Area Forecast Discussion

FXUS65 KVEF 221001 AAA
Area Forecast Discussion
National Weather Service Las Vegas NV
300 AM PDT Thu Mar 22 2018
.SYNOPSIS...Widespread rain and high elevation snow is expected 
today as a moist Pacific weather system moves through. Drier 
conditions will move in tomorrow with near normal temperatures. By 
Saturday and Sunday widespread gusty conditions and a cooling trend 
can be expected, with cool temperatures lasting into early next 
week. &&
.SHORT TERM...through Friday night. 
Wet conditions continue early this morning mainly across the Sierra 
and Owens Valley, while a bit of a lull in the shower activity 
occurs further south and east.  However, cooling cloud tops are 
indicated with the incoming moisture plume across SoCal, starting to 
spread into the western Deserts now. Additionally, some light 
reflectivity echoes have been increasing on radar across northern 
San Bern county, so I suspect precipitation will be on the increase 
through the morning hours as the moisture plume begins to shift east 
and more favorable jet dynamics work into the region. 
All in all, still on tap for a rather wet and showery day for most 
of the region, especially north of I-40.  Unsurprisingly, desert 
valleys will be the hardest pressed to get significant 
precipitation, with expected totals across the Mojave Desert and Las 
Vegas areas in the one-tenth to one-quarter inch range.  Higher 
amounts are likely in the mountains, with up to two inches possible 
in the Spring Mountains. The Owens valley will also wind up fairly 
substancial totals of 1-1.5 inches of rainfall when all is said and 
There will be some modest instability around this afternoon, 
particularly as the lead shortwave forcing this moisture plume 
eastward lifts into central Nevada.  As such, I added Isolated 
thunderstorms to the forecast for much of Inyo County and the 
southern Great Basin this afternoon and evening.  Winds aloft would 
also support fairly gusty winds across the area, bordering on wind 
advisory thresholds in some places, but given the abundance of cloud 
cover and potential precipitation drag, I opted against any 
additional wind headlines besides the Wind Advisory for Lincoln 
county.  Some spotty wind gusts over 40 mph will be possible however 
in central Nye & Esmeralda counties this afternoon, as well as 
pockets of Mohave county. 
By late this evening, precipitation coverage will become more 
showery and focused across Northwest Arizona while gradually 
decreasing. Drier conditions are expected Friday with seasonable 
temperatures, though a stray shower or two will be possible across 
Lincoln county and northern Mohave counties thanks to some lingering 
.LONG TERM...Saturday through Thursday.
Both the GFS/ECMWF have a shortwave pushing into northern California 
and across the Great Basin Saturday-Sunday. Models are in much 
better agreement on most of the details with this shortwave through 
the weekend. As the shortwave approaches the region SAT afternoon, 
potentially advisory level southwest winds (25-35 MPH) will move 
across much of the Mojave Desert and higher terrain. With limited 
moisture only have some slight chances of precip Sunday morning 
(mainly north of Clark County) along the leading edge of a surface 
cold front. The cold front should push through Sunday leaving behind 
cooler temperatures (potentially 5-10 degrees cooler than Saturday) 
and gusty north winds. Beyond Sunday the evolution of this shortwave 
remains unclear, but overall trends have been closing off the low 
just south and east of our area. This scenario would likely continue 
breezy north winds and continued CAA keeping temperatures cool 
through Tuesday before the low moves further east and ridging moves 
in behind it Wednesday-Thursday. &&
.AVIATION...For McCarran...Light south to southwest winds will 
continue early this morning before increasing later this morning. 
Southwest winds have the potential of gusting up to 20-25 kts this 
afternoon. Though, confidence on those winds speeds is very low with 
good potential of shower activity around the region significant 
precipitation drag should keep the wind speeds much lower. Lower 
ceilings around 040-060 will arrive by 17-18Z this morning with the 
better chances of shower activity. Better ceilings should arrive 
later this afternoon between 22-01Z with decreasing shower activity. 
For the rest of southern Nevada, northwest Arizona and southeast 
California...Rain chances will increase throughout the morning and 
into the afternoon for most terminals as well as low ceilings and 
terrain obscuration. Rain chances will end and clouds will decrease 
from west to east later tonight into Friday morning.
.SPOTTER INFORMATION STATEMENT...Spotters are encouraged to report
any significant weather or impacts according to standard operating 
procedures.  Rainfall and flooding reports are appreciated during 
periods of weather later this week.
LONG TERM/Aviation...Kryston
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