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Area forecast discussion
National Weather Service Las Vegas Nevada
1000 PM PST Sat Dec 14 2019

Synopsis...a weather system dropping from the Pacific northwest
into southern Nevada will bring considerable clouds, gusty winds,
and increasing chances of light rain and snow to southern Nevada and
northwest Arizona tonight through early Sunday. High pressure will
set up over the region Monday and Tuesday with dry conditions along
with slightly below normal temperatures. A dry trough will pass
across the Wednesday with more high clouds and breezy winds.
&&

Update...winds across the advisory area remain strong with the
potential for sustained winds to around 30 mph and gusts 40-45
mph continuing through the night. Thus, went ahead and extended
the Wind Advisory for the western and eastern Mojave Desert
through 6 am Sunday and also expanded the advisory area to
include the morongo basin due to strong winds being reported in
that area.
&&

Previous update... /issued at 909 PM PST Sat Dec 14 2019/

Update...a storm system over northern California will move over
the forecast area tonight into Sunday but is already producing
shower activity in parts of our area. Satellite imagery shows low
clouds over central Inyo County, across much of southern Nevada
and in northern Mohave County this evening. Radar shows light to
moderate showers over far southern Nevada and northwest Arizona
with up to a third of an inch of rain reported near Moapa in
northeast Clark County and up to a quarter inch in northwest and
north central Las Vegas.

Models forecast a band of showers with a few embedded
thunderstorms continuing across an area extending from the extreme
southern portion of Nye County, through Clark County and across
the northern half of Mohave County through the night before the
system moves east. In general, rainfall amounts should range from
a few hundreths up to third of an inch but some of the more
convective cells could produce locally up to a half inch.

Gusty winds will continue across portions of the Mojave Desert
overnight where a Wind Advisory remains in effect through 10 PM
this evening. New model data and MOS guidance suggest advisory
level winds could continue in this region through the night so, a
game time decision will need to be made on whether to allow the
advisory to expire on time or to extend it through the overnight
hours. The updated forecast will be out shortly.
&&

Aviation update...for McCarran...ceilings will remain low this
evening between 5 and 8 kft above ground level as a cold front approaches.
Showers in the vicinity of the terminal can be expected through
about 12z tonight before tapering off with daybreak. Winds
expected to remain mostly light through the overnight hours before
gusty northwesterly winds pick up by mid-morning with gusts 20-25
kts possible.

For the rest of southern Nevada, northwest Arizona and southeast
California...a cold front will sweep over southern Nevada and
northwest Arizona this evening and hold through early Sunday morning
before lifting away toward The Four Corners. This will produce a
wide band of clouds with ceilings 4-6 kft across southern Nevada and
northwest Arizona along with showers and mountain obscuration.
Westerly winds will continue across the western Mojave Desert
impacting kdag with periods of gusts of 35-40 kts expected through
the taf period. Elsewhere, gusty north-northwest winds 15-25 knots
will develop behind the cold front and continue into Sunday with
cigs 5-8 kft above ground level.
&&

Previous discussion... /issued at 315 PM PST Sat Dec 14 2019/

Short term...tonight through Sunday night.

Ingredients are coming together for a band of light precipitation to
set up across southern Nevada and northwest Arizona tonight through
early Sunday. A swath of low clouds was becoming more enhanced on
satellite imagery over Clark and northern Mohave counties this
afternoon with bases around 5-7 kft mean sea level. A cold low pressure digging
down from the Pacific northwest will interact with this moisture as
upward forcing increases this evening as the base of the system and
the associated cold Front Park over southern Nevada between 06z and
12z. Light snow amounts of 1-2 inches will be possible in the Spring
Mountains and rainfall amounts will generally be less than a tenth
of an inch, but some areas could see up to a quarter-inch,
especially across northeast Clark and northern Mohave counties.
The front and upper level system will continue sliding toward The
Four Corners region Sunday morning and lift away from our region
after 18z Sunday. Northwest breezes will spread across the region
behind the departing system Sunday along with increasingly dry air.
Temperatures Sunday night will drop 5-7 degrees from those observed
tonight.
&&

Long term...Monday through Saturday.

A ridge of high pressure will move overhead Monday and Tuesday
providing dry conditions, but north winds will increase, especially
along the Colorado River valley where speeds of 20-30 mph will be
possible near Laughlin-Bullhead City. Temps will be running several
degrees below normal as a cool air mass holds in place.

Wednesday will bring a quick change in the pattern as a fast moving
eastern Pacific trough swings inland almost directly over our
forecast area. However, it appears it will be too moisture starved
to produce any noticeable effects except isolated snow showers over
the southern Sierra. It lifts away by Thursday as another ridge
moves over the region for continued dry and tranquil weather through
Saturday.

&&

Aviation...for McCarran...ceilings will lower this evening
to around 5 kft above ground level with the approach of a cold front. Showers will
be possible in the terminal area between 06z and 12z tonight.
Showers and ceilings will dissipate 12z-18z Sunday. Northwest winds
will increase to 10-20 knots behind the cold front Sunday morning
and persist through the day.

For the rest of southern Nevada, northwest Arizona and southeast
California...a cold front will sweep over southern Nevada and
northwest Arizona this evening and hold through early Sunday morning
before lifting away toward The Four Corners. This will produce a a
wide band of clouds with ceilings 4-6 kft across southern Nevada and
northwest Arizona along with showers and mountain obscuration.
Westerly winds will continue across the western Mojave Desert.
Periods of gusts at kdag of 35-40 kts can be expected through 06z
this evening and may persist until about 12z Sunday morning. Gusty
north winds 15-25 knots will develop behind the cold front and
continue into Sunday.

&&

Spotter information statement...spotters are encouraged to report
any significant weather or impacts according to Standard operating
procedures.
&&

$$

Update...Salmen

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