Weather

986 
fxus65 kfgz 292205 
afdfgz 


Area forecast discussion 
National Weather Service Flagstaff Arizona 
305 PM MST Friday Aug 29 2008 


Synopsis....a trough of low pressure is expected to move into Arizona over 
the Labor Day weekend producing widespread precipitation and 
scattered thunderstorms across the Northland. Overnight rainfall and 
thunderstorm activity is a strong possibility with this system on 
Saturday night. 


&& 


Discussion...an early season short wave trough will move into the 
southwest this weekend...bringing up moisture from Mexico and 
decreasing atmospheric stability to produce widespread showers and 
scattered thunderstorm activity this weekend. By early next week a 
more stable airmass will move into the region producing sunny skies 
and a dry weather pattern for the rest of the work week. 


Saturday and Saturday night...the latest forecast guidance for 
Saturday shows the deepest moisture and greatest instability moving 
up into northern Arizona through Yavapai County and western Coconino 
County just ahead of the trough. This means the western and southern 
forecast zones will have the highest chances for showers and 
thunderstorms on Saturday. As we move into Saturday night the upper 
level wind speeds increase...the moist layer deepens and temperature 
profile becomes moist adiabatic. This should produce an extensive 
cloud layer Saturday night with a temperature and moisture profile 
that will likely produce widespread rain showers and possibly even a 
few thunderstorms. The strong flow will likely anchor some of these 
storms over the higher terrain which could lead to localized higher 
precipitation amounts in some areas. The widespread shower activity 
coupled with terrain based heavy rainfall has potential for a 
localized flash flooding threat on Saturday night. 


Sunday through Monday...the trough is expected to slowly sweep the 
moisture through Arizona from southwest to northeast. This means the 
chances for precipitation in our southwestern zones will be highest 
Sunday morning...as drier more stable air moves into Yavapai County 
chances for precipitation will slowly decrease from morning to 
afternoon. Most areas in northern Arizona will see a 50 to 70 
percent chance for showers and thunderstorms during the day...with 
20 to 40 percent chance in Yavapai County. From Sunday night to 
Monday...as the trough pushes the moisture and instability eastward 
the best chances for showers move into our eastern forecast zones. 


Tuesday through Thursday...a stable and dry airmass will move into 
Arizona. Expect clearing skies and drier conditions by the middle 
of next week. 


&& 


Aviation...for the 00z package...expect isolated-scattered rain showers/thunderstorms and rain to 
continue mainly along and south of a line from kprc to ksjn. 
MVFR/IFR conditions may occur within the stronger storms. Convective 
activity diminishing between 02-04z. Aviation discussion not updated 
for amendments. 


&& 


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


Monday through Wednesday...an early season low pressure system will 
move across the southern Great Basin on Monday. Expect scattered 
showers and thunderstorms on Monday decreasing to isolated activity 
on Tuesday. Expect southwest winds of 10 to 20 miles per hour with gusts 
approaching 30 miles per hour during the afternoon on Monday. 


&& 


Fgz watches/warnings/advisories...none. 


$$ 


Public...............bohlin 
aviation/fire weather.....Db 


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