Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Reno Nevada
812 PM PDT Monday Aug 3 2015
except for right along the Churchill/Lander County line along
Highway 50...convection has ended over the forecast area. This is
a little earlier than forecast. Latest NAM does not support much
chance of anything developing overnight as next short wave trough
does not begin to impact the region until tomorrow afternoon and
evening. Will update to clean up convection wording this evening
but make few other changes. Updates out soon. 20
Previous discussion... /issued 209 PM PDT Monday Aug 3 2015/
Decreasing moisture is expected to keep thunderstorms isolated this
evening, waning to areas well north of Interstate 80 Tuesday.
Thunderstorm chances return on Friday as low pressure approaches
the Sierra and western Nevada. Afternoon temperatures will remain
around average this week.
Dry air is working into the region with southwest flow. Some
lingering moisture is still around, although precipitable water
has dropped down to around 0.5-0.6". Some isolated cumulus clouds
have developed north of Susanville and south of Highway 50 in
western Nevada. Could still see an isolated thunderstorm late this
afternoon and evening, as the hrrr is suggesting, but it will be
pretty isolated. Storms that develop today will be mostly dry with
little rainfall. See fire weather discussion below for details.
Isolated thunderstorms are expected again for Tuesday into Tuesday
night. An upper level wave and jet maximum will be moving through
northern California late Tuesday that will likely aid in kicking off some
isolated thunderstorms mainly north of Susanville. Any storms that
form will be isolated and fast moving with little rainfall.
Dry southwest flow continues through at least Wednesday with most
areas seeing typical August weather with hot, dry conditions and
breezy afternoons. There is a very slight chance of a thunderstorm
near the Oregon border on Wednesday, although it looks as though
areas to the north and east will have the better chances. Hoon
Long term...Thursday through Monday...
The main weather feature will be an upper low moving across the
eastern Pacific Thursday, then tracking inland across California/Nevada Friday-
Saturday. There are some timing differences between the faster GFS
and the slower ECMWF, but overall it appears the main impacts
for the region would occur Thursday night and Friday.
Thursday is likely to be dry with some afternoon cumulus and temperatures
near seasonal normals. For Thursday night, middle level moisture and
instability increases, with deformation zone setting up across northestern
California-northwestern Nevada ahead of the main low. With low levels rather dry and
fast steering flow, this could be a set up for fire weather concerns
Thursday night and Friday morning, due to potential for numerous
lightning strikes and limited rainfall.
By Friday, further increase in instability and forcing is likely as
the low moves across the Sierra, which could set the stage for
strong and possible severe storms. Both the GFS/European model (ecmwf) show a
favorable convective scenario at this time, but due to the inherent
nature of closed lows varying in location/track we will make only
incremental increases in probability of precipitation at this time, with the best chances
generally north of Highway 50 Friday afternoon and evening.
For the weekend and into early next week, drier and more stable air
mass is expected to prevail. As the low departs to the north on
Saturday, a few afternoon thunderstorms could develop north of
Susanville-Lovelock. Otherwise dry conditions are expected. Another
trough setting up along the West Coast Sunday-Monday keeps the
region in dry southwest flow, leading to typical late day Zephyr-
type breezes and holding temperatures slightly below normal,
generally around 90 degrees for the lower elevations. Mjd
VFR conditions prevail at main terminals through Tuesday with typical
SW-west breezes with gusts 20-25 knots mainly between 21z-04z. Isolated thunderstorms
possible through 04z this evening east of Bridgeport-Lovelock and near the
Oregon border. Another slight chance for thunderstorms Tuesday mainly north
of I-80, but less than 10% chance of cells impacting krno or ktrk.
Back to more of a typical Summer weather pattern this week in the
western Great Basin and the Sierra. A few storms possible over the
high terrain this afternoon and again tomorrow but coverage likely
limited (lal 2) due to meager instability. Normal afternoon Zephyr
breezes along the Sierra front and western Nevada each day but no
significant wind events expected this week. Plume of much drier air
in our simulations for tonight so have lowered humidity recoveries
especially in the middle-slopes and ridges. Keeping an eye on Thursday
night into Friday for a potential thunderstorm event with frequent
lightning (lal 3+), associated with vigorous low pressure and a
fairly unstable airmass aloft shown in our long range simulations.
Confidence in this scenario increasing but still low-medium. Cs
For more information from the National Weather Service visit...
http://weather.Gov/Reno (all lower case)