867 
fxus65 kpsr 131152 cca 
afdpsr 


Area forecast discussion...corrected 
National Weather Service Phoenix Arizona 
445 am MST Monday Oct 13 2008 


South-central and southwest Arizona...and southeast California 
forecast discussion 


Updated... 
updated fire weather discussion. 


&& 


Synopsis... 
a weakening low pressure system moving east across northern Arizona 
will result in very dry...sunny and warmer weather this Columbus 
day...but it will still be much cooler than average for middle October. 
It will be windy from the north in southwest Arizona and southeast 
California today with less wind Tuesday. High pressure aloft will 
build over the southwestern United States with warmer weather each 
day Tuesday through Friday...along with mostly clear nights and 
sunny days. Afternoon highs will climb into the 90s in the desert 
areas including Phoenix...Yuma...el centro and Imperial by Thursday 
through the coming weekend 


&& 


Discussion... 
under clear skies...temperatures were generally 2 to 4 degrees 
cooler well before sunrise very early this morning...except warmer 
along the lower Colorado River valley and much of southeast 
California. 


A weakening low pressure center will move slowly east across 
northern Arizona today with the very dry southern end of this system 
moving across our area. This will result in very dry...sunny and 
warmer weather today...but it will still be much cooler than average 
for middle October. The very dry air will result in afternoon relative 
humidity dropping into the single digits this afternoon. 


A strong Pacific high pressure system building into the western 
United States to the north of our area will result in gusty winds 
from the north in southwest Arizona...especially along the lower 
Colorado River valley and in southeast California today. These gusty 
winds will help bring in very dry air over the area with afternoon 
relative humidity dropping into the single digits. This means that a 
red flag warning will continue for the lower Colorado River valley 
and southeast California from 11 am today to 8 PM this evening. 
It will still be windy in those areas tonight with overnight low 
temperatures warmer there than they otherwise would be in this cool 
of an airmass. 


The low pressure system will move east of our area with less wind in 
southwest Arizona and southeast California Tuesday. 


High pressure aloft from the Pacific will expand into our area with 
warmer weather Tuesday. Then...high pressure aloft from northwest 
Mexico will extend north over the intermountain west with further 
warming Wednesday through Friday. Clear nights and sunny days are 
expected this Columbus day through Thursday. 


Some middle level moisture might move into the area from the south by 
the weekend...as the high pressure system aloft moves east and a weak 
subtropical low pressure system approaches from the west. However... 
for the time being have confined partly cloudy skies to the higher 
terrain east of the greater Phoenix area...and have dropped 
temperatures back slightly across the entire area. 


&& 


Aviation... 
no concerns for the Phoenix-area airfields today and tonight. 


For kipl...knyl and kblh... 
high pressure at the surface and aloft will strengthen today...with 
somewhat stronger winds than on Sunday. In fact...winds aloft in 
the blh area at 3 k feet will jump to about 30 kts by middle day. 
North winds likely to gust to 30-35 kts by around 18-20z with 
low level wind shear possible in spots. No blwg dust at the taf 
locations...but cannot rule it out in isolated spots today. 
Winds will slowly diminish tonight to less than 10 kts at most areas. 


Aviation discussion not updated for amended tafs. 


&& 


Fire weather... 
red flag warning valid from 11 am to 8 PM today for the lower 
Colorado River valley and all of southeast California zones comprised 
by eastern Riverside County...including Joshua Tree National Park... 
and Imperial County. Humidity criteria will easily be met except 
perhaps at elevations above 4000 feet. Winds will decrease in most 
areas tonight...except winds will continue to impact ridge tops in 
southeast California after dark...where gusts to 30 miles per hour could occur. 
Less wind is expected Tuesday across southeast California...but a 
slight increase is expected across zones 132 and 133. 


Wednesday through Sunday...locally breezy conditions are anticipated 
Wednesday over south-central Arizona...including the Phoenix area. 
Light winds will be the rule through the weekend along with a 
warming trend. An increase in clouds is anticipated Thursday 
through Saturday...but no rain is expected. 


&& 


Psr watches/warnings/advisories... 


Arizona...red flag warning for the lower Colorado River valley...fire 
weather zone 131...from 11 am to 8 PM today. 


California...red flag warning for southeast California including the lower 
Colorado River valley...fire weather zones 230...231...and 232 
from 11 am to 8 PM today. 


&& 


$$ 


National Weather Service Phoenix is on the internet at 


Weather.Gov/Phoenix 


Discussion...Ellis 
aviation...Sipple 
fire weather...Sipple