975
FXUS66 KPDT 231721
AFDPDT
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PENDLETON OR
1021 AM PDT SUN AUG 23 2026
KEY MESSAGES
- UPPER LEVEL HIGH PRESSURE BUILDS BACK OVER THE REGION THROUGH
THE MIDWEEK WITH WARMING TEMPERATURES AND MOSTLY DRY
CONDITIONS
- BREEZY WINDS RETURN WEDNESDAY, WITH MODERATE CONFIDENCE (55-60%)
IN ELEVATED FIRE WEATHER CONDITIONS DEVELOPING WEDNESDAY
- NEAR SEASONABLE TEMPERATURES AND DIURNALLY BREEZY CASCADE GAP
WINDS RETURN THURSDAY INTO THE WEEKEND
DISCUSSION
WATER VAPOR IMAGERY TONIGHT SHOWS AN UPPER LEVEL
LOW MOVING ACROSS WESTERN WA, WHILE NIGHTTIME SATELLITE AND
RADAR IMAGERY SHOWS LITTLE ACTIVITY ACROSS THE FORECAST AREA
WITH ONLY SCATTERED SHOWERS/THUNDERSTORMS ACROSS NORTHEAST WA.
WINDS IN THE LOWER ELEVATIONS HAVE MOSTLY WEAKENED, WITH BREEZY
CONDITIONS STILL REPORTED THROUGH THE CASCADE GAPS, PORTIONS OF
THE OR COLUMBIA BASIN, AND THE BLUE MOUNTAIN FOOTHILLS.
TODAY THROUGH TUESDAY: THE UPPER LOW OVER WESTERN WA WILL
CONTINUE TO PUSH EAST THROUGH THE REMAINDER OF TODAY, WEAKENING
AND BECOMING AN OPEN WAVE TROUGH DURING IT'S TRANSIT. ON THE
BACKSIDE OF THE TROUGH, A SLIGHT CHANCE (15-25%) OF LIGHT RAIN
SHOWERS WILL BE POSSIBLE ALONG THE WA CASCADE CREST THIS
MORNING, BUT WILL DIMINISH IN THE AFTERNOON AS THE TROUGH PUSHES
INTO CANADA. BREEZY WINDS THROUGH THE CASCADE GAPS AND PORTIONS
OF THE COLUMBIA BASIN WILL REMAIN THROUGH THE EVENING HOURS, AS
THE CROSS CASCADE SURFACE PRESSURE GRADIENT WILL BE SLOWER TO
WEAKEN.
LATE SUNDAY THROUGH TUESDAY, AN UPPER LEVEL RIDGE WILL BUILD
OVER THE PACNW AND NORTHERN ROCKIES, PRODUCING ANOTHER WARMING
TREND THAT WILL PERSIST INTO WEDNESDAY. FROM THE MOST RECENT NBM
RUN, 90TH PERCENTILE MAX TEMPERATURES REMAIN AROUND THE MID 90S,
WITH LOCALLY UPPER 90S IN THE WA COLUMBIA BASIN. OTHERWISE,
WHILE CONDITIONS ARE EXPECTED TO REMAIN MOSTLY DRY ACROSS THE
FORECAST AREA, THERE ARE LESS THAN 10% CHANCES OF ISOLATED
SHOWERS/THUNDERSTORMS DEVELOPING ACROSS THE SOUTHERN BLUES
MONDAY AFTERNOON, AND THE NORTHERN BLUES TUESDAY AFTERNOON.
WEDNESDAY THROUGH SATURDAY: WHILE WARMING IMPACTS FROM THE UPPER
LEVEL RIDGE IS EXPECTED TO PERSIST INTO WEDNESDAY, THERE IS GOOD
AGREEMENT AMONGST ENSEMBLE GUIDANCE THAT UPPER LEVEL TROUGHING
IN THE NORTHEAST PACIFIC WILL DROP CLOSER TO THE PACNW
WEDNESDAY, THEN PUSH INLAND DURING THE DAY THURSDAY (CONFIDENCE
55-65%). THE APPROACH OF THE UPPER TROUGH AND AN ATTENDANT
SURFACE LOW WILL TIGHTEN SURFACE PRESSURE GRADIENTS ALONG THE
CASCADE CREST, RESULTING IN A RETURN TO BREEZY WESTERLY WINDS
DEVELOPING WEDNESDAY. FIRE WEATHER CONDITIONS WILL BECOME
ELEVATED TO MARGINALLY CRITICAL ACROSS PORTIONS OF THE COLUMBIA
BASIN/GORGE AND ADJACENT VALLEYS IN THE AFTERNOON, AS RELATIVE
HUMIDITIES WILL BE NEAR CRITICAL VALUES (CONFIDENCE 55-60%).
THURSDAY, ENSEMBLE CLUSTER ANALYSIS SHOWS THE UPPER TROUGH
SWINGING INTO SOUTHERN BC, PUSHING THE UPPER RIDGE FURTHER EAST
OF THE REGION. NEAR SEASONABLE TEMPERATURES WILL RESULT WITH
A SLIGHT INCREASE IN RELATIVE HUMIDITY ACROSS THE FORECAST AREA
(CONFIDENCE 45-55%), WHILE BREEZY WINDS PERSIST THROUGH THE
CASCADE GAPS. CONFIDENCE IS MODERATE (45-60%) THAT FIRE WEATHER
CONDITIONS WILL BE ELEVATED, BUT REMAIN ABOVE CRITICAL
THRESHOLDS. FRIDAY INTO SATURDAY, ENSEMBLE CLUSTER SOLUTIONS
FAVOR UPPER LEVEL TROUGHING CONTINUING TO IMPACT THE PACNW,
THOUGH ENSEMBLE MEMBERS ARE IN DISAGREEMENT ON POSITION AND
STRENGTH OF THE TROUGH. CONFIDENCE IN FORECAST DETAILS IS LOW-
MODERATE (35-50%) DURING THIS PERIOD. LAWHORN/82
AVIATION /18Z TAFS THROUGH 18Z MONDAY/
SLIGHTLY BREEZY WINDS AT PDT/ALW/DLS TODAY WITH GUSTS (20-25KTS)
TAPERING OFF AROUND 7 OR 8 PM. ELSEWHERE LIGHTER (UNDER 12 KNOT)
WINDS AT YKM/PSC/RDM/BDN, WITH VFR AT ALL TERMINALS.
PRELIMINARY POINT TEMPS/POPS
PDT 82 49 90 54 / 0 0 0 0
ALW 84 55 93 61 / 0 0 0 0
PSC 86 53 93 57 / 0 0 0 0
YKM 86 57 91 61 / 0 0 0 0
HRI 85 53 92 58 / 0 0 0 0
ELN 77 51 87 57 / 0 0 0 0
RDM 83 45 91 49 / 0 0 0 0
LGD 85 49 93 56 / 0 0 0 0
GCD 87 52 95 57 / 0 0 0 0
DLS 83 59 94 64 / 0 0 0 0
PDT WATCHES/WARNINGS/ADVISORIES
WA...AIR QUALITY ALERT UNTIL NOON PDT MONDAY FOR WAZ026-522-523.
OR...AIR QUALITY ALERT UNTIL NOON PDT MONDAY FOR ORZ041-044-049-050-
502-503-505>507-509>511.
DISCUSSION...82
AVIATION...71
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