587
FXUS66 KPDT 142309
AFDPDT
Area Forecast Discussion
National Weather Service Pendleton OR
409 PM PDT Thu Aug 14 2025
Updated Aviation Discussion
.AVIATION...00z TAFs...VFR conditions expected. Breezy winds will
lighten this evening, with clouds building in overnight as a
weather system starts to move into the region, becoming bkn-ovc
around 10-15 kft for most sites by Friday morning. Winds will
become breezy again, mainly out of the W and SW, by late Friday
morning as well. There is a slight chance (<30%) of a shower
impacting YKM around sunrise Friday, but aviation impacts are
expected to be minimal. Evans/74
&&
.PREV DISCUSSION... /issued 155 PM PDT Thu Aug 14 2025/
DISCUSSION...Little to talk about on satellite this afternoon as
low cumulus/stratus that developed overnight has mostly dissipated
across the forecast area, except for some lingering cloud cover
over the Blues. Otherwise, breezy conditions have redeveloped over
portions of the Columbia Basin/Gorge, with calmer conditions
elsewhere.
Today: Broad troughing has developed over the region with mostly
quiet conditions across the forecast area. Temperatures are much
cooler than this time yesterday thanks to cooler air behind a cold
front passage yesterday. Some locally dry conditions have
developed across the southern half of OR and into southern
portions of central OR and the Ochoco-John Day Highlands,
resulting in increased fire weather concerns in those areas.
However, more widespread critical fire weather conditions are not
anticipated at this time. Later tonight, winds will begin to
weaken across the forecast area, but precipitation chances will
increase across the WA Cascade crest ahead of frontal passage
early tomorrow.
Friday through Sunday: High confidence (80-95%) that a cooler,
wetter pattern will develop across the PacNW beginning with a cold
front passage Friday into Saturday, with several
shortwaves/shortwave impulses swinging around the bottom of a
broad upper low in the Northeast Pacific/Gulf of Alaska through
Sunday. A weak to low end moderate atmospheric river (AR) will
accompany the passage of the cold front, increasing PWATs to 0.8
to 1.3 inches across the forecast area, allowing for plenty of
moisture to work with through the weekend. As for convection,
instability will be lacking across the region for Friday, with low
confidence (10-15%) that the cold front will be enough to produce
a thunderstorm or two across the mountainous terrain. As for
Saturday and Sunday, flow aloft will back to the southwest, with
surface based instability increasing in the afternoon across
central OR, OR Cascade east slopes, and the eastern mountains.
This will result in chances (15-30%) of isolated to widely
scattered thunderstorms to develop in the afternoons and early
evenings. With seasonably high PWATs across the region, these
thunderstorms will be capable of moderate to heavy rainfall and
small hail, with abundant lightning. While lightning may be
abundant, the increased rainfall with these storms will keep the
potential for new fire starts low. Winds Friday and Saturday will
be between 15-20mph across portions of the Columbia Basin and
through the eastern Gorge, with lighter winds elsewhere.
Moderate- High confidence (70-85%) that temperatures will cool
into the upper 70s to mid 80s through the weekend.
Monday through Wednesday: Good agreement amongst ensemble cluster
members (ECMWF, GFS, Canadian) that upper level troughing will
dig equatorward off the west coast while upper level ridging along
the Rockies will build into the Canadian Plains. By Monday,
ensemble members begin a drying trend across the forecast area as
the upper level ridging begins to nudge towards the PacNW, but
keep modest instability across the eastern mountains through
Monday evening(confidence 55-75%). This will result in isolated
thunderstorm chances (10-20%) across the mountains in the
afternoon. By Tuesday, ensemble cluster solutions favor pushing
the best instability parameters into ID, with much weaker
instability across far northeast OR and southeast WA. Chances
(5-15%) of isolated thunderstorms will be confined mainly to the
higher terrain in Wallowa county Tuesday afternoon. With
conditions gradually drying out, these thunderstorms will likely
be drier, increasing the fire weather concerns going into the
middle of next week. By Wednesday, ensemble cluster guidance has
changed the progression of the synoptic pattern as compared to
yesterday, with the upper trough weakening well offshore and the
upper ridge still building poleward. Confidence is moderate
(40-60%) that isolated thunderstorm chances will diminish, while
dry conditions prevail with a slight warming trend into the upper
80s and low 90s.
&&
.PRELIMINARY POINT TEMPS/POPS...
PDT 60 85 62 80 / 0 10 10 60
ALW 64 86 66 80 / 0 10 10 60
PSC 63 88 65 84 / 10 10 20 50
YKM 63 84 65 85 / 30 20 60 50
HRI 64 87 65 83 / 10 10 20 60
ELN 60 80 61 79 / 40 30 70 50
RDM 50 83 56 77 / 0 10 30 70
LGD 53 85 60 77 / 0 10 10 50
GCD 52 87 58 79 / 0 0 0 40
DLS 67 82 67 82 / 20 20 70 60
&&
.PDT WATCHES/WARNINGS/ADVISORIES...
OR...None.
WA...None.
&&
$$
SHORT TERM...82
LONG TERM....82
AVIATION...74
