108 
fxus65 kvef 200523 cca 
afdvef 


Area forecast discussion 
National Weather Service Las Vegas Nevada 
920 PM PST Wednesday Nov 19 2008 


Synopsis....temperatures will trend slightly cooler through the end 
of the week as a weak storm system passes by to our north late 
Thursday. Temperatures will remain above normal and cloud coverage 
will be limited through the weekend. A pattern change is likely by 
the middle of next week...with temperatures falling closer to normal 
and the chances of rain and mountain snow increasing. 
&& 


Update...very tranquil evening...forecast on track and no updates 
needed. 


Previous discussion...this mornings sounding indicated more than 
expected cooling in the lower 15kft...resulting in daytime maximum temperatures 
slightly cooler today. With further height falls over the next 24 
hours...and increasing upper level cirrus...there should not be any 
threat to maximum temperature records tomorrow...even though we will still be 
well above normal across the area. A shortwave trough will pass well 
north of the area late Thursday/early Friday...which will help to 
further lower heights...and continue the decreasing trend to 
temperatures on Friday. 


Long term...while fall-like temperatures have been reluctant to 
stick around long this year...it is looking more likely that a 
significant pattern change will take place next week. On Saturday we 
will be between two separate systems...a shortwave trough axis 
moving across the Pacific northwest and a weak upper level trough associated 
with the southern branch of the jetstream that will be off the coast 
of socal. Neither of these systems will do much of note other than 
spread in some high level moisture that results in scattered-broken cirrus 
clouds across the area. We may see a little cooling on Sunday in the 
wake of the shortwave trough that passed by to our north on 
Saturday...but the next upper ridge builds into the western Continental U.S. 
From the Pacific allowing for temperatures to warm right back up especially 
for Monday. Overall above normal temperatures are expected from Saturday 
afternoon through Monday afternoon. 


Things start to get more interesting by the middle of next week. 
Models are still disagreeing as to the timing of the next 
significant full latitude trough axis as well as to the track and 
timing of any pieces of energy that rotate through the trough and/or 
close off. For now slight chance probability of precipitation were spread into the higher 
elevations of the northwest on Tuesday afternoon...and then spread 
probability of precipitation southeastward by Wednesday though most of the southern areas 
still have ghost probability of precipitation in them for then. While the forecast was 
leaned towards the 12z European model (ecmwf)...it was not brought full-fledged...but 
overall high temperatures were lowered by 4-8 degrees from Tuesday. Snow 
levels will lower to around 7000 to 8000 feet by Wednesday night. It 
looks like nature is planning to serve US some cold Turkey for 
Thanksgiving as models are also suggesting a second deeper piece of 
energy could rotate through the area then along with another chance 
of showers. 
&& 


Aviation...for McCarran...light southwest winds this evening 
through around 14z Thursday...then winds are expected to become 
variable in nature...however periods of easterly winds around 5 kts 
will be possible late Thursday morning and in the afternoon. Clouds 
are expected to increase at or above 25k feet this evening. Scattered-broken clouds 
at or above 25k feet later tonight and tomorrow. 


For the rest of southern Nevada...northwest Arizona...and southeast 
California...generally light diurnal winds tonight and tomorrow. 
High level clouds will increase across the area this evening. For 
tomorrow scattered-broken clouds at or above 25k feet are expected. 
&& 


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


$$ 


Czyzyk/Kennedy/stachelski 


Http://weather.Gov/lasvegas