Area Forecast Discussion
Issued by NWS Pendleton, OR

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FXUS66 KPDT 021756 AAA
AFDPDT

Area Forecast Discussion...Updated
National Weather Service Pendleton OR
956 AM PST Fri Dec 2 2016

Updated aviation discussion

.UPDATE...A weak disturbance will move through a ridge of high
pressure over the pacnw today with clouds and showers accompanying
the system into tonight. The disturbance should push away from the
region tonight with drier conditions expected west to east.
Precipitation amounts should be light and the present short term
forecast appears on track with only minor adjustments to aftn high
temps.

&&

.AVIATION...18Z TAFs...A weak system is moving into the area and
clouds are increasing and lowering this morning. Expect BKN-OVC
conditions with mainly VFR ceilings and visibility through tomorrow
morning. Ceilings will be lowering to 3500-7000 feet this afternoon
with light rain and snow showers developing. KRDM and KBDN may have
a rain/snow mix and have indicated 6SM visibility due to the light
nature of any snow showers that develop. There could be brief MVFR
conditions with the snow showers but did not have enough confidence
to show less than VFR conditions. Other TAF sites will have all rain
and is likeliest at KDLS and KALW. Have -SHRA at those sites with
VCSH used at KYKM, KPSC and KPDT. Showers will generally end by 03-
06Z though they may linger on at KALW through much of the night.
Winds will be primarily 5-15 kts though KALW and KPDT may have gusts
to 20 kts after 08Z. Perry

&&

.PREV DISCUSSION... /issued 351 AM PST Fri Dec 2 2016/

SHORT TERM...Today through Sunday...An upper level ridge is located
offshore with northerly flow aloft over eastern WA and OR. Clouds
will increase today as a warm front moves through the area. It will
spread a chance of rain and mountain snow as snow levels slowly
increase to 3000 ft this afternoon. Most of the precipitation will
be in the afternoon. The front will be falling apart as it crosses
the area so precipitation amounts will be light. Warm advection from
the front will increase snow levels to 4000 to 5500 ft near the
Cascades by Saturday morning. Some snow showers will linger over the
mountains Saturday due to orographic effects and upslope northwest
flow aloft. A strong cold front will move eastern WA and OR Sunday.
This will bring rain and snow along with falling temperatures and
windy conditions. High temperatures for the day will mainly be in
the morning. Coonfield

LONG TERM...Sunday night through Thursday...Cold and unsettled
conditions will prevail during this period. Cold air will move into
the Interior Northwest Sunday night behind the system Sunday. Snow
levels will fall rapidly Sunday evening with snow being possible at
the lowest elevations by midnight and could see an inch or two along
the Blue Mountain foothills by Monday morning. Snow/rain showers
look to end by midnight Sunday/Monday in the Washington portion of
the Columbia Basin. Should see snow showers increase again Monday
afternoon and evening as another system drops southeast out of the
Gulf of Alaska and across the region. There remains considerable
differences on the timing of a system for mid week. The GFS is
quickest, bringing the system into the area Wednesday evening, while
the ECMWF is slower with this system not having it arrive until
Thursday night. Other solutions are between these two solutions. Our
current forecast leans toward the faster GFS and for now will leave
this forecast in place. 90

&&

.PRELIMINARY POINT TEMPS/POPS...
PDT  45  36  50  39 /  40  20  10  30
ALW  46  39  52  42 /  40  30  10  40
PSC  44  37  52  41 /  40  10  10  20
YKM  43  32  51  34 /  50  10  10  20
HRI  44  35  51  40 /  40  10  10  20
ELN  41  32  47  33 /  50  20  10  20
RDM  42  29  48  33 /  40  20  10  20
LGD  38  34  45  35 /  30  30  20  40
GCD  35  29  41  35 /  30  30  20  20
DLS  44  38  52  41 /  50  20  10  40

&&

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

$$

97/83



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