796
FXUS66 KPDT 040533
AFDPDT
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PENDLETON OR
1033 PM PDT MON AUG 3 2026
KEY MESSAGES
- ELEVATED TO LOCALLY CRITICAL FIRE WEATHER CONDITIONS TUESDAY
- WIDESPREAD SMOKE AND HAZE THROUGH AT LEAST MID-WEEK
- WIDESPREAD MODERATE TO LOCALLY MAJOR HEATRISK MIDDLE TO LATE
WEEK.
DISCUSSION
SATELLITE IMAGERY SHOWS WIDESPREAD SMOKE AND HAZE ACROSS THE
FORECAST AREA THIS AFTERNOON. UPPER-LEVEL TROUGHING HAS EXITED
TO THE EAST OVER THE NORTHERN GREAT PLAINS, AND AN AMPLIFYING
UPPER-LEVEL RIDGE IS NOTED OFFSHORE IN THE PACIFIC. THIS PATTERN
HAS SET UP A CLASSIC WEST COAST THERMAL TROUGH (WCTT) TO THE
WEST OF THE CASCADES, LEADING TO AN OFFSHORE-DIRECTED PRESSURE
GRADIENT AND AMPLE SOUTHWARD AND WESTWARD SMOKE TRANSPORT FROM
THE WILDFIRES TO OUR NORTH IN NORTHERN WASHINGTON AND CANADA.
WILDFIRE SMOKE IS EXPECTED (99 PERCENT CONFIDENCE) TO PERSIST
ACROSS THE REGION THROUGH AT LEAST MID-WEEK AS THE UPPER-LEVEL
RIDGE AMPLIFIES AND SLOWLY TRACKS EASTWARD. WINDS WILL REMAIN
DIURNALLY AND TERRAIN-DRIVEN AND SUPPORTIVE OF CONTINUED
ADVECTION OF SMOKE INTO THE REGION. AIR QUALITY HEADLINES HAVE
BEEN ISSUED BY OREGON DEPARTMENT OF ENVIRONMENTAL QUALITY, THE
WASHINGTON STATE DEPARTMENT OF ECOLOGY, BENTON CLEAR AIR AGENCY,
AND THE YAKIMA REGIONAL CLEAN AIR AGENCY, VALID UNTIL FURTHER
NOTICE.
THE RIDGE AXIS WILL MOVE INLAND WEDNESDAY THROUGH FRIDAY, WITH
INCREASINGLY HOT TEMPERATURES FORECAST DURING THE PERIOD.
CURRENTLY, WIDESPREAD MODERATE TO LOCALLY MAJOR HEATRISK IS
FORECAST DUE TO AFTERNOON TEMPERATURES IN THE 95-100 DEGREE
RANGE AND LOWS IN THE 50S AND 60S. THAT SAID, NOTE THAT WILDFIRE
SMOKE INHIBITS EFFICIENT SOLAR HEATING SO AFTERNOON
TEMPERATURES MAY END UP BEING SEVERAL DEGREES COOLER THAN
CURRENTLY FORECAST IF SMOKE IS SUFFICIENTLY DENSE. CONVERSELY,
THE DRY AIR MASS (PWATS OF 0.2-0.6") SHOULD FACILITATE EFFICIENT
NOCTURNAL COOLING, AND SMOKE DOES NOT SIGNIFICANTLY AFFECT
NOCTURNAL COOLING.
THE UPPER-LEVEL PATTERN WILL LIKELY CHANGE (70 PERCENT CHANCE)
BY LATE WEEK, MOSTLY LIKELY FRIDAY THROUGH THE WEEKEND, TO A
QUASI-ZONAL PATTERN AS ENSEMBLE CLUSTERS INDICATE SOME FLAVOR
OF UPPER-LEVEL LOW OR SHORTWAVE TROUGH WILL TRACK INLAND OVER
BRITISH COLUMBIA. THIS SOLUTION WOULD LEAD TO A REVERSAL OF
SURFACE PRESSURE GRADIENTS AND RESULT IN BREEZY TO WINDY
WESTERLY WINDS THROUGH THE CASCADE GAPS AND ACROSS THE BLUE
MOUNTAIN FOOTHILLS AND COLUMBIA BASIN. WIND COUPLED WITH LOW
RELATIVE HUMIDITY IN THIS SCENARIO WOULD LEAD TO INCREASING FIRE
WEATHER CONCERNS (SEE FIRE WEATHER SECTION BELOW). MOREOVER,
THE WESTERLY WIND REPRESENTS THE BEST CHANCE OF SCOURING THE
WIDESPREAD SMOKE.
AVIATION /06Z TAFS THROUGH 06Z WEDNESDAY/
SMOKE WILL CONTINUE TO IMPACT TERMINALS, ESPECIALLY IN THE
AFTERNOON AS REGIONAL WILDLAND FIRES TEND TO BURN MORE AND
MIXING LAYER INCREASES. FOLLOWED SOME OF THE TRENDS FOR TUESDAY
BASED ON THE TREND FROM MONDAY AFTERNOON THAT BROUGHT VISIBILITY
TO 5SM OR LOWER DURING THE MID TO LATE AFTERNOON. VARIABLE
LIGHT WINDS UNDER 7 KNOTS AFTER 16Z.
FIRE WEATHER
ELEVATED TO LOCALLY CRITICAL FIRE WEATHER CONDITIONS ARE
FORECAST TUESDAY AS LOCALLY BREEZY EAST TO NORTHEAST WINDS
OVERLAP WITH DRY AIR; DROPPED THE FIRE WEATHER WATCHES DUE TO
LOW CONFIDENCE IN WIDESPREAD OVERLAP OF CRITICAL CONDITIONS.
BY MID-WEEK, THE COMBINATION OF DRY AIR AND HOT TEMPERATURES
WILL DRIVE AFTERNOON RHS INTO THE SINGLE DIGITS TO TEENS. POOR
TO FAIR OVERNIGHT RH RECOVERY IS FORECAST THROUGH THE WEEK,
EXCEPT FOR LOCALLY BETTER RECOVERY IN DRAINAGES.
LATE WEEK, CONFIDENCE IS HIGH (70 PERCENT) IN A RETURN TO
BREEZY WESTERLY WINDS THROUGH THE CASCADE GAPS AND ACROSS THE
COLUMBIA BASIN AS A LOW-PRESSURE SYSTEM WILL LIKELY (70 PERCENT)
APPROACH OR MOVE INTO BRITISH COLUMBIA. CONFIDENCE IN THE
COMBINATION OF CRITICAL WINDS AND RELATIVE HUMIDITY LATE
THURSDAY IS LOW-MEDIUM (20-50 PERCENT) WITH MEDIUM-HIGH
CONFIDENCE (40-80 PERCENT) FOR FRIDAY.
PRELIMINARY POINT TEMPS/POPS
PDT 49 88 52 94 / 0 0 0 0
ALW 53 90 58 96 / 0 0 0 0
PSC 51 91 56 96 / 0 0 0 0
YKM 55 90 59 95 / 0 0 0 0
HRI 52 90 58 96 / 0 0 0 0
ELN 54 88 59 94 / 0 0 0 0
RDM 42 89 48 97 / 0 0 0 0
LGD 48 89 52 97 / 0 0 0 0
GCD 47 90 53 98 / 0 0 0 0
DLS 58 92 63 98 / 0 0 0 0
PDT WATCHES/WARNINGS/ADVISORIES
WA...AIR QUALITY ALERT UNTIL 5 AM PDT TUESDAY FOR WAZ024-026>030-
521>523.
OR...AIR QUALITY ALERT UNTIL 5 AM PDT TUESDAY FOR ORZ041-044-049-
050-502-503-505>507-509>511.
DISCUSSION...86
AVIATION...71
FIRE WEATHER...86
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