981
FXUS66 KPDT 211119
AFDPDT
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PENDLETON OR
419 AM PDT TUE JUL 21 2026
KEY MESSAGES
- UPPER LEVEL RIDGING OVER THE REGION WILL BRING A WARMING AND
DRYING TREND ACROSS THE FORECAST AREA, WITH HIGH END MODERATE
TO MAJOR HEATRISK DEVELOPING IN AND AROUND THE COLUMBIA BASIN
- MONSOONAL MOISTURE PUSH WITH SHORTWAVE IMPULSES WILL RESULT IN
A RETURN OF ISOLATED TO SCATTERED THUNDERSTORM ACTIVITY ACROSS
CENTRAL OR AND THE NORTHEAST OR MOUNTAINS
- UPPER LEVEL TROUGHING OFFSHORE WILL PRODUCE BREEZY WINDS IN
THE CASCADE GAPS AND COLUMBIA BASIN LATE THURSDAY INTO THE
WEEKEND
DISCUSSION
PARTLY CLOUDY CONDITIONS ACROSS THE FORECAST AREA
ARE EVIDENT ON SATELLITE IMAGERY TONIGHT, WITH LITTLE ACTIVITY
TO NOTE ON RADAR. SURFACE OBSERVATIONS ACROSS PORTIONS OF THE
FORECAST AREA DO SHOW LOWERED VISIBILITY FROM SMOKE SETTLING
NEAR THE SURFACE.
SENSIBLE WEATHER CONCERNS THROUGH THURSDAY WILL REVOLVE AROUND
A STRENGTHENING UPPER LEVEL RIDGE PRODUCING HOT TEMPERATURES IN
AND AROUND THE COLUMBIA BASIN; DAILY SHORTWAVE IMPULSES RIDING
UP THE RIDGE WILL TAP INTO MONSOONAL MOISTURE AND INCREASING
INSTABILITY, PRODUCING ISOLATED TO SCATTERED THUNDERSTORMS IN
THE AFTERNOONS AND EVENINGS.
THROUGH EARLY THURSDAY, THE PACNW WILL SEE AN UPPER LEVEL RIDGE
OF HIGH PRESSURE GRADUALLY STRENGTHEN EACH DAY WHILE DEEP
SOUTHERLY FLOW PERSISTS ALOFT. THIS WILL INTRODUCE INCREASINGLY
HOT TEMPERATURES ACROSS THE LOWER ELEVATIONS, WITH THE BRUNT OF
THE HEATING EXPECTED IN THE COLUMBIA BASIN/GORGE AND ADJACENT
FOOTHILLS/VALLEYS THROUGH THURSDAY. PORTIONS OF THE OR/WA
COLUMBIA BASIN AND THE EASTERN GORGE ARE FORECAST TO REACH THE
100 DEGREE MARK AS EARLY AS THIS AFTERNOON, WITH THE BLUE
MOUNTAIN FOOTHILLS, YAKIMA/KITTITAS VALLEYS, PORTIONS OF NORTH
CENTRAL OREGON, AND PORTIONS OF THE JOHN DAY BASIN REACHING 100
DEGREES WEDNESDAY(CONFIDENCE 60-85%). WHILE MODEL GUIDANCE
DEPICTS THE WARMING TEMPERATURES, THERE IS PLENTY OF UNCERTAINTY
SURROUNDING THE IMPACTS REGIONAL SMOKE MAY HAVE ON DAYTIME
HEATING. MODEL GUIDANCE STRUGGLED WITH THE IMPACTS OF THE SMOKE
YESTERDAY, WITH MANY AREAS SEEING AFTERNOON TEMPERATURES WELL
BELOW FORECAST HIGH TEMPERATURES. WITH SMOKE EXPECTED TO
CONTINUE IMPACTING PORTIONS OF THE REGION TODAY, THERE IS
MODERATE CONFIDENCE (45-55%) THAT THOSE AREAS(PORTIONS OF THE
BLUE MOUNTAIN FOOTHILLS, COLUMBIA BASIN, CENTRAL OR, AND EASTERN
MOUNTAINS) UNDER THE HEAVIEST SMOKE WILL SEE AFTERNOON
TEMPERATURES LOWER THAN FORECAST. HOT TEMPERATURES WILL
CONTINUE IN MOST AREAS THURSDAY, HOWEVER INCREASING WINDS
THROUGH THE CASCADE GAPS LATE AFTERNOON MAY LIMIT HEATING
THROUGH THE EASTERN GORGE AND THE KITTITAS VALLEY (CONFIDENCE
50-65%). BETWEEN ELEVATED AFTERNOON AND OVERNIGHT TEMPERATURES,
HEATRISK VALUES ACROSS MUCH OF THE LOWER ELEVATIONS WILL BE IN
THE MODERATE TO MAJOR CATEGORIES STARTING TUESDAY, RESULTING IN
THE ISSUANCE OF HEAT ADVISORIES ACROSS THE COLUMBIA BASIN/GORGE,
YAKIMA VALLEY, AND THE NORTHERN BLUE MOUNTAIN FOOTHILLS.
THROUGH THURSDAY, ENSEMBLE AND DETERMINISTIC GUIDANCE DEPICTS A
MONSOONAL MOISTURE PUSH RIDING THE SOUTHERLY FLOW INTO THE
INTERMOUNTAIN PACNW, WITH DAILY PWATS AROUND 0.75 TO 1.25
INCHES. INSTABILITY WILL BE INCREASING EACH DAY, WITH THE BEST
CHANCES OF THUNDERSTORM ACTIVITY EXPECTED WEDNESDAY AND
THURSDAY. THIS AFTERNOON, THERE IS A SLIGHT CHANCE (15-20%) OF
ISOLATED THUNDERSTORMS DEVELOPING ACROSS THE CENTRAL OR CASCADE
EAST SLOPES AND ACROSS THE MOUNTAINOUS TERRAIN OF SOUTHERN AND
EASTERN GRANT COUNTY. MUCAPE THIS AFTERNOON WILL PEAK AROUND
250-500 J/KG, WITH LOW LEVEL LAPSE RATES AROUND 8-9 C/KM AND
0-6KM SHEAR BETWEEN 20-30KTS. ON WEDNESDAY, THE MAIN
THUNDERSTORM ACTIVITY WILL BE FOCUSED ACROSS CENTRAL OR AND THE
MOUNTAINOUS TERRAIN FROM THE CASCADE EAST SLOPES TO THE ELKHORN
CREST. IN THESE AREAS, MUCAPE WILL BE BETWEEN 500-1000J/KG, LOW
LEVEL LAPSE RATES 8-10 C/KM, AND 0-6KM SHEAR BETWEEN 20-40KTS.
THESE CONDITIONS WILL BE MORE THAN ENOUGH FOR THUNDERSTORMS TO
DEVELOP IN THE AFTERNOON AND BECOME ORGANIZED AS THEY PROPAGATE
NORTH. BY THURSDAY, SIMILAR CONDITIONS WILL BE PRESENT ALONG THE
WA CASCADES, BLUE MOUNTAINS, AND WALLOWA COUNTY. EXPECT AT
LEAST SMALL HAIL, GUSTY OUTFLOW WINDS, FREQUENT LIGHTNING, AND A
FEW STORMS TO PRODUCE HEAVY DOWNPOURS.
LATE THURSDAY THROUGH THE WEEKEND, THERE IS GOOD AGREEMENT
AMONGST ENSEMBLE CLUSTER GUIDANCE THAT UPPER TROUGHING WILL
DEVELOP OFF THE COAST OF THE PACNW WHILE UPPER LEVEL RIDGING
PUSHES EAST AND SOUTH. SOUTHWEST FLOW ALOFT WILL PREVENT
MONSOONAL MOISTURE FROM ADVECTING INTO THE REGION, RESULTING IN
DRYING CONDITIONS ACROSS THE FORECAST AREA. THE PROXIMITY OF THE
UPPER TROUGH FRIDAY AND SATURDAY WILL ALSO RESULT IN BREEZY
WEST TO NORTHWEST WINDS(15-25MPH WITH GUSTS 25-35MPH) THROUGH
THE CASCADE GAPS AND ACROSS THE COLUMBIA BASIN. CONFIDENCE
REMAINS MODERATE (45-65%) THAT PEAK WINDS WILL OVERLAP WITH
CRITICALLY LOW RHS IN PORTIONS OF THE COLUMBIA BASIN AND CASCADE
GAPS FRIDAY AND SATURDAY, RESULTING IN ELEVATED FIRE WEATHER
CONDITIONS THOSE DAYS. SUNDAY THROUGH MONDAY, THERE REMAINS
GOOD AGREEMENT THAT THE TROUGH WILL RETROGRADE SLIGHTLY INTO
THE NORTHEAST PACIFIC, RESULTING IN WEAKER CASCADE GAP WINDS
AND CONTINUED DRY CONDITIONS(CONFIDENCE 50-60%). LAWHORN/82
AVIATION /12Z TAFS THROUGH 12Z WEDNESDAY/
MVFR TO VFR
CONDITIONS TO PREVAIL THROUGH THE PERIOD. SMOKE FROM AREA
WILDFIRES IS BRINGING REDUCED VSBY AT SITES PDT/ALW, WITH MVFR
CIGS AT SITES RDM/BDN/ALW. THIS WILL CONTINUE INTO THE MORNING
HOURS, WITH VFR CONDITIONS RETURNING DURING THE DAY. WINDS WILL
BE LIGHT AND DIURNALLY DRIVEN THROUGH THE PERIOD. LAWHORN/82
FIRE WEATHER
CONDITIONS WILL REMAIN HOT AND DRY INTO THE
MIDDLE OF THE WEEK, WITH HOTTEST CONDITIONS IN THE COLUMBIA
BASIN AND ADJACENT FOOTHILLS/VALLEYS. HOWEVER, AREAS UNDER HEAVY
SMOKE WILL SEE LESS HEATING THAN ANTICIPATED. MONSOONAL
MOISTURE AND INCREASING INSTABILITY WILL BRING ISOLATED TO
SCATTERED THUNDERSTORM CHANCES THROUGH THURSDAY. TODAY, A SLIGHT
CHANCE OF ISOLATED STORMS WILL BE FOCUSED OVER THE CENTRAL OR
CASCADE EAST SLOPES AND ELEVATED TERRAIN IN SOUTHERN/EASTERN
GRANT COUNTY. WEDNESDAY, CHANCES (15-30%) WILL BE FOCUSED ACROSS
CENTRAL OR AND THE EASTERN MOUNTAINS. CHANCES (15-30%) THURSDAY
WILL BE FOCUSED ALONG THE WA CASCADE CREST, BLUE MOUNTAINS, AND
WALLOWA COUNTY. THUNDERSTORMS WILL BE CAPABLE OF FREQUENT
LIGHTNING, GUSTY OUTFLOW WINDS, SMALL HAIL, AND BRIEF HEAVY
DOWNPOURS. WINDS WILL INCREASE THROUGH THE CASCADE GAPS AND
COLUMBIA BASIN FRIDAY AND SATURDAY, AND ARE EXPECTED TO OVERLAP
WITH NEAR TO CRITICALLY DRY CONDITIONS. EXPECT ELEVATED TO
CRITICAL FIRE WEATHER CONDITIONS THOSE DAYS. LAWHORN/82
PRELIMINARY POINT TEMPS/POPS
PDT 96 66 99 68 / 0 0 0 0
ALW 98 71 101 72 / 0 0 0 0
PSC 100 68 103 70 / 0 0 0 0
YKM 99 70 103 72 / 0 0 0 10
HRI 99 70 103 72 / 0 0 0 0
ELN 97 68 101 70 / 0 0 0 10
RDM 94 62 96 61 / 0 10 20 40
LGD 97 67 99 67 / 0 0 0 10
GCD 96 64 96 63 / 20 20 10 10
DLS 101 73 104 73 / 0 0 0 20
PDT WATCHES/WARNINGS/ADVISORIES
WA...HEAT ADVISORY FROM 11 AM THIS MORNING TO 9 PM PDT THURSDAY FOR
WAZ024-027>029.
AIR QUALITY ALERT UNTIL 9 AM PDT WEDNESDAY FOR WAZ028>030.
OR...HEAT ADVISORY FROM 11 AM THIS MORNING TO 9 PM PDT THURSDAY FOR
ORZ041-044-507.
AIR QUALITY ALERT UNTIL 4 PM PDT WEDNESDAY FOR ORZ044-049-050-
502-503-505>509-511.
RED FLAG WARNING FROM 11 AM TO 11 PM PDT WEDNESDAY FOR ORZ698-
700-705.
DISCUSSION...82
AVIATION...82
FIRE WEATHER...82
CLICK HERE TO GO TO PREVIOUS BULLETINS.
Main Text Page