of critical conditions on
  Thursday will be zones 420/458/458/270/278.

* Winds across upper slopes and ridgetops will hit their peak
  Thursday night into Friday morning where gusts across Sierra
  ridgetops (~10,000' elevation) could see gusts in excess of 80
  mph. Lower valleys will mainly see gusts of 30-40 mph by early
  Friday as the cold front sweep across western Nevada.

* A stronger west-east surface gradient could yield stronger
  sustained winds across portions of the Basin and Range Friday
  afternoon which could yield critical fire weather conditions while
  Sierra and Sierra Front areas become moderated by increasing
  moisture with the front. -Fuentes/078

&&

.REV Watches/Warnings/Advisories...
NV...Fire Weather Watch from Thursday afternoon through Thursday
     evening NVZ458.

     Fire Weather Watch from Thursday afternoon through Thursday
     evening NVZ420.

     Fire Weather Watch from Friday afternoon through Friday evening
     NVZ423-429.

CA...Fire Weather Watch from Thursday afternoon through Thursday
     evening CAZ270-278.

&&