446
FXUS66 KPDT 141730
AFDPDT
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PENDLETON OR
1030 AM PDT SUN SEP 14 2025
AVIATION...18Z TAFS
THE BULK OF THE SHOWER AND THUNDERSTORM
ACTIVITY HAS PUSHED EAST OF TAF SITES THIS MORNING. HOWEVER,
PARTIAL CLEARING THIS MORNING COUPLED WITH STEEPENING LAPSE RATES
SHOULD BE ABLE TO GENERATE A WEAKLY UNSTABLE AIR MASS AND PRODUCE
ADDITIONAL ISOLATED TO SCATTERED SHOWERS/THUNDERSTORMS THIS
AFTERNOON; THE BEST CHANCES OF RAIN WILL BE AT PDT/ALW/PSC WITH
LOWER CHANCES ELSEWHERE. SUB-VFR CIGS/VSBYS WILL BE POSSIBLE IN
SHOWERS/THUNDERSTORMS, BUT CONFIDENCE WAS TOO LOW (<30%) TO
INCLUDE MENTION AT ANY SITE.
WINDS WILL INCREASE IN MAGNITUDE LATE THIS MORNING THROUGH
AFTERNOON AT ALL SITES, GENERALLY SUSTAINED AT 10-15 KTS
WITH GUSTS OF 15-25 KTS, BEFORE SLACKENING OVERNIGHT.
SKIES WILL BECOME CLEAR TO PARTLY CLOUDY THIS EVENING THROUGH
TONIGHT. WILL NOTE THERE IS A LOW CHANCE (<30%) OF STRATUS
LINGERING OVERNIGHT AT BDN/RDM WITH BETTER CHANCES ALONG THE BLUE
MOUNTAIN FOOTHILLS AT PDT AND ESPECIALLY ALW. PLUNKETT/86
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 71 47 73 48 / 90 50 0 0
ALW 72 52 74 53 / 80 50 0 0
PSC 76 49 75 48 / 80 40 0 0
YKM 73 45 76 49 / 60 10 0 0
HRI 74 48 75 48 / 80 30 0 0
ELN 70 44 75 46 / 60 10 0 0
RDM 68 35 74 38 / 50 0 0 0
LGD 66 42 72 43 / 90 60 0 0
GCD 68 40 74 43 / 90 30 0 0
DLS 73 48 79 52 / 70 0 0 0
PDT WATCHES/WARNINGS/ADVISORIES
OR...NONE.
WA...NONE.
SHORT TERM...86
LONG TERM....86
AVIATION...86
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