879
FXUS66 KPDT 191107
AFDPDT
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PENDLETON OR
407 AM PDT WED AUG 19 2026
KEY MESSAGES
- DRYING AND WARMING TREND INTO FRIDAY AS UPPER LEVEL HIGH
PRESSURE BUILDS OVER THE REGION, WITH ELEVATED FIRE WEATHER
CONCERNS DUE TO DRY AND UNSTABLE CONDITIONS
- BREEZY WINDS DEVELOPING SATURDAY, WITH UNCERTAINTY IN
TIMING/EXTENT OF THUNDERSTORMS/SHOWERS FRIDAY THROUGH SUNDAY
DISCUSSION
SLOWLY BUILDING RIDGING THROUGH FRIDAY ACROSS THE INTERIOR
NORTHWEST WHILE THE UPPER FLOW ACROSS THE PAC NW BECOME MORE
SOUTHERLY WITH TIME. A LARGE AREA OF 500 MB LOW PRESSURE NEAR
35N AND -137W IS THE SYSTEM THAT WILL PIVOT TOWARD THE PACNW
COAST BY FRIDAY NIGHT AND SATURDAY TIME-FRAME, EFFECTIVELY
BREAKING DOWN THE RIDGE OVER THE INTERIOR OF WA/OR AND BRINGING
AT LAST A SMALL RISK FOR SHOWERS AND THUNDERSTORMS TO THE
MOUNTAINS, AND OVERALL COOLER TEMPERATURES EACH AFTERNOON THROUGH
THE WEEKEND. AN ABRUPT INCREASE IN SURFACE WINDS IS LIKELY BY
FRIDAY THROUGH ANY OF THE THE GAPS AND MOST PRONOUNCED ACROSS
THE COLUMBIA RIVER GORGE AND LOWER BASIN THOUGH THE ENTIRETY OF
SATURDAY NIGHT UNTIL THE UPPER LOW EXITS NORTHEAST AS A TROUGH
INTO THE CANADIAN ROCKIES.
THURSDAY AND FRIDAY WILL BE THE HOTTEST DAYS OF THE NEXT 7 ,
WITH TEMPERATURES IN THE 90S ACROSS THE COLUMBIA BASIN, CENTRAL
OREGON, AND THE OTHER VALLEY FLOORS. THURSDAY , HEATRISK REACHES
AN ELEVATED MODERATE (ORANGE) LEVELS ACROSS PARTS OF THE
YAKIMA/KITTITAS VALLEYS, NORTH CENTRAL OREGON, AND SOUTHEAST
WASHINGTON, BUT NOT WIDESPREAD OR HIGH ENOUGH FOR HEAT
ADVISORIES. SHOWERS ARE FORECAST ACROSS THE CASCADE CREST ON
FRIDAY, AND RRFS SHOWS SOME LIGHTNING POTENTIAL LATE AFTERNOON
FRIDAY ALONG THE CASCADE CREST. UNCERTAINTY REMAINS AS THE NBM
DRY LIGHTING CHANCES ARE STILL UNDER A 10% CHANCES EVEN ACROSS
THE ACROSS THE BLUE MOUNTAINS, AND THE EC/GFS HAVE DIFFERING
TIMING SOLUTIONS WITH THE INCOMING WAVE. AT THIS TIME THE BEST
CHANCES FOR THUNDERSTORMS ARE ABOUT 15% ACROSS THE EASTERN BLUES
ON SATURDAY AFTERNOON COINCIDING WITH MAX HEATING.
AVIATION /12Z TAFS THROUGH 12Z THURSDAY/
SATELLITE AND METARS OVERNIGHT SHOWED CLEAR SKY OTHER THAN AN
NARROW CIRRUS BAND, AND LIGHT WESTERLY WINDS EVERYWHERE BUT FOR
PDT/ALW/PSC WHERE WINDS WERE LIGHT SOUTHEAST. WINDS REMAIN
LIGHT THROUGH THE TAF PERIOD WITH VFR CONDITIONS CONTINUING.
FIRE WEATHER
LOW RELATIVE HUMIDITY WILL BE EXPECTED EACH DAY THOUGH FRIDAY,
WITH WINDS THAT ARE LIGHT (UNDER 10 MPH) AND VARIABLE. WINDS
BECOME MUCH MORE SIGNIFICANT AROUND FRIDAY NIGHT AND ON SATURDAY
AS AN UPPER WAVE INFLUENCES THE REGION, WHILE NOT AS HOT
TEMPERATURES TEMPER THE LOW RELATIVE HUMIDITY IN THESE MORE
WIND PRONE AREAS. AT THIS TIME THE NEED FOR A FIRE WEATHER WATCH
IS LOW AS CHANCES FOR DRY THUNDER REMAIN LESS THAN 10% BASED ON
NBM MEMBERS ON FRIDAY AND NO CRITICAL HUMIDITY AND WIND
THRESHOLDS OVERLAP.
PRELIMINARY POINT TEMPS/POPS
PDT 91 57 93 62 / 0 0 0 0
ALW 92 64 95 68 / 0 0 0 0
PSC 93 58 96 61 / 0 0 0 0
YKM 93 62 97 65 / 0 0 0 0
HRI 93 60 95 64 / 0 0 0 0
ELN 89 59 93 63 / 0 0 0 0
RDM 93 51 95 56 / 0 0 0 0
LGD 94 57 97 61 / 0 0 0 0
GCD 96 57 98 60 / 0 0 0 0
DLS 92 62 97 66 / 0 0 0 0
PDT WATCHES/WARNINGS/ADVISORIES
WA...NONE.
OR...AIR QUALITY ALERT UNTIL 1 PM PDT THIS AFTERNOON FOR ORZ041-505-
506-509>511.
DISCUSSION...71
AVIATION...71
FIRE WEATHER...71
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