347
FXUS66 KPDT 200540 RRA
AFDPDT
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PENDLETON OR
1040 PM PDT SUN APR 19 2026
.UPDATED AVIATION DISCUSSION.
KEY MESSAGES
- WARMER TEMPERATURES CONTINUE THROUGH TUESDAY, WITH COOLER
TEMPERATURES TO FOLLOW BY A COLD FRONTAL PASSAGE IN THE
MIDWEEK.
- WIDESPREAD 10-25% CHANCES OF THUNDERSTORMS WITH ISOLATED TO
SCATTERED DEVELOPMENT TUESDAY, WITH MUCH LESS COVERAGE THROUGH
THE EARLY WEDNESDAY MORNING HOURS.
- BREEZY TO LOCALLY WINDY CONDITIONS POSSIBLE GOING INTO
WEDNESDAY AS THE COLD FRONTAL SYSTEM PASSES THROUGH THE
REGION.
DISCUSSION
MONDAY WILL BE THE WARMEST DAY OF THE 7 DAY FORECAST AS NBM
MEAN HIGHS REACH AROUND 80 DEGREES ACROSS THE LOWER COLUMBIA
BASIN, THE JOHN DAY BASIN, CENTRAL OREGON AND THE YAKIMA VALLEY.
ENSEMBLE CLUSTERING STILL SHOWS THE UPPER LOW SETTING UP OFF
THE CA COAST BY DAY 3 (TUESDAY) WITH A DIFFLUENT UPPER PATTERN
ACROSS THE INTERIOR NW. THE CLUSTERS SHOW SOME VARIANCE IN HOW
MUCH INSTABILITY WILL DEVELOP ACROSS THE MOUNTAINS ZONES ON
TUESDAY AFTERNOON, RANGING FROM FAIRLY LOW (UNDER 100 J/KG TO AS
MUCH AS 400 J/KG CAPE), LEAVING STILL UNCERTAINTY WITH RESPECT
TO HOW ISOLATED OR SCATTERED THE CONVECTION MAY BE. WETTING RAIN
CHANCES HOWEVER IS AN AREA OF EVER INCREASING CONFIDENCE AS
OVERALL POPS INCREASE FROM 70 TO 90 PERCENT LATE TUESDAY
AFTERNOON THROUGH THE NIGHTTIME HOURS. THE ESAT SHOWS THE EVENT
IS NOT EXTREME WITH ABOUT A 1-2 STANDARDIZED ANOMALY FOR IVT
INTO SOUTHERN OREGON TUESDAY. A LIMITED AREA OF THE NORTHERN
BLUE MOUNTAINS HAS 40 TO 50% CHANCES TO MEET OR EXCEED 2 INCHES
OF RAINFALL BY THURSDAY OVERNIGHT. THAT SAME 40 TO 50% THRESHOLD
LOWERED TO ONE INCH EXTENDS MORE BROADLY ACROSS THE ENTIRE
EASTERN MOUNTAINS AS WELL AS MUCH OF THE OREGON CASCADES CREST.
ALONG WITH THE INCOMING WET SYSTEM, THE TEMPERATURES WILL THEN
BECOME MODERATED BEGINNING TUESDAY ACROSS CENTRAL OREGON INTO
THE COLUMBIA BASIN AND THEN FARTHER NORTH ON WEDNESDAY AS THE
RAINS OVERSPREAD THE BROADER REGION. WEDNESDAY IS SHAPING UP TO
BE THE COOLEST DAY OF THE 7 DAY FORECAST WHERE NBM MEANS
PRINTING 50S FROM CENTRAL OREGON INTO THE LOWER COLUMBIA BASIN,
AND 60S FARTHER NORTH INTO THE YAKIMA AND NORTHERN BENTON
COUNTIES. WEDNESDAY ALSO MAY BE POINTING TOWARD POTENTIAL WIND
ADVISORIES FOR PARTS OF THE OREGON COLUMBIA BASIN AND SIMCOE
HIGHLANDS AS MODELS HINT AT GUSTS IN EXCESS OF 40 MPH.
RUSSELL/71
AVIATION /06Z TAFS THROUGH 06Z TUESDAY/
VFR CONDITIONS CURRENTLY ACROSS ALL SITES, WHICH WILL STAY THE
COURSE THROUGH THE PERIOD. SUSTAINED AFTERNOON WINDS BETWEEN 10-
15KTS EXPECTED FOR KRDM/KBDN, SUBSIDING LATER IN THE EVENING AS
CEILINGS DROP TO AROUND 10KFT. LIGHT WINDS ELSEWHERE BELOW 10KTS AS
CEILINGS OF 25KFT BECOME OVERCAST IN THE EVENING. 75
HYDROLOGY
WITHIN BANK RISES ON SOME AREA RIVERS ARE EXPECTED HEADING INTO
THE MIDDLE OF THE WEEK IN RESPONSE TO RUNOFF. THE NACHES RIVER
IS FORECAST TO REACH AND EXCEED THE ACTION STAGE AT NACHES
TUESDAY MORNING AND THEN AT CLIFFDELL TUESDAY NIGHT BEFORE
BEGINNING A GRADUAL FALL. THE GRANDE RONDE RIVER AT TROY IS
FORECAST TO REACH ABOUT 1 FOOT BELOW MINOR FLOOD STAGE LATE
WEDNESDAY. NO SCENARIOS IN THE HEFS EXCEEDANCE PROBABILITIES
SUGGEST FLOODING IS POSSIBLE (LESS THAN 10% CHANCES). RUSSELL/71
PRELIMINARY POINT TEMPS/POPS
PDT 44 76 48 71 / 0 0 10 30
ALW 49 76 52 73 / 0 0 10 30
PSC 44 80 49 78 / 0 0 10 10
YKM 47 79 49 75 / 0 0 10 10
HRI 44 79 49 74 / 0 0 10 10
ELN 44 75 47 68 / 0 0 10 20
RDM 40 75 42 62 / 0 10 20 30
LGD 41 75 44 72 / 0 0 10 40
GCD 44 77 44 70 / 0 0 10 60
DLS 52 78 52 67 / 0 10 20 20
PDT WATCHES/WARNINGS/ADVISORIES
WA...NONE.
OR...NONE.
DISCUSSION...71
AVIATION...75
HYDROLOGY...71
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