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fxus66 kotx 191139 
afdotx 


Area forecast discussion 
National Weather Service Spokane Washington 
439 am PDT Friday Mar 19 2010 


Synopsis... 
high pressure will build into the region through Saturday for dry 
conditions. Temperatures will warm several degrees on Saturday as 
the ridge moves overhead. The next system will arrive on Sunday 
and Monday bringing a chance for mostly rain in the valleys and 
snow in the mountains. 






&& 


Discussion... 
today and tonight...our weather pattern will continue to be 
dominated by a strong ridge of high pressure currently centered 
along 130 west latitude in the eastern Pacific. This feature will slowly 
progress farther eastward through the day today. A dry north to 
northeast flow pattern over the region will keep skies relatively 
clear with possibly some high clouds passing through from west to 
east over the northern zones. Temperatures will be similar to 
yesterday with a slight warming of a couple degrees reflected in 
the forecast. /Svh 


Saturday through Monday...again tonight the models seem to have a 
similar handle on the large scale features through the middle 
portion of the forecast. Also once again...the GFS has trended 
toward the quicker end of guidance...with the European model (ecmwf) lagging most 
of the other global solutions. Given recent trends and the fact 
that the gefs mean solution is trending slower than the 
operational GFS...a slower evolution is preferred for this 
forecast package through the weekend. 


In following a slower solution...dry conditions under a 
deamplifying ridge prevail through most of the area through Sunday 
morning. Under the ridge with 500 mb heights touching 567 dam and 
850 mb temperatures running around +7c per the model 
consensus...Saturday looks to be the warmest day of the weekend. 
Warming on Saturday will be helped out by abundant sunshine 
through a very dry column. In addition...850 mb flow of around 15 
kts and dry adiabatic lapse rates below about 800 mb per BUFKIT 
soundings suggest temperatures should again approach or surpass 
60f across large portions of the area...which Spokane itself even 
nears 60f yet again. 


However...the springtime party cannot last forever this time of 
the year. Nice weather gradually comes to an end on Sunday as the 
ridge loses its grip on the area and off shore troughing moves 
into the picture. Southwesterly flow will increase Pacific 
moisture flow into the area as 290-300k layer mixing ratios 
surpass 3 g/kg. Lift by Sunday afternoon will be largely 
controlled by an anti-cyclonically curved jet streak crossing the 
area during the afternoon with its right entrance region focusing 
lift across the Idaho Panhandle. In association with this 
jetlet...a negatively-tilted short wave trough with a formidable 
vorticity maximum running the base of the trough runs through the area. As 
a result...lift and hence probability of precipitation are maximized in that region 
through the afternoon hours. A second jet streak approaches from 
the southwest...pinning much the same area in its left exit region 
through the night Sunday night...so probability of precipitation remain elevated across 
the eastern zones through the time. 


Temperatures fall as probability of precipitation increase Sunday into Monday. Large scale 
troughing allows colder air aloft to sag into the northwestern 
U.S. Temperatures at 850 mb fall from around +7c on Saturday...to 
around +4c on Sunday...to near 0c Monday. As a 
result...temperatures look to fall back into the upper 40s to 
start the new work week. 


In the extended forecast...troughing looks to head east of the 
area by Tuesday with conditions markedly drying into mid-week. As 
this occurs...temperatures should moderate...however another 
system looks headed toward the coast by Thursday with cooler air 
and showers again returning. /Fries 


&& 


Aviation... 
high pressure continues to dominate the weather pattern over the 
inland northwest...resulting in weak surface winds and large scale 
subsidence. Expect VFR conditions through 12z with mostly clear 
skies except for some flat cumulus possible over the Idaho Panhandle mountains 
this afternoon. /Svh 




&& 


Preliminary point temps/pops... 
Spokane 53 26 58 34 54 35 / 0 0 0 0 20 30 
Coeur D'Alene 53 25 58 32 54 33 / 0 0 0 0 30 30 
Pullman 53 27 61 35 57 34 / 0 0 0 0 40 40 
Lewiston 58 31 66 39 61 39 / 0 0 0 0 30 30 
Colville 56 26 59 30 56 33 / 0 0 0 0 30 30 
Sandpoint 53 27 55 29 51 31 / 0 0 0 0 30 40 
Kellogg 53 28 57 33 54 33 / 0 0 0 0 40 50 
Moses Lake 59 28 62 36 58 35 / 0 0 0 0 10 10 
Wenatchee 57 31 60 38 56 37 / 0 0 0 10 10 20 
Omak 57 28 60 32 57 33 / 0 0 0 10 20 20 


&& 


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


$$