898 
fxus65 ktwc 230915 
afdtwc 


Area forecast discussion 
National Weather Service Tucson Arizona 
215 am MST sun Nov 23 2008 


Synopsis...a big change in the weather pattern will bring a chance 
of showers and cooler temperatures to Southeast Arizona by the 
middle of this week. Until then...warm and dry conditions will 
prevail today and Monday ahead of two storm systems forecast to 
impact the region later this week. 


&& 


Discussion...high pressure aloft will result in another couple of 
days of seasonably warm temperatures and dry conditions. Models 
continued to point to a big change in the weather pattern as two 
storm systems were poised to impact the region later this week. The 
first system was prognosticated by the GFS and European model (ecmwf) models to hit the West 
Coast early Tuesday. Both models indicated an increase in moisture 
and possibly a few showers spreading into Arizona as early as 
Tuesday afternoon ahead of the main system. This scenario was about 
12 hours faster than the previous thinking...but considering the 
latest model consensus a slight chance of showers Tuesday was 
warranted. Models track the bulk of this system through Arizona 
Wednesday into Thursday with a break in between systems late 
Thursday into early Saturday. The most recent medium range models 
placed a little more uncertainty on the second system which was due 
to arrive around Saturday before exiting sometime late in the 
weekend. The greater spread in the different model solutions 
suggested a need for a more conservative forecast than previously 
advertised. Therefore...a slight adjustment has been made to pop 
values and temperatures for this upcoming weekend. 


&& 


Aviation...scattered to broken cirrus near 25k feet and all taf 
sites today. Light diurnally driven winds at 5-15 kts expected 
through Monday morning. Aviation discussion not amended for taf 
amendments. 


&& 


Twc watches/warnings/advisories...none. 


$$ 


Weather.Gov/Tucson