108
FXUS66 KPDT 311219
AFDPDT
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PENDLETON OR
519 AM PDT MON MAR 31 2025
UPDATED AVIATION DISCUSSION
SHORT TERM...TODAY THROUGH WEDNESDAY NIGHT
KEY MESSAGES:
1. LIGHT BASIN RAIN AND MOUNTAIN SNOW TODAY
2. BREEZY WINDS TODAY, RETURNING WEDNESDAY
3. BELOW NORMAL TEMPERATURES AND CHILLY TUESDAY MORNING
CURRENT RADAR AND INFRARED SATELLITE IMAGERY SHOWS LIGHT TO
MODERATE SHOWERS MOVING ACROSS THE NORTHERN AND SOUTHERN BLUE
MOUNTAINS FROM SOUTHWEST TO NORTHEAST UNDER MOSTLY CLOUDY SKIES.
AREAS IN AND AROUND HEPPNER HAVE ALSO EXPERIENCED A COUPLE
DEVELOPING THUNDERSTORM CELLS OCCURRING SHORTLY AFTER MIDNIGHT,
WHICH DISSIPATED AS THEY REACHED INTO THE LOWER COLUMBIA BASIN AND
ALONG THE NORTHERN BLUE MOUNTAIN FOOTHILLS. THESE CONDITIONS ARE
IN RESPONSE TO AN UPPER LEVEL SHORTWAVE THAT EJECTED FROM THE
UPPER LEVEL LOW THAT IS CURRENTLY LOCATED OFF THE OREGON COAST.
THIS LOW WILL SLOWLY OPEN UP AND MOVE ONSHORE OVER THE NORTHERN
CALIFORNIA COAST INTO TUESDAY MORNING. AS THE SYSTEM STAYS PARKED
OFFSHORE TODAY, CONTINUED SOUTHWEST FLOW ALOFT WILL LEAD TO
PERIODS OF LIGHT RAIN AND MOUNTAIN SNOW, PREDOMINANTLY IN THE
MORNING AND EARLY AFTERNOON AS SNOW LEVELS STAY BETWEEN 3000-4000
FEET WEST TO EAST. 2 TO 5 INCHES OF SNOWFALL IS EXPECTED TODAY
ACROSS THE CASCADES AND NORTHERN BLUE MOUNTAINS ABOVE 4000 FEET.
CONFIDENCE IN THESE SNOW TOTALS IS HIGH (70-80%) OVER THE NORTHERN
BLUE MOUNTAIN AND THE OREGON CASCADES AS THE NBM SUGGESTS A
60-80% CHANCE OF 3 INCHES OF SNOW OR MORE. LOW CONFIDENCE (20-30%)
RESIDES WITH THESE SNOW TOTALS OVER THE WASHINGTON CASCADES AS
THE NBM ADVERTISES A 20-40% CHANCE OF 3 INCHES OF SNOW OR MORE.
RAIN AMOUNTS TODAY ARE EXPECTED TO STAY BELOW 0.05" FOR THE
MAJORITY OF LOWER ELEVATIONS OF THE COLUMBIA BASIN AND CENTRAL
OREGON, WITH 0.10-0.20" POSSIBLE ALONG THE NORTHERN BLUE MOUNTAIN
FOOTHILLS AND 0.20-0.40" OVER THE NORTHERN BLUE MOUNTAINS AND
OREGON CASCADES. CONFIDENCE IN TODAY'S RAIN AMOUNTS IS MODERATE TO
HIGH (60-80%) AS THE NBM ADVERTISES A 55-75% CHANCE OF 0.35" OF
RAIN OVER THE OREGON CASCADE AND NORTHERN BLUE MOUNTAINS, 50-75%
CHANCE OF 0.15" OF RAIN ALONG THE NORTHERN BLUE MOUNTAIN
FOOTHILLS, AND A 40-60% CHANCE OF 0.05" OF RAINFALL OVER LOWER
ELEVATIONS OF THE COLUMBIA BASIN AND CENTRAL OREGON. THE UPPER
LEVEL LOW PRESSURE PROCEEDS TO MOVE TO OUR SOUTH AND ALONG THE
CALIFORNIA/NEVADA BORDER ON TUESDAY AS A TRANSIENT UPPER LEVEL
RIDGE SLIDES OVER THE REGION. THIS WILL ALLOW FOR DRIER CONDITIONS
TUESDAY AND WEDNESDAY AS LIGHT PRECIPITATION WILL BE CONFINED
OVER CENTRAL OREGON AND THE CASCADE AND BLUE MOUNTAINS TUESDAY,
THEN PRIMARILY OVER HIGHER ELEVATIONS OF THE CASCADES AND NORTHERN
BLUE MOUNTAINS ON WEDNESDAY.
TODAY'S PASSING UPPER LEVEL SHORTWAVE WILL BRING WITH IT BREEZY
CONDITIONS, PEAKING BETWEEN NOON AND 4 PM. HIGHEST WINDS WILL
OCCUR ACROSS THE BLUE MOUNTAIN FOOTHILLS, CENTRAL OREGON, AND THE
SIMCOE HIGHLANDS. SUSTAINED WEST SOUTHWEST WINDS OF 15-20 MPH WITH
GUSTS UP TO 30 MPH WILL BE POSSIBLE. CONFIDENCE IN THESE WIND
VALUES IS MODERATE TO HIGH (50-70%) AS THE HREF SUGGESTS A 30-60%
CHANCE AND THE NBM HIGHLIGHTS A 70-95% CHANCE OF GUSTS REACHING 30
MPH OR GREATER TODAY. THE TRANSIENT UPPER LEVEL RIDGE THAT MOVES
ONSHORE TUESDAY WILL BUILD ACROSS CENTRAL OREGON AS AN UPPER LEVEL
SHORTWAVE FOLLOWS CLOSELY BEHIND. THESE FEATURES WILL ATTRIBUTE TO
SUSTAINED WEST WINDS OF 17-23 MPH WITH GUSTS REACHING UP TO 35
MPH, PEAKING BETWEEN 11 AM AND 3 PM WEDNESDAY FOR AREAS OF THE
SOUTHERN BLUE MOUNTAIN FOOTHILLS AND SIMCOE HIGHLANDS. CONFIDENCE
IN THESE WINDS IS HIGH (70-80%) AS THE NBM SUGGESTS A 85-95%
CHANCE OF WIND GUSTS REACHING 30 MPH OR GREATER AND A 60-80%
CHANCE OF GUSTS REACHING 35 MPH OR GREATER OVER THESE AREAS.
SOUTHWEST FLOW ALOFT TODAY WILL SHIFT TO BEING FROM THE WEST
TONIGHT BEFORE BECOMING MORE FROM THE NORTHWEST TUESDAY AND
WEDNESDAY ASSOCIATED WITH THE DROPPING UPPER LEVEL LOW PRESSURE
TROUGH. HIGH TEMPERATURES WILL STAY ABOUT 5 DEGREES BELOW NORMAL
AND IN THE MID-TO UPPER 50S ACROSS THE LOWER COLUMBIA BASIN, BLUE
MOUNTAIN FOOTHILLS, AND THE EASTERN GORGE THROUGH WEDNESDAY. SKIES
WILL BECOME MOSTLY CLEAR TO PARTLY CLOUDY TONIGHT INTO TUESDAY
MORNING AS THE TRANSIENT RIDGE ALLOWS FOR HIGH PRESSURE TO PASS
OVER THE REGION DURING THE OVERNIGHT HOURS. EFFECTIVE RADIATIONAL
COOLING WILL RESULT TO ALLOW TEMPERATURES TO DROP INTO THE MID-
TO LOW 30S ACROSS THE LOWER COLUMBIA BASIN AND BLUE MOUNTAIN
FOOTHILLS, AND IN THE UPPER 20S TO LOW 30S OVER CENTRAL OREGON AND
THE JOHN DAY BASIN. OVERNIGHT TEMPERATURES WILL INCREASE SLIGHTLY
TUESDAY NIGHT INTO WEDNESDAY MORNING AS CLOUD COVER IS EXPECTED
TO BREAK MUCH LATER IN THE OVERNIGHT PERIOD AS LOWS BOTTOM OUT IN
THE MID TO UPPER 30S ACROSS THE LOWER COLUMBIA BASIN AND STILL IN
THE UPPER 20S TO LOW 30S OVER CENTRAL OREGON AND THE JOHN DAY
BASIN. 75
LONG TERM...THURSDAY THROUGH MONDAY
THE LONG TERM WILL FEATURE AN
UPPER RIDGE GRADUALLY MOVING TO THE PACNW WITH THE TROUGH AXIS
SOUTHEASTERLY ACROSS THE FOUR CORNERS. LIGHT MOUNTAIN SNOW OVER THE
NORTHERN BLUES AND CREST OF OR CASCADES MAY LINGER THURSDAY MORNING
(30-40% CHANCE) BUT WITH LOW CHANCES (<20%) OF RAIN FOR THE
LOWLANDS. OTHERWISE, THIS PERIOD WILL BE PERSISTENTLY DRY THROUGH
THE WEEKEND. HOWEVER, MONDAY IS WHEN THE RIDGE MAY BREAK DOWN WITH
THE TROUGH MAKING ITS WAY ONSHORE, BRINGING MOUNTAIN SHOWERS. POPS
WILL BE BELOW 20% FOR THE BLUES BUT UP TO 40% OVER THE CASCADES. BUT
WITH THE DELAY ONSET OF MONDAY'S RIDGE BREAKDOWN AND THE DIFFERENCE
ON THE TROUGH'S AMPLITUDE, THIS CAN MAKE IT DIFFICULT TO DETERMINE
HOW MUCH RAIN WE COULD GET MONDAY AND ITS TIMING. NONETHELESS, THE
MODELS AND ENSEMBLES ARE OVERALL IN FAVORABLE AGREEMENT WITH THIS
PERIOD'S PATTERN.
WITH THE INCREASED NORTHWESTERLY FLOW FROM THE ONCOMING RIDGE,
OCCASIONAL BREEZES (UP TO 20 MPH) WILL DEVELOP OVER THE FOOTHILLS OF
THE BLUES AND WA/OR CASCADES DURING MORNING AND AFTERNOON HOURS
THROUGH FRIDAY (30-50% CONFIDENCE). OVER THE WEEKEND, WINDS WILL BE
SLIGHTLY DECREASE AT THE LOWLANDS BUT WILL REMAIN OCCASIONALLY
BREEZY OVER THE MOUNTAIN AREAS. BY MONDAY, WINDS MAY GRADUALLY
INCREASE UP TO 25 MPH ACROSS THE FORECAST AREA AS THE FLOW CHANGES
FROM NORTHWEST TO SOUTHWESTERLY (60% CONFIDENCE).
HIGH TEMPERATURES WILL GRADUALLY SHOW A WARMING TREND AS THE RIDGE
BUILDS OVER INTO NEXT WEEK. THURSDAY AND FRIDAY, THE COLUMBIA BASIN
WILL BE IN THE HIGH 50S AND LOW 60S WITH THE BLUES AND CASCADES IN
THE 50S. SATURDAY ONWARDS, TEMPERATURES WILL THEN BE 5-15 DEGREES
ABOVE NORMAL WITH THE FORECAST AREA RANGING BETWEEN THE 60S AND 70S.
FEASTER/97
AVIATION...12Z TAFS
ALL SITES WILL BE VFR THROUGHOUT THIS TAF
PERIOD. SHOWERS ARE STILL ONGOING FOR KALW BUT WILL END WITHIN THE
NEXT COUPLE OF HOURS BEFORE RETURNING AT 18Z-22Z. RAIN MAY OCCUR FOR
THE KDLS THIS AFTERNOON FOR A COUPLE OF HOURS AS WELL. ALSO, KPSC
COULD POTENTIALLY RECEIVE VINICITY SHOWERS THIS AFTERNOON THROUGH
THE EARLY EVENING HOURS. WINDS WILL BE BREEZY FOR KDLS, KPDT, KBDN,
KALW, AND KPSC UP TO 25KTS THROUGH THE DAY BEFORE DECREASING IN THE
EVENING. KRDM WILL HAVE BREEZY WINDS AS WELL, BUT MAINLY DURING THE
MORNING HOURS. KYKM COULD HAVE SHOWERS STARTING THIS LATE MORNING
BUT CONFIDENCE WAS VERY LOW (<25%) IN MENTIONING IN THE TAFS.
FEASTER/97
PRELIMINARY POINT TEMPS/POPS
PDT 53 33 55 37 / 50 20 20 10
ALW 54 37 55 39 / 70 20 20 20
PSC 59 37 60 37 / 30 10 10 10
YKM 57 35 59 33 / 20 10 10 0
HRI 57 36 58 38 / 40 10 10 10
ELN 54 35 55 35 / 40 20 10 10
RDM 49 29 49 29 / 30 20 30 20
LGD 49 29 50 33 / 80 40 30 30
GCD 47 28 48 32 / 60 50 50 40
DLS 56 36 57 40 / 40 20 20 10
PDT WATCHES/WARNINGS/ADVISORIES
OR...NONE.
WA...NONE.
SHORT TERM...75
LONG TERM....97
AVIATION...97
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