Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Reno Nevada
818 PM PDT Tuesday Aug 4 2015
speed maximum moving northeast across the region this evening is aiding
the development of a band of showers across western Nevada. This
band should persist for a couple more hours...but is not producing
significant amounts of rain. Elsewhere showers and middle level
moisture are lifting north and northeast across northern
California and northwest Nevada. Instability is limited in this
area...but it is still not out of the question that we could see a
few thunderstorms later this evening over the far northern County Warning Area.
This would be in response to the speed maximum bringing increased
lift...but any activity would be very isolated.
Clouds are starting to clear a bit from the southwest as drier air
aloft is noted in satellite imagery. It will take some time for
this to work over the region...but many areas south of Gerlach to
Susanville line may be mostly clear by morning. 20
Previous discussion... /issued 240 PM PDT Tuesday Aug 4 2015/
Low pressure moving into northern California will bring low chances
for thunderstorms this evening well north of Interstate 80. Drier
west flow returns for middle week, then an increased chance for
showers and thunderstorms returns Thursday night and Friday as low
pressure approaches the Sierra and western Nevada. For this weekend,
dry weather returns with temperatures slightly below normal.
The blm reported that the Dodge fire in a remote area of northeast
Lassen County had burned 3,500 acres as of noon today. Zephyr wind
gusts this evening and again Wednesday with peak gusts up to 30
miles per hour should increase smoke output from the Dodge fire during the
late afternoon and evening periods. Smoke and haze from this fire
may reach the Surprise Valley and northern Washoe County through
this evening as west winds prevail. As winds shift to the
northwest overnight, smoke may spread across Gerlach and possibly
as far south as Lovelock and Pyramid Lake.
Current satellite imagery shows a weather impulse which will
track across northeast California and northern Nevada this evening and
overnight. Hrrr model forecast indicates showers as far south as
Mono/Mineral counties with this feature. However, trends and
operational models show more energy and instability near the
Oregon border. The GFS solution is preferred with isolated
thunderstorms roughly north of a Susanville-Lovelock line and
virga/sprinkles along the Sierra from the Tahoe basin south to
The eastern Sierra and western Nevada are between systems Wednesday
through Thursday with typical afternoon Zephyr wind gusts up to
30 miles per hour expected. A significant weather system is expected to
arrive Thursday night. There is potential for elevated, quick
moving nocturnal thunderstorms Thursday night across the Sierra.
The main concern with these storms Thursday night is the threat
for new fire starts.
Current guidance shows the upper jet crossing the Sierra over the
Tahoe basin Thursday evening, which would provide the best
chances for these nocturnal storms from the Tahoe basin north
across Plumas and Lassen counties. Forecast confidence is medium
and above average regarding the track of this low and its
associated moisture plume. However, subtle changes to the forecast
timing and track may change the location, intensity and coverage
of the storm threat Thursday night (so please stay tuned to the
Long term...Friday through Monday...
For Friday, we have continued to trend upward with thunderstorm
chances, as medium range guidance continues to move a potent upper
low across the Sierra and western Nevada. The minor timing differences
between guidance data may affect the amount and location of
convection Friday morning, but overall it appears that much of the
region can expect at least scattered thunderstorm coverage Friday
afternoon and evening. There are some fire weather concerns with
possible new fire starts due to fast cell motion and lightning
strikes outside main precipitation cores. However, low level moisture is
more likely to increase rather quickly as stronger storms develop.
The amount of instability and forcing associated with this low will
bring an elevated threat for severe storms producing hail, strong
outflow winds and locally heavy rainfall. With widespread outdoor
events taking place across much of the region Friday, participants
are strongly encouraged to plan ahead and ensure a quick access to
safe shelter before dangerous storms arrive.
For Friday night, this low is projected to exit to the northeast
with convection winding down. For Saturday, there may be a few
afternoon cells in far northeast California and northwest Nevada near the Oregon
border, but overall a drier and more stable air mass will spread
across the region as flow aloft becomes west. Maximum temperatures on Saturday
are expected to be a few degrees below normal, generally in the middle-
upper 80s for most lower elevations.
For Sunday through next Tuesday, trough developing in the Pacific
northwest is expected to keep dry southwest flow aloft over the
Sierra and western Nevada. Scattered cirrus and some flat afternoon
cumulus are possible each day, but thunderstorms are unlikely.
Temperatures will rebound slightly to near seasonal normals around 90
degrees in lower elevations by Sunday, and should hold nearly steady
through Tuesday. Afternoon Zephyr-type breezes with gusts 25-30 miles per hour
are forecast each day, which could lead to emergence and spread of
any holdover lightning fires resulting from friday's thunderstorm
VFR conditions expected at the main terminals through Wednesday,
although widespread middle-high level cloud cover will prevail with
possible brief light showers through this evening. The probability
for measurable rainfall at any of the main terminals is less than 20
percent. Isolated thunderstorms are possible north of Susanville and
Gerlach through tonight. Also, areas of smoke and haze from the
Dodge fire may spread across northwest Nevada and produce some reduced
visibility from Gerlach northward to the Oregon border. Additional
smoke could spread south to near Pyramid Lake by Wednesday
Cloud cover likely to limit wind speeds this afternoon, but some
gusts 20-25 knots are possible this evening as shortwave passes
through. For Wednesday, typical west-northwest Zephyr type breezes expected at
area terminals with peak gusts up to 25 knots mainly between 21z-04z.
For more information from the National Weather Service visit...
http://weather.Gov/Reno (all lower case)