884
FXUS66 KPDT 091720
AFDPDT
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PENDLETON OR
1020 AM PDT SAT AUG 9 2025
UPDATED FOR AVIATION
AVIATION
18Z TAFS...VFR CONDITIONS ARE EXPECTED FOR THE NEXT SEVERAL DAYS
WITH WINDS MAINLY 10 KTS OR LESS. THE ONLY EXCEPTION IN KBDN,
WHERE SOME MVFR VSBYS IN HZ MOVED IN OVERNIGHT THROUGH EARLY AM
AND ARE EXPECTED AGAIN TONIGHT. GUIDANCE DID NOT HANDLE THIS WELL
AND CONTINUES NOT DOING SO. LOOKING AT NEARBY CAMERAS, NOT SEEING
ALL THAT MUCH IN THE WAY OF HZ, BUT THERE COULD BE SOME LOCAL HZ
DUE TO SMOKE FROM REGIONAL FIRES.
PREV DISCUSSION
/ISSUED 1036 PM PDT FRI AUG 8 2025/
UPDATED AVIATION DISCUSSION.
AVIATION...06Z TAFS...VFR CONDITIONS CURRENTLY ACROSS ALL SITES,
WHICH WILL STAY THE COURSE THROUGH THE PERIOD. FEW/SCT HIGH LEVEL
CLOUDS THROUGH EARLY SATURDAY AFTERNOON WILL BECOME MORE BKN BY
LATE AFTERNOON AND EXTEND THROUGH THE EVENING. WINDS WILL BE
DIURNALLY DRIVEN AND BELOW 10 KTS, WITH THE EXCEPTION OF BREEZY
LATE AFTERNOON WINDS AT KDLS WITH GUSTS OF 20 KTS LIKELY. 75
PREV DISCUSSION... /ISSUED 436 PM PDT FRI AUG 8 2025/
DISCUSSION...NORTHWEST FLOW WILL CONTINUE OVER THE REGION THROUGH
EARLY SATURDAY. THEN, A STRONG HIGH PRESSURE SYSTEM WILL BEGIN TO
MOVE EASTWARD FROM THE PACIFIC OCEAN LATER SATURDAY INTO SUNDAY.
THIS HIGH WILL REMAIN OVER THE AREA MONDAY INTO TUESDAY BEFORE BEING
SUPPRESSED SOUTHWARD.
HIGH TEMPERATURES WILL INCREASE INTO THE WEEKEND AND EARLY NEXT
WEEK, WITH MONDAY LIKELY BEING THE HOTTEST DAY, WITH UPPER 90S TO
TRIPLE DIGITS IN THE COLUMBIA BASIN AND SURROUNDING AREAS.
HEATRISK VALUES WILL BE WIDESPREAD MODERATE AND MAJOR HEATRISK IN
THE LOWER VALLEYS. THESE TEMPERATURES WILL BE 10 TO 15 DEGREES
ABOVE NORMAL.
HOWEVER, BEFORE WE GET TO THE HOT TEMPERATURES, ANOTHER RELATIVELY
COOL NIGHT IS IN STORE TONIGHT WITH MANY LOCATIONS IN THE 40S AND
50S.
SUNDAY LOOKS TO HAVE HIGH TEMPERATURES IN THE MID TO UPPER 90S
WITH AREAS OF MODERATE HEATRISK.
THERE IS STILL SOME UNCERTAINTY AS TO TUESDAY'S HIGHS BUT
TEMPERATURES HAVE TRENDED UPWARD WITH TODAY'S MODEL RUNS, AND
TEMPERATURES LOOK SIMILAR TO MONDAY AT THIS POINT.
BASED ON ALL OF THIS INFORMATION, HAVE OPTED TO ISSUE AN EXTREME
HEAT WATCH FOR SUNDAY THROUGH TUESDAY. WILL SEE HOW LATER GUIDANCE
TRENDS FOR LATER HEADLINES, AND IT IS POSSIBLE SOME OF THE WATCHES
END UP AS ADVISORIES AND OTHERS AS WARNINGS.
NBM PROBABILITIES OF HIGH TEMPERATURES >= 100 DEGREES RANGE FROM
20 TO 50 PERCENT ON SUNDAY, MAINLY ACROSS PORTIONS OF THE BASIN
AND CENTRAL OREGON, AND JUMP TO 60 TO OVER 90 PERCENT MONDAY AND
TUESDAY. THE GFS HAS ABOUT 50 PERCENT OF ITS ENSEMBLE MEMBERS
>=100 DEGREES ON SUNDAY FOR THE COLUMBIA BASIN, WHILE IN THE
ECMWF, ITS ABOUT 80 PERCENT.
THE ECMWF EFI BRINGS 0.7 TO 0.8 ANOMALIES FOR HIGH (AND LOW)
TEMPERATURES ESPECIALLY ACROSS THE BASIN BY MONDAY AND TUESDAY,
WITH A LARGE AREA OF 0.6 TO 0.7 SURROUNDING IT.
HIGH TEMPERATURES WILL BEGIN TO COOL ON WEDNESDAY AS A WEAK TROUGH,
MOVES INTO THE PACIFIC NORTHWEST, FOLLOWED BY ZONAL FLOW. HIGH
THURSDAY WILL BE EVEN COOLER THAN WEDNESDAY, AND WILL END UP CLOSE
TO NORMAL BY THE END OF THE WEEK.
NO PRECIPITATION IS FORECAST THROUGH THE WEEK. WITH HUMIDITIES
STAYING LOW AROUND OR BELOW 20 PERCENT THROUGH WEDNESDAY IN MANY
ARES, ANY INCREASE IN WINDS WITH THE TROUGH MOVING ONSHORE WILL
BRING ENHANCED FIRE WEATHER CONCERNS AND THIS IS SOMETHING WE WILL
HAVE TO WATCH ESPECIALLY IN THE LATER TUESDAY INTO WEDNESDAY TIME
FRAME. BEYOND WEDNESDAY, THE COOLER TEMPERATURES WILL BRING
INCREASED HUMIDITY, WHICH SHOULD HELP ALLEVIATE ANY FIRE WEATHER
CONCERNS.
PRELIMINARY POINT TEMPS/POPS
PDT 88 59 95 64 / 0 0 0 0
ALW 88 65 95 70 / 0 0 0 0
PSC 91 60 98 65 / 0 0 0 0
YKM 91 63 97 66 / 0 0 0 0
HRI 91 60 97 66 / 0 0 0 0
ELN 88 61 97 64 / 0 0 0 0
RDM 88 51 95 56 / 0 0 0 0
LGD 87 55 91 59 / 0 0 0 0
GCD 87 54 93 59 / 0 0 0 0
DLS 91 67 99 71 / 0 0 0 0
PDT WATCHES/WARNINGS/ADVISORIES
OR...EXTREME HEAT WATCH FROM SUNDAY AFTERNOON THROUGH TUESDAY EVENING
FOR ORZ041-044-505-507-508-510-511.
WA...EXTREME HEAT WATCH FROM SUNDAY AFTERNOON THROUGH TUESDAY EVENING
FOR WAZ024-026>029-521.
SHORT TERM...77
LONG TERM....77
AVIATION...77
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