Area forecast discussion 
National Weather Service Phoenix Arizona 
820 PM MST Tuesday Sep 30 2014 

anticipate little change in temperatures Wednesday as a weather 
system passes far to the north. A ridge of high pressure building 
into the region will then lead to a warming trend Thursday and 
Friday with temperatures climbing at least a few degrees above 
normal. Off and on breeziness from the north and northeast can also 
be expected. There will be little change in temperatures over the 
weekend along with light winds. High pressure weakens next weak for 
a very slow cooling trend. 


broad area of low pressure across the western Continental U.S. This 
evening...with Arizona on the southwestern periphery and under dry west/northwest 
flow aloft. Infrared imagery at 8 PM showed clear skies across southeastern California and 
Arizona. Surface dewpoints this evening were rather low and generally ranged 
from the middle 30s to upper 40s. For the rest of tonight dry westerly 
flow aloft...clear skies and light winds will be the rule. Forecasts 
in fine shape and no updates needed at this time. 

Previous discussion... 
rest of today through Friday... 
radiosonde observation trends from this morning indicated little change in lower level 
temperatures over eastern portions of Arizona with increasing 
warming further west. Surface temperature trends for early this 
afternoon reflect this pattern with little change in our eastern 
areas and 5-10 degree of warming in southeast California...compared to 
24 hours ago. An upper trough moving through the Pacific northwest 
and Great Basin will brush Arizona Wednesday keeping temperature 
trends Pretty Flat. A ridge of high pressure over the northeast 
Pacific will then slowly move inland leading to a warming trend 
Thursday and Friday. That means highs in the upper 90s on the 
south-central Arizona deserts and around 100 or slightly higher over 
southwest Arizona and southeast California. At the same time...strong surface 
high pressure becomes centered over the Great Basin. With lower 
pressure over northwest Mexico...this leads to a north and northeast 
oriented pressure gradient across Arizona and Southern California. 
In turn there will off and on breeziness...most noticeably over the 
lower Colorado River valley and foothill locations of northern 
Maricopa County. 

Saturday through Tuesday... 
anticipate little change in temperatures over the weekend. The 
surface pressure gradient weakens and the light diurnal wind 
patterns will prevail. The ridge starts to weaken early next week 
and some high clouds move through as well which leads to a very slow 
cooling trend. 


south-central Arizona including kphx...kiwa...and ksdl...and 
southwest Arizona and southeast California including kipl and kblh... 

Clear skies and light winds will prevail across the region through 
Wednesday evening. Winds across the central Arizona deserts will favor 
normal diurnal tendencies but often will be rather light and 
variable. VFR conditions all airfields next 24 hours. 

Aviation discussion not updated for amended tafs. 


Fire weather... 
Friday through Tuesday... 
a few degrees of additional warming can be expected Friday with 
little change Saturday and Sunday before a subtle cooling trend 
Monday and Tuesday. Minimum humidities will be quite low Friday 
through Sunday before trending up Monday and Tuesday. 
Similarly...overnight recovery will be poor over southeast 
California and only fair elsewhere through Sunday before trending 
upward. North and northeast breezes continue Friday before light and 
variable wind patterns take hold over the weekend. 


Psr watches/warnings/advisories... 





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