405 
fxus65 kpsr 200327 
afdpsr 


Area forecast discussion 
National Weather Service Phoenix Arizona 
825 PM MST Wednesday Nov 19 2008 


Synopsis... 
high pressure aloft will continue to weaken tonight and Thursday 
under mostly clear skies. By Friday and Saturday...some high level 
clouds will drift into the area...but temperatures should remain 
above the seasonal normals. By the middle of next week...a major 
change in the pattern will lead to cooler weather...and a slight 
chance for showers to the east of Phoenix. 


&& 


Discussion... 
clear skies were noted over the forecast area (southeast California to south 
central az) at 03z as a strong high pressure system continued over 
the region. 


Strong high pressure however is forecast to weaken a bit the next 
several days as a series of Pacific storms move onshore and mainly 
across the northern tier of states (washington/Oregon...Idaho...and 
montana). As a result...we should begin to see afternoon 
temperatures edge down a few degrees...exacerbated also by periods 
of high clouds Thursday night through the weekend. 


Current dry forecasts look OK through Saturday. No updates 
necessary. Excepts from previous discussion still apply. 




Excerpts from previous discussion... 
height and thicknesses are prognosticated to remain above normal into this 
weekend. However...models are pretty similar in advertising variable 
amounts of clouds above 15 thousand feet...while the lower levels stay 
on the dry side. Except for a weak back door frontal system that 
will produce a little stronger breeze in our eastern zones early 
Friday...no strong winds expected. 


As we have been talking about...the big changes in the pattern may 
come about next week...with both European model (ecmwf) and GFS now carving out a 
major trough near the West Coast on Wednesday. This will be a cold core 
low that could result in considerable large scale forcing and 
thicker cloud coverage...and possibly some showers. Best chances for 
showers on Tuesday still appear to be over the higher terrain of 
zone 24. 


&& 


Aviation... 
high pressure aloft combined with a dry airmass will keep skies 
clear and winds light through at least 02z Friday. No aviation 
concerns anticipated. 


Aviation discussion not updated for amended tafs. 


&& 


Fire weather... 
temperatures will begin to cool as the high pressure...that has been 
dominating of late...begins to weaken by the end of the week. As 
this occurs...high clouds should spread over the area at times while 
winds remain light and minimum relative humidity values reach the middle teens by 
early next week. 


&& 


Psr watches/warnings/advisories... 


Arizona...none. 


California...none. 


&& 


$$ 


National Weather Service Phoenix is on the internet at 


Weather.Gov/Phoenix 


Discussion...vasquez/Sipple 
aviation...vasquez 
fire weather...paddock