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Next 12 Hours

Forecast data from the National Digital Forecast Database.

5 Day Forecast

• Monday
• 
• High: 40 °
• Low: 25 °
• Snow Showers

• Tuesday
• 
• High: 38 °
• Low: 25 °
• Chance of Snow

• Wednesday
• 
• High: 40 °
• Low: 23 °
• Chance of Snow

• Thursday
• 
• High: 43 °
• Low: 27 °
• Chance of Snow

• Friday
• 
• High: 43 °
• Low: 27 °
• Chance of Snow

Area forecast discussion...updated 
National Weather Service Pendleton or 
911 PM PST sun Feb 12 2012 


Updated for evening discussion and aviation discussion 


Update...current forecast remains on track with a few slight 
adjustments. Latest observation have shown dewpoints on the rise and are 
several degrees above some of the forecasted low temperatures. The 
frontal system may lower these temperatures by morning...but for now 
have bumped up the overnight lows. Have also raised snow levels 
slightly for areas not expected to get below freezing. This mainly 
affects the slight chance of snow that was forecast over the lower 
Columbia Basin and the foothills of the Blue Mountains. Expect the 
precipitation over these areas to be in the form of rain. For now 
it appears that snow levels will be right around 3000 feet. Some 
areas from 2000-3000 feet may see a rain snow mix or snow due to the 
wet bulb affect. But surface temperatures are expected to be above 
freezing at these elevations...so any snow will likely melt on 
contact with the surface. Weber 




&& 


Aviation...06z tafs...a cirrus band continues to move in from the 
west this evening ahead of the next weather disturbance. Expect 
middle-level clouds to increase overnight. Rain will begin moving 
into kdls and a rain snow mix into krdm...with snow expected at kbdn 
around 06-09z. At this point ceilings may lower to MVFR or even some 
isolated IFR conditions. Kpdt...kpsc and kalw should not see 
showers until around 12z. Stratiform rain and snow will become more 
showery and begin to diminish Monday afternoon. Surface winds will 
be less than 10 kts. Weber 




&& 


Previous discussion... /issued 330 PM PST sun Feb 12 2012/ 


Short term...tonight through Wednesday. Two main low pressure 
systems will bring periods of snow and rain through the short term 
period. The first upper level trough is developing along 133w. The 
trough will shear apart with the strongest energy diving south along 
the Oregon coast tonight and into California Monday morning. Very 
few changes were made to tonight's forecast. Precipitation will 
spread east of the Cascades tonight and will be as far east as the 
lower Columbia Basin and the John Day basin by 4 am Monday morning. 
The low will strengthen into a closed circulation near Montana Shasta 
Monday morning...circulating moisture across the southern half of 
Oregon. The weaker northern portion of the split trough will bring 
light snow to the Washington Cascades Monday. Will keep 30-40 percent 
probability of precipitation for the NE third of the forecast area on Monday. Precipitation 
will taper off Monday night with the exception of the northern blues 
and Wallowa County. The northern shortwave will track across 
northern Washington and dive southeast as it approaches the Idaho 
Panhandle. Models are hinting at enhanced precipitation over our NE zones so 
will indicate 40-60 percent chance of snow Monday night. Snow levels 
are forecast to lower to near 2500 feet Monday then 1500-2000 feet 
Monday night. No significant accumulations are expected...thus no 
winter highlights are in effect. 2-4 inches of snow are expected 
along the east slopes of the Oregon Cascades late tonight through 
Monday afternoon. These amounts are just under advisory criteria. 


The next low is not handled very well by models...making for a 
challenging forecast on pops, qpf, and snow amounts. The European model (ecmwf) 
seems to have the best run-to-run continuity...but overall 
consistency has been less than desirable in all model runs. The 18z 
NAM and 12z Canadian is approx. 400 miles farther NE with the low on 
Tuesday morning and are also advertising an open trough. Will lean 
towards the 12z European model (ecmwf) and will anticipate that the closed system 
will take a similar track as tonight's trough and will move south 
along the Oregon coast on Tuesday then over northern California late 
Tuesday night. This will be followed by a shortwave ridge and drier 
conditions on Wednesday. I decided to go a little conservative for 
Tuesday night and Wednesday and not make many changes to the current 
forecast. If models are consistent at dry conditions on 
Wednesday...the 20-40 percent probability of precipitation in the grids for eastern Oregon and 
southeast Washington could be lowered or removed. Wister 


Long term...Wednesday night through Sunday...a ridge of high 
pressure will remain over the area on Wednesday night for dry 
conditions and cool overnight lows. Then on Thursday a weather 
disturbance will move through the top of the ridge spreading rain 
and mountain snow eastward. The high pressure ridge should 
restrengthen on Thursday night into Friday but mountain showers may 
persist due to orographic lift. A deep closed low will approach the 
Pacific northwest on Friday night and Saturday. Model details are 
inconsistent but abundant moisture and lowering snow levels could 
lead to several inches of snow in the higher terrain. Unsettled 
weather is likely to continue on Sunday as well. Temperatures 
throughout the period will be near seasonal normals with daytime 
highs in the 40s to near 50 degrees. Locally breezy winds will be 
possible Friday through the weekend. Trimarco 


&& 


Preliminary point temps/pops... 
PDT 29 44 32 44 / 20 30 30 20 
alw 34 47 35 45 / 10 30 30 20 
psc 36 48 31 47 / 20 30 20 20 
ykm 34 43 26 44 / 40 50 10 20 
hri 31 47 30 46 / 20 30 20 20 
eln 32 42 27 42 / 40 50 10 20 
rdm 31 43 25 42 / 70 60 30 20 
lgd 28 44 30 43 / 10 30 40 30 
gcd 29 44 28 41 / 20 50 30 20 
dls 38 46 33 46 / 60 50 20 20 


&& 


PDT watches/warnings/advisories... 
or...none. 
Washington...none. 
&& 


Threat index 
Monday : green 
Tuesday : green 
Wednesday : green 


Green: none or limited need for watches, warnings, or advisories. 
Yellow: a few watches, warnings, or advisories possible or in effect. 
Red: numerous watches, warnings, or advisories possible or in effect. 


For additional weather information, check our web site at... 
www.Weather.Gov/Pendleton 


$$ 


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