Area Forecast Discussion
Issued by NWS Pendleton, OR

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FXUS66 KPDT 261734 AAA

Area Forecast Discussion...Update
National Weather Service Pendleton OR
1033 AM PDT Sun Mar 26 2017

Updated Aviation Discussion

.SHORT TERM...Today and tonight...A weather system is moving into
the region this morning. A warm front will lift through the forecast
area today followed by a cold front this evening and overnight.
Light rain is already falling in central Oregon and expect this to
spread across the forecast area through the day. Snow levels will
rise today but could see a little light snowfall in portions of
central Oregon this morning as well as along the east slopes of the
Cascades before snow levels rise. Higher elevations of the Blue
Mountains will also see some light snow accumulations. The cold
front will will move over the cascades early this evening. Models
are indicating that a shortwave moving up the front will help to
enhance precipitation from central Oregon to Northeast Oregon from
this evening and overnight so have kept chance of precipitation high
for these areas ahead of the front. Behind the front precipitation
will decrease rapidly.

.AVIATION...18z TAFS...VFR and Tempo MVFR conditions are expected to
prevail at all terminals through the day today. Conditions should
improve to VFR for most terminals overnight and into Monday morning.
Rain showers will be moving through the area today and into this
evening...the showers could be moderate at times, especially this
afternoon, as the atmosphere will again have some marginal
instability. Thunderstorms are not expected. CIGS will mainly range
from about 4k to 8k feet AGL in the rain showers, but could
occasionally drop to between 2.5k to 4k feet AGL in any heavier
showers...Vis could also occasionally drop to 3-5SM in these
showers. CIGS/VIS should tend to lift and improve tonight as the
main axis of precipitation moves east. Expect sct to bkn clouds
mainly between 5k to 10k feet AGL overnight and into Monday morning.
If skies clear enough overnight, there is the potential for some
localized pockets of shallow fog to form, due to the wet ground
conditions. Not enough confidence on where, when or if this fog will
form yet to include in the TAFs. Winds will remain light through the
period...AOB 15kts for most locations. 77


.PREV DISCUSSION... /issued 300 AM PDT Sun Mar 26 2017/

SHORT TERM...Today through Tuesday...An upper level trough has
moved into Idaho tonight and a brief transitory ridge is over the
region early this morning. This is leading to the current dry
conditions. This will not last long as a system is approaching the
Pacific Northwest coast. The warm front of this system will cross
the Cascades later this morning and bring a chance of showers to the
Cascades and Central Oregon in the morning and a chance of showers
across the area in the afternoon. The cold front will arrive Sunday
evening and showers will be likely before starting to taper off late
in the evening with just a slight chance of showers in the Columbia
Basin and North Central Oregon overnight. Precipitation will be
mainly rain with snow levels rising from around 4500 feet this
morning to around 5500-6000 feet this evening before dropping down
to 3500 to 4000 feet behind the front by tomorrow morning.
Precipitation amounts will be around a tenth of an inch in the
Columbia Basin, up to a quarter of an inch in the rest of the lower
elevations and up to a half inch in the mountains. Snow amounts in
the mountains will be up to 3 inches in the higher mountain passes.
On Monday as the front departs, the associated trough will cross the
area. Instability with the front will keep a chance of rain and snow
showers in the mountains in the afternoon and a slight chance of
rain showers in the lower elevations. Snow levels will remain around
3500-4000 feet and precipitation amounts will be less than a tenth
of an inch. Monday night and Tuesday a ridge will be over the area
for mainly dry conditions. Another system  will be trying to cross
the Cascades, but a chance of light rain and showers will be
confined to the Cascades Crest region. Temperatures will be in the
mid 40s to mid 50s today then warm Monday and Tuesday to the mid to
upper 50s in the Columbia Basin and in the mid 40s to mid 50s
elsewhere. Perry

LONG TERM...Tuesday night through Sunday night...The latest GFS
model run is more in line now with the ECMWF and Canadian models for
the extended period...especially this coming mid week. The main
concern during the extended period will be a couple of weather
systems bringing more rain to the CWA. While these will mostly be
just spring time rain events with little hazardous impacts it may
cause rivers and streams to rise again. However at this time rivers
are not expected to reach flood stage anymore. There are a few that
will be at bankfull which will be covered with river statements.
Tuesday night and Wednesday a weather system will move into the
region with a period of rain followed by mainly mountain rain
showers behind the system by Wednesday afternoon, caused by upslope.
Snow levels will be quite high so there will be no concern with
winter weather at this time. Conditions will dry out by Friday and
then it will stay mostly dry until next Sunday night. However that
far out the models do not agree well with each other anymore, and
therefore only made minor changes to the previous forecast until the
forecast becomes more certain. It may be breezy at times...
especially on the ridge tops and open grassy terrain. Temperatures
will be near normal through the extended period. 88


PDT  53  40  55  38 /  60  80  40  10
ALW  56  43  57  43 /  60  70  40  20
PSC  54  42  59  41 /  60  60  20  10
YKM  55  38  61  38 /  70  60  20  10
HRI  53  41  57  39 /  60  60  20  10
ELN  48  35  51  36 /  70  60  20  10
RDM  55  35  52  31 /  70  70  30  10
LGD  56  39  53  35 /  50  80  60  20
GCD  56  38  53  33 /  60  90  50  10
DLS  53  42  56  43 /  70  70  20  10




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