Area Forecast Discussion
Issued by NWS Pendleton, OR

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FXUS66 KPDT 160538
AFDPDT

Area Forecast Discussion
National Weather Service Pendleton OR
938 PM PST Mon Jan 15 2018

UPDATED AVIATION DISCUSSION

.SHORT TERM...Tonight and Tuesday...A negative tilted upper level
trough in the Gulf of Alaska is nudging closer to the Pacific
Northwest with a cold front moving onshore. This front will be
slowly moving eastward over the next 12 to 18 hours produce a narrow
band of precipitation. It is currently moving over the Cascades and
will reach the Columbia Basin by early Tuesday morning then into the
eastern Mountains in the afternoon. Snow levels will be high so the
precipitation will main be rain below 5000 feet. There will be some
increasing southerly winds ahead of the front which will bring some
windy conditions to places like the southern Grande Ronde Valley.
Low clouds and fog will persist most of the night from central
Oregon into the Lower Columbia Basin but expect this to breakup
early Tuesday due to the rain and some increasing westerly winds
behind the front.

.AVIATION...06Z TAFs...Stratus and fog will continue to impact
most sites overnight and there will be increasing chance of
precipitation mainly rain as a cold front arrives overnight and
early Tuesday. Conditions will vary from VFR to LIFR overnight
with some improvement Tuesday behind the frontal passage to
MVFR or better. Winds will be light through the next 24 hours.

&&

.PREV DISCUSSION... /issued 359 PM PST Mon Jan 15 2018/

SHORT TERM...Tonight through Thursday. A ridge of high pressure
was slowly moving away from the region as a low pressure system
approaches from the west. Mid and high level clouds will increase
overnight and some showers will develop along the WA/OR Cascades and
then spread into the remainder of the region toward Tuesday morning.
The showers and periods of rain will increase in intensity tomorrow
before rapidly moving east and away from the region Tuesday night. A
brief rest bit in between storm systems is anticipated into
Wednesday morning before another low pressure system brings rain to
the region Wednesday afternoon and night. Although some drying is
possible over the lower Columbia Basin...this system lingers across
the two state area and the pcpn is forecast to persist into Thursday.

Snow levels are expected to remain above 5k feet although they
should dip around 4500 feet Tuesday night only to rise again
Wednesday afternoon. High temps should remain near or above normal
through the period rising into the 40s and 50s.

LONG TERM...Thursday night through Monday...A mid/upper level trough
in the NE Pacific will be just off the Canadian coast Thursday night
and push a cold front through the forecast area Thursday evening
resulting in snow levels lowering to 2000-3000 feet before daybreak
on Friday. Snow showers will taper off and end late Thursday evening
in the southern Blue Mountains and the Ochoco-John Day Highlands.
Snow levels during the day on Friday will remain around 1600-2300 so
the mountains will see scattered snow showers on Friday with the
Lower Columbia Basin remaining dry on Friday. Late Friday night
through Saturday another disturbance moves across the region for a
chance of rain showers in the Columbia Basin and the Yakima Valley
and snow showers in the mountains. Sunday a strong mid/upper level
trough approaches the coast and sweeps a cold front and attendant
precipitation east of the Cascades with snow levels areawide 1500-
2500 feet. This will be followed by a warm front and overrunning
precipitation on Monday with the snow level 1500-2000 feet.  Polan


&&

.PRELIMINARY POINT TEMPS/POPS...
PDT  33  47  34  47 /  20  90  10  10
ALW  35  48  36  48 /  10  90  10  10
PSC  35  46  34  43 /  20  90  10  10
YKM  38  45  32  40 /  60  90  10  20
HRI  37  49  34  46 /  20  90  10  10
ELN  35  42  31  37 /  60  90  10  30
RDM  33  48  30  49 /  80  50  10  10
LGD  37  45  33  43 /  10  70  10  10
GCD  36  48  32  46 /  20  90  10  10
DLS  41  51  37  45 /  80  70  10  30

&&

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

$$

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