011 
FXUS65 KVEF 091644 AAA
AFDVEF

Area Forecast Discussion
National Weather Service Las Vegas NV
840 AM PST Sat Feb 9 2019

.SYNOPSIS...Two storm systems will bring increasing chances for 
precipitation and gusty winds to the area over the weekend. The 
heaviest snow is expected in the Sierra with the strongest winds 
over the western deserts. Temperatures will moderate somewhat over 
the weekend but remain below normal. Quiet conditions settle over 
the region Monday and Tuesday before more unsettled weather arrives 
mid week. 
&&

.UPDATE...
Radar imagery showing enhancement of showers to the southwest of Las 
Vegas that will gradually push into the valley through 11 AM. With 
low dewpoints currently in the lower to mid 20s we could see some of 
these showers start at light snow, especially over the western and 
southern portions of the valley where elevations climb above 2800-
3000 feet. These showers are expected to late into the late morning 
with some clearing expected during the afternoon. 
&&

.AVIATION...For McCarran...Through the mid-morning, light and
variable winds will prevail before sporadic light showers creep into 
the valley as well as a wind shift to the southwest. Winds are then 
expected to increase in the afternoon becoming 12-15 kts with gust 
potential peaking at 25 kts this afternoon. Light rain showers are 
possible through 11 AM with CIGs down to 5k feet at times. Improving 
conditions are expected this afternoon with clouds clearing. Winds 
are expected to decrease to around 10-12 kts this evening as CIGs 
decrease in coverage. 

For the rest of southern Nevada, northwest Arizona and southeast 
California...Breezy with a possible light shower or two is possible 
for valley sites by mid morning. KBIH briefly saw some snow this 
morning and another couple hours of light snow may be possible 
before clearing by the afternoon. KDAG may also see a brief shower 
this morning along with breezy southwest winds. 

&&

PREV DISCUSSION 409 AM PST Sat Feb 9 2019

.SHORT TERM...Today through Sunday Night.
The first of two systems is ongoing across the western Sierra
slopes struggling to reach the eastern slopes early this morning.
MMH is reporting steady snowfall and KBIH has just begun reporting
light snow as of 330AM. Latest hi-res depictions bring this area 
of moisture across the CWA throughout the day today but much like 
previous systems, will be very spotty in nature in regard to QPF. 
An added upslope component may bring a few inches to the Spring 
Mountains today but should be rather minor. 

As the shortwave translates across the Sierra, strong easterly 700
mb winds will result in mountain winds that increase throughout
the day today and peak overnight tonight. Many hi-resolution
models as well as the NBM really crank up wind potential after
00Z tonight and through 12Z Sunday morning. Considered upgrading
to a High Wind Warning for the eastern slopes but held off for
now, just upping the wording to 70 mph gusts in the advisory for
now.

The WSW was also moved up in time for the eastern Sierra as
moderate to heavy snowfall may begin a bit earlier than previously
thought. HREF and NBM both indicate moderate to heavy snowfall
beginning between 06Z and 12Z so moved up the start time of the
advisory to capture when additional impacts may begin. 

For Sunday, NBM seemed to be overdoing QPF generation associated
with the frontal passage Sunday, producing 8-10 inches of snowfall
in the higher elevations of Lincoln County. Other guidance such as
SuperBlend, CONSALL, WPCGuide, and others were considerably lower.
With the poor performance of the NBM on QPF over the last few
events, tempered QPF down quite a bit. That being said, the
tempered values still came close to advisory level snow for the
Spring Mountains and Lincoln County mountains after 18Z tomorrow.
Did not pull the trigger just yet on any additional WSW as I
believe the trend of the HRRR and other hi-res will be decreasing
in QPF generation as it has in the previous several events. Wind
potential still looks well into advisory levels for much of the
CWA. Saw no significant changes in expectations there so NPW was
continued without change. 


.LONG TERM...Monday through Friday.
This upcoming week is still shaping up to be fairly active with a 
succession of upper level Pacific low pressure systems tracking 
along a progressive northern stream and across the western states. 
Similar to previous discussions, there is a high degree of 
uncertainty in the extended forecast period due to significant 
differences among model solutions and continuous lacking of run-to-
run consistency. There are two potential weak to moderate 
atmospheric river events being resolved this week the first on 
Wednesday and a second Friday/Saturday. The setup may lead to 
another significant/impactful snow in the eastern Sierra, where a 
couple feet of additional snow will be possible by the end of the 
week. 

Monday and Tuesday are expected to be fair as Sunday's weather 
system exits to the east, though below average temps are expected in 
its wake. Increasing southerly winds ahead of the next system along 
with increasing high clouds should quickly warm temperatures on 
Tuesday. The moisture associated with the first system has trended 
slower, now expected to reach the southwest on Wednesday.

For Wednesday, the forecast is taking a drier trend, favoring the 
GFS solution, with the best forcing focused north of the CWA and the 
main fetch of moisture tracking further south into the Sonoran 
Desert areas. For the Mojave Desert and southern Great Basin zone 
valleys, QPF amounts are generally below 0.25", with the exception
of the Owens Valley where spill over could lead higher amounts 
around 0.50". 

Mean pattern indicates a break on Thursday/Friday before another 
large, deep upper trough tracks along the west coast. This system 
may have a higher potential to bring a bout of rain to the Mojave 
Desert as it phases with a Rex low near the Hawaiian Islands and 
surges rich moisture into the region. Confidence is low on any 
specific details. Keep an eye on future updates, as this forecast 
will likely evolve over the next few days.

&&

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

$$ UPDATE...Gorelow
SYNOPSIS/SHORT TERM/AVIATION...TB3 LONG 
TERM....Boothe

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