FXUS65 KVEF 271015
Area Forecast Discussion
National Weather Service Las Vegas NV
315 AM PDT MON JUN 27 2016
.SYNOPSIS...High pressure will shift across the southern Great
Basin today with a weak disturbance moving across the southwest
deserts. This disturbance will bring an increase in moisture to the
area and a chance of thunderstorms for portions of the region
through at least midweek. Hot conditions are expected again today
with slightly cooler temperatures and more cloud cover on Tuesday.
Temperatures rebound on Wednesday then lower again late in the week.
.SHORT TERM...Today through Wednesday night.
An inverted trough continues its push westward this morning with the
upper circulation located over the northern Gulf of California at 2
am. As the trough turns in a northwest direction today, high
pressure will transition over the southern Great Basin into Utah.
This will allow moisture to spread further north today with an inch
and quarter PWAT values reaching near Needles by late afternoon and
one inch PWATs extending from Barstow CA east through Kingman AZ.
Within this higher moisture content airmass lies the best
instability and potential for shower and thunderstorm development.
Forecast soundings show dry lower levels so any storms that are able
to form will start out high based and present a strong wind gust
threat initially. With the trough axis lifting north across the area
tonight, nocturnal thunderstorms are a possibility but overall
coverage is not expected to be too widespread.
Low pressure extends from the southern California coast up through
the northwestern CWA on Tuesday and better shower/tstorm coverage is
forecast across the Sierra and southern Great Basin. Mohave county
and the higher terrain of Clark county could get into the action as
well with sufficient moisture and weak instability in place. The
interesting thing is what models have been advertising Tuesday as
another hot day but are now trending temperatures cooler as they
increase cloud cover. The current forecast is warmer than guidance
and may need to be adjusted down.
On Wednesday, the center of circulation is forecast over Esmeralda
county and the trough is forecast to move across the southern Great
Basin through Wednesday night. The best shower/storm coverage is
forecast over the Sierra and in central Nye and Lincoln counties
during the day with coverage diminishing Wednesday night. Kept a
mention of thunder in Clark and Mohave counties Wed/Wed night
however with models trending drier across the southern half of the
area, pops may need to be decreased. With less cloud cover and
shower activity Wednesday across the southern CWA, temperatures may
recover and be warmer than Tuesday's temperatures. The last several
MOS guidance collectives have shown the cooler Tuesday/warmer
Wednesday temperature trend.
Any storms that form over the next several days will be primarily a
wind threat but brief heavy rain leading to localized nuisance
flooding could be an issue as well.
.LONG TERM...Thursday through Sunday.
By Thursday, moisture that was pulled northward earlier in the week
will lessen as the GFS shows the 1 inch PW line retreating back east
into southern Arizona. Did lower POPs in the valleys of southern
Nevada and eastern San Bernardino County since both the GFS/ECMWF
lack instability to generate thunderstorms.
Models agree there will be a resurgence of moisture back west across
the Colorado River into far eastern San Bernardino, Clark and
Lincoln Counties Friday/Saturday. Maintained highest POPs in Mohave
County where instability is the greatest with slight chance POPs for
eastern San Bernardino, Clark and Lincoln Counties. Models differ in
the overall pattern by July 4 with the ECMWF building a ridge
overhead while the GFS shows a deeper trough moving through the
Pacific Northwest. However outcome would be similar with drier more
stable air mass in place.
Influx of moisture/cloud cover Friday/Saturday looks to have minimal
impact of temperatures as guidance keeps values at or above normal
heading through the long holiday weekend.
.AVIATION...For McCarran...Areas of smoke are possible this
morning with wildfires to the west of the valley. Southwest to west
winds with speeds 5-7 kts becoming light and variable after 14z and
then favoring a northeast direction around 6-7 kts after 19z. A few
clouds around 10-12k feet over the Spring Mountains today with a
slight chance of thunderstorms affecting the Peach Spring corridor.
For the rest of southern Nevada...northwest Arizona...and southeast
California...Smoke from fires will remain aloft in most areas,
reducing slant range visibility but probably not surface visibility
except in high terrain. Expect typical diurnal winds in most areas
with no significant clouds or weather over most of the area through
the morning. More cloud cover is expected today across the southern
areas including KEED, KIFP and KDAG. Thunderstorms will be possible
across Mohave and far southern San Bernardino Counties this
afternoon into the evening hours. Outside of thunderstorm
outflow, winds will generally remain below 10 kts.
.SPOTTER INFORMATION STATEMENT...Spotters are encouraged to report
any significant weather according to standard operating procedures.
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