Scientific Forecaster Discussion
fxus65 kvef 271016
Area forecast discussion
National Weather Service Las Vegas Nevada
315 am PDT Thu Jul 27 2017
Synopsis...the threat of thunderstorms will shift into central
Nevada and northern Mohave County today and Friday as a drier and
warmer airmass works into the region. Another uptick in moisture and
thunderstorm chances is expected this weekend into early next week.
Short term...today through Saturday night.
The focus for thunderstorm activity will shift north today as
somewhat drier and more stable air works into the southern portions
of the forecast area. Precipitable water values will generally range around an inch
across the forecast area, but the best instability will be over
Esmeralda, central Nye, Lincoln and northern Mohave counties.
Yesterday we saw the best shear located over Esmeralda County, but
today that expands more toward central Nye and Lincoln, although not
as strong. Still, any storm that develops in those areas could
produce strong winds and small hail. Any storm that develops over
northern Mohave will tend to move slower and shear in that area is
fairly weak, so the main threat will be flash flooding. It's also
not out of the question that we could see some convection develop
over the Spring and sheep ranges today, but the flow is not suitable
to bring those into the Las Vegas Valley.
The best instability will continue to shift north and east Friday
with Lincoln and northern Mohave counties seeing the better
thunderstorm chances, but overall storms should be rather isolated.
The models are starting to indicate some deeper monsoonal moisture
starting to work northward over southwest Arizona Friday afternoon
ahead of an easterly wave located over northern Mexico. The newer
models runs have slowed the northwest progression of this wave on
Saturday and it looks like the deeper moisture will remain over the
far southern areas. We could see a few thunderstorms develop
Saturday, but overall it looks like most of the area will remain
dry. The deeper moisture looks to start pushing north Saturday night
which could have more of an impact on Sunday for thunderstorm
Temperatures will be close to normal through Friday, but lower over
the weekend due to an increase in overall cloud cover.
Long term...Sunday through Wednesday.
An inverted trough will move slowly westward to the south of the
area during the long term period with areas of high pressure setting
up over roughly New Mexico and over northern Nevada. As a result, we
will see monsoon moisture increase again Sunday with an east to
southeast flow then keeping moisture in place through Wednesday. At
this time it is a little difficult to pick one day over the others
as the most active day but if the northern extension of the inverted
trough sharpens and pushes a little farther north, the period from
late Sunday into Monday could see the best chances of thunderstorms
and flash flooding. Right now however, it looks just generally moist
and unstable with thunderstorm chances across the entire forecast
area with the deepest moisture over Mohave, Clark and San Bernardino
counties. As usual, extensive cloud cover on any particular day
could limit convection, which is extremely difficult to forecast in
the long term range.
Fire weather...drier and more stable air will work across southern
Inyo and San Bernardino counties today with thunderstorm activity
mainly confined to northern areas along with northern Mohave
County. Humidity values will gradually decrease through the day with
most areas trending downward about 8 to 18 percent. Overnight
recoveries will be moderate in most areas. Temperatures will be
close to normal through Friday then lower a few degrees over the
weekend due to increased cloud cover.
Hydrology...creeks, streams and rivers in northern Inyo County
have shown decreasing flows over the last couple of days.
However, some Road closures continue in the area. Bishop creek
bypass and Big Pine creek bypass continue to be utilized to
minimize flows through Bishop and Big Pine. Remember, never drive
through flooded roadways or around barricades. Also, pastureland
or farmland adjacent to creeks, streams or rivers could experience
areas of standing water.
Aviation...for McCarran...weak northerly gradient expected to keep
winds out of the north this morning before turning more easterly
after 16z and then gradually southeast. Speeds are generally
expected to remain below 8 kts through the day. There is an outside
chance of a thunderstorm developing over the Spring and Sheep Range,
but storms are expected to remain out of the Las Vegas Valley.
Few-sct clouds aoa 10k feet this afternoon.
For the rest of southern Nevada, northwest Arizona and southeast
California...mainly light southwest winds are expected over most
areas today with thunderstorm activity mainly confined to Esmeralda,
central Nye and Lincoln counties. There could be an isolated storm
south of those areas, but those storms will generally be confined to
the higher terrain. Outflow winds will be possible this afternoon
across those areas.
Spotter information statement...storms are expected to remain
isolated over most areas with the better chances over Esmeralda,
central Nye, and Lincoln counties. Spotters are encouraged to report
any significant weather or impacts according to Standard operating
Short term/aviation/fire weather...gorelow