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Area forecast discussion...retransmission 
National Weather Service Flagstaff Arizona 
325 am MST sun Nov 23 2008 


Synopsis...warm and dry conditions will continue across northern 
Arizona through Monday. Then a series of Pacific storm systems will 
begin to move across the southwest Tuesday continuing into the 
Holiday weekend with much cooler temperatures and chances for snow 
in the mountains and rain in the valleys. 


&& 
Discussion...high pressure aloft is forecast to build across the 
southwest states today and Monday before the ridge breaks down and a 
series of cool and wet weather disturbances move across the 
southwest. For today and Monday look for dry conditions and above 
normal daytime temperatures. 


Beginning on Tuesday a close low pressure system takes position off 
the Southern California coast. Between the low off the coast and the 
upper level high to the east of Arizona...a southerly flow sets up 
drawing on subtropical moisture southwest of Baja California. This system will 
likely have the most moisture to work with than compared to the 
other systems later on during the week. For now model forecast 
guidance is still v east r y uncertain in the timing of the low coming 
on shore and then moving east across the southwest. Latest model 
runs delays the system off the coast through Wednesday afternoon. It 
now appears that the best lift...and surge of moisture into this 
system will come on Wednesday evening into Thursday morning. 
Forecast grids have this trend built in...so no additional changes 
need to be made. 


The upper low is forecast to cross the state on Thanksgiving day. It 
appears now that the best precipitation will fall in the upslope areas of 
the Yavapai and Gila County mountains and also along the Mogollon 
Rim and White Mountains. Temperatures aloft will be cold enough to 
bring forecast snow levels down between 6500 to 7000 feet. 


After the first upper low moves out into the Central Plains another 
low will either take position off the California coast per 00z GFS 
solutions or move south southeast through the intermountain west per 
European model (ecmwf). Even though HPC has favored the GFS solutions on this 
one...the European model (ecmwf) on the Long Run has been performing better over the 
GFS. We will lean toward the European model (ecmwf) on this one and Taylor our 
forecast grids to a more intermountain position on the second upper 
level disturbance that comes through the southwest. The 06z GFS has 
begun to show trends toward the European model (ecmwf) which is a good indication 
that the European model (ecmwf) may have a better handle on this weather scenario. We will 
pass along to the day shift that if the 12z models trend to a more 
intermountain position on the second weather disturbance...then we may 
be able to back down on precipitation chances for the Thanksgiving weekend. 
&& 




Aviation...for the 12z package...expect VFR conditions and light 
winds for the next 24 hours. Aviation discussion not updated for 
amendments. 


&& 


Fgz watches/warnings/advisories...none. 


&& 
$$ 


Public.........Tc 
aviation.......kd 


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