915
FXUS66 KPDT 281652
AFDPDT
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PENDLETON OR
952 AM PDT MON SEP 28 2026
KEY MESSAGES
- LIGHT TO MODERATE MOUNTAIN SHOWERS ACROSS THE WA CASCADES AND
NORTHERN BLUES WITH BREEZY LOW ELEVATION WINDS TUESDAY
- NEAR TO ABOVE NORMAL TEMPERATURES THROUGHOUT THE WEEK
- HIGH UNCERTAINTY IN RETURN OF LIGHT MOUNTAIN SHOWERS THURSDAY
OR FRIDAY, WITH BETTER AGREEMENT OF DRY CONDITIONS AND ABOVE
NORMAL TEMPERATURES OVER THE WEEKEND
DISCUSSION
LITTLE TO TALK ABOUT ON SATELLITE TONIGHT AS MUCH
OF THE PACNW IS UNDER CLEAR SKIES. AT THE SURFACE, WEAK
DIURNALLY WINDS HAVE DEVELOPED, WHILE AREAS OF CENTRAL OR AND
THE KITTITAS VALLEY HAVE SEEN TEMPERATURES DROP INTO THE 30S. IF
WINDS BECOME CALM, THERE IS A POTENTIAL FOR RADIATIVE COOLING
PROCESSES TO DROP TEMPERATURES TO AT OR JUST BELOW FREEZING
TONIGHT (CONFIDENCE 30-60%).
TODAY THROUGH WEDNESDAY: DRY AND QUIET CONDITIONS WILL PREVAIL
ACROSS THE FORECAST AREA FOR MUCH OF TODAY AS ZONAL FLOW WILL
DEVELOP OVER THE PACNW WHILE AN UPPER TROUGH DROPS THROUGH THE
GREAT BASIN INTO THE DESERT SOUTHWEST. WHILE WINDS WILL REMAIN
LIGHT ACROSS MUCH OF THE AREA, WINDS WILL INCREASE THROUGH THE
EASTERN COLUMBIA GORGE AHEAD OF AN APPROACHING COLD FRONT.
MONDAY NIGHT INTO TUESDAY, FLOW ALOFT WILL REMAIN ZONAL, HOWEVER
AN UPPER SHORTWAVE TROUGH PASSING THROUGH BC WILL CLIP THE WA
CASCADES AND NORTHERN BLUE MOUNTAINS. THIS WILL RESULT IN
LIGHT TO MODERATE RAIN SHOWERS DEVELOPING ACROSS THESE AREAS,
WITH A 35-45% CHANCE OF 0.1 INCHES IN THE NORTHERN BLUES AND A
55-95% CHANCE OF 0.25 INCHES ALONG PORTIONS OF THE WA CASCADES
AND EAST SLOPES (HIGHEST CHANCES IN CENTRAL WA CASCADES, LOWEST
SOUTH CENTRAL WA CASCADES). IN THE COLUMBIA BASIN AND GORGE, A
COLD FRONT PASSAGE WILL RESULT IN BREEZY WEST TO SOUTHWEST
WINDS (15-25MPH WITH GUSTS 25-40 MPH) DEVELOPING THROUGHOUT THE
DAY, WITH LIGHT TO LOCALLY BREEZY WINDS ELSEWHERE.
FLAT UPPER LEVEL RIDGING IN THE EASTERN PACIFIC WILL BUILD INTO
THE WESTERN CONUS BY WEDNESDAY MORNING, RESULTING IN A RETURN TO
DRY CONDITIONS AND LIGHT WINDS.
THURSDAY THROUGH SUNDAY: HIGH UNCERTAINTY AMONGST DETERMINISTIC
AND ENSEMBLE GUIDANCE IN THE EVOLUTION OF THE SYNOPTIC PATTERN
THURSDAY THROUGH FRIDAY, HOWEVER THERE IS GOOD CONSENSUS AMONGST
THE MOST RECENT ENSEMBLE MEMBERS FOR LOW IMPACTS DURING THIS
PERIOD. OVERALL, DISAGREEMENT SURROUNDS THE EVENTUAL PASSAGE OF
A SHORTWAVE TROUGH THAT WILL BRING LIGHT MOUNTAIN SHOWERS. ENSEMBLE
MEMBERS ARE IN DISAGREEMENT IF THE TROUGH COMES THROUGH
SOMETIME THURSDAY OR SOMETIME FRIDAY, SO CONFIDENCE IN
PRECIPITATION TIMING/EXTENT IS VERY LOW (15-20%).
AFTER FRIDAY, AGREEMENT GROWS IN UPPER LEVEL RIDGING BUILDING
OVER THE PACNW THROUGH THE WEEKEND, RESULTING IN DRY AND QUIET
CONDITIONS WITH ABOVE NORMAL TEMPERATURES. (CONFIDENCE 45-60%).
LAWHORN/82
AVIATION /18Z TAFS THROUGH 18Z TUESDAY/
VFR CONDITIONS PREVAIL WITH DRY AND MOSTLY CLEAR CONDITIONS
THROUGH THE FORECAST PERIOD. WINDS WILL BE A BIT ELEVATED IN THE
7 TO 12 KNOT RANGE, WITH BREEZIER CONDITIONS DEVELOPING IN THE
DLS BY THE AFTERNOON. OTHERWISE, NO CIG OR VIS ISSUES EXPECTED.
PRELIMINARY POINT TEMPS/POPS
PDT 70 45 75 49 / 0 0 0 0
ALW 71 52 75 54 / 0 0 0 10
PSC 75 47 78 50 / 0 0 0 0
YKM 73 48 74 49 / 0 0 10 0
HRI 74 49 77 51 / 0 0 0 0
ELN 68 45 66 46 / 0 0 20 20
RDM 71 37 75 39 / 0 0 0 0
LGD 71 41 75 46 / 0 0 0 10
GCD 72 40 75 43 / 0 0 0 0
DLS 76 50 73 54 / 0 0 0 10
PDT WATCHES/WARNINGS/ADVISORIES
WA...NONE.
OR...NONE.
DISCUSSION...82
AVIATION...95
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