678
FXUS66 KPDT 140711
AFDPDT
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PENDLETON OR
1211 AM PDT SUN SEP 14 2025
UPDATED AVIATION DISCUSSION
AVIATION...06Z TAF UPDATE
AMENDED BDN AND RDM TO INCLUDE
MENTION OF -TSRA OVERNIGHT, AS SOME ISOLATED THUNDERSTORMS HAVE
FORMED OVER LAKE COUNTY LATE THIS EVENING AND LOOK TO MOVE TOWARD
BOTH SITES. EVANS/74
PREV DISCUSSION
/ISSUED 1038 PM PDT SAT SEP 13 2025/
AVIATION...06Z TAFS...A COLD FRONT IS EXPECTED TO BRING SHOWER
CHANCES TO ALL TAF SITES STARTING OVERNIGHT, BECOMING MORE
WIDESPREAD BY AROUND DAYBREAK SUNDAY. LOCALIZED MVFR CONDITIONS
MAY OCCUR AS A RESULT. SHOWERS WILL MOVE OUT OF MOST OF THE
FORECAST AREA BY LATE SUNDAY MORNING, HOWEVER ISOLATED SHOWERS MAY
DEVELOP NEAR PDT,ALW, AND PSC DURING THE AFTERNOON AND EVENING
HOURS (20-30% CHANCE) SUNDAY. A FEW SHOWERS MAY CONTAIN ISOLATED
THUNDERSTORMS, HOWEVER CONFIDENCE WAS NOT HIGH ENOUGH TO INCLUDE
MENTION OF TS ANYWHERE IN THE TAFS. WINDS WILL ALSO PICK UP BEHIND
THIS FRONT ACROSS ALL SITES HEADING INTO SUNDAY AFTERNOON, WITH
W/NW GUSTS UP TO 25 KTS EXPECTED.
PREV DISCUSSION... /ISSUED 133 PM PDT SAT SEP 13 2025/
DISCUSSION...SATELLITE IMAGERY REVEALS AN UPPER-LEVEL RIDGE OF
HIGH PRESSURE OVER THE PACIFIC NORTHWEST. MEANWHILE, BROAD
TROUGHING, WITH MULTIPLE EMBEDDED WAVES, IS PRESENT DOWNSTREAM.
UPSTREAM, ANOTHER BROAD TROUGH IS LOCATED JUST OFFSHORE, AND A
WELL-DEFINED COLD FRONT IS ALSO VISIBLE OVER THE OCEAN. THIS
TROUGH, AND ATTENDANT SURFACE COLD FRONT, WILL DRIVE OUR WEATHER
TONIGHT THROUGH SUNDAY BEFORE EXITING THE REGION TO THE EAST
THROUGH MONDAY.
THIS AFTERNOON, A CUMULUS FIELD HAS DEVELOPED OVER THE BLUE
MOUNTAINS AND CENTRAL OREGON CASCADES. CANNOT RULE OUT AN ISOLATED
SHOWER THROUGH THIS EVENING, BUT PROBABILITIES ARE LOW AT 10% OR
LESS, HIGHEST FOR THE NORTHERN BLUE MOUNTAINS REGION.
OVERNIGHT, SCATTERED TO NUMEROUS SHOWERS ARE FORECAST, WITH THE
MOST NOTEWORTHY AREA TO THE LEE OF THE CASCADES FROM CENTRAL
OREGON THROUGH THE LOWER COLUMBIA BASIN AND FARTHER EAST INTO THE
BLUE MOUNTAINS AND THEIR FOOTHILLS. FORECAST SOUNDINGS FROM CAMS
SUGGEST SOME MODEST (250-500 J/KG) MUCAPE AND AMPLE MOISTURE
(PWATS GENERALLY 0.7-1.3"). THIS, COUPLED WITH GOOD SYNOPTIC-SCALE
FORCING AS THE VORT MAX SLIDES ONSHORE, SHOULD INDUCE THE
AFOREMENTIONED SHOWERS AND ALSO FACILITATE A SLIGHT CHANCE OF
EMBEDDED THUNDERSTORMS. OF NOTE, THE ECMWF EFI FOR QPF DOES
HIGHLIGHT A REGION OF 0.6-0.8 ROUGHLY FROM THE TRI-CITIES
SOUTHEASTWARD THROUGH THE NORTHERN BLUE MOUNTAINS FOR 00Z SUNDAY
TO 00Z MONDAY.
BREEZY WESTERLY WINDS (GENERALLY 10-20 MPH WITH GUSTS OF 20-35
MPH) WILL ACCOMPANY FRONTAL PASSAGE SUNDAY MORNING AND CONTINUE
THROUGH AFTERNOON IN THE FRONT'S WAKE. CONFIDENCE IN ADVISORY-
LEVEL SUSTAINED WINDS OR GUSTS IS LOW (20-40%) EXCEPT FOR THE
MOST WIND-PRONE AREAS OF THE EASTERN COLUMBIA RIVER GORGE AND
KITTITAS VALLEY WHERE THERE ARE LOCALLY HIGHER CHANCES (50-80%)
OF PEAK WIND GUSTS REACHING ADVISORY LEVELS (45 MPH OR HIGHER).
DRIER CONDITIONS WILL RETURN MONDAY THROUGH MUCH OF WEDNESDAY AS
ANOTHER RIDGE OF HIGH PRESSURE MOVES OVER THE PACIFIC NORTHWEST.
LATE WEDNESDAY INTO THURSDAY, ENSEMBLE MEANS AND CLUSTERS SUGGEST
ANOTHER UPPER-LEVEL TROUGH WILL APPROACH FROM THE PACIFIC.
UNCERTAINTY BURGEONS BY FRIDAY, WITH ROUGHLY HALF OF ENSEMBLE
MEMBERS SHOWING SOME FORM OF A CLOSED LOW OVER THE PACIFIC
NORTHWEST WHILE THE OTHER HALF SHOW WEAKER TROUGHING OVERHEAD WITH
A MORE PRONOUNCED LOW OFF THE SOUTHERN CALIFORNIA COAST. THE
FORMER SOLUTIONS WOULD GENERALLY BE COOLER AND WETTER, WHILE THE
LATTER WOULD BE WARMER AND DRIER.
CONFIDENCE IS MEDIUM-HIGH (60-80%) IN BREEZY TO WINDY WESTERLY
WINDS THROUGH THE CASCADE GAPS AND WIND-PRONE PORTIONS OF THE
COLUMBIA BASIN AND BLUE MOUNTAIN FOOTHILLS ON WEDNESDAY. NBM
PROBABILITIES OF ADVISORY-LEVEL GUSTS ARE STILL LOW (20-50%),
HIGHEST FOR THE EASTERN COLUMBIA RIVER GORGE AND KITTITAS VALLEY.
THAT SAID, RAW GUIDANCE HAS PIQUED MY INTEREST; 12Z DETERMINISTIC
NWP RUNS ARE SHOWING 8-12 MB SURFACE PRESSURE DIFFERENCES FROM
PDX TO GEG, AND THE RAW OUTPUT FROM THE ECMWF ENSEMBLE IS ALSO
SUGGESTING WEDNESDAY HAS POTENTIAL FOR ADVISORY-LEVEL WINDS.
PLUNKETT/86
PRELIMINARY POINT TEMPS/POPS
PDT 47 73 48 81 / 50 0 0 0
ALW 52 74 53 83 / 50 0 0 0
PSC 49 75 48 83 / 40 0 0 0
YKM 45 76 49 82 / 10 0 0 0
HRI 48 75 48 82 / 30 0 0 0
ELN 44 75 46 80 / 10 0 0 0
RDM 35 74 38 83 / 0 0 0 0
LGD 42 72 43 80 / 60 0 0 0
GCD 40 74 43 82 / 30 0 0 0
DLS 48 79 52 86 / 0 0 0 0
PDT WATCHES/WARNINGS/ADVISORIES
OR...NONE.
WA...NONE.
SHORT TERM...86
LONG TERM....86
AVIATION...74
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