Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Las Vegas Nevada
1015 am PDT Thursday Jul 28 2016
Synopsis...excessive heat will continue today before a slight
cooldown arrives for the weekend. Isolated thunderstorms will be
possible once again today especially near the mountains. More
widespread thunderstorm activity is expected over the weekend and
into early next week.
Update...morning models are not showing any radical new thinking
compared to the previous runs so I plan on letting the current
forecast ride for now. Extensive debris cloud cover over the eastern
2/3 of the area when I arrived earlier this morning has drifted east
over the past several hours...thinning is some areas and thickening
in others. This could impact the forecast high temperatures for
today however, the warm morning lows...a pending record 94 degrees
in Las Vegas...will allow temperatures to warm rapidly given even a
brief period of clearing on a late July day. Many areas under the
excessive heat warning have seen little to no cloud cover today and
are on track for another hot day even if clouds/showers limit
heating in other areas. With all this in mind, I will leave the
excessive heat warning in place.
Previous discussion...215 am PDT...
Short term...through Sunday night.
Conditions today will closely mirror Thursday with very hot
temperatures once again along with isolated to scattered
thunderstorm activity. Widespread midlevel clouds and even a few
light showers persist at this early morning hour across the southern
Great Basin and parts of southern Clark County. This lingering
moisture will work to keep our overnight lows elevated making for a
warm start to our day on today. Despite afternoon highs dropping a
few degrees this afternoon, excessive heat remains probable today
thanks to the elevated morning temperatures and long duration of
very weather, thus the excessive heat warning will continue through
this evening. Continue to avoid the outdoors during the hottest
parts of the day and drink plenty of water to stay hydrated.
Thunderstorms, much like Thursday, will be possible again today
initiating over the higher terrain and developing into the desert
valleys during the afternoon and evening. While most of the storms
will be very brief, pulse type storms, a few of the stronger
downdrafts could produce severe winds along with torrential
rainfall. Moisture will continue to increase over the weekend, with
thunderstorm activity becoming more widespread especially in
northwest Arizona and the lower Colorado River valley. We will also
need to keep an eye on thunderstorm complexes which develop across
the Sonoran Desert the next few days as they could either develop
westward into parts of our forecast area, or push strong outflows
into our forecast area and increase our available moisture content
as well as our regional cloud cover. There will be lots to watch as
far as thunderstorm activity GOES over the weekend and into early
next week. With the added cloud cover and moisture, temperatures
will return closer to mid Summer normals.
Long term...Monday through Thursday.
The upper level pattern next week will be characterized by broad,
but low amplitude troughing across the Pacific northwest and a slow
decrease in the strength of high pressure across the southwest US.
This will result in temperatures near or even slightly below normal.
It will also leave the door open for monsoon moisture and diurnal
convection to continue to impact the region through next week. At
this time, there is little unanimous support for any focusing
features or major pushes that jump out in model guidance. Therefore,
the latest extended forecast has broad-brushed precipitation chances
with the best chances over Mohave County, decreasing to the west.
Aviation...for McCarran...similar conditions to Thursday expected
again today. Winds should favor diurnal trends though they become
complicated by thunderstorm chances and outflow boundaries. One or
more outflow boundaries are likely in the late afternoon and evening
which will disturb the diurnal wind pattern and result in periods of
gustiness. Otherwise, slight chance of thunderstorm activity today
and if thunderstorms impact the terminal strong winds are likely.
Sct-bkn clouds between 10-15k feet expected much of the afternoon
For the rest of southern Nevada...northwest Arizona...and southeast
California...sct-bkn clouds across the Great Basin will give way to
scattered thunderstorm activity during the afternoon. Thunderstorms
possible across northwest Arizona and parts of the Mojave Desert as
well. Storms will be capable of producing strong winds, blowing
dust, and very heavy rainfall. Otherwise..diurnal wind patterns with
increasing afternoon cloud development.
Fire weather...isolated thunderstorms expected again today capable
of producing strong winds and very heavy rainfall. Hot temperatures
expected once again before cooling to more typical mid Summer heat
over the weekend. Increasingly moist conditions are expected next
week. Winds will be fairly light though thunderstorm outflows will
result in periods of gustiness.
Spotter information statement...spotters are encouraged to report
significant weather according to Standard operating procedures.
Short term/fire weather/aviation...outler
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