Area Forecast Discussion
Issued by NWS Las Vegas, NV
FXUS65 KVEF 250820
Area Forecast Discussion
National Weather Service Las Vegas NV
120 AM PDT TUE OCT 25 2016
.SYNOPSIS...Showers and isolated thunderstorm activity will become
more scattered tonight and gradually diminish from west to east by
Tuesday early morning. Pleasant conditions will return Tuesday
through Thursday before more active weather returns Friday through
.UPDATE..Quick update to include patchy fog in the forecast for all
but the far northwest portion of the forecast area. Lowest reported
visibility was down to 1/4 mile briefly at Barstow-Daggett Airport.
Other areas are reporting 3-6 miles at this hour. Will continue to
monitor. Regular morning forecast package coming later this morning.
1110 PM PDT MON OCT 24 2016
Made some significant changes to the forecast for the next 24 hours.
First order of business was to update the PoP/QPF/Sky forecast
through 12z. The band of precip that has been moving across through
the afternoon and evening continues to progress a bit slower than
forecast. As such, I added showers to the forecast across eastern
San Bernardino County and increased PoPs significantly across Mohave
County where the brunt of the activity is expected over the next 6
hours. Also removed PoPs from Lincoln County where precip has ended
and skies are clearing out. Also dropped both high and low
temperatures for the next 24 hours and raised dew points and RH`s.
In fact fog is a distinct possibility in areas that received rain
today and is already beginning to form around Kingman.
Additional areas of fog will be possible as mid to high level clouds
clear out through the morning hours. Additional updates possible to
handle fog and the end of shower activity as the morning progresses.
.AVIATION...For McCarran...Most shower activity is now in the Peach
Spring corridor, and will continue to press east overnight. In
general skies will gradually clear overnight. However, with wet
surface conditions in the valley patchy low clouds or even fog are a
distinct possibility overnight. Winds will be light and variable
overnight. During the day expect light winds to return to a typical
diurnal pattern with a FEW-SCT clouds at 5-10kft.
For the rest of southern Nevada...northwest Arizona...and southeast
California...Line of showers and embedded thunderstorms moving east
will impact eastern San Bernardino County, Colorado River Valley and
Mohave County through tonight. Generally clearing skies expected
behind the line, and could lead to areas of low clouds/fog during
the morning hours. Mainly light and variable winds overnight. During
the day expect light winds to return to a typical diurnal pattern
with a FEW-SCT clouds at 5-10kft.
300 PM PDT MON OCT 24 2016
.SHORT TERM...through Wednesday Night.
Heaviest rainfall during this event has occurred in a corridor from
Barstow-Pahrump/Spring Mountains-Alamo. Some 24 hour rainfall
totals through 2 pm within the corridor include:
Barstow, CA 0.50
Shoshone, CA 1.16
Pahrump, NV 1.17
Kyle Canyon, NV 1.98
Rainbow Canyon, NV 2.28
Alamo, NV 0.86
So far the official station at McCarran International Airport has
registered 0.18 inches with the valley as a whole between a tenth
and a quarter of an inche. The exception would be the far west
central valley out near Red Rock near a third of an inch and locally
up to two-thirds of an inch in southeast Henderson/Railroad Pass.
Since late morning, line of numerous showers and embedded
thunderstorms has been running along Interstate 15 from southern
California into southwest Utah. Based on the current movement of
this line worst looks to be over for Las Vegas and areas northwest
of Interstate 15. Placed highest POPs this evening in part of
Eastern San Bernardino, eastern Clark, Colorado River Valley and
Mohave County as line shifts eastward. This is good news for the
lower Colorado River Valley and Mohave County which so far have seen
little rainfall. Last of the rain should be moving out of eastern
Mohave County between 11 pm and 2 am tonight.
A return to our more typical desert weather expected Tuesday through
Wednesday night as ridge amplifies over the Intermountain West as
the next trough takes shape in the eastern Pacific.
.LONG TERM...Thursday through Monday.
It looks like a fairly active pattern through the weekend as an area
of low pressure move inland late in the week and also the
possibility of moisture form Hurricane Seymour getting into the
picture. The models are still showing differences in timing with the
ECMWF model continuing to be the faster run. By Thursday afternoon
the EC already has precipitation reaching the southern Sierra while
the GFS/Canadian models keep the moisture off shore until early
Friday morning. However, the current track and position of the low
that will impact the is similar with all the model runs and it still
look like Inyo, Esmeralda, and central Nye Counties will see a
significant rain event Friday. Snow levels will generally be around
10K feet where several inches of snow will likely accumulate at the
higher peaks. Rain shadowing looks to be rather minimal due to the
southwest flow of the system. So places like Death Valley could see
some decent rain on Friday. Although the more widespread rain will
remain over the northwest portions of the forecast area, southern
Nevada, eastern San Bernardino, and Mohave Counties will also see at
least a chance Friday afternoon and evening. Rainfall amounts over
those areas are expected to be much less. However, moisture from
Hurricane Seymour could also come into play late in the week which
could throw a wrench into how much and where precipitation falls.
For now will increase pops with more areas in the likely category
for the northwest zones, but keep southern areas in the chance
There are some additional differences in the models on Saturday as
the GFS show a second wave and qpf spreading over mainly the two
thirds of the area while the ECMWF has generally dry conditions
areawide. Its possible that the GFS is hanging on to additional
Seymour moisture that the EC is not picking up on. No additional
changes to the grids based on these new and different runs. The
models do show another low approaching northern California Sunday
afternoon with additional moisture spreading into the southern
Sierra, but this system is forecast to move rather quickly and most
of the area is expected to be dry by Monday and Tuesday.
Temperatures will generally remain around normal, but areas under
thicker clouds and precipitation will see cooler temperatures.
.SPOTTER INFORMATION STATEMENT...Scattered showers and
thunderstorms are expected this evening southeast of Interstate 15.
Spotters should report significant weather according to standard
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