166
FXUS66 KPDT 211000
AFDPDT
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PENDLETON OR
300 AM PDT SAT MAR 21 2026
KEY MESSAGES
1. MOUNTAIN RAIN WILL PERSIST THROUGH SATURDAY OVER THE OR CASCADES
AND EASTERN MOUNTAINS
2. TEMPERATURES WILL RETURN TO NEAR SEASONAL AVERAGES
3. DRY AND COOLER CONDITIONS THROUGH MONDAY NIGHT
DISCUSSION
CURRENT RADAR SHOWS A FEW RETURNS OVER THE CASCADES AND THE BLUES AS
THE REMNANTS OF THE ATMOSPHERIC RIVER REMAIN OVER THE AREA. CURRENT
GROUND OBSERVATIONS SHOW THAT THE LAST HOUR THESE RETURNS HAVE ONLY
PUT DOWN BETWEEN 0.01-0.02 INCHES OF RAIN. RAIN IS EXPECTED TO
CONTINUE OVER THE MOUNTAINS THROUGH TODAY (SATURDAY) WITH RAIN
ACCUMULATIONS NEARING 0.05-0.1 INCHES IN THE OR CASCADES AND THE
EASTERN MOUNTAINS THROUGH 11 PM TONIGHT (70-90% CONFIDENCE). RADAR
COUPLED WITH MODELS SHOW THE MAJORITY OF THE PERCEPTION WILL
CONTINUE A SOUTHWEST TRAJECTORY OVER THE OR CASCADES AND BLUE
MOUNTAINS BEFORE TAPERING OFF SATURDAY NIGHT.
MODELS SHOW A WEAK COLD FRONT MOVING ACROSS THE REGION LATE LAST
NIGHT AND THROUGH THIS MORNING. THIS WILL BRING WITH IT INCREASED
CLOUD COVER AS WELL AS COOLER TEMPERATURES. IN HOUSE COMPARISONS
SHOW THAT TEMPERATURES WILL DECREASE NEARLY 20 DEGREES FROM
YESTERDAY WITH TEMPERATURES AT OR NEAR SEASONAL NORMAL. WITH THAT
SAID, NBM RAW ENSEMBLES AS WELL AS HREF RAW ENSEMBLES SHOW 80-90%
CONFIDENCE THAT THE BASIN, YAKIMA, THE GORGE AND CENTRAL OR SEEING
TEMPERATURES IN THE MID TO UPPER 50S SATURDAY WHILE ELSEWHERE WILL
SEE UPPER 40S TO LOW 50S WITH EVEN COOLER TEMPERATURES ALONG THE
HIGHER TERRAINS. SUNDAY BOTH RAW ENSEMBLES SETS SHOW TEMPERATURES TO
BE EVEN COOLER WITH 70-80% OF THE AFOREMENTIONED AREAS SEEING LOW TO
MID 50S WITH ISOLATED LOCATIONS IN CENTRAL OR AND THE BASIN SEEING
MID TO UPPER 50S. AFTER SUNDAY, MODELS SHOW A SLOW WARM UP THROUGH
THE BEGINNING OF NEXT WEEK.
MODELS SHOW PERSISTENT COOL AND DRY WEATHER THROUGH MONDAY NIGHT AS
SOUTHWEST FLOW ALOFT CONTINUES OVER THE AREA. THIS WILL SLOWLY BRING
TEMPERATURES UP THROUGH THE BEGINNING OF THE WEEK. MODELS ALSO SHOW
THAT PRECIPITATION WILL BE LACKING WITH THE SOUTHWEST FLOW KEEPING
THE REGION DRY AHEAD OF A PATTERN CHANGE WITH AN UPPER LEVEL
SHORTWAVE BRINGING IN INCREASED CHANCES OF PRECIPITATION, BREEZY
WINDS AND A RETURN TO COOLER CONDITIONS.
AVIATION /06Z TAFS THROUGH 06Z SUNDAY/
VFR CONDITIONS ARE EXPECTED THROUGH THE TAF PERIOD. A COLD FRONT
WILL CROSS THE REGION THROUGH SATURDAY MORNING. WINDS HAVE
SUBSIDED AT MOST TAF SITES AND EXPECTED WINDS GENERALLY 10 KTS
OR LESS THROUGH THE NIGHT. WINDS ARE EXPECTED TO INCREASE ON
SATURDAY IN THE 20 TO 25 KT RANGE AND 25 TO 30 KT RANGE AT DLS.
YKM MAY KEEP THE GUSTINESS THROUGH THE NIGHT.
OTHERWISE SOME -RA IS POSSIBLE TOWARD MORNING AT PDT AND ALW
(AND CAN'T BE RULED OUT ELSEWHERE).
HYDROLOGY
THE CASCADE SLOPE BASINS HAVE RECEIVED THE BULK OF THE
PRECIPITATION THAT WILL BE IMPACTING RIVER FORECASTS OVER THE
WEEKEND. ALL TRIBUTARIES WITH MOUNTAIN HEADWATERS WILL CONTINUE
TO RUN HIGH. FORECAST POINTS ALONG THE NACHES AND YAKIMA RIVERS
WILL BE THE MOST IMPACTED BY THE SURGE OF MOUNTAIN RUNOFF AS
SEVERAL OF THESE POINTS ENTER INTO FLOOD BY SATURDAY, IF NOT
ALREADY IN FLOOD LIKE THE NACHES AT NACHES. THE YAKIMA RIVER AT
EASTON IS FORECAST TO REACH JUST OVER THE 52.1 FT LEVEL, (ABOUT
1 FT OVER MODERATE FLOOD) BUT HAS A 30% CHANCE OF REACHING 52FT.
AT KIONA, THE RIVER IS FORECAST TO REACH THE 13.9 FT LEVEL, BUT
HAS A 10% CHANCE OF REACHING 14 FT. RUSSELL/71
PRELIMINARY POINT TEMPS/POPS
PDT 58 30 57 33 / 80 0 0 0
ALW 58 34 57 37 / 90 0 0 0
PSC 64 33 60 34 / 50 0 0 0
YKM 58 29 56 33 / 0 0 0 0
HRI 62 32 60 33 / 70 0 0 0
ELN 50 29 52 30 / 0 0 0 0
RDM 59 24 60 29 / 20 0 0 0
LGD 56 28 58 34 / 80 0 0 0
GCD 58 29 60 35 / 60 0 0 0
DLS 60 34 61 37 / 10 0 0 0
PDT WATCHES/WARNINGS/ADVISORIES
WA...NONE.
OR...NONE.
DISCUSSION...90
AVIATION...77
HYDROLOGY...71
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