Area Forecast Discussion
Issued by NWS Pendleton, OR

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481
FXUS66 KPDT 211800 AAA
AFDPDT

Area Forecast Discussion...Update
National Weather Service Pendleton OR
1000 AM PST Sat Jan 21 2017

Updated Aviation Discussion

.UPDATE...The forecast is pretty much on track. There will be
several weak weather disturbances moving across the forecast area
over the next couple of days with a very slow cooling trend. Despite
the cooling trend most lower elevation precipitation will be in the
form of rain...except possibly a mix at night. In the mountains it
will be snow...but only light amounts and less than winter weather
alert criteria. One system is moving out of the region at this time.
There will be a short break before the next one tonight which will
be followed quickly by another on Sunday and Sunday night. Sunday
has the best chance of snow in the lower elevations but most of the
precipitation will be over by the time the colder air moves into the
forecast area. Temperatures will mainly be in the 30s to lower 40s
lower elevations today cooling to the 20s and 30s by Monday. It will
be about 10-15 degrees cooler in the mountains. It will become
breezy to windy, especially south, and on Sunday. 88

&&

.AVIATION 18z TAFs...Upper level trough pushing through the region
today through Sunday. Some lingering BR around this morning should
gradually improve through the day. CIGS/VIS ranging from MVFR/IFR
this morning should be mostly MVFR or VFR this afternoon. A weaker
disturbance is evident on IR Sat currently moving into Central OR.
This will spread a mixture of rain and wet snow/sleet showers over
most of the region through the day today. Only very light rain
showers or VCSH are expected at KPDT and KALW due to
light...downsloping winds off the Blue Mtns here. Expect a break in
the weather later this evening after about 22/03-05z. Then another,
slightly stronger weather system will move into Central OR and the
Columbia Gorge (KBDN/KRDM/KDLS)after 22/12z. The precipitation will
spread north, reaching the remainder of the TAF sites by about
22/15z. Precip type will be a mixture of SN..RA..PL and perhaps even
some light frz rain. Again, KALW and KPDT should mainly only see
very light rain showers with this system. Winds will remain mostly
under 12 kts at most terminals...however KBDN and KRDM could see
southerly winds gust up to 20 kts at times. 77

&&

.PREV DISCUSSION.../issued 455 AM PST Sat Jan 21 2017/

SHORT TERM...Today through Monday...An upper level trough will
continue to be positioned off the West Coast through the short term
period. There will be occasional surges of moisture kicking out of
the trough and across the Pacific Northwest. The first will occur
this afternoon and evening then followed by another on Sunday.
Precipitation type for both systems will mainly be rain and snow in
the lower elevations and all snow in the mountains. By Monday the
upper level trough moves into the Pacific Northwest but most of the
storm energy and precipitation heads towards California so just
expecting some showers over the mountains which will be on the
decrease.

LONG TERM...Monday night through Friday night...Monday night
through Thursday night a large amplitude mid/upper level ridge of
high pressure builds just offshore thus putting the interior Pacific
Northwest on the eastern flank of the ridge for a dry northerly flow
aloft yielding dry conditions from Monday night through Friday
night. As the ridge builds slowly over the region surface-based
inversion will trap moisture in the boundary layer thus producing
patchy freezing fog and low stratus clouds across the Lower Columbia
Basin.  Polan

&&

.PRELIMINARY POINT TEMPS/POPS...
PDT  43  33  41  26 /  10  40  60  10
ALW  39  34  43  28 /  10  30  70  10
PSC  38  29  38  25 /  10  30  60  10
YKM  38  26  36  21 /  30  60  90  10
HRI  38  29  37  26 /  10  30  60  10
ELN  37  27  35  20 /  30  70  90  10
RDM  40  27  39  21 /  40  50  70  20
LGD  38  32  36  21 /  20  40  70  20
GCD  40  30  39  21 /  30  30  70  20
DLS  38  30  38  28 /  60  40  80  10

&&

.PDT WATCHES/WARNINGS/ADVISORIES...
OR...None.
WA...None.
&&

$$

88/99/77



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