Weather

837 
fxus65 ktwc 070900 
afdtwc 


Area forecast discussion 
National Weather Service Tucson Arizona 
200 am MST sun Sep 7 2008 


Synopsis...shower and thunderstorm chances will gradually increase 
Sunday and through most of next week as moisture returns to 
Southeast Arizona. Hot afternoon temperatures continue on 
Sunday...before a cooling trend sends temperatures below normal by 
the middle of next week. 


&& 


Discussion...the hot temperatures seen on Saturday will continue on 
Sunday...but relief is on the way with a nice cooling trend sending 
temperatures below normal by the middle of this week. High 
temperatures still close to 100 in Tucson Sunday...but that will be 
the last of the triple digit heat for awhile. 00z ktwc sounding 
still dry with a precipitable water of only 0.70 inch...but this is expected to 
slowly climb Sunday and into next week as moisture slowly returns to 
Southeast Arizona. Already seeing some evidence of moisture 
returning this morning with some midlevel cloudiness...even a few 
showers and lightning bolts near Green Valley and North Komelik. 
Will likely see increased shower and thunderstorm activity this 
afternoon thanks to this moisture increase...especially from the 
Tucson metropolitan area eastward on the higher terrain. 00z NAM suggests 
dewpoints returning to the 50s today...along with better instability 
/cape near 600 j/kg and Li near -4c/. Inherited slight chance probability of precipitation 
should cover the situation...although we should definitely see an 
uptick today over what was seen on Saturday. 


Some rather significant changes made to next week's forecast 
tonight. 00z GFS and European model (ecmwf) show temperatures on a steady decline 
Monday through Thursday...with high temperatures well below normal 
by Wednesday. We followed suit and dropped the temperature grids 
about 3-5 degrees for the period Tuesday through Thursday. The low 
pressure trough west of Arizona will ensure a steady moisture supply 
from the south...helping to keep temperatures down and probability of precipitation up. In 
fact...we raised probability of precipitation into the low chance category from roughly 
Tucson eastward for Tuesday and Wednesday...but several model pop 
fields are much higher than that...and later shifts may have to 
raise them even higher. One wildcard that will have to be monitored 
is newly christened Tropical Storm Lowell in the eastern Pacific. 
Southwest flow ahead of the low pressure to our west may get some of 
Lowell's moisture involved as well. The bottom line is it should be 
a rather active week for showers and thunderstorms for Southeast 
Arizona...and that we haven't seen the last of the monsoon 2008 
season just yet. 


&& 


Aviation...mostly clear skies expected 12z Sunday. Cumulus/towering 
cumulus developing on the higher terrain beginning near 18z...with 
isolated showers and thunderstorms expected from ktus eastward this 
afternoon and evening. Light diurnally driven winds outside of any 
thunderstorms. Aviation discussion not updated for taf amendments. 


&& 


Twc watches/warnings/advisories...none. 


$$ 


Turner 


Weather.Gov/Tucson