781 
FXUS65 KVEF 160548 CCA
AFDVEF

Area Forecast Discussion
National Weather Service Las Vegas NV
945 PM PST Tue Jan 15 2019

Corrected day of week in product header

.SYNOPSIS...A complex and active weather pattern will continue to 
evolve through mid week, eventually coming to an end by Friday.
A potent storm will slam the Sierra and White mountains with heavy 
snow Wednesday night through Thursday. The rest of the region will 
also see another round of widespread rain and high elevation snow.
&&

.UPDATE...The batch of concentrated precipitation that moved into 
southern Nevada this evening for a few hours will continue pulling 
away toward northwest Arizona and southwest Utah overnight. 
Considerable low level moisture will linger in its wake and areas of 
fog and some drizzle can be expected, but measurable rain should 
come to an end for Las Vegas until early Thursday. Pop/WX/QPF grids 
have been adjusted based on the latest radar and model trends. 

The Winter Weather Advisory for the Southern Sierra was cancelled 
tonight as the back edge of the main moisture band has cleared the 
crest leaving only scattered snow showers making it to the east 
slopes and no significant accumulations the rest of the night. The 
Winter Storm Watch for the Southern Sierra and White Mountains of 
Inyo County was upgraded to a Winter Storm Warning from 4 PM PST 
Wednesday to 4 AM PST Friday.
&&

.PREV DISCUSSION...
251 PM PST Tue Jan 15 2019

.SHORT TERM...through Tuesday night

Upper level disturbance that has brought the light-moderate rain to 
parts of southeast California, southern Nevada and all of northwest 
Arizona will be lifting northeast into southern Utah early this 
evening. That means precipitation will be winding down across the 
above mentioned locations over the next several hours. Can confirm 
this as satellite shows breaks in overcast and no precipitation 
behind the disturbance over the western Mojave Desert in San 
Bernardino County. Decided to cancel the Flash Flood Watch for 
southern Mohave County as moderate rainfall threat diminishes over 
the next 1 to 2 hours. Automated gauges within the Big Sandy Wash 
and Burro Creek drainage basin have recorded some impressive 24 hour 
rain totals between 2 to 3 inches, so far stream gauges indicate the 
runoff is being easily contained within the washes or streams.

A weaker lobe of vorticity will quickly traverse the region later 
this evening setting off another wave of light rain/snow showers. 
Decreased the new snow accumulations for the Spring Mtns to 1 to 3 
inches overnight. These values fall below our winter weather 
advisory criteria so went ahead and cancelled the advisory for the 
Spring Mtns. Kept the advisory going for the Sierra as generally 4-8 
inches expected.

As juiced as the air mass is expect areas of fog tonight/Wednesday 
morning. 

.LONG TERM...Wednesday through Tuesday

Moving into Wednesday, a lull in activity is expected before the 
last, more potent, system begins to come on-shore by Wednesday 
night. This system has by and large not changed substantially, 
however snowfall amounts have come into question given the recent 
overforecasted amounts suggested by models up until this point. 
However, broad divergence coupled with very strong 850 mb moisture
flow out of the south paralleling the Sierra range as depicted by
both the ECMWF and GFS will hit the Sierra overnight Wednesday. 
Still do not see a reason to back off from the potentially over 3
feet of snow at the highest elevations of the Sierra. Winds could
also be quite strong as 700 mb winds over 50 kts have been noted 
in both GFS and ECMWF solutions. As a result, also needed to hoist
a Winter Storm Watch for the eastern Sierra and White mountains,
again, in conjunction with REV and HNX from Wednesday evening
through late Thursday. 

Finally beginning Friday, the system is expected to begin
transitioning east and PoP chances along with it. Other than the
easternmost parts of the CWA, PoP chances will be over with by
Friday afternoon. Then, ridging begins to build over the region
and clear skies as well as warm temperatures a bit for the weekend. 
Another trough will progress across the region late Sunday into 
Monday. Right now, it looks to be more of a wind bag then a 
precipitation maker.   
&&

.AVIATION...For McCarran...Improving conditions expected after 06z 
with the last round of showers moving away from the area. Lower 
clouds will persist overnight with BKN CIGS around 5k feet. Areas of 
fog are possible around the valley overnight into the early morning 
hours after daybreak. Dry conditions are forecast for Wednesday 
before low clouds and chances for showers return Wednesday night and 
Thursday. 

For the rest of southern Nevada, southeast California, and northwest 
Arizona...Expect generally improving conditions overnigt with 
showers and low CIGS persisting in portions of Mohave County through 
daybreak. Areas of fog will be possible through early Wednesday 
morning. Minaly dry conditions are expected on Wednesday with more 
showers and lower CIGS forecast for Wednesday night and Thursday. &&

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

$$

UPDATE...Adair
AVIATION...Salmen
SHORT TERM...Pierce
LONG TERM...Boucher

For more forecast information...see us on our webpage:

http://weather.gov/lasvegas or follow us on Facebook and Twitter

187 
FXUS65 KVEF 160546
AFDVEF

Area Forecast Discussion
National Weather Service Las Vegas NV
945 PM PST Wed Jan 15 2019

.SYNOPSIS...A complex and active weather pattern will continue to 
evolve through mid week, eventually coming to an end by Friday.
A potent storm will slam the Sierra and White mountains with heavy 
snow Wednesday night through Thursday. The rest of the region will 
also see another round of widespread rain and high elevation snow.
&&

.UPDATE...The batch of concentrated precipitation that moved into 
southern Nevada this evening for a few hours will continue pulling 
away toward northwest Arizona and southwest Utah overnight. 
Considerable low level moisture will linger in its wake and areas of 
fog and some drizzle can be expected, but measurable rain should 
come to an end for Las Vegas until early Thursday. Pop/WX/QPF grids 
have been adjusted based on the latest radar and model trends. 

The Winter Weather Advisory for the Southern Sierra was cancelled 
tonight as the back edge of the main moisture band has cleared the 
crest leaving only scattered snow showers making it to the east 
slopes and no significant accumulations the rest of the night. The 
Winter Storm Watch for the Southern Sierra and White Mountains of 
Inyo County was upgraded to a Winter Storm Warning from 4 PM PST 
Wednesday to 4 AM PST Friday.
&&

.PREV DISCUSSION...
251 PM PST Tue Jan 15 2019

.SHORT TERM...through Tuesday night

Upper level disturbance that has brought the light-moderate rain to 
parts of southeast California, southern Nevada and all of northwest 
Arizona will be lifting northeast into southern Utah early this 
evening. That means precipitation will be winding down across the 
above mentioned locations over the next several hours. Can confirm 
this as satellite shows breaks in overcast and no precipitation 
behind the disturbance over the western Mojave Desert in San 
Bernardino County. Decided to cancel the Flash Flood Watch for 
southern Mohave County as moderate rainfall threat diminishes over 
the next 1 to 2 hours. Automated gauges within the Big Sandy Wash 
and Burro Creek drainage basin have recorded some impressive 24 hour 
rain totals between 2 to 3 inches, so far stream gauges indicate the 
runoff is being easily contained within the washes or streams.

A weaker lobe of vorticity will quickly traverse the region later 
this evening setting off another wave of light rain/snow showers. 
Decreased the new snow accumulations for the Spring Mtns to 1 to 3 
inches overnight. These values fall below our winter weather 
advisory criteria so went ahead and cancelled the advisory for the 
Spring Mtns. Kept the advisory going for the Sierra as generally 4-8 
inches expected.

As juiced as the air mass is expect areas of fog tonight/Wednesday 
morning. 

.LONG TERM...Wednesday through Tuesday

Moving into Wednesday, a lull in activity is expected before the 
last, more potent, system begins to come on-shore by Wednesday 
night. This system has by and large not changed substantially, 
however snowfall amounts have come into question given the recent 
overforecasted amounts suggested by models up until this point. 
However, broad divergence coupled with very strong 850 mb moisture
flow out of the south paralleling the Sierra range as depicted by
both the ECMWF and GFS will hit the Sierra overnight Wednesday. 
Still do not see a reason to back off from the potentially over 3
feet of snow at the highest elevations of the Sierra. Winds could
also be quite strong as 700 mb winds over 50 kts have been noted 
in both GFS and ECMWF solutions. As a result, also needed to hoist
a Winter Storm Watch for the eastern Sierra and White mountains,
again, in conjunction with REV and HNX from Wednesday evening
through late Thursday. 

Finally beginning Friday, the system is expected to begin
transitioning east and PoP chances along with it. Other than the
easternmost parts of the CWA, PoP chances will be over with by
Friday afternoon. Then, ridging begins to build over the region
and clear skies as well as warm temperatures a bit for the weekend. 
Another trough will progress across the region late Sunday into 
Monday. Right now, it looks to be more of a wind bag then a 
precipitation maker.   
&&

.AVIATION...For McCarran...Improving conditions expected after 06z 
with the last round of showers moving away from the area. Lower 
clouds will persist overnight with BKN CIGS around 5k feet. Areas of 
fog are possible around the valley overnight into the early morning 
hours after daybreak. Dry conditions are forecast for Wednesday 
before low clouds and chances for showers return Wednesday night and 
Thursday. 

For the rest of southern Nevada, southeast California, and northwest 
Arizona...Expect generally improving conditions overnigt with 
showers and low CIGS persisting in portions of Mohave County through 
daybreak. Areas of fog will be possible through early Wednesday 
morning. Minaly dry conditions are expected on Wednesday with more 
showers and lower CIGS forecast for Wednesday night and Thursday. &&

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

$$

UPDATE...Adair
AVIATION...Salmen
SHORT TERM...Pierce
LONG TERM...Boucher

For more forecast information...see us on our webpage:

http://weather.gov/lasvegas or follow us on Facebook and Twitter