Area Forecast Discussion
Issued by NWS Las Vegas, NV

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FXUS65 KVEF 190258
AFDVEF

Area Forecast Discussion
National Weather Service Las Vegas NV
658 PM PST Mon Feb 18 2019

.SYNOPSIS...An abnormally cold weather pattern will persist over our
region through the coming week. This will allow cold low pressure
systems to drop out of Western Canada, bringing chances for snow
down to the desert floors. The next system, slated for Wednesday
night through Friday, could be colder and wetter than the one on its
way out.
&&

.UPDATE...Light shower activity is on a downward trend and much of
it is likely virga as drier air moves in behind the exiting low.
The current forecast looks on track and no updates are necessary
this evening. &&

.PREV DISCUSSION... /issued at 348 PM PST Mon Feb 18 2019/

.SHORT TERM...through Wednesday.

Looking for shower activity to end across Mohave County this evening
with dry conditions expected area wide on Tuesday. Northerly breezes
will continue across the region Tuesday morning then gusts will drop
off and wind speeds decrease in the afternoon. Cold temperatures are
expected Tuesday morning with another cool day forecast Tuesday
with temperatures 10-15 degrees below normal.

Focus shifts to the next system currently taking shape over the
Aleutian Islands. Pacific high pressure is forecast to help guide
this system as it is driven southward along the western coast of
Canada by a 140+ knot jet on Tuesday. The developing trough spreads
out over the Pac NW and Great Basin on Wednesday. Models have been
in very good agreement with the overall synoptic weather pattern and
in particular with the timing and intensity of this system. With the
system on approach Wednesday, initial impacts will be showers
breaking out across the Sierra and southern Great Basin and windy
conditions developing across the western portions of the Mojave
Desert Wednesday afternoon. Morning model solutions did not change a
whole lot so the long term discussion below, written earlier this
morning, still applies.

.LONG TERM...Wednesday night through Monday.

The track of this next system appears to have shifted eastward over
the days, as the upper-level low center is forecast to dig from the
Canada/US border Wed AM to a low center directly over the region by
Thursday evening. This next system in fact looks a lot like the one
currently impacting the area. It is still on track to bring plenty
of moisture and plenty of cold air, allowing for widespread
precipitation with snow levels down to valley floors. Once again,
most things appear to come together the best in Mohave county, with
the heaviest snow occuring there, and more showery activity
elsewhere.

Have not been too happy with the model QPF with the next system.
Blends seem to be coming in on the lower end, with a recent trend of
the operational GFS coming in on the lower end of its own ensemble.
Will hold off on major manual edits for now, and hope increasing
high-resolution models will assist with this as the event gets
closer and in range.

This upper-level low is progged to get kicked out during the weekend
by yet another low sagging into the PacNW which itself will get
kicked by another Pacific low before it has chance to dig very far
south. That is a very specific line of events that has to happen to
get a closed low that will be happy to stick around otherwise to
leave. This would bear watching, and would probably favor a cooler
and more unsettled regime.
&&

.AVIATION...For McCarran...Gusty north winds will continue at the
airfield through Tuesday; speeds 8-12 knots and gusts up to 20
knots. Gusts may taper off briefly tonight after sunset but will
increase predawn Tuesday. Dry conditions expected, with isolated
showers over area mountains this afternoon/evening. Scattered to
broken low cloud with ceilings around 10-12 kft will shift east
early Tuesday; clear skies prevail through Tuesday.

For the rest of southern Nevada, northwest Arizona and southeast
California...Gusty north winds will continue at most sites through
Tuesday with gradual decrease Tuesday afternoon and evening. Dry
conditions anticipated with scattered to broken low clouds with
ceilings around 8-12 kft. Low clouds will mostly breakup on Tuesday
with a few high clouds filtering in aoa 20 kft Tuesday evening.
.SPOTTER INFORMATION STATEMENT...Spotters are encouraged to report
any significant weather or impacts, especially snow related,
according to standard operating procedures.
&&

$$

UPDATE...Kryston
SHORT TERM...Salmen
LONG TERM...Steele
AVIATION...Boothe

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