977
FXUS66 KPDT 232206
AFDPDT
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PENDLETON OR
ISSUED BY NATIONAL WEATHER SERVICE SPOKANE WA
306 PM PDT WED APR 23 2025
SHORT TERM...TODAY THROUGH FRIDAY
LIGHT WINDS AND WARM, DRY
CONDITIONS FOR THE REST OF TODAY INTO TOMORROW MORNING AS THE
UPPER RIDGE CONTINUES MOVING ACROSS THE PACNW. WITH THE ONGOING
NORTHWESTERLY FLOW ALOFT, WINDS REMAIN LOCALLY BREEZY (15-25 MPH)
OVER THE BLUE MOUNTAIN-FOOTHILLS EXTENDING THROUGH CENTRAL OR THIS
AFTERNOON INTO EVENING WHEN THEY WILL THEN DECREASE. SKIES WILL
REMAIN CLEAR AS WELL BEFORE CLOUD COVERAGE INCREASES TOMORROW LATE
MORNING ONWARDS ALONG WITH LOCALLY BREEZY CONDITIONS OVER THE
CASCADE GAPS UNTIL TOMORROW EVENING. THE RIDGE GRADUALLY MOVES
EAST TOMORROW EVENING AS A UPPER TROUGH DEVELOPS AND DEEPENS NEAR
THE WEST COAST WITH THE SHORTWAVE TROUGH MOVING ACROSS THE PACNW
FRIDAY. SHOWERS WILL DEVELOP AT OR CASCADES FIRST TOMORROW EVENING
BUT CHANCES ARE LOW (<20%).
WITH THE SOUTHWESTERLY FLOW TAKING OVER AND INCREASED MOISTURE AND
INSTABILITY, THUNDERSTORMS COULD DEVELOP FRIDAY EVENING OVER THE
GRANDE RONDE VALLEY AND PORTIONS OF THE WALLOWAS. HOWEVER, CHANCES
ARE LOW (<20%) ON THEIR DEVELOPMENT AND EXTENT WITH CAPE VALUES
BEING RELATIVELY LOW (500 J/KG OR BELOW) AND WEAK MOISTURE CONTENT.
THE SOUNDINGS FOR THE AFOREMENTIONED AREAS WERE ALSO DRY IN THE
LOWER TROPOSPHERE AS WELL THUS LOWERING CHANCES ON ITS SEVERITY.
CHANCES OF SHOWERS WILL INCREASE FRIDAY MORNING BEFORE SPREADING
ACROSS MOST OF THE FORECAST AREA THROUGH THE DAY WITH THE LOWER
BASIN, KITTITAS AND YAKIMA VALLEY, AND SIMCOE HIGHLANDS DRY. THE RAW
ENSEMBLES REMAIN HAVING LESS THAN 20% PROBABILITY FOR QPF AMOUNTS UP
TO 0.10” OVER THE LOWER PART OF THE EAST SLOPES OF OR CASCADES AND
OCHOCO-JOHN DAY HIGHLANDS, BUT INCREASES TO 30-50% PROB FRIDAY
NIGHT. WINDS WILL REMAIN LOCALLY BREEZY UP TO 25 MPH ACROSS THE
CASCADE GAPS AS THE SOUTHWESTERLY FLOW ALOFT PERSISTS DURING THE DAY
FRIDAY. HIGH TEMPERATURES WILL CONTINUE TO BE SEASONABLY WARM
THROUGH THIS FORECAST PERIOD. FEASTER/97
LONG TERM...SATURDAY THROUGH WEDNESDAY
KEY MESSAGES:
1. BREEZY TO WINDY CONDITIONS SATURDAY AND SUNDAY.
2. RAIN CHANCES SATURDAY AND SUNDAY, THUNDERSTORMS POSSIBLE SATURDAY.
3. COOLING ON SUNDAY BEFORE A WARMING TREND THROUGH MIDWEEK.
THE EXTENDED PERIOD IS CHARACTERIZED BY AN UPPER LEVEL LOW PRESSURE
SYSTEM TO OUR SOUTH AND EAST THROUGH THE WEEKEND AHEAD OF AN INCOMING
UPPER LEVEL RIDGE THAT MOVES OVER THE PACIFIC NORTHWEST MONDAY. THIS
WILL BRING ELEVATED WINDS ACROSS THE SLOPES OF THE CASCADES, GORGE,
AND BLUE MOUNTAIN FOOTHILLS, WIDESPREAD RAIN ACROSS OREGON AND
COOLING TEMPERATURES THROUGH THE WEEKEND. CONDITIONS MODERATE INTO
THE WORKWEEK AS UPPER LEVEL RIDGING TAKES HOLD, BUT ANOTHER WEAK
SHORTWAVE MAY RETURN SLIGHT RAIN CHANCES TO OUR MOUNTAIN AND
FOOTHILL ZONES TUESDAY. HOWEVER, THE PRIMARY CONCERN THROUGH THE
WEEKEND IS ASSOCIATED WITH WINDY AFTERNOON AND EVENING CONDITIONS
BOTH SATURDAY AND SUNDAY. A PRESSURE GRADIENT WILL DEVELOP ALONG
THE CASCADES AS A RESULT OF THE UPPER LEVEL LOW PRESSURE TO OUR
SOUTHEAST AND INCOMING HIGH PRESSURE ALONG THE COAST. SUSTAINED
WEST-NORTHWEST WINDS OF 20-30 MPH WITH GUSTS OF 35-45 MPH WILL BE
POSSIBLE OVER THE AFOREMENTIONED AREAS BOTH DAYS. THESE WIND VALUES
APPROACH ADVISORY CRITERIA, WITH THE NBM SUGGESTING A 40-60%
CHANCE ON SATURDAY AND A 50-70% CHANCE ON SUNDAY OF WIND GUSTS
REACHING 45 MPH OR GREATER - WITH THE BEST CHANCE OCCURRING ACROSS
THE KITTITAS VALLEY. ENSEMBLES ARE IN FAIRLY GOOD AGREEMENT WITH
THE SYNOPTIC PATTERN OVER THE WEEKEND, SO CONFIDENCE IN WIND
ADVISORIES BEING ISSUED OVER THE WEEKEND FOR THESE AREAS IS
MODERATE TO HIGH (60-80%) - ESPECIALLY ON SUNDAY.
THE PROXIMITY OF THE UPPER LEVEL LOW TO OUR SOUTH WILL ATTRIBUTE
TO ENHANCED INSTABILITY ACROSS THE JOHN DAY BASIN, GRANDE RONDE
VALLEY, NORTHERN BLUE MOUNTAINS, AND WALLOWA COUNTY SATURDAY
AFTERNOON AND EVENING WITH SURFACE CAPE OF 150-300 J/KG. THESE
PARAMETERS WOULD ALLOW FOR ISOLATED, DISCRETE THUNDERSTORMS TO BE
POSSIBLE, BUT CURRENT CONFIDENCE IS 25% OF OCCURRENCE. LIGHT RAIN
IS EXPECTED TO BE ONGOING ACROSS THE JOHN DAY BASIN SATURDAY
MORNING BEFORE EXTENDING INTO CENTRAL OREGON, GRANDE RONDE VALLEY,
NORTHERN BLUE MOUNTAIN FOOTHILLS, AND WALLOWA COUNTY BY MID-
AFTERNOON. LIGHT RAIN IS ANTICIPATED TO CONTINUE THROUGH THE
EVENING AND OVERNIGHT BEFORE TAPERING OFF SUNDAY MORNING. RAIN
AMOUNTS OF 0.05-0.15 OF AN INCH ARE EXPECTED OVER THE
AFOREMENTIONED AREAS. CONFIDENCE IN THESE RAIN AMOUNTS IS MODERATE
40-60%, AS 59% OF ENSEMBLE DO HINT AT SLIGHTLY LESS RAIN AMOUNTS
OF 0.03-0.05 OF AN INCH.
FLOW ALOFT WILL BE OUT OF THE SOUTH ON SATURDAY TO ALLOW FOR HIGH
TEMPERATURES TO PEAK INTO THE LOW TO MID-70S SATURDAY. NORTH-
NORTHWEST FLOW ALOFT DEVELOPS SUNDAY TO BRING IN SIGNIFICANTLY
COOLER TEMPERATURES SUNDAY AHEAD OF A SLOW WARMING TREND THROUGH
THE FIRST HALF OF THE WEEK AS MORE WESTERLY FLOW ALOFT DEVELOPS.
75
AVIATION...18Z TAFS
VFR CONDITIONS CURRENTLY ACROSS ALL SITES,
WHICH WILL STAY THE COURSE THROUGH THE PERIOD. CLEAR SKIES AND
LIGHT, TERRAIN-DRIVEN WINDS LESS THAN 10 KTS WILL EXTEND THROUGH
THE PERIOD. 75
PRELIMINARY POINT TEMPS/POPS
PDT 38 70 43 74 / 0 0 0 10
ALW 40 70 46 75 / 0 0 0 10
PSC 37 75 42 80 / 0 0 0 0
YKM 39 73 45 78 / 0 0 0 0
HRI 37 74 43 78 / 0 0 0 10
ELN 38 71 43 76 / 0 0 0 10
RDM 29 70 38 67 / 0 0 10 30
LGD 34 67 38 71 / 0 0 0 20
GCD 32 69 39 70 / 0 0 0 40
DLS 42 75 46 78 / 0 0 0 10
PDT WATCHES/WARNINGS/ADVISORIES
OR...NONE.
WA...NONE.
SHORT TERM...97
LONG TERM....75
AVIATION...75
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