Weather

418 
fxus66 kotx 070929 
afdotx 


Area forecast discussion 
National Weather Service Spokane Washington 
229 am PDT sun Sep 7 2008 


Synopsis... 
the inland northwest will be under the influence of high pressure 
Sunday and Monday. The next low pressure system expected to affect 
the region will arrive late in the day on Tuesday...bringing an 
increase in clouds and locally windy conditions. 




&& 


Discussion... 


Today and tonight...we are beginning to see the start of a pattern 
change early this morning. The eastern Pacific Ridge is breaking 
down and the northwest flow that has been the predominant flow 
pattern over the last week will break down over the next 24 hours. 
Water vapor imagery at 09z shows a strong upper level trough 
entering the Gulf of Alaska. The darkening on the water vapor 
imagery nearing 150w will lead to the demise of the the expansive 
upper level ridge over the eastern Pacific by tonight. Surface 
pressure charts are already showing that the upper ridge is moving 
east. Pressure falls are subtle over western Washington...but are 
an indication that the upper ridge is moving east and that low 
level easterly flow has begun. Even though a pattern change is 
underway...there will be little change in the sensible weather 
over the inland northwest today. Very little change is expected in 
the low level thermal fields...so high temperatures today will be 
comparable to the last couple of days. We will probably see fewer 
clouds today than previous days. The dissipation of altocumulus 
over southern British Columbia and eastern Washington is another 
indication that the upper ridge is on the move. We expect that the 
8-10 thousand foot cloud deck in the Wenatchee and Moses Lake 
areas will continue to dissipate this morning...yielding a mostly 
sunny day for all of eastern Washington. /Gkoch 


Monday through Saturday...fairly consistent solution in the models 
is resolved in higher probability of precipitation for Tuesday afternoon into early 
Wednesday morning as a well developed low pressure system takes 
the northwest to southeast oriented trajectory to the east of the 
longwave ridge axis off the coast. After the low drops through the 
ridge has a flop over/extreme positive tilt to it allowing for 
improvement to a benign forecast for whats left of Wednesday and 
through Thursday. Then for next weekend...the ridge pattern then 
shows enough retrogression of the axis back into the Gulf of 
Alaska to allow a return to an active northwest flow. So...we may 
have to reintroduce probability of precipitation...mainly for the mountains...for fairly 
low quantitative precipitation forecast spitty showers similar in nature to those which have 
occurred over this weekend. /Pelatti 


&& 


Aviation... 
VFR conditions through 06z Monday. Upper level ridge will slowly 
build over the region...however somewhat unsettled northwest flow will 
continue to produce the threat of sprinkles through the night. Most 
of sprinkles will avoid the taf sites...however if one were to 
impact a taf site...the best chances will occur at kmwh through 
08z. Fx 




&& 


Preliminary point temps/pops... 
Spokane 74 46 78 49 79 47 / 0 0 0 0 0 20 
Coeur D'Alene 73 43 77 45 77 45 / 0 0 0 0 0 20 
Pullman 74 43 77 44 78 45 / 0 0 0 0 0 10 
Lewiston 81 51 83 54 84 54 / 0 0 0 0 0 10 
Colville 78 40 81 45 81 44 / 0 0 0 0 0 30 
Sandpoint 70 38 73 43 75 43 / 10 0 0 0 20 30 
Kellogg 69 42 74 48 75 43 / 10 0 0 0 0 30 
Moses Lake 81 48 83 51 85 49 / 0 0 0 0 0 0 
Wenatchee 81 52 82 57 84 53 / 0 0 0 0 0 0 
Omak 81 47 83 50 84 49 / 0 0 0 0 0 0 


&& 


Otx watches/warnings/advisories... 
Idaho...none. 
Washington...none. 
&& 


$$