Dense Smoke Advisory 4, NWS Reno, NV

Area Forecast Discussion
National Weather Service Reno NV
228 AM PDT Wed Aug 19 2020

.SYNOPSIS...

Isolated thunderstorms are expected over the Basin and Range of
central Nevada and south of Highway 50 today. Breezy conditions are
expected today and Thursday, with dry conditions lasting into the
weekend. Afternoon highs remain hot, although morning lows look to
fall late this week for relief from daytime heat. Smoke and haze
continue with wildfires in the region.

&&

.SHORT TERM...

Very minor changes were made to the forecast. The main messages in
the short term are the continued daytime heat with a reduction in
overnight warmth, enhanced afternoon winds the next couple of
afternoons, the absence of thunderstorms Thursday into the weekend
as dry conditions return, and the continued smoke and haze from
nearby fires.

* Thunderstorms: Isolated thunderstorms are possible this afternoon
  mainly south of US Highway 50 and out into the eastern portions of
  Churchill and Pershing counties. Similar to yesterday, storm
  motions will be swift towards the northeast at 15 to 20 mph.
  Surface heating in the afternoon will contribute to rather deep
  inverted-v profiles and sufficient surface-based CAPE to maintain
  strong thunderstorms capable of producing brief heavy rainfall,
  small hail, and strong outflows to 50 mph. Dry lightning outside
  of thunderstorm cores is also possible. Drier air begins to enter
  the region today, which will move the thunderstorm threat out of
  our region through at least Sunday.

* Smoke and Haze: Several fires have been burning across central
  and northern California for the past couple of days. With
  increasing westerly flow expected through the end of the week,
  we will likely see smoke and haze impacts across our region for
  the next few days. Air quality has remained moderate across
  western Nevada and the northern Sierra this morning as the
  Loyalton fire has burned less actively. Thicker smoke will be
  possible downwind of the North Complex southwest of Susanville,
  the Claremont fire south of Quincy, and the W-5 fire east of
  Madeline through this afternoon.

* Heat: The Heat Advisory continues for western Nevada through this
  evening. Temperatures will be hot again today with upper-90s to
  low-100s expected for the lower valleys of western Nevada and
  upper-80s to low 90s likely in Sierra valleys. With drier air
  moving into the region, daytime highs will cool a few degrees and
  overnight lows will cool at least 5 to 8 degrees through Saturday.
  This will bring much-needed relief from the oppressive mild lows
  the past few mornings. Warmer temperatures look to return
  Saturday, so heat-health impacts may increase again.

* Winds: An area of low pressure will move through the Pacific
  Northwest today into Thursday, which will strengthen afternoon
  breezes each day mainly along the northern Sierra Front, in
  northeast California, and into portions of west-central Nevada.
  Hazardous lake recreation and critical fire weather conditions are
  expected today. See the fire weather discussion below for more
  details regarding the critical fire weather conditions. -Johnston

.LONG TERM...Saturday through Wednesday.

Daytime high temperatures are expected to remain around 5-7
degrees above average through the weekend and in early next week
as the ridge of high pressure remains more or less over the 4
corners region. This aspect of the forecast is fairly certain with
much less certainty on the amount of moisture available for
thunderstorms.

Small difference in the developing pattern of another incoming
trough to the Pacific Northwest and potential for moisture from
Hurricane Genevieve create uncertainty in the thunderstorm aspect of
the forecast. The most likely scenario is for at least some
thunderstorm development in the favored areas of Mono and Mineral
counties returning by Sunday and into early next week potentially
spreading northward into the Tahoe Basin and the Sierra front. If
the high pressure builds farther west, and/or remnant moisture
from Genevieve moves into the region then more widespread
thunderstorms could be possible early next week. -Zach

&&

.AVIATION...

Thunderstorms are expected this afternoon and evening mainly south
of Highway 50 and across west-central Nevada. Storms will be capable
of producing brief heavy rainfall, small hail, and strong outflows
to 35-40 kts. Visibility reductions and mountain obscurations are
possible near storms due to blowing dust and heavy rainfall.
Thunderstorms will vacate the region Thursday through Saturday as
drier air moves into the region but look to return early next week.

Smoke and particulate matter from fires burning in northeastern
California will generate haze across our region, which will limit
slantwise visibility. Smoke from fires in northeastern California
near KSVE and KRTS will likely reduce both surface and slantwise
visibility near these areas today. This looks to continue for the
next few days as westerly flow returns to the area. -Johnston

&&

.FIRE WEATHER...

No significant changes to the fire weather forecast for today with
Red Flag Warnings in effect this afternoon from 1 to 9 pm for
northeast California, the Sierra Front and far northwest Nevada for
gusty winds and low humidity. South of highway 50, another day of
thunderstorms is expected during the afternoon with a few strong
storms possible. Storm motions will again be in the 15-20 mph range
to the northeast with significant moisture available and brief
heavy rain and gusty outflow winds likely, but strikes outside of
rain cores always remain possible.

Dry air will push into the region today, mainly north of highway 50,
ahead of a trough moving into the Pacific Northwest. Minimum
humidities are expected to drop back to 10-15% this afternoon with
drier air continuing to work into the region through Thursday. A
slot of very dry air at 700 mb is forecast to move into the region
Wednesday night into Thursday likely creating poor overnight
recoveries Wednesday and Thursday nights, especially along mid-
slopes and ridges. Daytime minimum humidities are forecast to be
even drier on Thursday afternoon with some areas likely dropping
into the single digits.

The incoming trough will also tighten surface pressure gradients
increasing the usual afternoon zephyr winds today. Widespread
winds of 15 to 25 with gusts of 35 mph are expected to combine
with incoming dry air to create critical fire weather conditions
this afternoon along the Sierra Front, northwest Nevada and
northeast California. A jet streak is forecast to form over
northwest Nevada tonight which will keep wind elevated through
the overnight hours along the higher terrain and exposed
midslopes. Gradients will ease some on Thursday but winds are
still expected to gust into the 25 to 30 mph range with isolated
areas of critical fire weather conditions likely, especially in
the more wind prone areas. If the jet streak lingers over the
region into Thursday another day of more widespread critical fire
weather conditions is a possibility. -Zach

&&

.REV Watches/Warnings/Advisories...
NV...Lake Wind Advisory from 1 PM this afternoon to 9 PM PDT this
     evening NVZ004.

     Heat Advisory until 11 PM PDT this evening NVZ001-003>005.

     Red Flag Warning from 1 PM this afternoon to 9 PM PDT this
     evening NVZ420-423-458.

     Lake Wind Advisory from 1 PM this afternoon to 9 PM PDT this
     evening for Washoe Lake in NVZ003.

CA...Red Flag Warning from 1 PM this afternoon to 9 PM PDT this
     evening CAZ270-271-278.

     Lake Wind Advisory from 1 PM this afternoon to 9 PM PDT this
     evening CAZ071.

&&

For more information from the National Weather Service visit...
http://weather.gov/reno