Area Forecast Discussion
Issued by NWS Las Vegas, NV

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FXUS65 KVEF 250347
AFDVEF

Area Forecast Discussion
National Weather Service Las Vegas NV
847 PM PDT Fri Mar 24 2017

.SYNOPSIS...
High pressure will push eastward tonight as next system approaches
the west coast. Gusty winds and chances for rain and higher elevation
snow will increase tonight and Saturday. Widespread showers are
expected to develop across the Sierra, the southern Great Basin,
and northern Mohave county. Elsewhere, isolated, light showers
will be possible. A couple more rounds of weather are expected
next week with similar conditions as additional disturbances pass
across the region.

&&

.UPDATE...Radar shows a 50-100 mile wide band of light rain running
from Santa Barbara County northeast across the San Joaquin Valley
and into the southern Sierra Nevada. Have had some light rain in
northern Inyo County around Bishop while an automated station near
South Lake above 10000 feet indicates around 2 inches of new snow.

As upper trough moves in off the Pacific tonight, models in
agreement line of showers will fill in across northwest San
Bernardino, eastern Inyo, Esmeralda and Nye Counties around
midnight. The line will move east toward Pahrump, Las Vegas and
Lincoln County during the early morning hours. HRRR shows this band
moving through Las Vegas between 5 and 7 am Saturday. The widespread
precipitation will stay confined to Lincoln County Saturday morning.
Isolated to scattered showers will redevelop Saturday afternoon as
cold pool aloft associated with trough passes over. Precipitation
looks to end quickly over Mohave County Saturday evening as upper
trough races east. No update this evening as package looks in good
shape.
&&


.PREV DISCUSSION...231 PM PDT Fri Mar 24 2017
.SHORT TERM...through Saturday night

Ridge will continue its progression eastward as a Pacific trough
pushes onshore of the west coast Saturday morning. Ahead of the
trough precip chances will spread southeastward towards the the
I-15 corridor by tomorrow morning and continue towards I-40
throughout the day on Saturday as trough passes across the region.
Best chances remain along the Sierra, the southern Great Basin,
and northern Mohave county where numerous showers are expected to
develop. Snow levels should briefly lower to around 6500` late
tonight into tomorrow morning over the Great Basin where between
a trace to 3 inches of snow is possible across the higher
elevations. An isolated thunderstorm cannot be ruled out across
northern Mohave and eastern Lincoln counties Saturday afternoon
but confidence is low in this occurrence so have left out of
forecast for now. Elsewhere, primarily dry conditions expected with
a brief light rain shower possible. Gusty winds will accompany
this system overnight Friday into Saturday morning shifting from
southwest to northwest on Saturday in the wake of the trough.
Sustained winds around 20 mph gusting 30 mph are likely overnight.
Rain chances diminish quickly Saturday night on the backside of
trough as weak ridge builds over the area through Sunday morning.

.LONG TERM...Sunday through Thursday.

Active pattern continues as two storms are likely to affect the
region during the period. Models have come into better agreement
with the first storm Monday and Tuesday, so confidence is increasing
then, but agreement is poor for the second storm Thursday, so
confidence is below average then. Sunday should be dry areawide
until the first storm rolls in from the west, with precip chances
increasing in the Sierra in the afternoon and possibly spreading
into the southern Great Basin overnight. The models have come into
better agreement this morning on what is essentially a compromise
solution between the weaker and faster ECMWF of the past few days
and the slower and stronger GFS of the past few days. This
compromise shows the shortwave trough passing through Monday, with
precip chances limited to areas near and north of Las Vegas, before
deepening and digging over the Four Corners region Monday night.
This will keep precip chances going mainly in Lincoln and Mohave
counties Monday night, but the biggest impact will likely be gusty
north winds beginning over the northwest zones Monday afternoon and
spreading areawide by Tuesday. Wind Advisories may be needed. After
a dry period Tuesday and Wednesday, the next storm could start to
bring precip chances back to the area Thursday. The models agree on
the existence of this storm, but do not agree on its track or
timing, so confidence in where to put the best precip chances is
very low. Temperatures should stay close to late March averages
through the period, with areas of well below normal temps possible
wherever precip and/or thick clouds persist through the day on
Monday or Thursday.

&&

.AVIATION...For McCarran...Winds will continue to veer around to
the southwest by this evening becoming gusty overnight around
20 to 25 knots. Westerly winds Saturday morning are expected to
shift to the northwest Saturday afternoon as trough passes across
the area. This system will also result in increasing mid and high
cloud coverage and very isolated shower activity across the Vegas
area on Saturday.

For the rest of southern Nevada, northwest Arizona and southeast
California...Winds will continue to veer around to the southwest
by this evening becoming gusty overnight around 20 to 25 knots in
most areas. Higher gusts will be possible in the vicinity of the
Sierra and Spring mountains. Westerly winds Saturday morning are
expected to shift to the northwest throughout the day as trough
passes across the area. This system will also result in increasing
cloud cover and rain chances across the Sierra this evening,
spreading across central and southern Nevada and northwest Arizona
on Saturday. A very isolated thunderstorm will be possible across
northwest Arizona Saturday afternoon.

&&

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

$$

Update...Pierce

Long Term...Morgan
Short Term/Aviation...Guillet

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