Weather

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Area forecast discussion...corrected 
National Weather Service Las Vegas Nevada 
935 am PDT Sat Oct 11 2008 


Synopsis...an unseasonably cold low pressure system will linger 
over the region through Sunday. In addition to gusty northwest winds 
and colder temperatures...scattered showers can be expected today 
with snow levels as low as 4500 feet across southern Nevada. The 
system will move off to the east early next week...allowing for a 
warming trend and a return to mostly clear conditions. && 


Update...low centered over central Nevada continues to produce 
light snow showers...mainly across Lincoln County. Enough 
instability/dynamics to keep mention of showers further south and 
over Lincoln County...per current forecast. Amounts look to be light 
so do not expect any problems. Surface gradients slowly decreasing 
with main winds remaining over Esmeralda/central Nye counties and 
will continue with Wind Advisory through 6 PM for now. Current 
forecast on track...thus no updates planned at this time. 
&& 


Aviation...for McCarran...west to northwest winds expected through 
today across the Las Vegas Valley. Wind speeds will generally be 
14-24kts with gusts to 30kts. Winds are expected to diminish after 
22z to around 10kts as the pressure gradient relaxes. Expect 
generally scattered-broken clouds at or above 8k feet through 03z Sunday...with a few 
showers possible in around the Las Vegas Valley from 20z-23z 
Saturday as the main upper trough axis swings by. After 03z 
Sunday...expect few-scattered clouds at or above 10k feet gradually decreasing 
with northwest winds of 5-10 kts. Mountain obscuration likely in the 
Spring and sheep ranges around the Las Vegas Valley this afternoon 
due to clouds. 


For the rest of southern Nevada...northwest Arizona...and southeast 
California...an upper level low will bring a variety of weather to 
the area today before it departs eastward this evening into tonight. 
Northwest wind gusts of 20-30 kts are expected across the southern 
Great Basin through 21z Saturday. Expect sustained winds of 10-15 
kts in the remainder of the area for the most part through around 
00z sun...afterwards winds should lessen. Scattered-broken clouds at or above 6k feet 
with ceilings lowering locally and possible mountain obscuration. Scattered 
rain showers and shsn are expected across the area with snow levels lowering 
to around 4000 feet in the southern Great Basin by this afternoon 
and 5000 feet across the northern Mojave Desert. The best chance for 
showers will be across Lincoln County this afternoon into early 
tonight. As the upper low departs to the east tonight clouds will 
decrease across the area. Although dry weather will return to most 
of the area tomorrow with generally few-scattered clouds at or above 10k 
feet...ceilings of 6-8k feet and snow showers are still possible in 
Lincoln County. 
&& 


Previous discussion...430 am PDT short term...the upper low center was 
over south central Nevada this morning and the cold front pushed 
into the Las Vegas Valley between 10z and 11z. Surface observations 
showed winds speeds and pressure gradients were decreasing between 
Las Vegas and Tonopah since midnight as the front lost some 
momentum. The Wind Advisory was cancelled for all areas except 
Esmeralda and central Nye counties based on the latest observations 
and guidance. The 06z NAM and GFS indicate the upper low center has 
bottomed out and will begin to lift northeast into western Utah 
between 12z and 00z. Showers will dip down into Clark and northern 
Mohave counties today but will be more numerous across Lincoln 
County. Snow accumulations of a couple inches are possible north of 
Caliente...but mainly in the mountains. Temperatures tonight and 
Sunday will be cold areawide and the latest guidance for Bishop has 
lows below record readings for Sunday morning. As the system slowly 
lifts northeast Sunday...additional shortwave energy dives down the 
backside of the system through southern Nevada Sunday night. This 
will increase north winds...especially down the Colorado River 
valley Monday. 


Long term...as the departing system pulls away further to the east 
on Tuesday surface p-grads will gradually relax through the day but 
should still remain tight enough to keep breezy northeast to north 
winds going down the Colorado River valley. An upper ridge over the 
eastern Pacific will poke eastward into the Mojave Desert and help 
to transition the flow aloft to a westerly direction allowing 
temperatures to rise considerably from Monday with high temperatures 6 to 
10 degrees warmer. Although further warming will take place on 
Wednesday ahead of an approaching shortwave trough axis that moves 
across the Pacific northwest...model soundings from both the GFS and European model (ecmwf) do 
show an inversion holding through the day around 800-850 mb that 
would keep the lowest levels from mixing at all and thus would hold 
back a substantial jump in temperatures in the lower elevations. 


The aforementioned short wave will pass by to the east by Thursday 
opening the door for an upper level ridge to build into the 
southwestern Continental U.S. For Thursday. This will result in further warming 
with above normal temperatures that lasts into Friday as the ridge remains 
in place. By next weekend...the ridge gets shunted east in response 
to an approaching trough axis. Models still hint at a weak southern 
stream shortwave possibly moving towards the region but are much 
drier with it this morning so toned down probability of precipitation for Saturday. 
&& 


Vef watches/warnings/advisories... 
Nevada...Wind Advisory until 6 PM PDT today for nvz014. 
Arizona...none. 
California...none 
&& 


$$ 


Jensen/gorelow/Adair/stachelski 


Http://weather.Gov/lasvegas