Area Forecast Discussion
Issued by NWS Las Vegas, NV

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FXUS65 KVEF 200744
AFDVEF

Area Forecast Discussion
National Weather Service Las Vegas NV
1145 PM PST Thu Jan 19 2017

.SYNOPSIS...A brief break in precipitation is expected overnight
before a second system moves in Friday into Saturday. Yet another
wet system will move through Sunday and Monday.
&&

.UPDATE...Quick update to add in a mention of patchy fog across most
of Lincoln, Clark, and Mohave counties overnight. Rest of the
forecast looks ok for the moment and will be digging in deeper
shortly. -Wolcott-
&&

.PREV DISCUSSION...
309 PM PST Thu Jan 19 2017

.SHORT TERM...through Saturday night.

Dynamics/instability associated with the first in the series of
storms will be winding down this evening. Break in the action is
brief as orographic generated precipitation will start to
enhance on the west-side of the Southern Sierra after midnight.

Second storm is deeper/colder and progged to bring another round of
widespread rain/snow to the region. Only changes of note made were
to upgrade southern Mohave County mountains to a Winter Storm
Warning Friday; and bump up snow amounts a few more inches based on
accumulations from this first system. Models continue to show a
broad area of instability move across southern Nevada/northwest
Arizona Friday afternoon and evening which could lead to 2 inch/per
hour snow rate in the mountains.

Held off for now, but later shifts may take a hard look at the need
for a Flood Watch, especially for parts of Mohave County/Colorado
River valley Friday night based off GEFS Mean QPF and M-Climate
percentile.

This second system packs a quick punch but quickly shifts east with
decreasing showers from west-east Saturday. Winds do increase
across the western Mojave Desert with wind products likely needed.
&&

.LONG TERM...Sunday through Thursday.

One more round of rain and snow will move into the area beginning on
Sunday morning in the Sierra and western deserts. This system has
the potential to be one of the wetter system of the winter so far
for the many desert locations as integrated vapor transport (IVT)
values will be between 250 and 500 units across the interior
locations, of San Bernardino, Clark and Mohave Counties.
Additionally GEFS M-Climates are indicating anomalously high QPF
values in the lee of the Sierra and into Esmeralda and southern Nye
Counties. The upper level jet will be coming onshore on Sunday at
170+ kts, sinking southward and located across the deserts on Sunday
night into Monday. The precipitation will spread across the entire
forecast area by early Sunday afternoon and persist into much of
Monday. On average rainfall or liquid equivalent amounts will be one
half to one inch but locally higher amounts are expected. Initially
snow levels will climb to 5500-6500 feet on Sunday afternoon but
drop back down to 4000-5000 feet Sunday night. Significant snow
accumulations are likely in much of the higher terrain of southern
Nevada, southeast California and northwest Arizona and Winter Storm
Warnings will likely be extended to cover those areas. Gusty south
to southwest winds will be common on Sunday. Rapidly running washes,
ponding of water on roadways and minor flooding is possible on
Sunday into Monday. Northwest flow will develop on Monday night and
into Tuesday and begin to provide some drying. A shortwave trough
will dig into the southern Great Basin on Tuesday afternoon/evening,
providing another cool push of air and increased clouds followed by
northerly winds down primarily down the Colorado River Valley on
Wednesday and Thursday.
&&

.AVIATION...For McCarran...Can not rule out a shower in the vicinity
of the valley terminals this evening. Winds should relax some this
evening and may briefly take on a west to northwest direction before
settling back to the southwest. Expect CIGS to be above 10 kft
tonight before starting to lower again Friday morning as a strong
system rolls in. Widespread rain develops in the afternoon with CIGS
lower to 4-5 kft while the VSBY could lower to 3-5 miles in moderate
rain.

For the rest of southern Nevada...northwest Arizona...and southeast
California...Isolated rain showers possible this evening in southern
Nevada, northwest Arizona and eastern California this evening. Most
areas will see a break in the action tonight before the weather
starts deteriorating again Friday. Widespread rain/high elevation
snow in southeast California will spread east into southern Nevada
and northwest Arizona during Friday afternoon and evening. This
will bring lower CIGs and VSBYs to the region, generally in the 3-4
kft range and VSBYs 3-5 miles during period of moderate rain. Gusty
west winds will persist at KDAG through the period, generally
southerly winds elsewhere.
&&

.SPOTTER INFORMATION STATEMENT...Spotters are encouraged to report
rain and snow amounts as well as any weather-related impacts or
damage.
&&

$$

Short Term/Aviation...Pierce
Long Term.............Czyzyk

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