Heat in Nevada, August 16 to 20, 2018

Area Forecast Discussion
National Weather Service Las Vegas NV
828 PM PDT Wed Aug 15 2018

.SYNOPSIS...Storm coverage will increase again on Thursday as well
as spread north and west before precipitation chances decrease for
the second half of the week. Temperatures will trend down through
Thursday as thunderstorm chances increase then warm again Friday
with decreasing thunderstorm chances strengthening high pressure.
&&

.UPDATE...
Storms continue this evening across Mohave County and portions of
San Bernardino County where there is still enough lingering
instability to sustain convection. Movement of these storms is slow
and flooding remains a concern with PWATs between 1.0-1.6 inches.
The wind threat has come down over the last few hours and DCAPE
values continue to slowly decrease. Following current trends storms
should continue to weaken through 09z; lingering longest over
eastern Mohave County. The forecast has been adjusted accordingly.

&&
.SHORT TERM...Through Friday night.

The quiet period may be short lived though as Thursday is setting up
to be an active day. Cyclonic flow aloft from a wave pushing
westward with a weak 300mb jet will provide for better overall
forcing across the area Thursday afternoon. Instability will also be
better than what we saw today as CAPE values showing moderate
instability over much of southern NV into California and Arizona
combined with general area of forcing. With these factors in mind,
current thinking is scattered to widespread thunderstorm development
after 18Z Thursday is becoming more likely. Increased precipitation
chances on Thursday, including at least a slight chance for almost
all locations Thursday afternoon. Shear will continue to be limited,
so pulse storms with gusty winds are a potential impact. The more
significant worry for Thursdays storms will be flooding. Moisture
will be increasing as southwest flow pushes PWATs in the Colorado
River Valley into southern Mohave county near or over 2.00+ inches.
With continued slow moving and training storms, think the flash
flooding potential will be higher on Thursday than it has been the
past fews days. Will need to refine precipitation potential with
additional trends and tomorrows morning mesoanalysis, and heavy rain
may need to be added to the forecast for some locations. Storms may
last longer Thursday evening into the overnight as the weak
shortwave lifting through the area.

After Thursday, the overall flow becomes more southwest and the
area will dry out for the end of the week. Friday could still have
some thunderstorm activity, but it will be more limited and in
the higher terrain. With less moisture and anticyclonic flow,
temperatures on Friday will be warmer than it has been this past
week.

&&

.LONG TERM...Saturday through Tuesday.

Medium range guidance is in good agreement this morning on moisture
being temporarily scoured out across the southern Great Basin and
Mojave Desert this weekend. Once the moisture is scoured out, a
ridge of high pressure will build in from the west. As it does,
subsidence and mid-level warming should suppress any convective
development through Sunday. Under the ridge temperatures are
expected to increase and hover around 5-7 degrees above normal.

As high pressure moves eastward and sets up across central Arizona
early next week (Monday/Tuesday), more monsoonal moisture should seep
into the area. A southeasterly flow will tap a moisture pool across
southern Arizona and the Sonora Desert and advect it northward into
the Mojave Desert. There is low confidence in how far north this
moisture will spread, so only slight adjustments were made to the
PoP grids. Although moisture is expected to spread northward next
week, temperatures have been kept in the above average category for
now. If this moisture surge signal stays consistent over the next
few runs, temperatures will need to be adjusted downward to account
for cloud cover and surface moistening.
&&

.AVIATION...For McCarran...There is a chance for storms to develop
in and around the valley through today. With any thunderstorms that
develop there will be the chance for strong outflow winds with gusts
to 30 kts to reach KLAS. There is a slightly better chance for more
widespread activity tomorrow afternoon as well. Besides storm
chances, expect southerly winds generally less than 10 kts with
typical diurnal winds kicking in by 05-06Z this evening. Skies will
be FEW to BKN aoa 10 kft through the period.

For the rest of southern Nevada, northwest Arizona and southeast
California...There is at least a slight chance for storms to develop
near all TAF sites today. With any thunderstorms that develop there
will be the chance for strong outflow winds with gusts to 30 kts.
There is a slightly better chance for more widespread activity
tomorrow afternoon as well. Besides storm chances, expect southerly
winds generally less than 10 kts with diurnal winds kicking in by 04-
06Z this evening. Skies will be FEW to BKN aoa 10 kft through the
period.
&&

.SPOTTER INFORMATION STATEMENT...Spotters are encouraged to report
any significant weather or impacts according to standard operating
procedures.
&&

SHORT TERM...Wolf
LONG TERM....Booth
AVIATION...Kryston
UPDATE...Guillet

For more forecast information...see us on our webpage:

http://weather.gov/lasvegas or follow us on Facebook and Twitter

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE LAS VEGAS NV
735 PM PDT WED AUG 15 2018

..TIME...   ...EVENT...      ...CITY LOCATION...     ...LAT.LON...
..DATE...   ....MAG....      ..COUNTY LOCATION..ST.. ...SOURCE....
            ..REMARKS..

0511 PM     TSTM WND DMG     18 WSW ZZYZX            35.07N 116.42W
08/15/2018                   SAN BERNARDINO     CA   DEPT OF HIGHWAYS

            CHP REPORTS TWO SEMIS OVERTURNED. 1 MINOR
            INJURY. LARGE MILEAGE SIGN BLOWN DOWN.

&&

TB3