Flash Flooding and Damaging Winds in Nevada, July 11 to 15, 2021

Area Forecast Discussion
National Weather Service Las Vegas NV
142 PM PDT Sun Jul 11 2021

.SYNOPSIS...Major heat wave will persist a couple more days before
temperatures gradually ease through the week. Isolated storms
forming over the high terrain will again be possible today, with
coverage increasing Monday through Wednesday as deeper moisture
moves into the region. Conditions will dry out by late in the week
with typical mid-summer heat continuing.

&&

.SHORT TERM...Through Tuesday.

Heat through Tuesday: Dangerously hot temperatures will persist
across the entire area through Monday. As we look into Tuesday, two
factors look to be limiting the HeatRisk values across southeast
Nevada, northwest Arizona and eastern San Bernardino County. The
first is the additional injection of monsoon moisture into those
area while the second is likely rain cooled air from the passage of
showers and thunderstorms through the area Monday evening into
Tuesday morning. With that said, the previous shift did extend the
Excessive Heat Warning out through Tuesday evening for Nye,
Esmeralda, Inyo and northwest San Bernardino County. Does not look
like any spots will need to be extended into Wednesday, Thank
Goodness.

Storm chances through Tuesday: Outflow winds from last nights
complex of storms over south central Arizona did push the monsoon
moisture boundary further north and west into southern Nevada and
eastern California today. This moisture in poised to push further
northward into south central Nevada Monday before retreating back
southward to areas generally along and southeast of I-15 Tuesday. As
the area remains situated under the high center itself there are no
defined features that really stand out in helping support organized
convection. Therefore, convective initiation will occur over the
higher terrain with outflow winds (cool pools) pushing development
into the valleys during the late afternoon and evening hours.
Convective allowing models sending a mixed message regarding storm
chances for Clark County this evening. HRRR and HRW FV3 both show an
area of storms moving south out of Lincoln County and through Clark
County this evening. The 3 other members that make up the HREF
indicate a lower probabilities of this scenario occuring. Did blend in
the camPoPs to expand coverage of storms this evening to account for
the possibility. It looks like a very similar scenario on Monday and
Tuesday with storms moving from northwest to southeast out of south
central Nevada through Clark County and the Lake Mead NRA during the
evening and potentially lasting well into Tuesday morning and
Wednesday morning through the lower Colorado River Valley and Mohave
County. Gusty winds and locally heavy rain will be the primary
concern with any storms that move into the deeper monsoon moisture
across Clark, Mohave and eastern San Bernardino Counties the next
few days. Further north across central Nevada where moisture values
are not as great gusty winds and isolated dry lighting will be the
primary concern.

.LONG TERM...Wednesday through next Sunday.

Heat will gradually moderate through the long term period and there
should be no need for additional heat headlines.

Meanwhile, Wednesday will continue to see elevated monsoonal
moisture, with best storm chances favoring southern Nevada and
Northwest Arizona. Locally heavy rainfall and gusty thunderstorm
winds will be the main concerns through this period, though details
in storm coverage and intensity remains a little unclear. Moisture
appears fairly abundant, but forcing will be limited to daytime
heating and terrain influences. By Thursday, high pressure ridge
will flatten out with a more westerly flow kicking in aloft. This
will tend to shift the deeper moisture eastward and focus any
remaining storm chances into Northwest Arizona. The forecast
thereafter remains fairly dry until the Four Corners high rebuilds
sometime over the weekend or early next week.
&&

.CLIMATE...Listed below are a few climate locations showing both the
record high maximum and high minimum temperature for each location and
the year the record was last set for Saturday, Sunday and Monday.

LOCATION            SUN-JULY 11       MON-JULY 12
(HIGH MAX)          Record(year)      Record(year)

Las Vegas NV          116(1959)         114(2003)
Bishop CA             107(2020)         108(2020)
Barstow CA            115(2003)         115(2020)
Needles CA            120(2020)         124(1925)
Kingman AZ            110(1961)         111(2020)
Desert Rock NV        110(2012)         111(2020)
Death Valley CA       129(1913)         130(1913)

LOCATION             SUN-JULY 11       MON-JULY 12
(HIGH MIN)           Record(year)      Record(year)

Las Vegas NV           91(2012)         94(2020)
Bishop CA              70(2013)         69(1990)
Barstow CA             85(2002)         87(2012)
Needles CA             94(2012)         92(2019)
Kingman AZ             81(1906)         83(1925)
Desert Rock NV         81(1996)         81(2003)
Death Valley CA       105(1920)        107(2012)
&&

.AVIATION...For McCarran...An easterly wind will continue
into the early evening hours. Forecast becomes much more complicated
this evening between 03Z-06Z. There is the potential of storms
moving north to south across the valley. Initial push of winds looks
to come from the northeast but once storms enter the valley just
covered the period with variable winds 20 kts gusts to 30 kts.
Expecting southerly winds overnight into Monday morning. Can't be
too specific in the details but it looks like a very similar
situation could occur Monday evening.

Extreme temperatures are expected again today and Monday, with
temperatures reaching 100 degrees each morning by 9-10 AM and
falling below in the 12-2 AM time frame. High temperatures will be
near 116 today and 112 on Monday.

For the rest of southern Nevada, northwest Arizona, and southeast
California...Isolated thunderstorms possible across southeast
California, southern Nevada and northwest Arizona this evening.
Gusty surface winds primary concern for general aviation. Similar
conditions expect for Monday with storms developing over the higher
terrain then moving into the lower valleys in the late afternoon and
evening hours. Potential of gusty winds and locally heavy rain.
&&

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

SHORT TERM/AVIATION...Pierce
LONG TERM...Outler

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