923
FXUS66 KPDT 120946
AFDPDT
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PENDLETON OR
246 AM PDT WED AUG 12 2026
KEY MESSAGES
- NEAR-SEASONAL TEMPERATURES THROUGH THE WEEK.
- BREEZY WESTERLY WINDS THROUGH THE CASCADE GAPS TODAY.
- TRANSITION TO A CONVECTIVE WEATHER PATTERN TODAY WITH DAILY
SHOWER AND THUNDERSTORM CHANCES INTO NEXT WEEK, MAINLY FOR THE
MOUNTAINS.
DISCUSSION
WATER VAPOR IMAGERY REVEALS A PATTERN TRANSITION IN PROGRESS
WITH FLOW ALOFT TURNING SOUTHWESTERLY OVER THE FORECAST AREA
EARLY THIS MORNING; A WEAK TROUGH IS NOTED OVER THE PACIFIC
NORTHWEST, WITH AN EMBEDDED SHORTWAVE DIVING SOUTHEAST IN THE
VICINITY OF VANCOUVER ISLAND. AT THE SURFACE, A MODEST CROSS-
CASCADE PRESSURE GRADIENT REMAINS IN PLACE (4-6 MB DIFFERENCE
BETWEEN PDX AND DLS AS WELL AS SEA AND ELN) WHICH IS KEEPING
BREEZY WESTERLY WINDS IN PLACE THROUGH THE CASCADE GAPS. AS THE
DAY PROGRESSES, GAP WINDS WILL STRENGTHEN, REACHING WIDESPREAD
BREEZY TO LOCALLY WINDY LEVELS THIS AFTERNOON.
NWP GUIDANCE IS IN EXCELLENT AGREEMENT THAT THE SHORTWAVE
MENTIONED ABOVE WILL CONTINUE TO TRACK SOUTHEAST INTO
WASHINGTON AND NORTHERN OREGON TODAY, SERVING AS THE SYNOPTIC-
SCALE CATALYST FOR A SLIGHT CHANCE TO CHANCE (15-35 PERCENT) OF
AFTERNOON CONVECTION ALONG THE EAST SLOPES OF THE WASHINGTON
CASCADES. LOWER CHANCES (5-10 PERCENT) OF SHOWERS AND
THUNDERSTORMS EXTEND ACROSS THE COLUMBIA BASIN AND PORTIONS OF
THE BLUE MOUNTAINS.
THE WAVE WILL THEN EXIT TO THE NORTHEAST INTO THE NORTHERN
ROCKIES OVERNIGHT INTO THURSDAY, ALBEIT WITH A WEAK BROAD
TROUGH REMAINING OVER THE PACIFIC NORTHWEST ON THURSDAY IN ITS
WAKE. ALTHOUGH POPS ARE QUITE LOW, WILL MENTION THAT NWP
GUIDANCE IS ADVERTISING SYNOPTIC-SCALE FORCING COUPLED WITH
SUFFICIENT MID-LEVEL (700-500 HPA) MOISTURE AND NEGATIVE MID-
LEVEL (700-500 HPA) THETA-E LAPSE RATES TO FACILITATE SOME WEAK
NOCTURNAL CONVECTION (PREDOMINANTLY SHOWERS WITH ISOLATED
EMBEDDED THUNDERSTORMS) OVERNIGHT INTO THURSDAY MORNING ACROSS
MAINLY THE HIGHER TERRAIN OF SOUTH-CENTRAL WASHINGTON AND
EASTERN OREGON.
LOOKING AHEAD, ENSEMBLE NWP GUIDANCE SUGGESTS CONTINUED SOUTHWEST
FLOW ALOFT THROUGH THE REMAINDER OF THE FORECAST PERIOD. THIS
WILL KEEP A CONVECTIVE PATTERN IN PLACE RESULTING IN DAILY
SHOWER AND THUNDERSTORM CHANCES, MAINLY OVER THE MOUNTAINS.
THAT SAID, ANALYSIS OF ENSEMBLE CLUSTERS REVEALS SIGNIFICANT
UNCERTAINTY IN PATTERN DETAILS BEYOND SATURDAY. BY SUNDAY AND
MONDAY, ENSEMBLE NWP INDICATES ROUGHLY EQUAL CHANCES (40-60
PERCENT) OF A DEEP OFFSHORE CLOSED LOW OR A WEAKER OPEN WAVE
TROUGH. EITHER SOLUTION PUTS THE FORECAST AREA UNDER SOUTHERLY
TO SOUTHWESTERLY FLOW ALOFT, FAVORABLE FOR CONVECTION.
FIRE WEATHER WATCHES MAY BE NEEDED IF CONFIDENCE IN WIDESPREAD
LIGHTNING INCREASES THIS WEEK OR OVER THE WEEKEND.
LASTLY, AIR QUALITY ALERTS/ADVISORIES ISSUED BY AIR QUALITY
AGENCIES REMAIN IN EFFECT FOR THE MAJORITY OF OUR FORECAST AREA
DUE TO WILDFIRE SMOKE FROM ONGOING REGIONAL WILDFIRES.
AVIATION /06Z TAFS THROUGH 06Z THURSDAY/
VFR CONDITIONS PREVAIL WITH SMOKE CLEARING OUT FOR THE MOST
PART. NOT EXPECTING ANY IMPACTFUL EVENTS FROM THE SMOKE THIS
PERIOD, BUT THERE IS A SMALL 5 TO 15 PERCENT CHANCE THAT A LARGE
PLUME OF SMOKE CAN PASS OVER A TAF SITE, CAUSING TEMPORARY MVFR
CONDITIONS. OTHERWISE, BREEZY WINDS DEVELOP IN DLS/RDM/BDN IN
THE EARLY AFTERNOON HOURS WITH WEAKENING BY THE EVENING HOURS.
PRELIMINARY POINT TEMPS/POPS
PDT 85 52 85 56 / 0 0 0 0
ALW 87 57 86 61 / 0 0 0 0
PSC 90 57 89 57 / 0 0 0 0
YKM 89 58 88 60 / 0 20 0 10
HRI 88 55 88 58 / 0 0 0 0
ELN 83 54 83 57 / 10 30 20 10
RDM 84 44 84 48 / 0 0 0 0
LGD 87 53 85 54 / 0 0 0 20
GCD 89 52 87 54 / 0 0 0 30
DLS 83 60 89 62 / 0 0 0 0
PDT WATCHES/WARNINGS/ADVISORIES
WA...AIR QUALITY ALERT UNTIL 11 AM PDT THURSDAY FOR WAZ026>030-
521>523.
OR...AIR QUALITY ALERT UNTIL NOON PDT TODAY FOR ORZ041-049-050-502-
503-505-506-508>511.
DISCUSSION...86
AVIATION...95
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