305
FXUS66 KPDT 060539
AFDPDT
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PENDLETON OR
1039 PM PDT WED AUG 5 2026
KEY MESSAGES
- ELEVATED TO CRITICAL FIRE WEATHER CONDITIONS THROUGH THE WEEK
DUE TO PERIODS OF BREEZY CONDITIONS, LOW RH, AND HOT, DRY, AND
UNSTABLE CONDITIONS. FIRE WEATHER WATCHES IN EFFECT FRIDAY
MORNING THROUGH SATURDAY EVENING FOR WIND AND LOW RELATIVE
HUMIDITY.
- WIDESPREAD SMOKE AND HAZE VERY LIKELY (99% CONFIDENCE) TO
PERSIST THROUGH THURSDAY, THEN IMPROVEMENT FRIDAY THROUGH THE
WEEKEND EXCEPT IN THE VICINITY OF OR DOWNWIND OF ONGOING
WILDFIRES.
- WIDESPREAD MODERATE TO LOCALLY MAJOR HEATRISK THURSDAY AND
FRIDAY.
DISCUSSION
SATELLITE IMAGERY SHOWS WIDESPREAD SMOKE AND HAZE ACROSS THE
FORECAST AREA THIS AFTERNOON, THE RESULT OF SMOKE TRANSPORT FROM
EARLIER IN THE WEEK AND CONTINUED SMOKE OUTPUT FROM ONGOING
REGIONAL WILDFIRES. WITH REGARD TO THE UPPER-LEVEL PATTERN,
WATER VAPOR IMAGERY REVEALS AN UPPER-LEVEL RIDGE AXIS EXTENDING
FROM THE GREAT BASIN NORTHWEST TO JUST OFFSHORE OF BRITISH
COLUMBIA, WEST OF THE FORECAST AREA. MEANWHILE, A LOW-PRESSURE
SYSTEM IS LOCATED WELL OFFSHORE IN THE VICINITY OF 45N, 144W.
WIDESPREAD WILDFIRE SMOKE IS EXPECTED (99 PERCENT CONFIDENCE)
TO PERSIST ACROSS THE REGION THROUGH AT LEAST THURSDAY, AND AIR
QUALITY HEADLINES ISSUED BY AIR QUALITY AGENCIES REMAIN IN
EFFECT FOR OUR ENTIRE CWA UNTIL FURTHER NOTICE.
HOT TEMPERATURES WILL ACCOMPANY THE UPPER RIDGE TOMORROW THROUGH
FRIDAY AS ITS AXIS SHIFTS INLAND. CURRENTLY, WIDESPREAD
MODERATE TO LOCALLY MAJOR HEATRISK IS ANTICIPATED DUE TO
FORECAST AFTERNOON TEMPERATURES IN THE 95-100 DEGREE RANGE AND
LOWS IN THE 50S AND 60S. THAT SAID, WILDFIRE SMOKE INHIBITS
EFFICIENT SOLAR HEATING SO AFTERNOON TEMPERATURES MAY END UP
BEING SEVERAL DEGREES COOLER THAN CURRENTLY FORECAST IF SMOKE IS
SUFFICIENTLY DENSE; SIMILAR TO YESTERDAY FORECAST HIGHS WERE
DECREASED BY ROUGHLY 2-5 DEGREES FOR THIS AFTERNOON ACROSS MUCH
OF OUR FORECAST AREA TO ACCOUNT FOR HOW THE SMOKE HAS AFFECTED
TEMPERATURES. CONVERSELY, THE DRY AIR MASS (PWATS OF 0.2-0.6")
SHOULD FACILITATE EFFICIENT NOCTURNAL COOLING, AND SMOKE DOES
NOT SIGNIFICANTLY AFFECT NOCTURNAL COOLING. HAVE OPTED TO HOLD
OFF ON ISSUING ANY HEAT HEADLINES FOR NOW, BUT WILL CONTINUE TO
ASSESS THE NEED.
ENSEMBLE NWP GUIDANCE CONTINUES TO ADVERTISE A CHANGE TO A
QUASI-ZONAL UPPER-LEVEL PATTERN BY LATE WEEK THROUGH THE
WEEKEND. ENSEMBLE CLUSTERS KEEP THE AFOREMENTIONED UPPER LOW
TO THE NORTHWEST OF THE REGION, BUT A COUPLE SHORTWAVES ARE
LIKELY (80% CONFIDENCE) TO FLATTEN THE RIDGE FRIDAY THROUGH THE
WEEKEND. THIS PATTERN WILL FACILITATE 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 WILL
LEAD TO INCREASING FIRE WEATHER CONCERNS (SEE FIRE WEATHER
SECTION BELOW). MOREOVER, BREEZY TO WINDY WESTERLY WINDS
REPRESENT THE BEST CHANCE OF SCOURING THE WIDESPREAD SMOKE.
AVIATION /06Z TAFS THROUGH 06Z FRIDAY/
WILDLAND FIRES CONTINUE TO CREATE SMOKE AND HAZE RESULTING IN
VISIBILITIES BELOW VFR CATEGORIES FOCUSED MORE IN THE MORNING
AND AFTERNOON PERIODS WHEN MIXING IS ENHANCED. LOCALLY 2 MILES
WILL BE COMMON LATE MORNING THROUGH MID AFTERNOON. LIGHT AND
AND VARIABLE WINDS UNDER 10 KNOTS CAN BEGIN TO IMPROVE
VISIBILITIES TO 5 MILES LATE AFTERNOON AND EVENING.
FIRE WEATHER
PERIODS OF ELEVATED TO CRITICAL FIRE WEATHER CONDITIONS ARE
ANTICIPATED TODAY INTO THE WEEKEND DUE TO A COMBINATION OF
LOCALLY BREEZY WINDS AND LOW RELATIVE HUMIDITY AS WELL AS HOT,
DRY, AND UNSTABLE CONDITIONS.
TODAY THROUGH FRIDAY, THE COMBINATION OF DRY AIR AND HOT
TEMPERATURES WILL DRIVE AFTERNOON RHS INTO THE SINGLE DIGITS TO
TEENS. PREDOMINANTLY POOR TO FAIR OVERNIGHT RH RECOVERY IS
FORECAST THROUGH THE WEEK, EXCEPT FOR LOCALLY GOOD TO EXCELLENT
RECOVERY IN DRAINAGES. OF NOTE, DEEP MIXING ACROSS THE REGION
COUPLED WITH LOCALLY BREEZY WINDS, ESPECIALLY CENTRAL OREGON AND
VICINITY, MAY SUPPORT PLUME-DOMINATED FIRE THIS AFTERNOON AND
THURSDAY. HAVE HELD OFF ON ISSUING ANY RED FLAG WARNINGS FOR
HOT, DRY, AND UNSTABLE CONDITIONS, BUT WILL CONTINUE TO MONITOR
THE NEED. ADDITIONALLY, HIGH-RESOLUTION WEATHER MODELS (12Z
HREF AND 12Z REFS) INDICATE SOME POTENTIAL (BROADLY 30-70%) IN
OVERLAP OF CRITICAL WIND/RH THRESHOLDS IN CENTRAL AND EAST-
CENTRAL OREGON TODAY, EXPANDING TO INCLUDE THE CASCADE GAPS OF
OR/WA THURSDAY.
FRIDAY THROUGH SATURDAY, CONFIDENCE IS VERY HIGH (80 PERCENT)
IN A RETURN TO BREEZY WESTERLY WINDS THROUGH THE CASCADE GAPS
AND ACROSS THE COLUMBIA BASIN AS A COUPLE WEAK SHORTWAVES
FLATTEN THE RIDGE. COUPLED WITH THE DRY AIR MASS, FORECAST
ELEVATED TO CRITICAL FIRE WEATHER CONDITIONS HAVE PROMPTED THE
ISSUANCE OF MULTIPLE FIRE WEATHER WATCHES; CONFIDENCE IN THE
COMBINATION OF CRITICAL WINDS AND RELATIVE HUMIDITY IS HIGH
(60-80 PERCENT) FOR FRIDAY AND SATURDAY.
PERSISTENT WEAK TROUGHING WILL LIKELY (70% CONFIDENCE) KEEP
BREEZY WESTERLY GAP WINDS IN PLACE SUNDAY INTO EARLY NEXT WEEK.
CONFIDENCE IN MEETING WIND/RH CRITERIA IS LOW (40% OR LESS)
SUNDAY AND MONDAY.
PRELIMINARY POINT TEMPS/POPS
PDT 54 97 61 97 / 0 0 0 0
ALW 60 98 67 99 / 0 0 0 0
PSC 58 98 60 100 / 0 0 0 0
YKM 56 98 63 100 / 0 0 0 0
HRI 56 99 64 99 / 0 0 0 0
ELN 55 96 63 95 / 0 0 0 0
RDM 53 99 54 98 / 0 0 0 0
LGD 54 100 60 100 / 0 0 0 0
GCD 56 100 59 100 / 0 0 0 0
DLS 57 99 64 96 / 0 0 0 0
PDT WATCHES/WARNINGS/ADVISORIES
WA...AIR QUALITY ALERT UNTIL 5 AM PDT TUESDAY FOR WAZ024-026>030-
521>523.
FIRE WEATHER WATCH FROM FRIDAY MORNING THROUGH SATURDAY
EVENING FOR WAZ690.
OR...AIR QUALITY ALERT UNTIL 5 AM PDT TUESDAY FOR ORZ041-044-049-
050-502-503-505>511.
FIRE WEATHER WATCH FROM FRIDAY MORNING THROUGH SATURDAY
EVENING FOR ORZ691-703.
FIRE WEATHER WATCH FROM SATURDAY MORNING THROUGH SATURDAY
EVENING FOR ORZ701-702.
DISCUSSION...86
AVIATION...71
FIRE WEATHER...86
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