Flash Flood Warning 32, NWS Las Vegas, NV

109 
WGUS75 KVEF 122308
FFSVEF

Flash Flood Statement
National Weather Service Las Vegas NV
408 PM MST THU JUL 12 2018

AZC015-122318-
/O.EXP.KVEF.FF.W.0032.000000T0000Z-180712T2315Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/
Mohave AZ-
408 PM MST THU JUL 12 2018

...THE FLASH FLOOD WARNING FOR CENTRAL MOHAVE COUNTY WILL EXPIRE AT
415 PM MST...

The heavy rain has ended. Flooding is no longer expected to pose a
threat. Please continue to heed any remaining road closures.

LAT...LON 3516 11391 3513 11408 3532 11410 3530 11394

$$

AB

Area Forecast Discussion
National Weather Service Las Vegas NV
403 AM PDT Thu Jul 12 2018

.SYNOPSIS...A very moist airmass will remain firmly in place
across the region. Widespread showers and thunderstorms are expected
again today, with the strongest activity expected north of Las
Vegas. Storms today will have the potential of producing flash
flooding and a Flash Flood Watch is in effect for portions of the
region. A slow decline in thunderstorm activity is expected
Friday through the weekend while temperatures begin to rise.
&&

.DISCUSSION...Today through Wednesday.

Now...As of 400 AM there are two decaying MCSs still holding on.
One is located just north of Mesquite and other other was hugging
the Colorado River south of Pipe Spring National Monument. I
expect a continued downward trend in these two area through the
early morning hours. A small remnant circulate can be seen near
Prescott and this is currently enhancing clouds and light showers
over southern Mohave County. A few weak echoes were noted
elsewhere, but little is expected of them through sunrise.

Today/Tonight...The focus of the convective activity will shift
north today with the strongest potential for storms across Lincoln
Nye, Esmeralda, northern Clark, and northern Mohave counties. That
said, there will be at least a slight chance in all areas.
Plentiful moisture remains in place with widespread PW values of
1.50-2.00 inches from Clark County south, and 1.00-1.50 inches to
the north will allow for rain rates of 1-2 inches per hour, with
isolated rates in intense storms up to 3 inche per hour. Flash
flooding concerns are enhanced today in several areas due to very
slow westward storm motion of 0-5 MPH. A Flash Flood Watch has
been issued for much of the area north of Las Vegas as well as
Death Valley where enough storm activity is possible to warrant a
watch there. Storm activity may get an early start today, with
some models beginning to fire convection between 9 and 10 AM.
Storms will be driven by surface heating and terrain, and
therefore early morning cloud cover will play a role. Conditions
appear favorable today for one or more cluster of storms to
develop over central NV, southwest UT, and northwest AZ. Models
hint at the development of a good cold pool to the north that
would help push these storms south toward Clark and southern Nye
counties. Increasing low-level inflow this evening would aid in
sustaining storms as they progress south/southwest. There are some
important differences between several of the high-res models with
respect of the timing of this development. In general, a faster
progression would generally be more favorable for storms to make
it into the Las Vegas area (the latest HRRR runs favor this
scenario) while a slower progress typical results in the line
diminishing to isolated showers before reaching the valley
(several of the local WRF models favor this). We will have to
monitor the situation through the day and adjust the forecast as
needed. Most convection should be wrapped up by midnight, with a
few remnant showers/storms around during the overnight hours.

Friday/Friday Night...High pressure will begin to strengthen
overhead by Friday. This begin to hamper storm development,
especially over the lower Mojave Desert locations. Convective
activity will again be focused in areas north of Las Vegas, though
overall there will be a downward trend in activity. One or more
MCSs will be possible moving in a southerly direction out of
central NV by the late afternoon/evening.

Saturday and beyond...Monsoon moisture will remain in place
through the next week. High pressure overhead will continue to
inhibit storm development and increase temperatures in the lower
elevations this weekend. Activity will be mainly driven by
diurnal heating over the high terrain. There is some indication of
a wave slowly moving into the area sometime in the late Sunday
through Tuesday timeframe. This could bring another increase in
activity to parts of the area (most likely south of I-15).
&&

.AVIATION...For McCarran...The forecast for today is expected to
follow a similar trend as yesterday. Southeast winds to start the
period this morning will turn more easterly around 16z with speeds
remaining at 10 knots or less for the morning hours. Showers and
storms may develop as early as late this morning over the higher
elevations of Clark County with better chances moving into the lower
elevations of the valley later this afternoon and early this
evening. Convection in the vicinity of the terminal could produce
gusty, erratic winds during this time. Otherwise, winds should
remain out of the south to south southeast at 10-15 knots mid
afternoon through this evening. Winds should come down below 10
knots tonight, remaining out of the southeast. Persistent mid/high
clouds will continue throughout the period.

For the rest of southern Nevada, northwest Arizona and southeast
California...Showers and storms may develop as early as late morning
across the higher elevations of Clark County before coverage of
activity increases this afternoon and evening primarily over the
southern Great Basin and Mohave County. Storms affecting the
terminals will likely produce gusty, erratic winds and locally heavy
downpours. Stronger storms could also reduce visibility and lower
cigs to 5k-9k feet. Intensity of storms will decrease tonight but
lingering isolated showers and storms are likely through late
tonight. Outside of storms, winds will favor the southerly direction
around 10 knots this afternoon and evening before decreasing
overnight. SCT to BKN mid/high cloud decks persist for the period.
&&

.SPOTTER INFORMATION STATEMENT...Active monsoon conditions are
expected again today. Spotter activation may be needed, especially
for areas north of Las Vegas. Regardless of activation, spotters
are encouraged to report any significant weather or impacts
according to standard operating procedures.
&&

DISCUSSION...Wolcott
AVIATION.....Guillet

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