506
FXUS66 KPDT 160000
AFDPDT
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PENDLETON OR
500 PM PDT SUN MAR 15 2026
KEY MESSAGES
- WALLA WALLA RIVER FLOODING THROUGH MONDAY MORNING
- WARMING TREND THROUGH THE WEEK
- RAIN IN THE WA CASCADES WILL LEAD TO INCREASED SNOWMELT
DISCUSSION
UPPER LEVEL RIDGING WILL BEGIN TO BUILD OVER THE PACNW TONIGHT,
BRINGING A PROLONGED PERIOD OF WARMING TEMPERATURES, WA CASCADE
PRECIP, AND DRY CONDITIONS ELSEWHERE.
TONIGHT, AN UPPER LEVEL RIDGE OFFSHORE WILL BEGIN ITS TRANSIT
TOWARDS WESTERN CONUS, WHERE IT WILL GRADUALLY PUSH EAST THROUGH
THURSDAY. ACCOMPANYING THE UPPER RIDGE WILL BE A WEAK TO
MODERATE ATMOSPHERIC RIVER, THAT WILL CLIP NORTHERN AND CENTRAL
WA THROUGHOUT THE WEEK. AHEAD OF THE RIDGE, A SURFACE WARM FRONT
WILL LIFT ACROSS THE PACNW, WITH THE FRONTAL BOUNDARY USHERING
IN SNOW LEVELS BETWEEN 8KFT TO 10KFT. MOST LOCATIONS ACROSS THE
FORECAST AREA WILL SEE THE WARM AIRMASS MIX TO THE SURFACE WITH
LITTLE TROUBLE, HOWEVER WARM AIR WILL REMAIN ALOFT ACROSS THE
SHELTERED AREAS OF THE WA CASCADE CREST AND EAST SLOPES. AS THE
AR IMPACTS THE WA CASCADES, PRECIPITATION WILL START OFF AS
SNOW, BUT WILL TRANSITION INTO A WINTRY MIX IF FREEZING RAIN AND
SNOW LATE THIS EVENING AS FALLING PRECIP INTERACTS WITH THE
WARM AIR ALOFT. BY MONDAY MORNING, THE WINTRY MIX/FREEZING RAIN
IS EXPECTED TO TRANSITION TO RAIN AS WARM AIR BEGINS TO MIX DOWN
TO THE SURFACE. A WINTER WEATHER ADVISORY IS IN EFFECT FOR THE
UPPER EAST SLOPES OF THE WA CASCADES BETWEEN 8PM TONIGHT AND 5AM
MONDAY MORNING.
SNOW LEVELS WILL REMAIN ABOVE 7-8KFT THROUGH AT LEAST THURSDAY
AS THE UPPER RIDGE CONTINUES TO MOVE ACROSS WESTERN CONUS
(CONFIDENCE 75-90%). THIS WILL MEAN THAT PRECIPITATION ALONG
THE WA CASCADES WILL MAINLY FALL AS RAIN THROUGH THIS PERIOD.
COMBINED WITH IMPENDING WARMING TEMPERATURES UNDER THE UPPER
RIDGE, THE INCREASED SNOWMELT WILL RESULT IN RIVER LEVELS RISING
ACROSS RIVERS AND STREAMS ORIGINATING FROM THE WA CASCADES. AT
THIS TIME, NONE OF THE RIVERS/STREAMS ARE FORECAST TO REACH
FLOOD STAGE, AND WILL REMAIN WITHIN ACTION STAGE. OF NOTE
HOWEVER, AREAS OF THE YAKIMA RIVER UP RIVER FROM CLE ELUM MAY
SEE MINOR FLOODING IMPACTS DUE TO CHANNEL STRUCTURE CHANGE FROM
FLOODING IN DECEMBER.
AS MENTIONED EARLIER, TEMPERATURES ARE EXPECTED TO WARM ACROSS
THE REGION AS THE UPPER LEVEL RIDGE MOVES OVERHEAD. BY TUESDAY,
WIDESPREAD AFTERNOON TEMPERATURES IN THE LOWER TO MID 70S ARE TO
DEVELOP ACROSS THE LOWER ELEVATIONS, WARMING FURTHER INTO THE
MID TO UPPER 70S THURSDAY AND FRIDAY. THERE IS A POTENTIAL FOR
THE REGION TO SEE AFTERNOON TEMPERATURES WARM EVEN FURTHER INTO
THE 80S THIS WEEK, WITH LATEST NBM GUIDANCE INDICATING A 60-80%
CHANCE OF CENTRAL OR AND THE JOHN DAY BASIN REACHING 80 DEGREES
BY WEDNESDAY, AND A 25-40% CHANCE ALONG THE BLUE MOUNTAIN
FOOTHILLS AND COLUMBIA BASIN ON THURSDAY.
FRIDAY INTO SATURDAY, THE UPPER RIDGE WILL PUSH INTO CENTRAL
CONUS AS AN UPPER LEVEL LOW DEEPENS IN THE NORTHEAST PACIFIC.
ENSEMBLE CLUSTER IS IN GOOD AGREEMENT THAT WEAK SHORTWAVES
EJECTING FROM THE LOW WILL PUSH ACROSS THE PACNW, BRINGING A
SHOT OF COOLER AIR AND LOWERING SNOW LEVELS ACROSS THE CASCADES
AND THE NORTHERN BLUES (CONFIDENCE 55-70%). EACH SHORTWAVE
PASSAGE WILL BRING LIGHT RAIN AND SNOW TO THE CASCADES AND
NORTHERN BLUES FRIDAY INTO SATURDAY, WITH DRY CONDITIONS
CONTINUING IN THE LOWER ELEVATIONS INTO NEXT WEEKEND. LAWHORN/82
AVIATION /00Z TAFS THROUGH 00Z TUESDAY/
VFR CONDITIONS ARE LIKELY (80-95 PERCENT CONFIDENCE, VARYING BY
SITE) THROUGH THE PERIOD.
A WARM FRONT IS TRACKING NORTHEAST ACROSS THE PACIFIC NORTHWEST
THIS AFTERNOON, AND IT WILL BRING LOW (20-40 PERCENT) CHANCES
OF LIGHT RAIN TO DLS/PDT/YKM/ALW/PSC BETWEEN 00-06Z. WILL NOTE
THAT THE LOWER LEVELS OF THE ATMOSPHERE ARE QUITE DRY, WHICH
REDUCES CONFIDENCE IN PREVAILING RAIN. INSTEAD, HAVE INCLUDED
SOME PROB30 GROUPS FOR THE RAIN CHANCES.
PRECIPITATION CHANCES RAMP UP AGAIN TO 15-30 PERCENT AT
PDT/YKM/ALW/PSC EARLY TO MID-MORNING MONDAY, BUT CONFIDENCE IN
PREVAILING LIGHT RAIN WAS TOO LOW TO INCLUDE IN THE 00Z TAFS.
CIGS WILL LOWER TO AROUND 5-8 KFT AGL AT MOST SITES AS THE WARM
FRONT MOVES THROUGH THE REGION THIS EVENING INTO THE OVERNIGHT
PERIOD, AND THERE IS LOW CONFIDENCE (20 PERCENT) IN CIGS
DROPPING AS LOW AS 3 KFT AT YKM/ALW THIS EVENING.
WINDS WILL REMAIN MOSTLY LIGHT AT 12KTS OR LESS THROUGH THE
PERIOD. 86
PRELIMINARY POINT TEMPS/POPS
PDT 40 66 45 70 / 30 20 0 10
ALW 42 63 49 66 / 40 40 10 20
PSC 40 66 48 71 / 20 20 0 10
YKM 33 63 42 68 / 40 20 0 10
HRI 40 66 46 71 / 20 20 0 10
ELN 31 55 38 60 / 60 30 10 30
RDM 37 71 38 75 / 10 10 0 0
LGD 37 61 42 68 / 70 40 10 10
GCD 37 67 41 71 / 40 10 0 0
DLS 40 68 45 66 / 30 10 0 20
PDT WATCHES/WARNINGS/ADVISORIES
WA...WINTER WEATHER ADVISORY FROM 8 PM THIS EVENING TO 5 AM PDT
MONDAY FOR WAZ522.
OR...NONE.
DISCUSSION...82
AVIATION...86
CLICK HERE TO GO TO PREVIOUS BULLETINS.
Main Text Page