367 
fxus65 kpsr 160207 
afdpsr 


Area forecast discussion 
National Weather Service Phoenix Arizona 
705 PM MST Wednesday Oct 15 2008 


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


Synopsis... 
high pressure aloft will build over the region the next couple of 
days resulting in added warming through Friday. Temperatures by the 
weekend will be well above normal...perhaps approaching the century 
mark at the warmest desert spots. A weak disturbance expected to 
pass across the region early next week will bring some minor cooling 
along with an increase in clouds. There will also be a slight chance 
of showers Sunday night and Monday over the south-central higher 
terrain. 


&& 


Discussion... 
clear skies the rule around the County Warning Area this afternoon as a dry westerly flow 
aloft prevails. Gusty Ely winds finally beginning to decrease by middle- 
afternoon as east/west surface pressure grads relax...but likely to get 
lclly breezy again next couple of late nights/mornings over scntrl 
Arizona as grads tighten a bit each night. Model relative humidity forecasts show not much 
chance of any cloud cover next day or two. So full sunshine...along 
with building heights aloft...will serve to give further daytime 
warming through Friday...with peak temperatures likely Friday or Saturday. 


Meanwhile...cutoff low off the central Baja California coast is prognosticated to open 
up and eventually lift northeastward towards the desert SW over the weekend 
..giving some increase in clouds across the area by Saturday and 
Sunday. Doubt if they will be sufficient to lower temperatures much. By 
late Sunday and Monday another shortwave trough will lift towards 
the region from the Pacific and will inject a bit more moisture into 
the area. Model forecast soundings hint that we may have sufficient 
moisture by Sunday night and Monday to warrant a slight chance of 
showers over zone 24. Middle shift introduced this possibility...and 
this still appears reasonable. As the shortwave pushes across the 
region...will probably see a slight lowering of our maximum temperatures early 
next week. 


&& 


Aviation... 
no aviation concerns anticipated through Thursday evening. Pressure 
gradient will again tighten overnight...resulting in an easterly 
flow around 20 knots at 1500 feet above ground level in the Phoenix metropolitan area. 
However...at the surface winds will be considerably 
lighter...generally less than 5 knots. The downslope flow will subside 
during the middle-morning Thursday...though a few gusts to around 15 knots will 
be possible during the late-morning as the atmosphere mixes out. A 
switch over to upslope westerly is not expected Thursday afternoon. 


Near the Colorado River valley (kyum/kipl/kblh)...drainage flow overnight 
will generally remain light through the period. 


Aviation discussion not updated for amended tafs. 


&& 


Fire weather... 
Friday through Sunday... 
high pressure aloft will continue building north over our area with 
sunny and warmer weather Friday. A flow aloft from the south and 
southwest will bring some cloudiness mainly over southeast 
California and southwest Arizona Saturday...and mainly over 
southwest and south-central Arizona Sunday. However...it will be 
another warm day Saturday and temperatures are only expected to drop 
back slightly Sunday. 


The atmosphere is not expected to be quite as dry...but it will 
still be relatively dry with low afternoon relative humidity values and minimal 
overnight recovery. Somewhat more recovery in relative humidity is expected by 
early Sunday morning. Winds are expected to remain generally light. 


&& 


Psr watches/warnings/advisories... 


Arizona...none. 


California...none. 


&& 


$$ 


National Weather Service Phoenix is on the internet at 


Weather.Gov/Phoenix 


Discussion...estle 
aviation...Hirsch 
fire weather...Ellis