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fxus66 kotx 231131 
afdotx 


Area forecast discussion 
National Weather Service Spokane Washington 
330 am PST sun Nov 23 2008 


Synopsis... 
a strong ridge of high pressure will bring mainly clear skies to 
the inland northwest today and tomorrow. High pressure will weaken 
on Tuesday...but the storm track will remain well north of the 
region through the end of the week. Dry and seasonably cool 
weather is expected to persist until the weekend. 




&& 


Discussion... 
issued 239 am 
today and tonight...early morning water vapor imagery shows an 
upper level ridge building along the Washington/Oregon coast. This 
ridge will amplify over the inland northwest today and be the 
predominant weather feature over the western U.S. Through early in 
the week. By late tonight...a split flow pattern will develop. The 
southern branch of the polar jet will form a closed low off the 
California coast...and a weak northern branch will remain over 
central British Columbia. This split flow regime is forecast to 
persist through the end of the week. 


For this morning...fog will be patchy at best in the Spokane 
area. Surface dewpoints have fallen through the night...and with 
very dry air above the boundary layer...the fog that does develop 
will be shallow and short lived. The valleys north and east of the 
metropolitan will likely have patchy shallow fog as well. Further west...we 
will be keeping an eye on the potential for fog and low stratus 
this morning along the east slopes and into the Okanogan Valley. 
The 06z runs of the NAM and GFS are forecasting light easterly 
upslope winds into the Chelan...Brewster...and Omak areas. 
Boundary layer moisture on the models looks marginal...but the MOS 
guidance is hinting at the development of fog and stratus. Current 
satellite imagery does not suggest any fog development yet...and 
my confidence in the low level moisture fields from the models 
isn't that high. I have retained the mostly sunny forecast for 
these areas today...but will maintain a close eye on conditions 
this morning. 


Temperatures at 850mb will warm by 2c-4c today under the 
amplifying ridge...but poor mixing today will keep temperatures at 
or below yesterday's readings. Ridges and middle-slopes will be the 
exception...especially over the Idaho Panhandle where elevations 
above 4000 feet will have a good chance to break the low level 
inversion. 


Monday through Wednesday...by 12z Monday the system currently 
amplifying and dropping southward near 150w will have closed off 
and be on a Beeline toward Southern California. The remnant energy 
left in the northern stream as the aforementioned system splits 
off southward will gradually shear out and advance toward the area 
per the GFS/European model (ecmwf) consensus by Tuesday night or Wednesday. The 00z 
NAM took a much less split flow approach...and with no support 
from any other guidance including the Canadian or UKMET or even a 
single gefs member...the forecast has been total rid of any 
influence of the NAM. The net result is basically a dry forecast 
from Monday Onward with the very weak and moisture starved 
dynamics resulting in little outside of the Cascade crest as the 
wave passes Wednesday. 


While the system passing Wednesday may stir up the boundary layer 
a bit...both before and after that interlude...mixing looks very 
weak. Because of the poor mixing...air stagnation could become a 
concern again by the end of the week. However...air quality 
concerns aside...a dry and a bit warmer than normal forecast is 
the general idea from Monday through the end of the week. /Fries 


&& 


Aviation... 
some shallow fog will be possible in the Spokane and Coeur D'Alene 
areas through 16z. Patchy fog will also be possible in the valleys 
north of Spokane toward Colville...Kettle Falls...and Sandpoint. 
Given the very dry airmass...any fog that does develop should 
dissipate within a couple hours after sunrise. /Gkoch 




&& 


Preliminary point temps/pops... 
Spokane 40 24 41 24 41 26 / 0 0 0 0 0 0 
Coeur D'Alene 42 27 42 25 44 28 / 0 0 0 0 0 0 
Pullman 45 30 45 28 45 30 / 0 0 0 0 0 0 
Lewiston 43 30 47 30 46 33 / 0 0 0 0 0 0 
Colville 43 22 41 23 41 26 / 0 0 0 0 0 10 
Sandpoint 40 23 41 22 43 26 / 0 0 0 0 0 10 
Kellogg 40 29 41 29 44 29 / 0 0 0 0 0 10 
Moses Lake 42 24 42 26 43 28 / 0 0 0 0 10 10 
Wenatchee 42 27 44 29 44 31 / 0 0 0 0 0 0 
Omak 38 23 41 26 42 28 / 0 0 0 0 0 0 


&& 


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


$$