Area Forecast Discussion
Issued by NWS Pendleton, OR

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729
FXUS66 KPDT 200520
AFDPDT

Area Forecast Discussion
National Weather Service Pendleton OR
920 PM PST Fri Jan 19 2018

.UPDATE...Tonight and Saturday...There are some showers moving
across the Cascades...especially in Washington and also some
sprinkles over the Blues. These are due to an upper level
disturbance aloft moving across the region. Most places will remain
dry. Another upper trough will move across the region on Saturday
with colder air aloft and a more unstable atmosphere. This will
result in some showers...mainly a slight chance in the mountains
again while elsewhere it will be dry. A shortwave high pressure
ridge will then build over the region for Saturday night before
another weather system moves into the region on Sunday. 88

&&

.AVIATION...06Z TAFS...VFR conditions will prevail for the next 24
hours. There may be a few showers around near the mountains, but
visibilities will remain good as will ceilings remain high. Winds
will remain light overnight and on Saturday. 88

&&

.PREV DISCUSSION... /issued 147 PM PST Fri Jan 19 2018/

SHORT TERM...Tonight through Sunday night. Satellite shows large
upper level trough remains over the Pacific northwest extending
offshore. A short wave within the trough will cross the region
this evening and overnight. This will bring some enhancement to
the snow along the Cascades with several inches accumulation. Snow
showers also likely for the Blues. Remainder of the forecast area
will be mostly cloudy. Not much change expected for Saturday as
the pattern remains similar. Cool onshore flow with mostly cloudy
skies and scattered rain and snow showers. Highest pops once again
will be the Cascades. A much stronger upper low now moving through
the Gulf of Alaska will then start to spread clouds over the
region Saturday night. This upper low and cold front will impact
the Pacific northwest Sunday into Sunday night with lower elevation
rain and higher elevation snow. Significant accumulations are possible
over the Cascades and to a lesser extent the northeast Oregon
mountains. Current forecast has 5-10 inches total accumulation for
the Cascades. Surface gradients ahead of the cold front will create
locally breezy to windy conditions during the day. Strongest winds
will likely be over central and northeast Oregon. 94

LONG TERM...Monday through Friday...Medium range models
continue to be in good agreement, with a progressive weather pattern
through the end of next week. Flat zonal flow will prevail Monday
and Monday night for a break in precip for most areas, with some
chance PoPs for the higher elevations. Precip amounts will be
rather light, so any mountain snow accumulations will be minor.
Models continue to slow down the progression of the next system
until later Tuesday/Tuesday night, when a warm font is progged to
move north across the area Tuesday night, with the systems cold
front crossing Wednesday/Wednesday night. Snow levels will rise
Tuesday night to 2000-4500 feet, falling behind the cold front to
1500-3000 feet Wednesday night. Models continue to depict a stronger
system than the last couple of systems, thus will use likely to
categorical PoPs for the mountains, with high end chance to likely
PoPs for the lower elevations, with the greatest chances occurring
Wednesday. At this time, looks like the greatest risk for
significant accumulating snows will occur over the Cascade east
slopes. In the wake of the front, west to northwest flow aloft will
result in continued upslope snow showers for the mountains, with
minor precip chances for the lower elevations. Near to slightly
above normal temperatures through midweek will cool to slightly
below normal for Thursday/Friday.

&&

.PRELIMINARY POINT TEMPS/POPS...
PDT  34  46  32  48 /  10  10  10  70
ALW  37  47  34  49 /  10  10  10  70
PSC  36  48  33  47 /  10  10  10  70
YKM  31  46  30  43 /  10  10  10  70
HRI  35  47  31  48 /  10  10  10  70
ELN  30  42  29  39 /  30  20  20  80
RDM  27  43  28  45 /  10  10  10  60
LGD  29  41  28  40 /  20  20  20  60
GCD  26  40  26  39 /  10  10  10  70
DLS  35  47  34  45 /  40  30  20  80

&&

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

&&

$$

88/80/88



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