703
FXUS66 KPDT 210525
AFDPDT
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PENDLETON OR
1025 PM PDT TUE OCT 20 2026
.UPDATED AVIATION DISCUSSION.
KEY MESSAGES
- ABOVE NORMAL TEMPERATURES AND DRY CONDITIONS THROUGH WEDNESDAY
- RETURN OF SHOWERS AND ISOLATED THUNDERSTORMS TO THE EASTERN
MOUNTAINS THURSDAY, WITH BREEZY CONDITIONS IN THE LOWER
ELEVATIONS THURSDAY AND FRIDAY
- MODERATE CONFIDENCE (60-70%) IN FREEZING MORNING TEMPERATURES
SATURDAY
DISCUSSION
SATELLITE IMAGERY THIS AFTERNOON SHOWS AN UPPER CLOSED LOW
SPINNING AWAY OFF THE COAST OF CA WHILE A BAND OF MID TO UPPER
LEVEL CLOUD COVER REACHES UP INTO CENTRAL AND NORTHEAST OR.
TODAY THROUGH WEDNESDAY: WHILE AN UPPER LOW CONTINUES TO SIT OFF
THE CA COAST TODAY, AND UPPER LEVEL RIDGE WILL SLIDE ACROSS
NORTHERN WA AND BC. THE FORECAST AREA WILL BE UNDER THE
INFLUENCE OF THIS UPPER RIDGE, RESULTING IN DRY CONDITIONS,
ABOVE NORMAL TEMPERATURES, AND LIGHT WINDS THE REST OF TODAY. BY
TOMORROW, THE UPPER RIDGE WILL BE EAST OF THE REGION WITH SOUTH
TO SOUTHWEST FLOW OVER THE FORECAST AREA. THIS WILL RESULT IN
CONTINUED DRY CONDITIONS AND LIGHT WINDS. TO THE SOUTH, THE
UPPER LOW WILL BEGIN TO SWING INTO CENTRAL CA, WITH
PRECIPITATION AHEAD OF THE LOW REACHING SOUTHERN OR BY WEDNESDAY
NIGHT.
THURSDAY AND FRIDAY: LATER THIS WORK WEEK, THE PACNW WILL BE
IMPACTED BY TWO SYSTEMS: THE UPPER CLOSED LOW PASSING TO THE
SOUTH AND EAST AND UPPER TROUGH WITH ATTENDANT COLD FRONT
SLIDING ACROSS THE PACNW.
THE UPPER CLOSED LOW PASSAGE WILL BE THE MAIN PRECIPITATION
MAKER THROUGH THIS PERIOD. SHOWERS WILL BEGIN TO DEVELOP ACROSS
THE HIGH TERRAIN SOUTH AND EAST OF JOHN DAY WEDNESDAY NIGHT,
THEN THROUGH THURSDAY WILL SPREAD TO THE REMAINDER OF THE
EASTERN MOUNTAINS, CENTRAL OR, AND THE EASTERN HALF OF THE
COLUMBIA BASIN BY THURSDAY AFTERNOON. SHOWER CHANCES WILL
DISSIPATE FROM WEST TO EAST THURSDAY EVENING INTO FRIDAY
MORNING AS THE UPPER LOW CONTINUES EAST OF THE REGION. THURSDAY,
24-HR CHANCES BETWEEN 75-95% OF 0.25 INCHES OF RAIN ARE FOCUSED
AROUND THE NORTHERN BLUE MOUNTAINS, ELKHORN CREST, AND WALLOWA
COUNTY; ALONG THE BLUE MOUNTAIN FOOTHILLS AND THE REMAINDER OF
THE EASTERN MOUNTAINS, CHANCES OF 0.1 INCHES ARE 45-65%. IN THE
REMAINDER OF THE AREAS, THERE IS A 30-50% CHANCE OF AT LEAST
0.01 INCHES.
THE UPPER TROUGH AND COLD FRONT PASSAGE LATE THURSDAY THROUGH
FRIDAY WILL BRING WIND IMPACTS THROUGHOUT THE FORECAST AREA.
WINDS WILL BEGIN TO INCREASE THROUGH THE CASCADE GAPS THURSDAY
AFTERNOON, AND CONTINUE TO STRENGTHEN OVERNIGHT AS THE COLD
FRONT DRAGS ACROSS THE INTERMOUNTAIN PACNW. WINDS ARE CURRENTLY
EXPECTED (CONFIDENCE 55-70%) TO PEAK OVERNIGHT THURSDAY INTO
FRIDAY MORNING BETWEEN 25-35 MPH WITH GUSTS TO AROUND 45 MPH
THROUGH THE EASTERN GORGE AND KITTITAS VALLEY, WHILE WINDS WILL
BE SLIGHTLY WEAKER (20-30 MPH WITH GUSTS UP TO 40 MPH) IN
PORTIONS OF THE COLUMBIA BASIN, CENTRAL OR, CASCADE EAST SLOPES,
AND EASTERN MOUNTAINS (INCLUDING GRANDE RONDE VALLEY). BREEZY
WINDS WILL CARRY ON INTO THE AFTERNOON FRIDAY, BUT BECOME LIGHT
BY THE NIGHTTIME HOURS.
LASTLY, THE UPPER CLOSED LOW SWINGING INLAND WILL BECOME AN OPEN
TROUGH WITH A NEGATIVE TILT BY THURSDAY AFTERNOON. AHEAD OF THE
TROUGH'S AXIS, SBCAPE BETWEEN 200-250 J/KG WILL DEVELOP ACROSS
THE EASTERN MOUNTAINS. INCREASED CAPE AND THE NEGATIVE TILT WILL
RESULT IN CHANCES (15-25%) OF ISOLATED THUNDERSTORMS DEVELOPING
THURSDAY AFTERNOON.
SATURDAY THROUGH MONDAY: AFTER FRIDAY, ENSEMBLE GUIDANCE IS
NEARLY SPLIT 50/50 IN THE EVOLUTION OF THE SYNOPTIC PATTERN. THE
MORE IMPACTFUL OF THE TWO SOLUTIONS INVOLVES AN UPPER CLOSED LOW
SWINGING OUT OF THE NORTHEAST PACIFIC AND ACROSS THE PACNW
LATE SATURDAY THROUGH MONDAY. THIS WOULD RESULT IN A RETURN OF
LOWER ELEVATIONS RAIN SHOWERS WHILE SNOW LEVELS WILL BE LOW
ENOUGH (~5KFT) FOR LIGHT MOUNTAIN SNOW SHOWERS TO DEVELOP. THE
OTHER SOLUTION WOULD BE FOR UPPER LEVEL RIDGING DEVELOPING OVER
THE PACNW AND FOR ANY UPPER TROUGH/LOW TO BE BLOCKED FROM
SWINGING INTO THE REGION. UNDER THIS SCENARIO, DRY CONDITIONS
WOULD REDEVELOP AND PERSIST ACROSS THE FORECAST AREA. FORECAST
CONFIDENCE SATURDAY AFTERNOON THROUGH MONDAY IS LOW (20-25%).
OTHERWISE, THERE IS GOOD AGREEMENT THAT THE EARLIER TROUGH/COLD
FRONT PASSAGE WILL ALLOW FOR A COLDER/DRIER AIRMASS TO SETTLE
INTO THE AREA FRIDAY NIGHT THROUGH SATURDAY MORNING. THE DRY
CONDITIONS AND POTENTIALLY CLEAR SKIES WILL AT LEAST HELP WITH
LOWERING TEMPERATURES TO OR BELOW FREEZING IN LOWER ELEVATION
LOCATIONS SATURDAY MORNING (CONFIDENCE 60-70%). WILL CONTINUE TO
MONITOR FOR NEED OF FREEZE WARNINGS. LAWHORN/82
AVIATION /06Z TAFS THROUGH 06Z THURSDAY/
VFR CONDITIONS CURRENTLY ACROSS ALL SITES, WHICH WILL STAY THE
COURSE THROUGH THE PERIOD. LIGHT WINDS BELOW 7KTS ARE EXPECTED
TO PERSIST, WITH MINIMAL CLOUDS. KRDM AND KBDN WILL EXPERIENCE
MORE BKN/SCT CLOUD COVER AT 25KFT. 75
PRELIMINARY POINT TEMPS/POPS
PDT 35 68 38 62 / 0 0 0 60
ALW 41 68 44 61 / 0 0 0 70
PSC 38 68 34 65 / 0 0 0 30
YKM 40 69 39 69 / 0 0 0 0
HRI 36 68 36 63 / 0 0 0 30
ELN 35 67 36 67 / 0 0 0 0
RDM 30 72 31 63 / 0 0 0 30
LGD 41 74 45 64 / 0 0 0 90
GCD 40 76 43 64 / 0 0 10 90
DLS 41 72 42 70 / 0 0 0 0
PDT WATCHES/WARNINGS/ADVISORIES
WA...NONE.
OR...NONE.
DISCUSSION...82
AVIATION...75
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