596
FXUS66 KPDT 202338
AFDPDT
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PENDLETON OR
438 PM PDT FRI MAR 20 2026
KEY MESSAGES
- RAIN CHANCES DIMINISHING OVER THE WA CASCADES WHILE RAMPING UP
ACROSS THE OREGON CASCADES AND BLUE MOUNTAINS TONIGHT AND
SATURDAY.
- MOUNTAIN HEADWATER RIVERS TO RUN HIGH OR FLOOD THROUGH THE
WEEKEND
DISCUSSION
A WEAK TO MODERATE ATMOSPHERIC RIVER CONTINUES IMPINGING ON THE
PACNW COASTLINE AS WELL AS INLAND ACROSS WASHINGTON. OVER THE
NEXT 24 HOURS THIS EFFECTIVE COLD FRONTAL ZONE WILL SHIFT
SOUTHWARD AND LOSE THE MORE ROBUST IVT ALTOGETHER. THE VERY HIGH
POPS (90% THIS AFTERNOON) ACROSS THE WA CASCADES DROP OFF
DRAMATICALLY (15 TO 25 PERCENT BY THIS EVENING) WHILE THE OREGON
CASCADES BEGIN TO GET A MARKED INCREASE IN RAIN PROBABILITIES
THROUGH THE EVENING AND OVERNIGHT. DEW POINTS HAVE BECOME MORE
STABLE ACROSS THE CENTRAL OREGON COUNTIES/ZONE WESTERLY AND AND
PROBABLY DUE TO SURFACE WINDS BEING LIGHTER AND TRENDING
WESTERLY AND NORTHWESTERLY ALLOWING SOME BOUNDARY LAYER MOISTURE
THROUGH THE CASCADE GAPS. AS FOR THE TEMPERATURES, THIS
WEEKENDS ANOMALOUSLY WARM REGIME IS ABOUT TO COME TO AN END AS
A COLD FRONT ASSOCIATED WITH THE DECAYING AR INFLUENCES THE
ENTIRE REGION THROUGH LATE SATURDAY MORNING. DETERMINISTIC NBM
HIGHS TEMPS FOR SATURDAY ARE RUNNING ABOUT 20 DEGREES COOLER
ACROSS ALL AREAS OF THE CWA. STILL WARMER AREAS LIKE THE LOWER
COLUMBIA BASIN AND EASTERN RIVER GORGE, AS WELL AS CENTRAL
OREGON AND THE JOHN DAY BASIN CAN SEE TEMPS WARM UP THROUGH THE
LOW 60S. A SLOW MODERATION IN TEMPERATURES SHOWS UP IN THE
ENSEMBLES THROUGH MONDAY BUT IS ONLY NOTABLE ACROSS THE JOHN DAY
BASIN AND HELLS CANYON REACHING LOW 70S. MEANWHILE THE
DECAYING ATMOSPHERIC RIVER MAY HELP DROP UP TO A QUARTER INCH OF
PRECIPITATION (RAIN) ACROSS THE EASTERN MOUNTAINS ON SATURDAY.
A SECOND ATMOSPHERIC RIVER IS ON THE HORIZON WHICH COULD HAVE
SENSIBLE WEATHER IMPLICATIONS BY TUESDAY (DAY 5) FOR THE
WASHINGTON CASCADES. THAT MOISTURE FLUX IS LOCATED AROUND 155W
AND 25N RIGHT NOW, AND MODELED BY BOTH GFS AND EC TO HIT THE
PACNW COAST, ALTHOUGH THE GFS APPEARS MUCH STRONGER THAN THE EC
AT THIS TIME. RUSSELL/71
AVIATION /00Z TAFS THROUGH 00Z SUNDAY/
VFR CONDITIONS ARE EXPECTED THROUGH THE TAF PERIOD. A COLD FRONT
WILL CROSS THE REGION THROUGH SATURDAY MORNING. WINDS AT MOST
SITES WILL GUST IN THE 20 TO 25KT RANGE THROUGH THIS EVENING AND
AGAIN SATURDAY. THERE WILL ALSO BE SOME -RA WITH THE FRONT. IT
IS POSSIBLE THAT THERE COULD BE SOME LOCAL MVFR CIGS IN A FEW
LOCATIONS, MAINLY AT PDT AND ALW WITH THE FRONT AS WELL, BUT
CONFIDENCE IS TOO LOW TO INCLUDE IN THE INDIVIDUAL TERMINALS AT
THIS TIME.
FIRE WEATHER
A THIRD DAY WITH SEEMINGLY VERY SIMILAR FIRE WEATHER RISK ACROSS
CENTRAL OREGON, WITH SOME CAVEATS. OVERALL LIGHT DOWNSLOPING
WINDS IN THE SINGLE DIGITS TO AROUND 15 MPH WILL BE COMMON FOR
THE BALANCE OF THE AFTERNOON, HOWEVER GUSTS WILL COMMONLY BE IN
THE 20 TO AS MUCH AS 30 MPH RANGE. THE ONLY CAVEAT IS THE WIND
DIRECTION AND SUBTLE BOUNDARY LAYER MOISTURE THAT MAY BE COMING
THROUGH THE CASCADE GAPS. THAT SAID THE FIRE WEATHER RISK WILL
BE LIMITED THIS AFTERNOON. RUSSELL/71
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 45 57 30 57 / 50 60 0 0
ALW 47 57 34 56 / 70 70 0 0
PSC 47 62 33 60 / 40 20 0 0
YKM 39 58 29 56 / 10 0 0 0
HRI 48 61 31 59 / 40 30 0 0
ELN 37 49 28 52 / 20 0 0 0
RDM 41 58 23 61 / 20 10 0 0
LGD 45 55 28 58 / 40 80 0 0
GCD 45 57 28 60 / 10 60 0 0
DLS 45 59 33 61 / 30 10 0 0
PDT WATCHES/WARNINGS/ADVISORIES
WA...NONE.
OR...NONE.
DISCUSSION...71
AVIATION...77
FIRE WEATHER...71
HYDROLOGY...71
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