Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Las Vegas Nevada
1052 PM PDT sun Jul 5 2015
Synopsis...moist and unstable air will allow for isolated to
scattered showers and thunderstorms to continue through Monday
before drier air begins to work into the region Tuesday. This will
start a trend of drying conditions that will last through the
remainder of the week. Temperatures will remain slightly below
normal through the week.
Update...based on the latest radar trends, grids and thus the
forecast were updated for the rest of tonight to keep in the mention
of showers and thunderstorms across central and southeast Mohave
County as the moist-dry interface continues to touch off activity in
this area. This area has been reluctant to shut down and so it
appears things here will likely slowly diminish.
Further north a large outflow boundary running from near Moapa to
Primm has pushed east generating wind gusts of 20-30 miles per hour (locally
higher) as it rolled on through. A few showers have popped up along
the back edge of this boundary mainly over the higher terrain. As a
result, I added in a slight chance of showers/thunderstorms to allow
for this activity which should end in another hour so at most.
The rest of the forecast remains on track outside of some minor sky
cover adjustments based on where probability of precipitation were tweaked.
issued at 903 PM PDT sun Jul 5 2015
Update...a nicely defined moist-dry interface boundary has been
lifting northeast across the area this evening on water vapor. We
have seen the bulk of the more intense convection fire on this
moisture content boundary which is not surprising. This boundary
currently extends from eastern Inyo County toward eastern San
Bernardino County and into far southwest Mohave County. Areas
southwest of this line are done with seeing any shower or
thunderstorm activity for the rest of tonight as the atmosphere has
stabilized nicely. The most active areas will continue to be along
this boundary as it works northeast, especially in central Mohave
County. The latest run of the hrrr suggests that activity will take
until around midnight or shortly after to weaken altogether in
southern Nevada and thus probability of precipitation were increased here to allow for
showers and thunderstorms into a later period tonight for western
Clark, southern Nye and southwest Lincoln counties which based on
present radar trends would be most at risk to see activity work on
in. Further south, the hrrr forecasts activity to weaken in Mohave
County, however, given the current look on radar, this activity will
need to be watched as it may go longer than what the hrrr thinks.
Cloud cover will stream east from ongoing convection and the sky
grids were adjusted up for the rest of tonight across the eastern
half of the area.
The rest of the forecast looks in good shape.
Aviation...for McCarran...some showers may make it into the Las
Vegas Valley from the west. Confidence on this is low but if any do
we could see erratic and gusty winds as well reduced ceilings. The best
time on this would be through 08z or so Monday. Otherwise look for
winds to favor typical diurnal directions through Monday evening.
Once again there could be a few rain showers and thunderstorms and rain on Monday in and
around the Las Vegas Valley mainly after 20z. Generally scattered-broken
clouds at or above 10k-15k feet with lower bases in and near any shra/tsra.
For the rest of southern Nevada...northwest Arizona...and southeast
California...shra/tsra will continue through the evening and should
decrease gradually between 06z and 10z Monday. Activity will mainly
be east of ktph-kdra-keed line. Gusty and erratic winds in and near
any rain showers/thunderstorms and rain with ceilings and visibility reduced to MVFR or lower. Otherwise
winds will favor typical diurnal directional trends overnight into
Monday evening. Once again on Monday scattered rain showers/thunderstorms and rain across the area
mainly after 20z and ending between 03z and 07z Tuesday. Favored
areas will be in the higher elevations with rain showers/thunderstorms and rain moving
northeast. Scattered-broken ceilings mainly at or above 10-15k feet with lower bases near
any shra/tsra. Visibility may be reduced to MVFR or lower in and near any
issued at 120 PM PDT sun Jul 5 2015
Discussion...moisture and instability will remain across the area
Monday for another day of isolated thunderstorms. Do not see any
specific trigger for storms other than heating and terrain. A dryer
southwest flow is expected to push the moisture east Tuesday with
just a few isolated storms over the far east County Warning Area Tuesday afternoon.
Wednesday through the end of the week we will see dry conditions as
the southwest flow remains in place. Temperatures will also remain a
few degrees below normal through the week.
Spotter information statement...spotters are encouraged to report
any significant weather conditions according to Standard operating
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