Area forecast discussion...updated aviation discussion 
National Weather Service Pendleton or 
920 am PST Monday Dec 22 2014 

Update...the latest radar was showing a few showers lingering in 
the area mountains in response to a persistent upslope flow. 
Meanwhile a ridge of high pressure is forecast to build into the 
region today with decreasing clouds and showers expected. Afternoon 
high temperatures were adjusted some and the present short term forecast 
appears on track for now. 


Previous disc... /issued 345 am PST Monday Dec 22 2014/ 

Short through Wednesday...a weather system that 
brought abundant rainfall and wind is now moving away from the County Warning Area 
and is being replaced by high pressure aloft. There are still some 
showers over the northeast Oregon/southeast Washington mountains as 
well as the east slopes of the Cascades early this morning. These 
should decrease today as the day progresses. High pressure will 
amplify tonight and Tuesday with dry conditions and mild 
temperatures. Winds should also be light during this period. Patchy 
fog will develop over the lower Columbia Basin and adjacent valley 
areas tonight and Tuesday morning...especially along the Columbia 
and Yakima rivers. The next weather system of concern will begin to 
spread moisture into the Cascades late Tuesday and Tuesday night. It 
will continue to spread eastward on Wednesday with likely probability of precipitation in 
most areas by Wednesday afternoon. Snow levels will be fairly high 
above 5000 feet in southern areas...and near 2500 feet in far 
northwest Kittitas County...along the Cascade east slopes. Thus 
there may be snow along the Washington Cascade east slopes...but 
elsewhere this looks to be primarily a rain event with snow only on 
the highest peaks on Christmas evening. May eventually need winter 
weather highlights for the Washington Cascade east slopes but it is 
still too soon for that and there is still too much uncertainty of 
snow amounts. This system will continue into the extended period 
beginning overnight Christmas evening. As previously mentioned 
conditions will be mild with maximum temperature readings mostly in 
the 40s to lower 50s today and Tuesday and then gradually cooling 
beginning Wednesday as cooler air moves into the region. It will 
also become locally breezy Wednesday afternoon and 
night...especially in the mountains. 88 

Long term...Wednesday night through Monday...a trough will move in 
Wednesday night with a chance of rain and mountain snow across the 
area. The trough will exit to the east on Thursday with just a 
chance of rain and snow confined mainly to the mountains. A 
northwesterly flow into the area Thursday night through Friday night 
will keep the area dry aside from a slight chance of snow in the 
mountains Thursday night. After that, another trough will move into 
the area but the GFS and European model (ecmwf) disagree about the timing. The GFS 
brings it through on Saturday while the European model (ecmwf) brings it through on 
Saturday night. Have added a slight chance of lower elevation rain 
and mountain snow to both periods for now until models come into 
better agreement. The GFS moves the trough east on Sunday then has 
our area under an offshore ridge Sunday night and Monday. The European model (ecmwf) 
keeps the trough further west with a northerly flow into the area. 
This will give a slight chance of rain and snow in the lower 
elevations and a chance of snow in the mountains Sunday and Sunday 
night then tapering off on Monday. For now have leaned towards the 
European model (ecmwf) solution. Temperatures will be in the middle 30s to middle 40s 
Thursday through Saturday then cool a few degrees on Sunday and 
Monday. Perry 

Aviation...18z tafs...VFR conditions are expected over the next 24 
hours. Skies will be broken to overcast today and tonight with 
ceilings mainly above 5000 feet above ground level. Winds will remain below 15 kts 
for the next 24 hours. 93 


Preliminary point temps/pops... 
PDT 47 32 49 35 / 10 10 10 10 
alw 48 33 47 37 / 10 0 10 10 
psc 50 32 46 36 / 0 10 10 10 
ykm 45 32 43 34 / 10 10 10 30 
hri 49 34 47 37 / 10 10 10 10 
eln 42 31 41 33 / 10 10 10 30 
rdm 48 32 52 34 / 20 10 10 10 
lgd 43 30 43 34 / 20 10 10 10 
gcd 44 35 45 34 / 30 10 10 10 
dls 51 38 48 39 / 10 10 20 20 


PDT watches/warnings/advisories... 

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