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fxus66 kotx 090542 
afdotx 


Area forecast discussion 
National Weather Service Spokane Washington 
942 PM PST Monday Feb 8 2010 


Synopsis...tthe primary storm track for the first part of the 
week will remain over the southern United States leaving the Pacific 
northwest in a mild and dry...but occasionally foggy...weather 
pattern. A weak low pressure system will have the potential to bring 
mountain snow and valley rain back to the northwest Wednesday night 
through Friday. 




&& 


Discussion... 
tonight...with the extensive stratus deck covering nearly every 
inch of eastern Washington and north Idaho...our biggest challenge will be deciding 
if any large breaks develop in the ceilings. The vsbl satellite 
looper has shown numerous thin spots that have filled in almost 
immediately with cumulus...shutting out any brief glimpse of Blue 
Sky. For tonight...we'll have a higher chance of these breaks 
expanding...especially around the Palouse region and higher 
terrain around the northern Blue Mountains under slowly-increasing southeast winds 
below 800mb. Plan view relative humidity and wind plots show similar results. 
Forecast soundings...however...favor overcast skies all night for 
nearly all zones. If holes develop...it will be these small areas 
that would likely see temperatures drop rapidly and radiation-type fog 
develop. Given the uncertainty...we'll keep a cloudy persistence 
forecast. Light east upslope will promote cold and moist damming along 
and near the east slopes Cascades as winds become NE below 800mb. 
This should be sufficient to generate a few sprinkles. Bz 


Tuesday to Thursday...splitting/stretching systems will continue 
to move across the west...before a more organized system starts 
in Thursday. All models project the short-wave trough currently 
off the coast splits. The brunt moves to Southern California. What tracks north 
skims by the northern County Warning Area late Tuesday into Wednesday am. It brings very weak 
lift and instability. Tack on a west to SW flow starting Tuesday nt for 
some orographic lift...this still only supports low probability of precipitation over the 
north to NE mountains even then precipitation amounts look very light. Another 
short-wave breaks across the region later Wednesday. It is stretched... 
but remains more intact than the first. This will bring a slightly 
better chance of precipitation to the area...but still precipitation 
amounts look light. By Thursday a warm front leads a more organized 
and wetter system. It moves in from the west-southwest...expanding a higher 
chance of precipitation across the area. Snow levels will be near valley 
floors during the night/early morning hours. Snow levels rise to 
between 2-3.5kft Tuesday and Wednesday PM and about 2.5-4kft Thursday PM. Outside 
of the mountains...the best chance for accumulating snow will be near 
the Cascades and Canadian border on Thursday...including the 
Okanogan Valley...where colder air will be more difficult to 
scour. Right now only light accumulations are projected. Yet if 
precipitation moves in faster than temperatures can rise...those 
areas could see a little more in the way of accumulations. 
Temperatures will be near to slightly above normal. Low clouds and 
patchy fog remain in the forecast...especially in the night/morning 
hours. /Jcote 


Thursday night through Monday...there is good model agreement with 
a Pacific system moving through Thursday ngt/Friday. Snow levels look 
to be 2500-3500 feet near the Canadian border and 5000 feet over 
the Blue Mountains thus a mainly valley rain and mountain snow event 
is expected. While models support high probability of precipitation Thursday night/Friday the 
degree of how much the system splits as it moves through varies. 
For now given current split flow pattern...will lean more towards 
the weaker GFS solution compared to the more consolidated European model (ecmwf) 
solution with widespread light precipitation amounts expected. 


A short wave ridge brings drier conditions Friday night before a 
stronger system nears for the weekend. Models indicate a moist 
baroclinic boundary for Saturday and Sunday either over central 
and northern Washington per European model (ecmwf)...or over southern British 
Columbia per GFS. The Canadian and UKMET extension tend to favor 
the GFS solution. Meanwhile increasing 850mb winds out of the 
west-southwest will favor downslope flow off the Cascades reducing 
the chances of precipitation in the Moses Lake and Wenatchee areas. All 
these factors favor the highest precipitation chances near the 
Canadian border and in the mountains. Model 850mb and 1000-850mb 
thicknesses support rain in the valleys and a mix of rain and snow 
in the mountains. Then as the cold front comes through snow levels 
fall for Sunday night and Monday but precipitation chances will also be 
decreasing as drier air filters in behind the front. Temperatures 
will be above normal through the extended period. Jw 


&& 


Aviation... 


Status quo will be the general rule over the next 24 hours at most 
sites. Stubborn stratus will continue to dominate most sites...with 
only slight lowering overnight likely in most locales. However...for 
the most part...stratus should remain MVFR or higher away from keat. 
/Fries 


&& 


Preliminary point temps/pops... 
Spokane 28 42 30 42 31 43 / 0 0 10 10 20 50 
Coeur D'Alene 29 42 30 41 31 42 / 0 10 10 20 20 50 
Pullman 31 42 31 43 32 45 / 0 0 10 10 20 50 
Lewiston 34 47 33 48 35 49 / 0 0 0 10 20 30 
Colville 31 42 27 41 29 42 / 0 10 10 20 20 50 
Sandpoint 30 41 29 39 30 41 / 0 10 10 20 20 50 
Kellogg 31 40 27 38 29 40 / 0 10 10 30 40 50 
Moses Lake 35 45 31 47 32 47 / 0 0 0 0 20 40 
Wenatchee 35 43 31 42 31 43 / 0 10 0 10 20 40 
Omak 34 42 28 41 31 40 / 0 0 0 10 20 40 


&& 


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


$$ 

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