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153
FXUS65 KVEF 241651
AFDVEF

Area Forecast Discussion
National Weather Service Las Vegas NV
950 AM PDT Mon Jun 24 2024

.SYNOPSIS...Showers and thunderstorms will be possible this
afternoon and evening, with the highest chances in Mohave County
this afternoon. The anomalous moisture responsible for today`s
showers and thunderstorms will surge northwest tonight and
Tuesday, with precipitation chances also spreading northwest into
portions of Lincoln, Clark, and San Bernardino counties in
addition to Mohave County. Main threats for thunderstorms each day
will be sudden gusty winds and lightning, with only an isolated
flash flooding threat. Moisture will gradually be pushed out of
the area midweek, which will result in gradually decreasing
coverage when it comes to precipitation chances. Hotter than
normal temperatures will continue through at least the middle of
next week.

&&


.UPDATE...
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The 12Z sounding for LAS shows 1.08" of precipitable water
(PWAT) over the area, which is a slight increase over the 0.97"
measured 24 hours ago and .55" higher than the .53" that is normal
for this day.  However, despite the anomalous PWATs on the sounding,
the lower levels remain dry, and DCAPE values approaching 1900 J/kg
indicate an increased risk of strong outflow winds with any storms
that develop.  The latest HRRR guidance shows convective development
over Mohave and far southern Clark counties beginning 18-19Z (11 AM -
 12 PM PDT), spreading westward into eastern and southern San
Bernardino County by 21Z (2 PM PDT).  The HRRR also shows the
potential for a few isolated thunderstorms along the Sierra and
White Mountains this afternoon and early evening.  Along with the
strong winds mentioned above, locally moderate to heavy rainfall and
lightning can also be expected.  The storms will diminish this
evening and come to an end around sunset.  The current forecast is
on track, and no updates to the grids were needed this morning.

.SHORT TERM...Through Wednesday.

There is the potential for showers and thunderstorm each day through
midweek as area remains under moist southerly flow. Today`s
convection should again focus on Mohave County where the best
moisture will be situated, like it has the past few days. Most
unstable CAPE this afternoon climbs to 1000-1500 J/Kg, with lower
instability most everywhere else. Hi-res short term models also hint
at some potential shower and thunderstorm develop late this
afternoon in the terrain of southern Clark County as moisture begins
to push northward. Shower and thunderstorm chances will spread
further north and west on Tuesday as higher PWATs continue to surge
into the region. Instability and forcing will still be limited, with
again the highest instability and moisture focused on Mohave County
Tuesday afternoon. However, afternoon precipitation will be possible
in Lincoln, Clark and eastern San Bernardino counties as well as
anomalously high moisture settles in over the region. The HREF
probability for over 500 J/Kg surface based CAPE on Tuesday
continues to show the highest probabilities in Mohave County with
30% probabilities or less elsewhere, so the highest chances for
precipitation will be in the terrain outside of Mohave County where
modest instability should help in the development of afternoon
convection. By Wednesday, the anomalous moisture will begin shifting
east as an incoming trough shoves the southerly flow further east
and dry out the western portions of the region. Wednesday afternoon
convection should be limited to eastern Mohave County and far
eastern Lincoln County.

Despite the increasing overall moisture in PWATs,
forecast soundings show continued dry low levels. Isolated flooding
will be possible with any training storms, especially in Mohave
County where the best moisture and instability will be located, but
even there probabilities for over 1 inch of rainfall in any
timeframe is low (less than 20%). WPC`s excessive rainfall outlook
shows this well with a marginal threat mainly in Mohave County
today, then shifts the marginal threat area a bit further north on
Tuesday. Marginal excessive rainfall outlook would indicate isolated
flash flooding is possible, mainly in localized ares that are
sensitive to rapid runoff for heavy rainfall. The main threats with
any storms through the first half of the week will be sudden gusty
winds, lightning, and dry thunderstorms leading to fire starts. Dry
low levels with hints of dry air intrusion is noted on model
forecast soundings and downdraft CAPE looks impressive each
afternoon. Sudden outflow winds over 40 MPH will be possible with
any showers or thunderstorms the develop.

Outside of the precipitation chances, skies should remain mostly
clear today and Tuesday before increasing cloudiness fro m northwest
to southeast is expected Wednesday with the incoming trough.
Temperature over the next few days will remain nearly steady and
above normal in most locations.

.LONG TERM...Thursday through the weekend.

Models have a trough moving through the PacNW on Thursday, which
will flatten the ridge to our east and turn flow southwesterly. This
ushers in drier air, bringing an end to our first taste of the
monsoon. PoPs on Thursday become confined to far eastern Mohave
County, and are only 10-20%. By Friday, PoPs areawide drop to 5% or
less. As the aforementioned trough brings drier conditions, it will
also bring breezy southwest winds and slightly cooler temperatures
(albeit still above normal for the time of year). Forecast wind
gusts of 20-35 mph should yield at least elevated fire danger,
particularly in the lower elevations where fuels have cured and
afternoon RH values are expected to be around 8-12%.

As we head into the weekend, the southern US ridge begins to extend
westward into the Desert Southwest. As a result, winds weaken while
temperatures rise again. Based on the monthly temperature data thus
far and the latest model guidance, Las Vegas will be hard-pressed to
NOT experience its hottest June on record. A little number crunching
shows that even if the 5th percentile of high/low temperatures from
the NBM verify these last 7 days, we`ll still set the record. At
this point, its not a matter of "if" but "by how much" we break the
warmest June record.
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&&

.AVIATION...For Harry Reid...Southerly winds today with gusts of 15
to 20 knots in the afternoon. Say between 15Z and 19Z the wind
direction will probably be more between 150-180 degrees, before
becoming more 170-200 degrees this afternoon. Also there is a low,
but not zero, chance of thunderstorm outflow winds from the south or
east affecting the terminal early this evening. If that does not
occur, typical south southwest winds are expected overnight.

For the rest of southern Nevada, northwest Arizona and southeast
California...Isolated showers and thunderstorms developing this
afternoon over primarily the higher terrain of southern Nevada and
eastern California. Scattered thunderstorms once again over
northwest Arizona, likely producing outflow winds and lower ceilings
in pockets of heavy rain. Otherwise, southerly winds gusting 15 to
20 knots are expected, weakening overnight.

&&

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

&&

$$

UPDATE...Planz
SHORT TERM...Nickerson
LONG TERM...Woods
AVIATION...Pierce

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