704 
fxus65 kfgz 240401 
afdfgz 


Area forecast discussion 
National Weather Service Flagstaff Arizona 
900 PM MST Wednesday Jul 23 2008 


Synopsis...monsoon moisture will persist this week across eastern 
Arizona with scattered showers and thunderstorms each day. Western 
Arizona will see drier conditions through Thursday...with only 
isolated storms anticipated. Moisture is expected to increase from 
the south by the weekend...bringing a better chance of thunderstorms 
for all of northern Arizona. 


&& 


Discussion... 
tonight...showers and thunderstorms this evening have diminished 
across the Little Colorado River valley where heavy rain was 
reported in several locations today. A large outflow boundary is 
currently moving southwest off the Mogollon Rim 10 miles northeast 
of Payson which could bring some evening thunderstorms and wind 
gusts up to 30 miles per hour to communities in northern Gila County. 


On Thursday and Friday...models continue to show a drier air over 
the western zones with more moisture and instability over eastern 
Arizona. Expect isolated to widely scattered showers and 
thunderstorms over our western zones with scattered showers and 
thunderstorms each afternoon across eastern Arizona. 


For the weekend...upper level 300 mb model streamlines from the 
GFS...Eta model and European show an upper level low moving westward from 
Texas and reaching Southern California or western Arizona by 
Saturday. The flow pattern on the back side...eastern side...of this 
upper level feature may bring up additional Gulf moisture from the 
south and expand the coverage of showers the thunderstorms across 
northern Arizona just in time for the weekend. The forecast 
challenge for tonight is the difficulty in predicting the path of 
these upper level systems and flow patterns three days out. On 
Saturday for example...each of the three models...GFS...Eta and 
European have the upper level low position within 100 miles of each 
other. These position errors suggest the final location of the upper 
level low is less than certain. The location of the upper level low 
on Saturday will be critical in correctly forecasting the timing and 
extent of the southerly the moisture tap. Stay tuned. 


&& 


Aviation...for the 06z package...expect isolated -shra/-tsra overnight 
mainly from Interstate 17 eastward. Scattered showers and 
thunderstorms will likely redevelop around 11 am MST over mountain 
areas east of Flagstaff...with isolated to widely scattered activity 
for areas west of Flagstaff. Aviation discussion not updated for 
amendments. 


&& 


Fire weather...see fire weather forecast (fwffgz) for discussion of 
days 1 and 2. 


Saturday through Monday...a moist and unstable airmass will continue 
to bring scattered afternoon and evening showers and thunderstorms 
each day. Forecast models suggest a possible surge of moisture from 
the south which could expand scattered thunderstorm coverage further 
north and west over the weekend. 


&& 


$$ 


Public.............Bohlin 
aviation/fire weather...bohlin 


Visit weather.Gov/Flagstaff for northern Arizona weather 
information.