Area Forecast Discussion
Issued by NWS Pendleton, OR

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FXUS66 KPDT 202150
AFDPDT

Area Forecast Discussion
National Weather Service Pendleton OR
150 PM PST Sat Jan 20 2018

.SHORT TERM...Tonight through Tuesday. A weak short wave is
exiting the region into Idaho this afternoon with gradual
clearing. This will likely be short lived as satellite indicates
clouds will be increasing again later this evening and overnight.
This in response to a large upper level low approaching southern
BC and the Pacific northwest. The low has a fairly significant
fetch of moisture just its south as well. The low will push across
the area on Sunday along with a cold front. This will bring rain
and higher elevation snow. Highest accumulations are expected
along the Cascades where frontal boundary and cool onshore flow
will result in a prolonged period of snow. Have issued snow
advisories for this. The northeast Oregon mountains will also
receive some accumulating snow but less than the Cascades.
Precipitation will taper down Sunday night. With a surface low
passing by to the north expect increasing southerly winds
overnight becoming locally breezy to windy Sunday. These will
diminishing overnight. A westerly flow aloft returns Monday with
snow showers for the Cascades and mostly cloudy skies for the
remainder of the forecast area. The next upper low will be
approaching the west coast Monday night into Tuesday. A warm front
will bring rain and mountain snow on Tue. 94

.LONG TERM...Tuesday night through Saturday...Medium range models
continue to be in good agreement, with a progressive weather pattern
through the long term. A warm front will enter the region from the
south Tuesday night/early Wednesday, with the systems cold front
sweeping across Wednesday night/Thursday, exiting to the east
Thursday night. Sufficient moisture and mid level support exists for
likely/categorical PoPs for most areas Tuesday night. The flow will
turn to the W/NW behind the cold front Thursday, with high PoPs
continuing for the mountains and a bit less coverage for the lower
elevations with some precip shadowing. Snow levels will rise to 3000-
5000 feet by Wednesday, falling to 1500-2500 feet by Thursday as
cold air advection occurs. Several inches of snow accumulation will
be likely for the mountains, with winter highlights possible. Zonal
flow with upslope snow showers across the mountains will prevail
Friday, with the next system progged to enter the region Saturday.
Given the typical model differences, will use mainly chance PoPs
for now. Above normal temperatures will prevail for midweek, cooling
to near/slightly below normal for Friday/Saturday.

.AVIATION...00Z TAFs...VFR conditions will generally prevail for the next
24 hours, with cloud ceilings gradually lowering to 4000-6000 feet.
Precip coverage too limited for mention through Sunday morning, with
rain affecting most sites after 18Z with MVFR conditions possible. Winds
will generally remain 12 KT or less through tonight, with winds increasing
to 10-20 KT by Sunday afternoon.

&&

.PRELIMINARY POINT TEMPS/POPS...
PDT  31  47  34  45 /  10  80  70  10
ALW  33  49  36  46 /  10  80  70  10
PSC  32  47  34  47 /  10  80  50  10
YKM  29  42  29  44 /  10  60  30  10
HRI  31  47  34  48 /  10  80  50  10
ELN  28  38  27  40 /  10  70  30  10
RDM  27  46  28  42 /  10  60  40  10
LGD  26  38  30  42 /  20  60  80  20
GCD  24  39  29  39 /  10  80  60  20
DLS  33  45  34  46 /  10  70  50  20

&&

.PDT WATCHES/WARNINGS/ADVISORIES...
OR...Winter Weather Advisory from 4 AM to 10 PM PST Sunday for ORZ509.

     Wind Advisory from 7 AM to 10 PM PST Sunday for ORZ049.

WA...Winter Weather Advisory from 4 AM to 10 PM PST Sunday for WAZ520.

&&

$$

94/80/80


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