063 
fxus65 ktwc 200911 
afdtwc 


Area forecast discussion 
National Weather Service Tucson Arizona 
212 am MST Thursday Nov 20 2008 


Synopsis...the high pressure ridge over the western United States 
will weaken through the early part of next week...resulting in warm 
and dry conditions across Southeast Arizona. As the ridge weakens... 
some high level clouds will drift into the area from time to time... 
but temperatures will remain above seasonal normals. A shift in the 
weather pattern is expected during the middle to latter portions of 
next week...as a series of storm systems move into the West Coast. 
This will bring increasing clouds and cooler temperatures to all of 
Southeast Arizona...as well as a slight chance of showers. 


&& 


Discussion...the latest satellite pics show clear skies across 
Southeast Arizona early this morning...with high clouds noted over 
California being deflected to the north. The strong ridge of high 
pressure that has been in place across the Desert Southwest will 
continue to weaken and flatten into the early part of next week. As 
the ridge weakens...this will allow high clouds to move into the 
area...as well as a gradual lowering of daytime high temperatures. 
However...readings will still be above normal and the dry conditions 
will continue into at least Tuesday of next week. Except for some 
easterly breezes on Friday due to a tightening pressure gradient... 
no strong winds expected. 


It still appears that big changes in the pattern will occur next 
week with both the European model (ecmwf) and GFS carving out a major trough over the 
West Coast during the middle to latter portions of next week. This 
will result in increasing clouds and cooler temperatures across 
Southeast Arizona next week...as well as a slight chance/chance of 
precipitation. At this point...fairly confident above changes will 
happen. Just unsure of exact timing and if precipitation will occur 
on day 6...day 7...or day 8. As is the case with many these upper 
lows...the system tends to slow down (and the precipitation gets 
delayed) compared to model timing. However...the current pop grids 
for day 6/7 time frame match up well with the surrounding offices 
and reflect the higher guidance mex numbers. 


&& 


Aviation...mostly clear skies will prevail across Southeast Arizona 
today and tonight. Surface winds early this morning will be light 
and variable to east/southeast at 5-10 kts. Surface winds will then 
become west/northwest at 5-15 kts late this morning through the 
early evening hours tonight. Aviation discussion not amended for taf 
amendments. 


&& 


Twc watches/warnings/advisories...none. 


$$ 
Zell 


Weather.Gov/Tucson