Scientific Forecaster Discussion
fxus65 krev 280939
Area forecast discussion
National Weather Service Reno Nevada
239 am PDT Tue Mar 28 2017
dry conditions, light winds and a warming trend will be the story
for today and Wednesday before the next storm arrives early
Thursday morning. The Thursday storm will bring another round of
rain and snow showers, but also strong gusty winds. Thursday
afternoon and Friday will be much cooler behind this storm.
forecast remains on track early this morning. We are getting a
little bit of everything this week, which is pretty typical for
the Spring. Today/Wednesday will be warm and dry with light
winds, while Thursday we will get another storm into the region.
Main concerns with the Thursday system will be for a brief, but
intense period of strong winds and another round of rain and snow
Dry conditions with light winds are expected for today and
Wednesday as shortwave ridging builds in across the Sierra and
western Nevada. Temperatures will warm today and Wednesday as
well, with the warmest temperatures expected Wednesday afternoon.
By late Wednesday night, hints of the incoming storm will begin
across northeastern California and far northwest Nevada. Weak warm
air advection precipitation may begin to impact areas along the
California/or border late Wednesday night into early Thursday morning
before the main cold front pushes into the region.
The main storm will drop through on Thursday morning and will be
a quick hitter. This storm will bring strong winds along with
chances for rain and snow. Let's take a look at the wind potential
first. As the cold front approaches from the north, the surface
pressure gradients tighten drastically just before 8am on
Thursday. 700 mb wind speeds are right around 40-50kts along the
cold front as it pushes southward across the western Sierra front.
Since this appears to be a gradient-driven wind we could see
sustained winds not dramatically lower than the wind gusts, so
gusts between 45 to 55 mph will be possible for Thursday. Locally
higher gusts may occur in Mono and Mineral counties as the cold
front drops south through the day with gusts up to 60 mph
possible. Impacts due to the strong winds, include but are not
limited to, travel restrictions to high profile vehicles and
increased risk for turbulence and wind shear for aviation.
Now, onto the precipitation potential. The cold front associated
with the storm will produce a brief, but intense period of
precipitation early Thursday morning between 8am and 11am for
areas north of Interstate 80 and between 11am and 2pm for areas
south of Interstate 80. Although model forecasts do show the front
weakening as it drops southward past the Interstate 80 corridor.
Snow levels will drop quickly to most valley floors along and
behind the cold front, but since this is occurring during the day,
there should be limited accumulations for the lower valleys. Keep
in mind that wet roads can create slick driving conditions, and
that there may be a brief period of more intense precipitation
right along the cold front that may limit visibilities for the
morning commute. There is potential for some thunderstorms to
develop in the vicinity of the cold front as well, which may
result in some pellet showers. Precipitation liquid totals don't
appear to exceed 0.25 inch for the Sierra and western Nevada for
There is the potential for some upslope showers through early
Friday morning for alpine and Mono counties as the flow turns
northeast behind the front. Otherwise much of the precipitation
will have ended for areas north of Highway 50 by Thursday night.
Long term...Friday through Monday...
Minimal changes were made to the extended forecast this morning.
Forecast models continue to struggle with the evolution of the long
wave pattern...and thus the embedded short waves within that
pattern...beyond day 5.
An upper low exiting the region Friday should result in lingering
showers early east of Highway 95. Brisk north winds are also
possible Friday. This should keep the forecast highs a bit below
guidance. A ridge builds for Saturday offering lighter winds and
Then everything starts to break down. The European model (ecmwf) is still persisting
in dropping an open wave across the forecast area Sunday. This would
result in showers...breezier conditions and cooler highs. This is in
contrast to the GFS that keeps the ridge in place. But the more
interesting development in the GFS is an upper low dropping south
off the West Coast that becomes a closed low by Monday morning. The
gefs ensemble members are split for Sunday...but many do show some
type of trough over the region...closer to the European model (ecmwf).
The GFS brings a trough across the region Monday...but shower
coverage is minimal as energy is being sheared out between the low
off the Southern California coast and another trough over ern WA/OR.
Meanwhile the European model (ecmwf) is developing a ridge off shore with northwest
flow aloft. The ensemble members have a large spread in their
solutions by then with no one solution favored.
Given the difficulties the models are having with these transient
lows...not atypical for this time of year...we will stay with a dry
forecast for Sunday at this time and slight chance for precipitation
over the northern forecast area for Monday. Highs should be a bit
cooler with this scenario Monday following above average highs for
Saturday and Sunday.
today and Wednesday will be dry with light winds, while another
system queues up for Thursday. Rain and snow showers with gusty
winds are expected with that next system, with a few thunderstorms
possible over west central Nevada. Strong, gusty winds will increase
late Wednesday into early Thursday morning with increasing
potential for turbulence and low level wind shear for terminals in
the Sierra and western Nevada. -Edan