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Area forecast discussion 
National Weather Service Las Vegas Nevada 
825 PM PDT Wednesday Jul 23 2008 


Synopsis...high pressure will continue to produce hot and dry 
conditions across the area on Thursday before a chance of 
thunderstorms returns to Mohave County on Friday. Thunderstorms are 
then expected to push further west and north into the weekend. 
&& 


Update...cloud free skies across the County Warning Area this evening and with the 
exception of possible debris clouds moving into Mohave County later 
tonight...expect little cloud cover through Thursday. This to result 
in continued hot and dry conditions for the initial part of the 
short term. Overall current forecast depicts this...thus no updates 
planned for this evening. 
&& 


Aviation...for McCarran...southwest winds less than 10kts through 
05z before becoming light overnight and into Thursday. However a 
brief period of east winds 5-10 kts are possible between 18z-20z 
Thursday. Mostly clear skies forecast. 


For the rest of southern Nevada...northwest Arizona...and southeast 
California...VFR conditions expected through Thursday with generally 
light winds...though a few gusts around 15 kts are possible... 
mainly after 18z Thursday. Mostly clear skies forecast. 
&& 


Previous discussion...230 PM PDT short term...high pressure extends 
from the central rockies to the Desert Southwest and is producing 
hot and dry conditions over the forecast area. This is expected to 
hold true through Thursday before a return of easterlies brings an 
increase in moisture to the region. Models indicate that conditions 
will become more favorable for thunderstorm development across 
Mohave County late Friday and into Saturday. Both the GFS and European model (ecmwf) 
now forecast the high pressure area over the central rockies to 
shift east into the Southern Plains late Saturday. This would allow 
the remnant moisture from Hurricane Dolly to begin advecting 
northward around the western extension of the high and into eastern 
Arizona and New Mexico...leaving the County Warning Area on the western fringes of 
the more moist and unstable air. Adjusted probability of precipitation down in 
response...especially over the northwestern County Warning Area. Temperatures are 
expected to remain at or slightly above normal through Saturday over 
much of the area with a downward trend over the southeast where the 
greatest amount of cloud cover expected. 


Long term...the biggest issue concerning the extended forecast 
continues to be just how much moisture works into the area from what 
will eventually become the remnants of Hurricane Dolly. See the 
latest track from TPC concerning Dolly for specific details in the 
short range...but afterwards what eventually becomes the remnant low 
that was Dolly heads west-northwest across northern Mexico before 
recurving more towards the northwest towards southern Arizona by 
Saturday afternoon. One concern is just how fast this moisture from 
Dolly will work into the area if this system slows down enough. The 
European model (ecmwf) continues to be the most aggressive at bringing in deeper 
moisture the fastest into the County warning forecast area while other models are slower. 
For now even by Sunday the European model (ecmwf) is not bringing deeper moisture 
further west than a 29 Palms to Pioche line. The operational GFS is 
progging negative vorticity advection as well as Li/S of +3 to +6 across the area on Sunday 
afternoon...suggesting we may see some sort of subsidence across the 
area before the deeper moisture arrives. Thus I did tone down probability of precipitation 
up in the northwest County warning forecast area for then. The remnant moisture from Dolly 
should eventually get ejected into our County warning forecast area due to the southeast 
flow around an upper ridge centered over North Texas but the latest 
models hint it may just take some time for this moisture to come in. 
With this in mind I did not change much beyond Monday as future 
model runs will likely have a better grasp of the situation. Temperatures 
will be highly dependant on cloud cover and convection. 
&& 


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


$$ 


Jensen/Salmen/stachelski 


Http://weather.Gov/lasvegas