182
FXUS66 KPDT 060539
AFDPDT
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PENDLETON OR
1039 PM PDT MON OCT 5 2026
KEY MESSAGES
- WARM AND DRY CONDITIONS PERSIST THROUGH THE WEEK.
- INCOMING SYSTEM FRIDAY BRINGS BREEZY TO WINDY CONDITIONS.
- PATTERN SHIFTS TO COOLER AND WETTER OVER THE WEEKEND.
DISCUSSION
CURRENT RADAR AND VISIBLE SATELLITE IMAGERY SHOWS DRY CONDITIONS
UNDER MOSTLY CLEAR SKIES. THIS IS IN RESPONSE TO AN UPPER LEVEL
RIDGE THAT WILL STRENGTHEN ACROSS THE EASTERN PACIFIC THROUGH
MUCH OF THE WEEK. HIGH TEMPERATURES PEAK TODAY, REACHING INTO
THE MID-TO UPPER 80S ACROSS THE COLUMBIA BASIN AND CENTRAL
OREGON. A WEAK UPPER LEVEL SHORTWAVE WILL DISSIPATE AS IT MOVES
INTO THE AREA FROM THE NORTHWEST, ENHANCING WINDS SLIGHTLY
THROUGH THE COLUMBIA GORGE AND ACROSS THE KITTITAS VALLEY. WIND
GUSTS OF 33 MPH HAVE ALREADY BEEN RECORDED AT ELLENSBURG, WITH
GUSTS EXPECTED TO PEAK AROUND 5PM UP TO 38 MPH. WINDS OVER THE
COLUMBIA GORGE WILL ALSO BE ON THE RISE, WITH GUSTS UP TO 35
MPH POSSIBLE AT THE DALLES. FLOW ALOFT BECOMES MORE FROM THE
NORTHWEST IN THE WAKE OF THE PASSING SHORTWAVE ON TUESDAY AND
WEDNESDAY. THIS ALLOWS HIGH TEMPERATURES TO DIP INTO THE UPPER
70S TO LOW 80S BOTH DAYS. A SLIGHT INCREASE IN HIGH TEMPERATURES
IS LIKELY THURSDAY, IN ASSOCIATION WITH A BUILDING THERMAL
TROUGH ALONG THE OREGON COAST. THIS SYNOPTIC FEATURE WILL LEAD
TO WINDS BEING FROM THE EAST ACROSS THE COLUMBIA BASIN, DROPPING
AFTERNOON HUMIDITIES INTO THE LOW TO MID-20S ON THURSDAY. A
WEAK THERMAL TROUGH DOES DEVELOP ON WEDNESDAY WHICH KEEPS
OVERNIGHT HUMIDITY RECOVERIES INTO THURSDAY MORNING AROUND 40%
ACROSS AREAS OF THE JOHN DAY HIGHLANDS, NORTHERN BLUE MOUNTAINS,
AND CENTRAL OREGON.
THE UPPER LEVEL RIDGE SLIDES WEST AND FURTHER OFFSHORE ON
FRIDAY, OPENING THE DOOR TO A DROPPING UPPER LEVEL TROUGH THAT
ORIGINATES IN THE GULF OF ALASKA. THIS TROUGH WILL APPROACH THE
WASHINGTON-CANADIAN BORDER EARLY FRIDAY MORNING BEFORE MOVING
OVER THE REGION AND STRENGTHENING SOUTH INTO NORTHERN CALIFORNIA
OVER THE WEEKEND. THE ARRIVAL OF THE TROUGH WILL LEAD TO BREEZY
WINDS ACROSS MUCH OF THE AREA, AS INDICATED BY AN 11-12 MB
PRESSURE GRADIENT BETWEEN PORTLAND AND SPOKANE VIA THE GFS.
THIS GRADIENT ALIGNS WITH NEAR ADVISORY-LEVEL VALUES, BUT AT
THIS TIME THE NBM ONLY ADVERTISES A 15-30% CHANCE OF WIND GUSTS
REACHING 45 MPH OR HIGHER. THE TROUGH CONTINUES TO STRENGTHEN
AND DIG SOUTH ON SATURDAY, INTERACTING WITH THE REMNANTS OF
HURRICANE RACHEL AS IT TURNS NORTH AND BECOMES SUBTROPICAL. THIS
INFLUX OF MOISTURE IS STILL RATHER MINIMAL, WITH 33% OF
ENSEMBLE MEMBERS KEEPING THE AREA DRY ON SATURDAY, AND 67% OF
MEMBERS BRINGING ONLY 0.01-0.04" OF RAIN TO HIGHER ELEVATIONS.
THESE DIFFERENCES ARE A RESULT FROM GUIDANCE EITHER BRINGING IN
THE THROUGH (HIGHLY ADVERTISED BY THE ECMWF) OR KEEPING THE
RIDGE OR ZONAL PATTERN (SUGGESTED BY THE CANADIAN AND GEFS).
HOWEVER, IT IS IMPORTANT TO NOTE THAT BOTH THE AI ECMWF AND GEFS
ENSEMBLES SHOWCASE A TROUGHING SCENARIO. SUNDAY IS CURRENTLY
EXPECTED TO BE THE WETTER DAY THIS WEEKEND, BUT RAIN AMOUNTS
STILL STRUGGLE TO REACH WETTING RAIN AMOUNTS. 75
AVIATION /06Z TAFS THROUGH 06Z WEDNESDAY/
WITH HIGH PRESSURE REMAINING OVER THE AREA THROUGHOUT THE
PERIOD, VFR CONDITIONS WILL PERSIST. WINDS WILL GENERALLY
REMAIN BELOW 12KTS THROUGHOUT THE PERIOD AND DIRECTION IS
DIURNALLY TERRAIN DRIVEN. GARTY/26
PRELIMINARY POINT TEMPS/POPS
PDT 47 79 46 79 / 0 0 0 0
ALW 54 80 51 80 / 0 0 0 0
PSC 49 80 45 80 / 0 0 0 0
YKM 50 79 49 80 / 0 0 0 0
HRI 50 81 45 80 / 0 0 0 0
ELN 47 77 46 77 / 0 0 0 0
RDM 43 84 41 82 / 0 0 0 0
LGD 46 83 46 84 / 0 0 0 0
GCD 48 85 48 88 / 0 0 0 0
DLS 52 84 51 84 / 0 0 0 0
PDT WATCHES/WARNINGS/ADVISORIES
WA...NONE.
OR...NONE.
DISCUSSION...75
AVIATION...26
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