710
FXUS66 KPDT 041113
AFDPDT
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PENDLETON OR
413 AM PDT FRI SEP 4 2026
KEY MESSAGES
- PERIODIC SHOWER CHANCES (35-75%) ACROSS THE MOUNTAIN ZONES
WILL CONTINUE THROUGH EARLY NEXT WEEK, WITH LOWER CHANCES
ELSEWHERE
- SLIGHT CHANCE (15-25%) OF ISOLATED AFTERNOON THUNDERSTORMS
OVER THE MOUNTAINS THROUGH MONDAY
- BELOW NORMAL TEMPERATURES WILL CONTINUE THROUGH EARLY NEXT
WEEK, WITH NEAR NORMAL TEMPERATURES RETURNING MID WEEK
DISCUSSION
WATER VAPOR IMAGERY TONIGHT SHOWS AN UPPER LEVEL
CLOSED LOW OVER THE PACNW, WITH THE CENTER OF THE LOW POISED TO
MOVE INLAND ALONG THE CENTRAL OR COAST. MEANWHILE, NIGHTTIME
SATELLITE IMAGERY SHOWS CLOUDY CONDITIONS MAINLY ACROSS THE
CASCADE EAST SLOPES, CENTRAL OR, AND THE EASTERN MOUNTAINS WITH
CLEAR TO PARTLY CLOUDY SKIES ELSEWHERE. THOUGH CLOUD COVER IS
PRESENT, REGIONAL RADAR SHOWS RAIN SHOWERS MAINLY OUTSIDE OF THE
FORECAST AREA, THOUGH A FEW LIGHT SHOWERS ARE MOVING OVER THE
STRAWBERRY MOUNTAINS AND THE SOUTHERN ELKHORN CREST.
THE PACNW WILL CONTINUE TO BE UNDER THE INFLUENCE OF THE UPPER
CLOSED LOW THROUGH EARLY NEXT WEEK, WITH PERSISTENT RAIN CHANCES
(RAIN/SNOW MIX ABOVE 7.5KFT) OVER THE MOUNTAIN ZONES. AFTERNOON
TEMPERATURES ACROSS THE REGION WILL BE NEARLY 10-15 DEGREES BELOW
AVERAGE EACH DAY, WITH AFTERNOON HIGH TEMPERATURES AT THEIR LOWEST
IN THE MID 60S TO MID 70S TODAY (CONFIDENCE 85-95%). WHILE THE UPPER
CLOSED LOW WILL REMAIN PARKED OVER THE PACNW THROUGH SUNDAY, THE
CENTER OF THE LOW WILL REMAIN WEST OF THE CASCADE CREST THROUGH
SATURDAY BEFORE SLIDING EAST SUNDAY INTO MONDAY(CONFIDENCE 80-90%).
DURING THIS TIME, PERSISTENT RAIN SHOWER CHANCES (35-75%) WILL
REMAIN OVER THE CASCADES AND EASTERN MOUNTAINS EACH DAY, WITH
SHORTWAVE IMPULSES FRIDAY/SATURDAY AND THE LOW PASSAGE SUNDAY/MONDAY
PRODUCING LIGHT RAIN CHANCES (15-40%) IN THE LOWER ELEVATIONS.
ISOLATED THUNDERSTORMS WILL BE POSSIBLE OVER THE MOUNTAINS TODAY AS
WEAK INSTABILITY DEVELOPS WITH ADDITIONAL SUPPORT FROM THE COLD CORE
OF THE LOW ALOFT. AS FOR PRECIPITATION AMOUNTS, THE CASCADES AND
BLUES WILL SEE 0.1 TO 0.25 INCHES OF DAILY PRECIP (CONFIDENCE 70-
90%), WITH LOCALLY HIGHER AMOUNTS WHERE THUNDERSTORMS DEVELOP.
SUNDAY INTO MONDAY, ENSEMBLE AND DETERMINISTIC MEMBERS SHOW THE
UPPER CLOSED LOW BEGINNING TO PUSH EAST, WITH THE LOW OVER THE
FORECAST AREA DURING THE DAY SUNDAY. WHILE LIGHT TO MODERATE RAIN
SHOWERS ARE FORECAST ACROSS THE AREA, THE UPPER LOW BEING OVERHEAD
AND WEAK INSTABILITY DEVELOPING AT THE SURFACE WILL ALSO RESULT IN
SLIGHT CHANCES (15-25%) OF ISOLATED THUNDERSTORMS FOCUSED ACROSS THE
CENTRAL OR CASCADES AND THE EASTERN MOUNTAINS SUNDAY AFTERNOON AND
EVENING. BY MONDAY EVENING, WHAT IS LEFT OF THE UPPER LEVEL LOW WILL
HAVE PUSHED EAST OF THE REGION, WITH SHOWERS DIMINISHING AREA WIDE.
TUESDAY, ENSEMBLE MEMBERS ARE IN GOOD AGREEMENT OF WEAK UPPER
TROUGHING DEVELOPING FROM THE PACNW INTO THE EASTERN PACIFIC, THOUGH
THE FORECAST AREA WITHIN AN AREA OF SPLIT FLOW (CONFIDENCE 55-65%).
WINDS WILL REMAIN LIGHT UNDER THIS PATTERN, WITH A WARMING TREND
BRINGING TEMPERATURES CLOSER TO NORMAL. BY WEDNESDAY, ENSEMBLE
MEMBERS DEPICT A WEAK CUT-OFF LOW DEVELOPING, HOWEVER THERE IS
SPREAD IN THE LOCATION OF THE LOW AMONGST ENSEMBLE SOLUTIONS.
SOLUTIONS (25% OF CLUSTER MEMBERS) WITH THE LOW OFFSHORE THE OR/CA
BORDER FAVOR LIGHT SHOWERS ALONG THE OR CASCADE CREST AND OCHOCO-
JOHN DAY HIGHLANDS, WHILE SOLUTIONS (69% OF CLUSTER MEMBERS) WITH
THE LOW FURTHER SOUTH FAVOR DRY CONDITIONS PERSISTING.
SPREAD IN THE EVOLUTION OF THE CUT-OFF LOW ONLY GROWS THURSDAY AS
MEMBERS ARE SPLIT IN TIMING, LOCATION, AND STRENGTH OF THE LOW.
SOLUTIONS (53% OF MEMBERS) THAT HAVE THE LOW BECOME AN OPEN WAVE AND
APPROACH THE PACNW FAVOR THE RETURN OF WIDESPREAD UNSETTLED WEATHER
CONDITIONS, WHILE REMAINING SOLUTIONS (47% OF MEMBERS) FAVOR A
TROUGH EVOLUTION THAT RESULTS IN DRY CONDITIONS ACROSS THE FORECAST
AREA. CONFIDENCE IN FORECAST DETAILS IS LOW (15-20%) FOR THE MID-
WEEK PERIOD. LAWHORN/82
AVIATION /12Z TAFS THROUGH 12Z SATURDAY/
VFR CONDITIONS TO
PREVAIL THROUGH THE PERIOD. SHOWERS ARE EXPECTED TO IMPACT SITES
RDM/BDN BETWEEN 22Z-03Z TODAY, WITH DRY CONDITIONS EXPECTED
ELSEWHERE. THAT SAID, THERE IS A LOW CHANCE (15-25%) OF SHOWERS
IMPACTING SITES ALW/PDT BETWEEN 22Z-04Z AS WELL. CIGS/VSBY MAY
DROP TO MVFR CATEGORIES WITH HEAVY RAIN SHOWERS. WINDS WILL BE
12KTS OR LESS THROUGH THE PERIOD. LAWHORN/82
PRELIMINARY POINT TEMPS/POPS
PDT 71 42 69 45 / 10 10 40 0
ALW 72 48 71 49 / 30 10 30 10
PSC 74 45 73 45 / 10 10 30 0
YKM 73 47 71 47 / 10 10 30 10
HRI 74 45 72 45 / 10 10 40 0
ELN 69 41 68 42 / 20 10 40 10
RDM 64 34 67 37 / 50 60 10 40
LGD 68 40 71 41 / 40 20 50 10
GCD 68 40 70 41 / 20 30 40 0
DLS 75 51 74 52 / 20 20 50 30
PDT WATCHES/WARNINGS/ADVISORIES
WA...NONE.
OR...NONE.
DISCUSSION...82
AVIATION...82
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