349
FXUS65 KVEF 062009
AFDVEF

Area Forecast Discussion
National Weather Service Las Vegas NV
109 PM PDT Sat Jul 6 2024

.SYNOPSIS...A dangerous and historic heatwave is just getting
started across the area, with temperatures expected to peak during
the Sunday - Wednesday timeframe. Daily, and potentially a few all-
time records, will be threatened. Excessive heat will likely continue
through Friday, with uncertainty surrounding the return of monsoonal
moisture increasing next weekend.

&&

.DISCUSSION...through next weekend.

Water vapor satellite imagery depicts a very dry airmass over the
Western and Southwestern US as a nearly 600dm high looms overhead.
The dryness is confirmed by our morning sounding, having just 0.25"
of precipitable water which places it below the 10th percentile of
climatology for this time of year. These dry conditions appear to be
permitting more overnight recovery than anticipated, with lows this
morning 1-4 degrees below the forecast. However, the limited
overnight recovery is brief, with temperatures reaching 105 degrees
in Vegas just after 10 AM this morning. This places us ~2 degrees
ahead of schedule compared to yesterday`s observations, and on track
for ~115 degrees this afternoon. Today will be the hottest day of
the year so far, but that title is expected to be usurped tomorrow
and possibly the days to follow. Heat won`t be confined to the Las
Vegas Valley, however, as new Excessive Heat Warnings go into effect
for Lincoln and northern Mohave Counties today, and the existing
warnings remain in effect for the rest of the lower elevations in
our CWA. Combined with the Heat Advisories now in effect for the
Sierra, Spring, Sheep, and White Mountains, all of our zones have
some form of heat headline out through Wednesday. Temperatures will
challenge daily records in many locations, with all-time records
threatened at a few sites (mainly Las Vegas and Barstow). The
historic warmth is producing widespread major to extreme HeatRisk
(levels 3 and 4 on a scale to 4). These conditions now appear likely
to persist through at least Friday as model guidance continues to
delay the potential return of monsoonal moisture.

Heading into the weekend, ensemble guidance shows southerly flow
developing over the lower Colorado River Valley as we become
sandwiched between a high near the Four Corners and a weak
trough/cutoff low off the CA Coast. This southerly flow then advects
moisture up towards the I-15 corridor. However, the position of the
aforementioned synoptic features is going to be crucial to our
prospects of precipitation and "ending" this heat wave. Shifts of 50-
100 miles east/west could shut off the moisture tap, leaving us hot
and dry. Latest GEFS shows 1"+ PWAT probabilities ranging from 10-
20% along the I-15 corridor to over 50% near Lake Havasu on
Saturday. On Sunday, these probabilities along I-15 increase to 20-
40%. We`ll be monitoring trends in the these probabilities as well
as the positions of the upper-level high and upstream trough/cutoff
low over the coming days.

&&

.AVIATION...For Harry Reid...Variable winds begin to take a
northeasterly direction in the early afternoon, shifting to the
southeast later in the afternoon. By this evening, southwesterly
winds should be in place. Early tomorrow morning, variable winds
return. Speeds should be less than 10 knots throughout the forecast
period. Temperatures decrease to less than 100 degrees tonight
around 07Z, increasing to over 100 degrees by 16Z tomorrow
morning.

For the rest of southern Nevada, northwest Arizona and southeast
California...Diurnal winds with speeds of less than 10 knots are
expected at most locations. Moderately gusty westerly winds may
develop at KDAG starting this evening, lasting through the night.
Occasional gusts of less than 20 knots cannot be ruled out this
evening at KBIH. Highs in the 110s will occur in the afternoon today
and tomorrow at all terminals except for KBIH.

&&

.CLIMATE...Numerous climate locations have a forecast high
temperature and/or forecast warm low temperature within 3 degrees of
the daily record.

The table below shows the daily record maximum temperature and the
year the record was last set. An asterisk (*) denotes which records
are in jeopardy (within 3 degrees of the forecast).

MAX           SAT, JUL 6  SUN, JUL 7  MON, JUL 8  TUE, JUL 9
              Record(Yr)  Record(Yr)  Record(Yr)  Record(Yr)

Las Vegas     115(2007)*  116(2017)*  114(2021)*  116(2021)*
Bishop        105(2021)*  107(2021)*  109(2021)*  108(2021)*
Needles       120(1922)*  122(2017)   120(2017)*  120(2021)*
Daggett       115(2007)*  116(1989)*  114(2021)*  113(2021)*
Kingman       108(2017)*  112(2017)   108(2017)*  111(2021)*
Desert Rock   111(2007)*  111(2017)*  108(2017)*  111(2021)*
Death Valley  127(2007)*  129(2007)*  128(1913)*  130(2021)*

The table below shows the daily record warm minimum temperature
and the year the record was last set. An asterisk (*) denotes
which records are in jeopardy (within 3 degrees of the
forecast).

WARM MIN      SAT, JUL 6  SUN, JUL 7  MON, JUL 8  TUE, JUL 9
              Record(Yr)  Record(Yr)  Record(Yr)  Record(Yr)

Las Vegas     90(1957)    93(2018)    92(2017)*   93(2021)*
Bishop        67(1985)    72(2014)    70(1991)    72(1975)
Needles       97(1903)    95(1942)    95(2018)    95(2021)
Daggett       83(2007)*   80(2018)*   84(2021)*   85(2017)*
Kingman       79(1981)    80(1917)    84(2014)    82(2017)*
Desert Rock   83(1992)*   82(1981)    81(2021)    86(1985)
Death Valley  99(2013)    101(2021)*  105(1921)   104(2021)

&&

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

&&

$$

DISCUSSION...Woods
AVIATION...Meltzer

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