Area Forecast Discussion


from: NWS Pendleton, OR

494
FXUS66 KPDT 131127
AFDPDT

Area Forecast Discussion
National Weather Service Pendleton OR
330 AM PST Thu Feb 13 2025

Updated Aviation Discussion

.SHORT TERM...Today through Saturday...

Bottom Line Up Front

1) Winter Weather Advisories Thursday-Friday across all areas in
   Oregon

2) High Wind Warnings in foothills and Southern Grand Ronde Valley
   Thursday may cause visibility issues


...WINTER WEATHER ADVISORIES IN EFFECT FROM THURSDAY TO FRIDAY
FOR... The East Slopes of the Oregon Cascades, Central Oregon,
John Day Basin, Ochoco-John Day Highlands, North Central Oregon,
Eastern Columbia River Gorge of Oregon-Eastern Columbia River
Gorge of Washington, Lower Columbia Basin of Oregon-Foothills of
the Southern Blue Mountains of Oregon, Grande Ronde Valley,
Northern Blue Mountains of Oregon-Southern Blue Mountains of
Oregon-Northwest Blue Mountains, and the Foothills of the Northern
Blue Mountains of Oregon-Foothills of the Blue Mountains of
Washington.

CAMs HI-RES short term models are in firm agreement with the
occluded front lifting into the region and lingering through
Friday. Southwest flow aloft is bringing in ample moisture across
the region beginning in central OR and moving across the region to
the north east. Timing of the system is a bit difficult to pin
down, but many of the models show the onset of the snow to begin
between 4 AM in central OR before steadily moving north east.
Forty-eight hour snow totals across the region begin with over 80%
of the raw ensembles show central OR will receive 2-4 inches,
north central will see between 3-5 inches, east slopes between 5-8
inches, John_day Basin 1- 3 inches, Ochoco-John Day Highlands 3-7
inches, eastern Columbia River Gorge of WA & OR 1-3 inches, lower
Columbia Basin and foothills of the southern Blues will see 2-4
inches, Grand Ronde Valley 1-3 inches, Northern Blue Mountains of
Oregon: Southern Blue Mountains of Oregon: Northwest Blue
Mountains will all see 5-10 inches and lastly, Foothills of the
Northern Blue Mountains of OR & WA will se 3-5 inches.

Not only will the occluded front bring about decent precipitation
chances, the front will also bring with it southeast flow along the
eastern portion of the CWA. Primarily this will lead to very windy
situations through the Grande Ronde Valley and along the foothills
of the Blues due to downsloping affects. A high wind warning is out
for the aforementioned areas due to this and it began at 10 PM and
will remain in effect through 10 PM Thursday. Over 80% of the HREF
raw ensembles are in agreement that sustained winds between 25 to 40
mph with gusts of 50 to 60 mph will occur. As for the foothills of
the BLues, 60-80% of the HREF raw ensembles show sustained winds of
25 to 40 mph with gusts of 50 to 60 mph as well, especially through
the I-84 corridor. The winds coupled with the snowfall will cause
visibility issues and will be monitored constantly during the event
in case of white out conditions. Please drive extremely careful and
always check Tripcheck.com before taking to the roads. Bennese/90

.LONG TERM...Sunday through Thursday...Models are in fair agreement
with the synoptic pattern through Tuesday, but differences begin to
emerge on Wednesday, especially with the deterministic runs.  The
run-to-run continuity has been good for Sunday, as models show a
moist westerly flow aloft early in the day followed by a shortwave
trough during the afternoon and evening.  PoPs are around 60-100%
across the board with the lowest PoPs across the Columbia Basin down
to Central Oregon. Snow levels around 1500 feet are forecast for
south central and southeast Washington sloping upwards to 4500 feet
in central Oregon. Confidence is high that the Cascades, Blue Mtns,
and Wallowas will observe 4-8" of new snow and confidence is
moderate of 8-12". The pattern is not favorable for snow
accumulations in the lowlands, although a few locations will have a
chance for 0.5-1.0" of snow.

PoPs remain high over the mountains on Monday, and the northern Blue
Mtns have a good chance (50%) of observing 3-6" of additional snow.
There are no organized fronts advertised by the models, although the
forecast area will be under a northwest flow aloft ahead of a
developing offshore ridge, and there are weak impulses embedded in
the flow. PoPs in the lowland areas will generally range from 20-
40%.

Models agree that the offshore ridge will move inland on Tuesday,
but the ridge will be relatively flat.  This will allow showers to
develop along the Cascades and the eastern mountains with light
amounts of snow. There are some model differences on the amplitude
of the ridge, and the chance of precipitation may be reduced on
Tuesday if models agree more on a higher amplitude ridge.

For the most part, the ensembles agree that the ridge will flatten
and allow a shortwave trough to bring additional showers to the
forecast area on Wednesday. The deterministic ECMWF maintains a more
amplified ridge. Due to the model differences, there is some
uncertainty on whether the mountains will have another round of
moderate to heavy snow.  The differences are even more pronounced on
Thursday, and the deterministic runs appear out of alignment. Looking
at the overall mean of the ensembles, Thursday will be met with a
flat ridge and 30-50% chance of mountain snow showers. Wister/85


&&

.AVIATION...12Z TAFs...A moist southwest flow aloft is spreading mid
and high level clouds across the terminal airports.  WSR-88D at KMAX
and KATX show precipitation now approaching southwest Deschutes
County and right at the door of BDN.  Over the next hour or two,
CIGS and VSBY will lower to MVFR in light snow at BDN followed by
RDM. Light snow will develop over the remainder of the airports
later this morning and afternoon. YKM and PSC are the two sites that
will likely remain VFR this afternoon with very light snow or none
at all. DLS has the best potential for IFR or LIFR and moderate snow.
There will be two bands of precipitation over the next 24 hours, and
the second one tonight will keep flight conditions at or below MVFR
across the area. Winds will be 5-15 kts through tomorrow morning.
Wister/85


&&

.PRELIMINARY POINT TEMPS/POPS...
PDT  23  17  33  20 / 100  60  80  30
ALW  25  20  32  20 /  90  60  80  50
PSC  27  22  35  16 /  80  50  50  10
YKM  25  16  36  15 /  70  50  20   0
HRI  26  16  35  17 /  90  50  60  20
ELN  24  18  37  18 /  60  60  30   0
RDM  29  13  40  13 /  90  50  20   0
LGD  29  16  37  21 / 100  70  90  50
GCD  34  19  40  15 / 100  70  80  20
DLS  27  20  41  24 / 100  70  50   0

&&

.PDT WATCHES/WARNINGS/ADVISORIES...
OR...Winter Weather Advisory from 7 AM this morning to 10 AM PST
     Friday for ORZ041.

     Winter Weather Advisory from 7 AM this morning to 4 PM PST
     Friday for ORZ044-508.

     Cold Weather Advisory until 7 AM PST this morning for ORZ049-050-
     502-503-506-509-511.

     High Wind Warning until 10 PM PST this evening for ORZ049-507.

     Winter Weather Advisory from 7 AM this morning to 10 PM PST
     Friday for ORZ049-502-503-507.

     Winter Weather Advisory until 4 PM PST Friday for ORZ505-506.

     Winter Weather Advisory until 4 PM PST Friday for ORZ509.

     Winter Weather Advisory until 10 AM PST Friday for ORZ510.

     Winter Weather Advisory until 10 AM PST Friday for ORZ511.

WA...Winter Weather Advisory from 7 AM this morning to 10 AM PST
     Friday for WAZ024.

     Cold Weather Advisory until 7 AM PST this morning for WAZ030-522.

     Winter Weather Advisory from 7 AM this morning to 10 PM PST
     Friday for WAZ029-030.

&&

$$

SHORT TERM...90
LONG TERM....85
AVIATION...85

NWS PDT Office Area Forecast Discussion