918 
fxus65 ktwc 200330 
afdtwc 


Area forecast discussion 
National Weather Service Tucson Arizona 
830 PM MST Wednesday Nov 19 2008 


Synopsis...dry and warm under high pressure. The high pressure 
system is expected to weaken during the latter part of the week into 
next week. This will lead to some increase in cloudiness and a slow 
cooling trend. 


&& 


Discussion...infrared satellite imagery shows clear skies across the 
Desert Southwest with a batch of high cirrus clouds moving into 
California from the Pacific. Skies should remain mostly clear for 
the remainder of the night. 


This evenings ktwc sounding continues to show a very dry airmass in 
place with a precipitable water of only 0.04 inches. Relative humidity values fell 
into the single digits to low teens across much of the area this 
afternoon. High temperatures this afternoon ranged from 70 degrees at 
Bisbee to 90 degrees at Organ Pipe Cactus National Monument. The high 
at the Tucson International Airport was 85 degrees...which is 14 degrees above 
normal for this date...and 3 degrees shy of the record high for this 
date. 


As of 03z (8 PM mst)...temperatures ranged from the upper 40s at 
Douglas to 67 degrees at the Tucson International Airport. Will make some 
adjustments to the hourly temperature grids to better reflect 
ongoing trends and will update the point forecast matrix product. 
Otherwise...the forecast seems to be on track...so no significant 
changes are planned at this time. 


&& 


Aviation...mostly clear skies will prevail across Southeast Arizona tonight 
with any clouds of significance at or above 20k feet above ground level. Surface 
winds generally light from the southeast overnight...becoming 
northerly/northwesterly 5-15 kts Thursday afternoon. Aviation discussion not 
amended for taf amendments. 


&& 


Previous discussion...still looking for the ridge to break down into 
zonal flow with systems topping off the geometry through northern 
tier states late in the week. A few degrees of cooling... but still 
well above averages as actual height and thickness values will be 
slow to respond. No real chance at weather or significant pattern 
change until around the middle and second half of next week when we 
could see a southern branch split as a chaotic pattern comes in off 
the Pacific. Presumably a cooling trend with an increase in cloud 
cover...but lots of uncertainties remain about timing and trajectory 
of any precipitation features. 


&& 


Twc watches/warnings/advisories...none. 


$$ 


Mollere 


Weather.Gov/Tucson