Severe Thunderstorm Warning 68, NWS Las Vegas, NV

853 
WWUS55 KVEF 202317
SVSVEF

SEVERE WEATHER STATEMENT
NATIONAL WEATHER SERVICE LAS VEGAS NV
417 PM MST SAT AUG 20 2016

AZC015-202323-
/O.CAN.KVEF.SV.W.0068.000000T0000Z-160820T2330Z/
MOHAVE AZ-
417 PM MST SAT AUG 20 2016

...THE SEVERE THUNDERSTORM WARNING FOR CENTRAL MOHAVE COUNTY IS
CANCELLED...
                
THE STORM WHICH PROMPTED THE WARNING HAS WEAKENED BELOW SEVERE WIND
AND HAIL LIMITS AND THE WARNING IS CANCELLED. HOWEVER THE STORM
CONTINUES TO PRODUCE VERY HEAVY RAINFALL AND A FLASH FLOODING
WARNING REMAINS IN EFFECT UNTIL 7 PM.

LAT...LON 3513 11341 3500 11357 3514 11390 3536 11361
TIME...MOT...LOC 2310Z 134DEG 24KT 3524 11371 

$$

JS

Area Forecast Discussion
National Weather Service Las Vegas NV
240 PM PDT SAT AUG 20 2016

.SYNOPSIS...Scattered thunderstorms are possible across Northwest
Arizona this evening with chances increasing across much of the
region Sunday and Monday as a weather system moves through. Drier
conditions are expected by midweek but thunderstorms will remain
possible across the higher terrain of Southern Nevada and Northwest
Arizona. Temperatures will be near seasonal normals.

&&

.SHORT TERM...through Tuesday Night.

Convection so far today has been rather limited thanks to some drier
air which has pushed in behind a weak upper low. This low is
currently shearing apart across the Southwest while being absorbed
by a larger closed low off the California coast, giving it minimal
influence to provide dynamics for organized thunderstorms. Instead,
terrain driven convection has developed across Northern Arizona and
some of this activity may develop westward into Mohave county later
this evening with new development on the westward propagating
outflow. The westward extent of this convection will be limited to
roughly the Colorado River and points east due to limited
instability and moisture further west. Main concerns will be locally
heavy rain and gusty winds.

The aforementioned SoCal low will begin to have more influence late
tonight and Sunday as it drives a vort lobe northward towards
southern Nevada. This should work to keep at least some light rain
shower/sprinkles activity (like last night) going overnight from
whatever convective debris exists earlier in the evening. Greater
thunderstorm coverage will exist Sunday with the added dynamics in
place. However, the amount of cloud cover we wake up to could have a
big implication on how much and how strong the convection Sunday is.

This vort lobe will begin to push north Monday only to be replaced
by the closed low itself as it progresses from west to east Monday
into Monday night. Think the greatest coverage of storms Monday will
be across the Southern Great Basin and Inyo county closest to the
lows northeast quadrant (a favorable location for lift).
Thunderstorms Sunday and Monday will have the potential to deliver
locally heavy rainfall and strong, gusty winds.

Drier air will attempt to push in Tuesday behind the low, but
lingering moisture will promote the chance for at least isolated
activity across the higher terrain and trended the forecast this
direction.  Temperatures Sunday and Monday will be cooler than past
days thanks to cloud cover and deeper moisture, with a small warming
trend beginning Tuesday.

.LONG TERM...Wednesday through Saturday.

The long term starts with a drying trend as the system responsible
for the increased chances of storms early in the week departs the
region. Temperatures should climb to slightly above average values
with most if not all of the CWA seeing dry weather. However, an
upstream vorticity maximum will rapidly move ESE through central
California and southern Nevada on Thursday. Though moisture return
will be limited in advance of this system, large-scale ascent will
cool the midlevels sufficiently to produce at least marginal
instability in the southern Great Basin into portions of Mohave
County. Maintained/slightly increased PoPs in these areas westward
to the Sierra/White Mountains, where favorable orographic lift will
compensate for even more marginal moisture.

Operational models are further suggesting a reinforcing vorticity
maximum swinging through the area on Friday. Moisture should be
somewhat lower still during this second system's passage, but the
upper-level dynamics/thermodynamics once again should be sufficient
for at least isolated storms in many of the same areas as Thursday.
Though these days should be "low-grade" precipitation days at best,
I suspect the potency of these reinforcing weather systems will
allow for at least some organization to the precipitation, producing
isolated/scattered coverage despite marginal moisture. Operational
models are certainly in better agreement today than the previous
couple of days regarding this scenario, so confidence is a little
higher that northern and eastern parts of the CWA will see some
convective activity on these days.

What transpires by next weekend becomes more unclear as models
continue to struggle with the development of a more amplified
Pacific trough/Interior West ridge pattern. The trend today has been
for the subtropical ridge to be shunted farther south and west,
which would be largely unfavorable for precipitation in our area.
However, it would also allow for decreased heights to sag southward
into the southern Great Basin, keeping our temperatures near to even
slightly below normal. MOS guidance has noticeably trended this
direction today, and felt inclined to nudge temps a little downward
late in the long term. Winds would also become relatively breezy in
this pattern given the seasonably deep low in the northeast Pacific
with the ridge suppressed southeast of there -- increasing the
pressure gradient. Increased winds Thursday through Saturday as a
result.

All of this said, model volatility/variability is quite high, so
forecast confidence remains below average for the entire long term
period.

&&

.AVIATION...For McCarran...Light winds expected through the evening
with a push of southwest winds possible. Thunderstorm activity looks
confined to the Peach Springs corridor although a stray storm cannot
be outruled across the Spring Mountains. Overnight winds should
remain light and out of the south, although if a thunderstorm
complex organizes across Northwest Arizona then winds will be
impacted by that. Thunderstorms a better possibility tomorrow with
sct clouds above 12kft.

For the rest of southern Nevada...northwest Arizona...and southeast
California...Fair weather for most areas through this evening with
only isolated mountain thunderstorm activity across far southern
Nevada. Better thunderstorm coverage exists across Northwest
arizona and a thunderstorm complex may emerge late in the evening
and develop west towards the Colorado River. Otherwise...winds will
favor diurnal patterns aside from thunderstorm outflow. Increased
chances for widespread thunderstorms arrive tomorrow.

&&

.FIRE WEATHER...Scattered thunderstorms likely across Northwest
Arizona today and this evening with sct-bkn clouds and light shower
possible across Mohave county and the Mojave desert overnight
tonight. Widespread thunderstorms possible Sunday afternoon and
Monday as a weather system moves through followed by gradual drying.
Temperatures will be near seasonal normals.

&&

.SPOTTER INFORMATION STATEMENT...Spotters are encouraged to report
significant weather, including any flooding and/or wind reports,
according to standard operating procedures.
&&

Short Term/Aviation/Fire Weather:  Outler
Long Term:  Shafer

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

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