Scientific Forecaster Discussion
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Area forecast discussion
National Weather Service Las Vegas Nevada
910 PM PST Fri Dec 13 2019
Synopsis...Pacific systems will bring high clouds, gusty winds,
and precipitation chances to portions of the region through the
weekend. High pressure will set up over the region early next week
with dry conditions along with slightly below normal temperatures.
Another system is forecast to move through the region during the
late half of next week bringing a return to unsettled weather.
Update...another weak embedded shortwave is passing across
northern California/Nevada tonight bringing the bulk of shower
activity to the central Sierra and across the northern half of
Nevada. In our area, showers will continue overnight in the
southern Sierra and along portions of the County Warning Area bordering our
neighbor to the north, National Weather Service Elko. Abundant high clouds continue to
stream across the Mojave Desert with lower clouds over portions of
Esmeralda and central Nye counties, all of Lincoln County and
northern Mohave County. Went ahead and updated the first period
(tonight) with a blend of the latest short range models. The
updated forecast is out.
Previous discussion... /issued at 230 PM PST Fri Dec 13 2019/
Short term...through Sunday night.
As of early afternoon, downslope winds in the Sierra have been
relatively minor with a few gusts over 50 mph recorded. All signs
are still pointing to the potential of strong winds reaching the
western portions of the Owens Valley with the greatest threat
expected now through 5pm. There are a few showers starting to impact
the higher Sierra and these showers are expected to increase over
the next few hours. As this occurs the threat of downslope winds
will decrease as additional spillover occurs. Snow amounts in the
higher elevations of the Sierra will likely be over a foot, but in
areas 7000-9000 feet we are generally looking at snow totals
generally under 6 inches.
Upper level trough will move into the region Saturday bringing gusty
west winds to portions of the Mojave Desert. Strongest winds will
likely occur along the I-15 corridor in San Bernardino County
Saturday afternoon and evening with gusts over 40 mph possible. Have
gone ahead and issued a Wind Advisory for zones 523 and 524.
Westerly wind are not expected to reach advisory levels in southern
San Bernardino County Saturday, but as the winds turn northwest
behind a cold front the winds are expected to increase
significantly, especially in the morongo basin Saturday night. At
this time did not issued an advisory for that area, but it's
possible one may be needed.
A cold front will push south across the region Saturday with
precipitation spreading south along the front. This front is not
particulary strong and moisture will be rather limited. However, Nye
and Lincoln will see the better chances of precipitation with the
front and it's possible portions of Lincoln County could see a quick
burst of snow behind the front. Snow amounts are expected to remain
less than a couple of inches as this front will move through fairly
quick. Southern Nevada will be on the western fringes of the
precipitation, but a few showers will be possible Saturday evening
and overnight as the front moves through the area. Amounts will
remain light and most areas will see a trace or less. The front will
slow down late Saturday and Sunday with shower chances remaining in
place through much of Sunday across northwest Arizona. Snow levels
will generally remain around 6000 feet, but rain and snow amounts
will remain light.
System will exit the area late Sunday with a drier northwest flow.
Cooler temperatures are also expected with highs on Sunday dropping
about 5-8 degrees.
Long term...Monday through Friday.
The long term period starts with high confidence with a ridge of
high pressure building in behind the disturbance(s) of the short
term. By midweek, model consensus erodes quite a bit. While decent
agreement exists in bringing a Pacific system across the region
later in the week, significant timing and to a lesser extent,
strength differences exist. The GFS family is the quickest of the
camps, bringing the trough ashore on Wednesday, leaving the region
in it's wake by Friday, with the European model (ecmwf) almost 24 hours slower. In
any case, more unsettled weather is expected by the middle to late
week next week.
Aviation...for McCarran...light winds following close to typical
daily trends along with periodic high clouds will continue through
Saturday morning. Winds will increase out of the southwest Saturday
around noon, with gusts up to 20 knots possible. A cold front will
push through Saturday night, bringing a push of gusty north winds,
vicinity shower chances, and ceilings crashing to 5-7 kft. Frontal
edge will arrive between 04z-06z tomorrow evening.
For the rest of southern Nevada, northwest Arizona and southeast
California...low level wind shear in the Owens Valley and obscuration of the Sierra
crest will continue through Saturday morning. Gusty winds will
increase across the western Mojave Desert saturday; gusts at kdag
may reach 40-45 mph Saturday afternoon as a weather disturbance
passes overhead. Elsewhere winds will be lighter, but south to
southwest winds will develop ahead of a cold front. The cold front
will move through the Great Basin Saturday afternoon and exit the
Mojave Desert early Sunday morning. Gusty north winds and a period
of lower ceilings between 5-8 kft are expected with the frontal
Spotter information statement...spotters are encouraged to report
any significant weather or impacts according to Standard operating