Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Las Vegas Nevada
424 PM PDT Thursday Jul 28 2016
Synopsis...the weekend and next week will bring relief from the
very hot temperatures experienced the past several days although
increasing humidity could make it feel a bit sticky at times. Expect
isolated to scattered thunderstorm activity across parts of the area
through the next week.
Short term...through Monday night.
Once clouds scattered out over the Las Vegas Valley, temperatures
shot up and were just shy of the forecasted high for the day at the
Airport. Thunderstorm activity began south of I-15 over the Mohave
preserve late this morning and coverage has since expanded to many
other areas. Further development is anticipated through the
afternoon hours in these areas and elsewhere. Storms are moving
slowly and are capable of producing heavy rain in a short period of
time which could lead to localized flash flooding and strong winds.
Additional cooling is expected for the weekend with temperatures
settling back to around normal by Sunday. The 110+ degree
temperature streak in Vegas now stands at 9 days...1 day shy of a
record 10 days. Saturday's forecasted high is 108 with a low
probability of reaching 110 if early cloud cover holds the low
temperature up and then skies clear and no additional cloud cover
develops over McCarran during the day allowing full daytime heating.
Thunderstorm coverage on Saturday will be mainly over the eastern
half of the area with the best instability and deeper moisture over
the southeast portion of the County Warning Area. Localized flash flooding will be
the primary concern. However, there is greater potential for more
widespread flash flooding over the southeastern County Warning Area including
southern Mohave and southeast San Bernardino counties. Sunday and Monday
should bring more more of the same over roughly the eastern half of
the forecast area. With the monsoonal flow well entrenched in these
areas, very efficient rain producing processes will be in play and
flash flooding will continue to be a concern.
Long term...Tuesday through Friday.
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...diurnally-driven winds at or below 10 kts
and VFR conditions will be the predominant weather at the terminal
through tonight. However, isolated storms in the higher terrain
surrounding the valley will generate outflows that may affect the
terminal at times this evening. Although a storm affecting the
terminal is unlikely, this cannot be ruled out. Tomorrow, a stronger
south to southwest wind should develop by afternoon. Chances for
storms increase this weekend with impacts to air traffic possible.
For the rest of southern Nevada...northwest Arizona...and southeast
California...isolated/scattered storms will affect the high terrain
in much of the area through this evening, with outflows producing
gusty/erratic winds potentially affecting the taf sites. Chances for
storms increase across the entire area this weekend, with convective
turbulence, locally lower cigs/visibility, brief/gusty winds, and
lightning all threats. Light/diurnally-driven winds and VFR
conditions should occur well away from any storms tonight
with stronger S to SW winds becoming established Saturday afternoon.
Fire weather...scattered thunderstorm activity is expected
through next week across roughly the eastern half of the forecast
area with more isolated activity across the western areas. Strong
winds and very heavy rainfall will be the primary concerns.
Temperatures will begin cooling to more typical mid Summer heat over
the weekend and throughout next week. Winds overall should be
generally light although thunderstorm outflows will result in
periods of strong...erratic winds.
Spotter information statement...spotters are encouraged to report
significant weather according to Standard operating procedures.
Short term/fire weather...Salmen
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