747
FXUS66 KPDT 082336
AFDPDT
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PENDLETON OR
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.
AVIATION...00Z TAFS
VFR CONDITIONS ARE FORECAST THROUGH
THE VALID PERIOD FOR ALL SITES. ASIDE FROM SOME HIGH CLOUD, SKIES
WILL BE MOSTLY CLEAR. DIURNALLY DRIVEN WINDS OF 10 KTS OR LESS ARE
FORECAST, EXCEPT AT DLS, WHICH WILL SEE SOME GUSTS TO AROUND 20 KTS
LATE THIS AFTERNOON AND EVENING BEFORE RETURNING TO 10 KTS OR LESS
OVERNIGHT. PLUNKETT/86
PRELIMINARY POINT TEMPS/POPS
PDT 56 89 59 94 / 0 0 0 0
ALW 61 89 64 94 / 0 0 0 0
PSC 57 91 60 97 / 0 0 0 0
YKM 59 91 62 96 / 0 0 0 0
HRI 58 91 60 97 / 0 0 0 0
ELN 59 87 61 96 / 0 0 0 0
RDM 46 88 51 94 / 0 0 0 0
LGD 52 86 55 91 / 0 0 0 0
GCD 51 86 54 92 / 0 0 0 0
DLS 62 90 66 99 / 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...86
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