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Area forecast discussion 
National Weather Service Las Vegas Nevada 
953 am PDT Friday Jul 18 2008 


Synopsis...a temporary change in the weather pattern will bring an 
increase in temperatures and a decrease in cloud cover and shower 
activity today and Saturday. Monsoon moisture is expected to return 
Sunday and into early next week with thunderstorm coverage expanding 
into the area once again. 
&& 


Update...today should be a down day for thunderstorms across the 
County Warning Area as dry air has moved into the area. Model forecast parameters 
suggest that some afternoon cumulus possible over Clark...Mohave and 
Lincoln County mountains with a small chance of a thunderstorm in 
northern Mohave and far eastern Lincoln County. Temperatures are 
expected to be up several degrees today and Saturday with high 
pressure building back over the area and more efficient warming of 
the dry airmass. There will be an increase in middle to high level 
moisture Saturday...as monsoonal moisture begins to make a comeback. 
Sunday is still looking good for a substantial push of monsoon air 
into the area. Forecasted precipitable water values approach 1.5 inches Sunday 
afternoon which is actually higher than the last monsoon push last 
week. Current forecast is on track and no updates planned atmosphere. 
&& 


Previous discussion...300 am PDT... 


Short term...ripple in southwest flow pushing into Utah at this time with 
drying taking place across the County Warning Area. Enough instability/moisture left 
to produce isolated thunderstorms today over northern Mohave County 
and possibly along the eastern Lincoln County border...however all 
other areas should be under the more stable/drier air mass. Drying 
to be short lived however as next round of moisture to push across 
Arizona over the weekend. Some difference between NAM/GFS with NAM 
bringing increase moisture into Mohave County Saturday and then 
expanding west into Sunday. GFS waits to bring moisture in on Sunday 
but is very similar to the NAM at that time. For now will compromise 
with slight chance of thunderstorms over Mohave County Saturday and 
bring isolated/scattered back to southeast San Bernardino/Clark/ 
Lincoln/Mohave counties into Sunday. Locally heavy rain possible 
into Sunday as prec water values return to over an inch with two 
inches pushing north along the lower Colorado River valley. Drier 
air today to bring temperatures to above normal readings which are 
expected into Saturday also. However increase clouds/thunderstorms 
on Sunday will drop highs 5-10 degrees especially across the south. 


Long term...for the period beginning Monday...bumped up probability of precipitation again 
in the extended...with models continuing to show sufficient moisture 
and instability for daily afternoon/evening thunderstorms across 
much of the forecast area throughout the week. With that...dropped 
daytime maximum temperatures again...with better thunderstorm coverage expected than 
before. A slow moving easterly wave that initialized this evening 
over the Gulf of Mexico will slowly transition westward...and 
have an impact on our weather by the end of next week...bringing precipitable water 
values back over 1.5 inches across the southern half of the forecast 
area again. 
&& 


Aviation...for McCarran...thunderstorm chances are greatly reduced 
today as dry air works across the area. This is evident in current 
water vapor imagery...and even though surface dewpoints are still 
relatively high....they should drop significantly as soon as the 
nightime inversion breaks and air aloft mixes down the surface. Air 
temperatures should increase faster than previous days thanks to the 
decrease in moisture...thinking we will hit 100 degrees around 18z. 
Will continue no significant weather into Saturday...but by Sunday 
afternoon...monsoonal moisture will be back...along with increased 
chances for thunderstorms during the afternoon/evening. 


For the rest of southern Nevada...northwest Arizona...and southeast 
California...the thunderstorm threat is significantly less 
today...as dry air continues to work its way across the area. 
Mohave County will have an outside chance of convection 
today...otherwise no significant weather is expected. Monsoonal 
moisture...and associated thunderstorms will return to the area by 
Sunday afternoon. 
&& 


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


$$ 


Salmen/Jensen/Kennedy 


Http://weather.Gov/lasvegas