461
FXUS66 KPDT 300506
AFDPDT
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PENDLETON OR
1006 PM PDT SAT AUG 29 2026
KEY MESSAGES
- SHOWER CHANCES ACROSS THE WA CASCADES WITH LOW CHANCE (5-15%)
OF ISOLATED THUNDERSTORMS ACROSS THE WA CASCADE EAST SLOPES
AND NORTHERN BLUES THROUGH THIS AFTERNOON
- ELEVATED FIRE WEATHER CONDITIONS WILL CONTINUE THROUGH THIS
EVENING DUE TO BREEZY WINDS
- DRYING AND WARMING TREND SUNDAY THROUGH EARLY TUESDAY BEFORE
AN UPPER LOW PASSAGE LATE TUESDAY INTO FRIDAY BRINGS
INCREASING SHOWER CHANCES, BREEZY WESTERLY WINDS, AND COOLER
CONDITIONS
DISCUSSION
WATER VAPOR SATELLITE IMAGERY THIS AFTERNOON SHOWS
AN UPPER LEVEL LOW SLIDING ACROSS NORTHERN WA, WITH VISIBLE
SATELLITE AND RADAR IMAGERY SHOWING ISOLATED TO SCATTERED
SHOWERS/THUNDERSTORMS MAINLY IN THE UPPER COLUMBIA BASIN. BREEZY
WINDS HAVE DEVELOPED THROUGH THE CASCADE GAPS AND INTO THE LOWER
ELEVATIONS AS WELL, WITH STRONGEST WINDS BEING REPORTED THROUGH
THE KITTITAS VALLEY AND ALONG WA CASCADE EAST SLOPES.
REST OF TODAY THROUGH EARLY TUESDAY: SHOWERS AND ANY REMAINING
CONVECTION ACROSS THE FORECAST AREA WILL DIMINISH BEFORE THIS
EVENING AS THE UPPER LOW LIFTS NORTHEAST INTO CANADA. THE BREEZY
WESTERLY WINDS THAT DEVELOPED WITH THE LOW PASSAGE WILL CONTINUE
INTO THIS EVENING AS COLD AIR ADVECTION BEHIND THE LOW WILL
MAINTAIN TIGHTENED SURFACE PRESSURE GRADIENTS. WHILE RHS WILL
REMAIN ABOVE CRITICAL CRITERIA OVER THE REGION, THE BREEZY
WINDS WILL CONTINUE TO PRESENT ELEVATED FIRE WEATHER CONDITIONS
ACROSS THE LOWER ELEVATIONS AND ALONG THE CASCADE EAST SLOPES.
THE AFOREMENTIONED COLD AIR ADVECTION INTO THE REGION WILL KEEP
TEMPERATURES ABOUT 3 TO 8 DEGREES BELOW NORMAL THROUGH SUNDAY
AFTERNOON, WITH SOME MOUNTAIN VALLEYS IN THE EASTERN MOUNTAINS
LOOKING AT NEAR TO BELOW FREEZING TEMPERATURES TONIGHT
(CONFIDENCE 65-80%). WITH WINDS EXPECTED TO WEAKEN AND SKIES
REMAINING MOSTLY CLEAR, CONFIDENCE IS HIGH ENOUGH (65-80%) TO
WARRANT A FREEZE WARNING FOR TONIGHT IN THE WALLOWA VALLEY.
SUNDAY THROUGH EARLY TUESDAY, UPPER LEVEL RIDGING WILL MOVE OVER
THE REGION, RESULTING IN A WARMING AND DRYING TREND THROUGH THIS
PERIOD. AT THIS TIME, GIVEN THE INCREASED HIGH PRESSURE OVER
THE REGION AND EXPECTED WARMING, CONFIDENCE IS LOW (25-35%) IN
ANOTHER ROUND OF NEAR TO BELOW FREEZING TEMPERATURES DEVELOPING
ACROSS MOST OF OUR MOUNTAIN VALLEY LOCATIONS.
TUESDAY THROUGH FRIDAY: CONFIDENCE IS MOD-HIGH (60-80%) THAT AN
ACTIVE PERIOD OF WEATHER WILL DEVELOP THROUGH THE REMAINDER OF
THE WORK WEEK. ENSEMBLE CLUSTER AND DETERMINISTIC GUIDANCE ARE
IN AGREEMENT OF A WEAKENING UPPER LOW OFFSHORE BECOMING AN OPEN
WAVE AND LIFTING NORTHEAST. THE UPPER SHORTWAVE TROUGH PASSAGE
OVER THE PACNW WILL BRING SCATTERED SHOWER CHANCES ACROSS
MOUNTAIN AREAS AS WELL AS IN CENTRAL OR WITH SLIGHT CHANCE
(15-205% OF ISOLATED THUNDERSTORMS IN CENTRAL OR, WA CASCADES,
AND PORTIONS OF THE EASTERN MOUNTAINS. BREEZY WESTERLY WINDS
WILL DEVELOP ACROSS THE LOWER COLUMBIA BASIN, CENTRAL OR, AND
PORTIONS OF THE EASTERN MOUNTAINS TUESDAY AFTERNOON. RHS ALONG
THE PERIPHERY OF THE SOUTHERN BLUES WILL REMAIN LOW INTO TUESDAY
AFTERNOON, RESULTING IN ELEVATED FIRE WEATHER CONDITIONS AS THE
WINDS BEGIN TO INCREASE.
EARLY WEDNESDAY, ENSEMBLE CLUSTER GUIDANCE IS IN GOOD AGREEMENT
THAT AN UPPER LOW WILL DROP DOWN THE BC COASTLINE AND SETUP
JUST OFFSHORE THE PACNW, INCREASING SHOWER CHANCES ALONG THE
CASCADE CREST. LATE WEDNESDAY INTO FRIDAY, HOWEVER, ENSEMBLE
CLUSTER SOLUTIONS ARE SPLIT BETWEEN TWO SOLUTIONS. THE FIRST
SOLUTION BEING THE UPPER LOW SITTING OFFSHORE THROUGH THURSDAY
INTO EARLY FRIDAY, THEN MOVING INLAND. THE SECOND SOLUTION IS
FOR THE UPPER LOW TO PUSH INLAND ON THURSDAY AND SLOWLY MOVE
ACROSS THE REGION THROUGH FRIDAY. THE FIRST SOLUTION WOULD
RESULT IN RAIN SHOWER CHANCES DEVELOPING ACROSS THE EASTERN
MOUNTAINS LATE THURSDAY INTO FRIDAY; THE SECOND SOLUTION WOULD
RESULT IN SHOWER CHANCES AS EARLY AS WEDNESDAY NIGHT, WITH
WIDESPREAD MOUNTAIN CHANCES AND ISOLATED LOWER ELEVATION CHANCES
THROUGH FRIDAY. CURRENT CONFIDENCE IS MODERATE (50-60%) IN
SHOWER CHANCES DEVELOPING AREA-WIDE SOMETIME LATE IN THE
WORKWEEK, BUT CONFIDENCE IS LOW (20-30%) IN TIMING AND
PRECIPITATION AMOUNTS. LAWHORN/82
AVIATION /06Z TAFS THROUGH 06Z MONDAY/
VFR CONDITIONS ARE EXPECTED AT ALL TAF SITES THROUGH SUNDAY.
SOME LINGERING BREEZY CONDITIONS SHOULD DECREASE IN THE NEXT FEW
HOURS WITH ALL SITES 10 KTS OR LESS BY MORNING.
PRELIMINARY POINT TEMPS/POPS
PDT 43 76 45 86 / 0 0 0 0
ALW 49 76 51 89 / 0 0 0 0
PSC 47 79 48 88 / 0 0 0 0
YKM 49 79 53 85 / 0 0 0 0
HRI 48 78 48 88 / 0 0 0 0
ELN 43 75 47 80 / 0 0 0 0
RDM 35 78 40 86 / 0 0 0 0
LGD 40 78 43 89 / 0 0 0 0
GCD 41 79 46 91 / 0 0 0 0
DLS 52 80 55 87 / 0 0 0 0
PDT WATCHES/WARNINGS/ADVISORIES
WA...NONE.
OR...AIR QUALITY ALERT UNTIL NOON PDT MONDAY FOR ORZ041-505-506-
509>511.
FREEZE WARNING UNTIL 9 AM PDT SUNDAY FOR ORZ050.
DISCUSSION...82
AVIATION...77
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