Scientific Forecaster Discussion
fxus65 kvef 191638 aaa
Area forecast discussion
National Weather Service Las Vegas Nevada
937 am PDT Fri Jul 19 2019
Synopsis...dry conditions with afternoon breezes can be expected
through the weekend, with temperatures near to slightly above
normal. A pattern change beginning early next week will bring
increasing monsoon moisture into the region, with a marked
increase in clouds and humidity, along with daily thunderstorm
Update...midlevel debris clouds that increased overnight into
Mohave County have continued to shift northward into eastern Clark
and northern Mohave County. Low levels remain extremely dry with
surface dewpoints from Lake Havasu City-Kingman northward in the
upper 20s to around 40. As near surface winds stay southerly; mid
levels winds are forecast to shift more southwesterly this afternoon
which will start to sweep this midlevel moisture eastward out of
Mohave County. The several hours of clouds won't take away from a
sunny day. No update planned.
Short term...through Sunday.
Relatively tranquil conditions are expected through the weekend as
the monsoon high remains positioned to our south and a drier
southwesterly flow prevails across the Mojave Desert region. In
the immediate term, we do have some modest mid level moisture
(based in the 500-700mb layer based on the latest Yuma sounding)
which has seeped into our southeastern zones. This moisture won't
amount to much beyond some mid level clouds and perhaps some very
isolated sprinkles in the Lake Havasu to Wikieup vicinity during
the morning hours. By this afternoon, increasing southwest flow
will sweep this moisture east with clear skies and dry conditions
prevailing area wide.
Dry conditions expected to continue through the weekend with the
monsoon high migrating northward, to be positioned nearly overhead
by Sunday. This will result in warming temperatures over the
weekend, potentially approaching 110 degrees in the Las Vegas area
and nearing 120 in Death Valley. Precipitable water values will
begin to climb late Sunday as the high lifts north and Richer
monsoon moisture seeps in, but strong subsidence in close
proximity to the high should limit convective activity until
Long term...Monday through Thursday.
A much anticipated pattern change heralding the first substancial
monsoonal moisture push is still expected starting Monday. The
monsoon high will continue its northward progression Monday and
Tuesday to become set up in the more favorable Four
Corners/central rockies region. This positioning will allow for
deeper monsoonal moisture advection into much of the southwest,
with daily thunderstorm chances invading our forecast area.
Forecast soundings suggest much of the moisture on Monday may be
based more in the mid levels, with the airmass below 700mb still
fairly dry. This may limit instability somewhat and kept pops
fairly conservative Monday as it may take some time to moisten up
the desert valleys. However, whatever convection does form (most
likely in the higher terrain and northwest az) will have the
potential for strong downburst winds and dry lightning.
Low levels will moisten more substantially Tuesday, with GFS
guidance fairly consistent in advertising 1.25-1.75"
precipitable water values across the Mojave Desert Tuesday-
Friday. No sense in getting carried away with details as
convective evolution each day will be heavily dependent on cloud
cover trends, moisture surges, and convective complexes. Bottom
line is confidence is increasing in more typical monsoon
thunderstorm activity for much of next week with daily chances of
locally heavy rainfall, strong downburst winds, and dangerous
Fire weather...dry conditions will continue through the
weekend with afternoon breezes below any critical fire weather
thresholds. Pattern change early next week will bring increasing
clouds and moisture to the region. Thunderstorms on Monday will
carry at least a slight risk of some dry lightning before things
moisten up more from Tuesday Onward with markedly increasing
Aviation...for McCarran...similar conditions to Thursday
expected again today. Southerly winds with increasing gusts to
around 20 knots with mostly clear skies will be the theme, though
there is a chance the winds may briefly take on a more
southeasterly component during the mid to late morning hours.
Gusts will drop off again this evening.
For the rest of southern Nevada, northwest Arizona and southeast
California...mostly clear skies are expected across all area taf
sites today with south or southwesterly winds favored. Winds may
gust 15 to 20 knots at times, with the strongest gusts closer to
25 knots likely around kdag this evening. Gusts will gradually
diminish this evening.
Spotter information statement...spotters are encouraged to report
any significant weather or impacts according to Standard operating