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Area forecast discussion 
National Weather Service Las Vegas Nevada 
326 am PDT sun Jul 6 2008 


Synopsis...a weak trough will pass by to the north today...bringing 
drier air to the region. There will be a slight chance of 
thunderstorms over Mohave County high pressure will then build over 
the area early next week...with temperatures possibly approaching 
excessive heat warning criteria by the middle of the week. There is 
a chance for the first significant monsoon moisture push of the 
season late next week...which would bring increasing chances of 
showers and thunderstorms. 
&& 


Short term...satellite shows mostly clear skies areawide. Northern 
stream trough is clearly evident...with clouds skirting our northern 
border as the trough axis progresses eastward. Drier middle level air 
associated with this trough had already overspread our entire area 
as seen on water vapor loop...but low level moisture was still in 
place over northwest Arizona per surface plots and 24 hour change 
chart. With that in mind...slight chance of thunder is still 
warranted over eastern Mohave County this afternoon...but dry 
forecast looks good for Monday and Tuesday as ridging builds in from 
the west and drier air takes hold. This ridging will also bring 
increasing temperatures...with a risk of excessive heat conditions 
beginning on Tuesday. 


Long term...Wednesday to Saturday...Ridge still over the western 
Continental U.S. Wednesday to continue hot temperatures that will stay close to 
heat warning criteria. Thursday will be a tad 'cooler' as ridge 
heights lower in response to a short wave approaching and then 
passing well to the north of the area. A change to more moisture 
being drawn into the south parts of the forecast area is expected by 
Friday and into the weekend. GFS and European model (ecmwf) bring in impressive 
lifted indexes approach -4/5 in Mohave and Clark counties. In 
addition precipitable water values of an inch or more will be over 
Clark County Friday onwards and up to 2 inches in the far south part 
of the forecast area. Quantitative precipitation forecast is also looking impressive. Have increased 
the probability of precipitation in Mohave and Clark counties for Friday and Saturday. If 
the outlook stays the same subsequent forecasts could be for higher 
chances of thunderstorms this weekend. 
&& 


Aviation...for McCarran...southwest winds less than 8kts through 
18z Sunday..becoming 10-20kts after 18z through 03z Monday. Skies to 
be mostly clear except possible smoke layers aloft and very flat 
cumulus clouds. 


For the rest of southern Nevada...northwest Arizona...and southeast 
California...in the Sierra and Owens Valley areas smoke layers aloft 
are expected through the remainder of the weekend...otherwise mostly 
clear skies. Diurnal winds less than 10kts through 18z Sunday 
increasing to 10-20kts after 18z through 03z Monday. 
&& 


Fire weather...hot and dry conditions will persist through the 
first half of next week. Monsoon moisture is expected to return to 
areas southeast of Interstate 15 late in the week...bringing 
increasing chances for showers and thunderstorms. If the deeper 
moisture arrives as shown by the models...the main threat would be 
locally heavy rainfall Friday into the weekend. Relative humidity 
would also rise significantly over the entire area. There is still 
considerable uncertainty in the details...so stay tuned. 
&& 


Vef watches/warnings/advisories... 
Nevada...none. 
Arizona...none. 
California...none. 
&& 


$$ 


Morgan/Jacques 


Http://weather.Gov/lasvegas