760 
fxus66 kotx 200530 
afdotx 


Area forecast discussion 
National Weather Service Spokane Washington 
1030 PM PDT Tuesday Aug 19 2008 


Synopsis... 
a deep and unusually strong upper level trough will move over the 
inland northwest Wednesday...bringing wet weather and cooler than 
normal conditions to the area through Thursday. 




&& 


Discussion... 
rest of tonight...afternoon showers and thunderstorms are tapering 
off this evening with lingering activity confined over the 
northeastern portions of the forecast area. Persistent showers and 
storms over the north Cascades of Okanogan County tallied up some 
very impressive summertime rain fall amounts...with Aeneas RAWS 
reporting 1.24 inches in the 6 hour period ending at 7 PM...and 
Conconully coop report of 1.4 inches as of 7 PM. While no 
significant flood problems have been reported...have issued a 
small stream flood advisory for Okanogan County with saturated 
ground and more rain expected over the next 12 hours with the 
strong incoming front. 


Speaking of this front...radar and satellite indicate the front 
has reached the coast and will cross the Cascades overnight 
tonight. This front is unusually strong for this time of 
year...and fueled by a deep fetch of Pacific moisture which will 
be assisted in enhancement into precipitation by strong jet 
divergence and differential positive vorticity advection increasing with height as it moves 
through the region from 06z tonight through 18z Wednesday. The 
strength of the lift...massive moisture feed...and lack of 
westerly flow in the middle levels to promote downslope...will allow 
at least measurable and possibly significant rain amounts even in 
the normally dry Cascades Lee zones. Thus...forecast area still on 
track for a wet Wednesday morning at least...with onset of this 
rain expected overnight tonight over the Cascades and western 
zones...moving into the eastern zones around daybreak through 
early afternoon. Minor update to zone forecast to refine timing 
and probability of precipitation and tweak expected overnight low temperatures. Minor 
update to state forecast product expected as well. /Fugazzi 


&& 


Aviation... 
a wet Pacific system will spread heavy low VFR and areas of MVFR 
ceilings with rain over the Cascades and western basin from 06z to 
12z tonight and into the Idaho Panhandle by 15z Wednesday. This will 
create widespread mountain obscurations north and east of the 
basin...and MVFR and possible IFR ceilings at the kgeg...ksff and 
kcoe taf sites until 18z. A relative break period feturing scattered 
showers over the basin and isolated thunderstorms over the Idaho 
Panhandle during the afternoon will deteriorate into widespread rain 
showers from 00z to 06z Thursday as a sacond wave passes through. 




&& 


Preliminary point temps/pops... 
Spokane 55 68 55 65 49 78 / 20 80 60 50 20 0 
Coeur D'Alene 54 64 53 61 47 77 / 20 90 60 50 20 0 
Pullman 55 69 53 66 42 77 / 10 70 60 50 20 0 
Lewiston 61 75 60 72 54 84 / 10 50 50 40 20 0 
Colville 52 67 50 69 41 82 / 60 80 70 50 20 0 
Sandpoint 53 62 51 58 42 76 / 20 80 70 60 30 0 
Kellogg 53 63 51 59 45 76 / 20 80 80 60 30 10 
Moses Lake 59 73 54 74 48 82 / 50 50 30 20 10 0 
Wenatchee 58 72 56 76 55 83 / 70 50 40 20 10 0 
Omak 52 73 52 78 48 83 / 70 70 40 20 10 0 


&& 


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


$$