Area Forecast Discussion
Issued by NWS Las Vegas, NV

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FXUS65 KVEF 210136
AFDVEF

Area Forecast Discussion
National Weather Service Las Vegas NV
536 PM PST Mon Feb 20 2017

.SYNOPSIS...A storm system over central and northern California will
bring high elevation snow to the southern Sierra Nevada and White
Mountains through Tuesday morning. This system will bring strong
winds to the southern Great Basin zones Tuesday followed by
scattered showers and cooler temperatures Wednesday. This will lead
to a weather pattern change with cool and unsettled weather through
the weekend.
&&

.UPDATE...Quick update this evening to bump up PoPs over Death
Valley NP and other portions of southern Inyo and northern San
Bernardino counties as a band of precipitation pushes south across
those areas. I expect this band to diminish later this evening,
and it seems unlikely to make it to the I-15 corridor. However the
Spring Mountains could get a 1-2 hour period of light
precipitation this evening. The rest of the short term forecast is
in good shape at this time.
&&

.AVIATION...For McCarran...South to southeast winds occasionally
gusting 15-20 kts are expected through at least early evening,
but may persist through the night. Gusty southwest winds are
expected to develop by Tuesday afternoon with gusts 20-30 kts at
times. Additional SCT- BKN clouds will move across southern Nevada
tonight and early Tuesday but bases should generally remain above
6 Kft. Areas of mechanical turbulence should be expected near the
mountains tonight through Tuesday night.

For the rest of southern Nevada...northwest Arizona...and southeast
California...Low to mid level clouds as well as areas of
precipitation will continue to cover the area from the southern
Sierra to the southern Great Basin overnight and Tuesday morning
as a Pacific system directs moisture over the region. Gusty south-
southwest winds over 35 knots will be fairly widespread across the
southern Sierra and southern Great Basin Tuesday afternoon as
cloud cover diminishes. The Mojave Desert region will see gusts of
15-25 knots Tuesday afternoon and evening.
&&

.PREV DISCUSSION...
Issued at 318 PM PST Mon Feb 20 2017

.SHORT TERM...through Wednesday night.

The most pressing weather concerns for our area will be the
continued stream of moisture spilling over the southern Sierra
through Tuesday morning followed by strong winds Tuesday afternoon
as the Pacific system off the West Coast moves inland. About a half-
inch of rain has managed to spill into the western Owens Valley so
far and around 6 inches of snow has fallen in Aspendell. All though
the upstream moisture starts to decrease over the southern Sierra
tonight and Tuesday morning, there should be sufficient for several
more inches of snow at Aspendell and the Winter Weather Advisory
remains in effect. Precipitation reaching the Owens Valley will
probably become a little less plentiful later this evening.

South-southwest winds will become fairly strong late Tuesday morning
through Tuesday evening across central/southern Nye and Lincoln
counties along with the Spring Mountains in response to a vigorous
shortwave ejecting inland from the Pacific System. This could be
seen on recent water vapor loops. There is good agreement among high
res models that gusts over 40 mph will occur across the
aforementioned areas and a Wind Advisory is in effect from 10 AM
until 7 pm Tuesday. The body of the trough is then forecast to slide
across the Great Basin bringing a cold pool overhead with some
showers and a cold front that will push down through southern Nevada
Wednesday night with brisk northwest winds over the south central
Nevada zones. Temperatures will be noticeably cooler by Wednesday
night behind the cold front.

.LONG TERM...Thursday through Monday. Lingering cyclonic flow aloft
will keep small precip chances going over the southern Great Basin
Thursday and Thursday night before the flow briefly buckles into a
flat ridge Friday into Saturday for dry conditions areawide. The
models have come into slightly better agreement with the next storm,
but there is still enough spread to call confidence near to below
average in any details. Precip chances should return to the Sierra
Saturday afternoon or Saturday night, then spread across the
southern Great Basin and portions of the Mojave Desert Saturday
night or Sunday. This system should have a moisture tap available,
but it looks more like the typical winter tap which translates
across the entire region within 24 hours rather than remaining
focused in one area for a prolonged time as has been the case so
many times this winter. There are indications of another storm hot
on the heels of this one, so the timing and/or duration of any break
in the precip chances is in question. At some point as the storms
move in, there will probably be a period of breezy to windy
southwest winds across the desert, but timing and magnitude cannot
be pinned down at this point. Highest confidence at this point is in
below normal temperatures through the period as the storm track is
coming from the Gulf of Alaska.
&&

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

$$

Update/Aviation...Wolcott
Short Term........Adair
Long Term.........Morgan

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