Biggs Junction, Oregon Weather Forecast Discussion

665
FXUS66 KPDT 192048
AFDPDT
Area Forecast Discussion
National Weather Service Pendleton OR
148 PM PDT Fri Sep 19 2025
.DISCUSSION...Another day of dry conditions across the PacNW as
broad, flat upper level ridging has moved overhead. Satellite
imagery does show some lingering scattered mid to high level
cloud cover over portions of eastern and central OR with clear
skies elsewhere.
Tonight through tomorrow morning: Dry conditions with light winds
will prevail into early tomorrow as a a weak ridge of high
pressure continues to push east. The upper ridge will continue to
promote a slight warming trend through tomorrow, with
temperatures rising back into the mid to upper 80s in the lower
elevations today and lingering into Saturday. Otherwise, remnant
tropical moisture will push north into southern and south central
OR today. Increased surface lapse rates and instability in tandem
with the increased moisture will allow for an isolated
thunderstorm or two to develop this afternoon and early evening
from southern OR into southern Deschutes county.
Saturday Afternoon through Sunday Night: The upper ridge over the
area will be pushed east into the northern Rockies by Saturday
evening as a leading cold front and upper level trough dig
southeast out of the Gulf of Alaska. The cross Cascade pressure
gradient will begin to tighten again by late Saturday afternoon,
resulting in breezy to locally breezy west winds developing
through the Cascade gaps and into portions of the Columbia Basin.
Southwest flow aloft and a broad upper low offshore CA pushing a
weak post tropical moisture plume northward will result in
isolated chances (15-25%) of thunderstorms from the Ochoco-John
Day Highlands to the Elkhorn Crest, with a low chance (10-15%) of
an isolated storm or two moving into southern Deschutes and Crook
counties Saturday afternoon. By late Saturday night, the cold
front will reach the Cascade west slopes, resulting in increasing
chances of light to moderate rain showers across the Cascade
crest. Shower chances will spread to the eastern mountains Sunday
afternoon and evening, then will diminish area wide Sunday night.
Breezy winds 15-25mph (25-30mph Kittitas valley) and gusts up to
35mph (up to 40mph Kittitas valley) will develop through the
Cascade gaps and into the Columbia Basin as the cold front and
trough pass east of the Cascades Sunday. While critical fire
weather conditions are not expected, there is elevated concern
owing to dry air with downsloping winds along the WA Cascade east
slopes Saturday early afternoon, and dry air descending from
aloft behind the cold front passage Sunday. If new fires are to
start, the expected breezy winds will allow fires to spread more
easily with the drier conditions and in drier fuels.
Monday through Friday: Ensemble guidance is in good agreement
that upper level ridging will build back over the PacNW by Monday
morning, and will persist over the region through
Tuesday(confidence 60-80%). This will result in a warming and
drying trend with light winds to start the workweek. By early
Wednesday morning, around 80% of ensemble members made up from the
ECMWF, GFS, and Canadian ensemble suites depict remnants of an
upper closed low beginning to swing up into central and Northern
CA. By Wednesday afternoon, only around 60% of members depict the
low becoming an open wave that slides northeast into the great
Basin and eastern OR, however these remaining members become split
on whether southern and central OR will receive precipitation or
remain dry in the late morning and early afternoon hours.
Wednesday afternoon onwards there is great disagreement on the
evolution of the synoptic pattern, as members disagree on whether
there will be a troughing, zonal flow, or weak ridging over the
PacNW through the latter half of next week. Needless to say,
confidence in forecasted temperatures/winds/precipitation
Wednesday afternoon and beyond is very low (15%) at this time.
Lawhorn/82
&&
.AVIATION...Previous Discussion...18Z TAFs...VFR conditions to
prevail through the period. Few-Sct cloud decks AOA 25kft will be
over sites RDM/BDN through the period. Isolated thunderstorms will
be possible south of site BDN this afternoon, but chances are 

NWS PDT Office Area Forecast Discussion