169
FXUS66 KPDT 120530
AFDPDT
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PENDLETON OR
1030 PM PDT TUE AUG 11 2026
KEY MESSAGES
- DRY WEATHER, SEASONAL TEMPERATURES, AND BREEZY WESTERLY WINDS
THROUGH THE CASCADE GAPS TODAY.
- HIGH CONFIDENCE (70-95 PERCENT) IN A SHIFT TO A CONVECTIVE
PATTERN WEDNESDAY THROUGH THE WEEKEND.
DISCUSSION
WATER VAPOR IMAGERY SHOWS ZONAL (WASHINGTON) TO QUASI-ZONAL
(OREGON) FLOW OVER THE FORECAST AREA EARLY THIS MORNING. 00Z
AND 06Z SOUNDINGS AT UIL/SLE/MFR AND OTX, RESPECTIVELY,
CORROBORATE SATELLITE IMAGERY WITH PURE ZONAL FLOW ALOFT OVER
UIL/OTX AND WEST TO WEST-SOUTHWEST FLOW ALOFT OVER SLE/MFR. OF
NOTE, BUT PERHAPS OF LITTLE CONSEQUENCE AS FAR AS TODAY'S
WEATHER IS CONCERN, A WEAK CIRCULATION IS APPROACHING THE OR/CA
COASTAL BORDER.
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. REGARDING FIRE WEATHER CONDITIONS, 00Z
HREF/REFS AND LATEST NBM OUTPUT SUGGEST LOW CHANCES (40% OR
LESS) OF OVERLAPPING CRITICAL WIND/RH THRESHOLDS TODAY; HIGHEST
PROBABILITIES ARE IN THE KITTITAS VALLEY AND LOWER COLUMBIA
BASIN OF OREGON WEST OF BOARDMAN.
LOOKING AHEAD, ENSEMBLE NWP GUIDANCE SUGGESTS SOUTHWEST FLOW
ALOFT AMIDST AN AMPLIFYING 500-HPA HEIGHT FIELD WEDNESDAY
THROUGH THE REMAINDER OF THE FORECAST PERIOD. THIS WILL
FACILITATE A CHANGE TO A MORE CONVECTIVE PATTERN WITH DAILY
SHOWER AND THUNDERSTORM CHANCES, THOUGH ANALYSIS OF ENSEMBLE
CLUSTERS REVEALS UNCERTAINTY IN PATTERN DETAILS, ESPECIALLY
BEYOND THURSDAY. 00Z/06Z CAMS AND THE NBM INDICATE THE BEST
SHOWER AND THUNDERSTORM CHANCES (5-20 PERCENT) WEDNESDAY AND
THURSDAY OVER THE WASHINGTON CASCADES AND LIMITED PORTIONS OF
THE BLUE MOUNTAINS. SHOWER AND THUNDERSTORM CHANCES (10-30
PERCENT) EXPAND TO ENCOMPASS THE OREGON CASCADES AND ALL OF THE
BLUE MOUNTAINS BY FRIDAY AND SATURDAY. BY SUNDAY AND MONDAY,
ENSEMBLE NWP INDICATES AT LEAST SOME POTENTIAL (40-60 PERCENT)
OF A DEEP OFFSHORE CLOSED LOW, STRENGTHENING SOUTHERLY TO
SOUTHWESTERLY UPPER-LEVEL WINDS, AND AMPLE MOISTURE OVER THE
FORECAST AREA; THIS SOLUTION IS QUITE FAVORABLE FOR ROBUST
CONVECTION. FIRE WEATHER WATCHES MAY BE NEEDED IF CONFIDENCE IN
WIDESPREAD LIGHTNING INCREASES.
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 54 85 52 85 / 0 0 0 0
ALW 60 87 57 86 / 0 0 0 0
PSC 57 90 57 89 / 0 0 0 0
YKM 59 89 58 88 / 0 0 20 0
HRI 58 88 55 88 / 0 0 0 0
ELN 56 83 54 83 / 0 10 30 20
RDM 46 84 44 84 / 0 0 0 0
LGD 53 87 53 85 / 0 0 0 0
GCD 53 89 52 87 / 0 0 0 0
DLS 61 83 60 89 / 0 0 0 0
PDT WATCHES/WARNINGS/ADVISORIES
WA...AIR QUALITY ALERT UNTIL 11 AM PDT THURSDAY FOR WAZ024-026>030-
521>523.
OR...AIR QUALITY ALERT UNTIL NOON PDT WEDNESDAY FOR ORZ041-049-050-
502-503-505-506-508>511.
DISCUSSION...86
AVIATION...95
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