818 
fxus65 kvef 200315 
afdvef 


Area forecast discussion 
National Weather Service Las Vegas Nevada 
815 PM PDT Tuesday Aug 19 2008 


Synopsis...dry flow will remain over the area through the end of 
the week with temperatures near to slightly above normal. 
&& 


Update...upper trough to transition across southern Nevada tonight 
as main low circulation pushes into southwest Canada on Wednesday. 
This to result in dry westerly flow across the County Warning Area during the short 
term. Winds from this afternoon have diminished across central 
Nevada and although a few gusts will still be seen through the 
evening hours...widespread gusty winds are no longer expected. Thus 
the red flag warning was allowed to expire at 8 PM PDT. Current 
short term forecast on track. Will update zones later to remove 
evening/midnight wording...otherwise no further updates planned at this time. 
&& 


Aviation...for McCarran...southwest winds to diminish to less than 
10kts by 06z and then continue into Wednesday morning with south 
winds 10-12kts after 18z Wednesday. Variable high level moisture through 
Wednesday. 


For the rest of southern Nevada...northwest Arizona and southern San 
Bernardino County...winds will generally remain southwest 10-15kts 
overnight and then 10-20kts on Wednesday. Variable high level 
moisture through Wednesday. 
&& 


Fire weather...although relative humidity values will remain below 
15 percent across the area through the rest of the evening...winds 
have decreased and are no longer reaching red flag criteria. Thus 
the red flag warning has been allowed to expire. 
&& 


Previous discussion...309 PM PDT short term...minor shortwave moving 
southeast in central California not as impressive as it appeared 
this morning nor as moist as models indicated. Will trim back cloud 
cover forecast for the rest of today and this evening. Other minor 
challenge is the temperature forecast. Observed temperatures and 
forecast trends through the short term look to be lower than 
previously thought. Have lowered slightly the maximum and min 
temperatures which would bring Las Vegas temperatures to be at or 
slightly above normal. After Wednesday and the troughs passage 
pattern looks to be zonal then transitioning to a high setting up 
near The Four Corners area Saturday. It appears there will be no 
time for any return flow to bring moisture before then. 


Long term...somewhat tricky forecast in the extended with regards 
to monsoonal flow. Both the GFS and European model (ecmwf) show high pressure setting 
up in the vicinity of the 4-corners region with a somewhat favorable 
south to southeast low level flow. The European model (ecmwf) is more bullish in 
bringing higher dewpoints back into the eastern portions of the County Warning Area 
while the GFS is holding strong onto much drier air over much of the 
County Warning Area. The models are showing a trough pushing into the Pacific 
northwest early next week and depending on the strength of the 
southwest flow...moisture could be shunted to the south. Thinking is 
that Monday and Tuesday would be see the best chance of 
thunderstorms over the far southern and southeast portions of the 
County Warning Area...however not confident enough to put thunderstorm wording into 
the forecast. Looking further ahead...as the trough pushes closer 
onshore a stronger southwest flow develops and once again pushed low 
level moisture further south and bringing additional wind into the 
forecast. Temperatures are expected to remain above normal through 
the extended. 
&& 


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


$$ 


Jensen/Jacques/gorelow 


Http://weather.Gov/lasvegas