007
FXUS66 KPDT 312309
AFDPDT
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PENDLETON OR
409 PM PDT TUE MAR 31 2026
KEY MESSAGES
1. SHOWERS AND ISOLATED AFTERNOON THUNDERSTORMS THROUGH WEDNESDAY
2. MIDWEEK MOUNTAIN SNOWFALL, SIGNIFICANT SNOW OREGON CASCADES
*WINTER STORM WARNING AND ADVISORIES ISSUED*
3. DRIER AND WARMER CONDITIONS OVER THE WEEKEND
DISCUSSION
CURRENT RADAR SHOWS MUCH OF THE PRECIPITATION IS TRAVERSING OFF TO
THE NORTH WITH A LINE OF SHOWERS MOVING ACROSS THE NORTHERN BASIN
AND YAKIMA VALLEY. GROUND OBSERVATIONS ARE SHOWING NO ACCUMULATIONS
WITH THIS LINE OF SHOWERS SO THE SHOWERS ARE LIKELY VIRGA. LINGERING
SHOWERS ARE EXPECTED TO PERSIST THROUGH THE EVENING WITH LIGHT
ACCUMULATIONS ALONG THE FOOTHILLS OF THE SOUTHERN AND NORTHERN BLUES
OF 0.03-0.05 INCHES WITH 30-50% CONFIDENCE WHILE THE EASTERN
MOUNTAINS WILL SEE 0.10-0.15 INCHES WITH 70-90% CONFIDENCE AND OR
CASCADES WILL SEE SNOW SHOWERS ABOVE 4500 FEET WITH ACCUMULATIONS UP
TO 2 INCHES WITH 70-90% CONFIDENCE WHILE THE LOWER SLOPES WILL SEE
0.05 INCHES OF RAIN. LREF RAW ENSEMBLES SHOW THAT THERE IS 50-60% OF
THE MEMBERS IN AGREEMENT THAT THE NORTHERLY SHIFT WILL BRING WITH IT
15-25% CHANCES OF ISOLATED THUNDERSTORMS THROUGH GRANT AND COOK
COUNTIES THIS AFTERNOON. WEDNESDAY AHEAD OF THE FRONT, LREF SHOWS
15% PROBABILITIES OF ISOLATED THUNDERSTORMS ALONG THE LEADING EDGE
OF THE FRONT. ISOLATED THUNDERSTORMS WOULD FORM ALONG THE WESTERN
SLOPES OF THE EASTERN MOUNTAINS THROUGH GRANT, COOK AND INTO
SOUTHERN UMATILLA COUNTIES.
WEDNESDAY AND THURSDAY MODELS SHOW A STRONG UPPER LEVEL LOW WILL
MOVE IN OFF THE COAST OF B.C. AND AHEAD OF IT WILL BE ANOTHER FRONT.
MODELS SHOW THIS SYSTEM TO BE ROBUST WITH INCREASED CHANCES OF
MOUNTAIN SNOW, LOW ELEVATION RAIN AND INCREASED WINDS. CLUSTERS DO
SHOW SOME DEVIATION WITH THE MODELS WITH TIMING, HOWEVER, ALL MODELS
SHOW A ROBUST FRONT MAKING ITS WAY INTO THE REGION TUESDAY
NIGHT/WEDNESDAY MORNING. THE FRONT WILL MOVE ACROSS THE REGION
BRINGING SNOW LEVELS TO NEAR 2000 FEET. THIS WILL ALLOW FOR SOME
SNOW SHOWERS ACROSS A GOOD PORTION OF THE REGION WITH THE HIGHEST
AMOUNTS BEING ALONG THE CASCADES. A WINTER STORM WANING HAS BEEN
ISSUED FOR THE EAST SLOPES OF THE OR CASCADES WITH MODELS SHOWING
NEARLY 10-15 INCHES OF ACCUMULATION ALONG SANTIAM PASS WITH 60-80%
OF THE RAW ENSEMBLES ARE IN AGREEMENT. A WINTER WEATHER ADVISORY HAS
BEEN ISSUED FOR THE EAST SLOPES OF THE WA CASCADES THROUGH
SNOQUALMIE PASS DUE TO THE AREAS SEEING UP TO 7 INCHES OF SNOW 60-
70% CONFIDENCE. TOLLGATE AND PORTIONS OF THE NORTHERN BLUES WILL SEE
4-6 INCHES OF SNOW AS WELL WITH 30-50% CONFIDENCE. THE EASTERN
MOUNTAINS WILL SEE UP TO 1-1.5 INCHES WITH 60-80% CONFIDENCE. THE
LOWER ELEVATIONS MODELS ARE SHOWING QPF AMOUNTS NEARING 0.15-0.30
INCHES WITH 60-80% CONFIDENCE. THERE IS SOME SHADOWING SHOWING UP IN
THE MODELS RUNS AND PORTIONS OF THE WESTERN BASIN AS WELL AS THROUGH
CENTRAL AND NORTH CENTRAL OR WILL ONLY SEE 0.05-0.15 INCHES OF RAIN
WEDNESDAY THROUGH THURSDAY WITH 50-70% CONFIDENCE. LASTLY, WINDS
WILL BECOME A BIT BREEZY AS THE FRONT MOVES THROUGH THURSDAY BRINING
70-80% PROBABILITIES OF 25-35 MPH GUSTS ACROSS THE REGION.
THURSDAY NIGHT INTO FRIDAY MORNING MODELS SHOW THE NEXT INCOMING
SYSTEM COMING IN FROM OFF THE COAST. AN UPPER LEVEL RIDGE WILL SET
UP OVER THE REGION BRINGING WARMER AND DRIER CONDITIONS. CLUSTERS
SHOW THAT THE MAIN DIFFERENCE BETWEEN THE MODELS WILL BE POSITIONING
OF THE UPPER LEVEL RIDGE. LOOKING AT IN HOUSE MODEL COMPARISONS,
TEMPERATURES WILL BE ANYWHERE FROM 5 TO 10 DEGREES ABOVE SEASONAL
NORMAL THROUGH THE BASIN AND ADJACENT VALLEYS AND 10-15 DEGREES
ABOVE SEASONAL AVERAGE FOR THE OREGON POTION OF THE CWA.
TEMPERATURES WILL START OFF IN THE LOW TO MID 60S BEFORE INCREASING
AND SEEING UPPER 60S TO LOW 70S IN SOME AREAS. CONFIDENCE IN THE
TEMPERATURES IS 50-70% PEAKING SUNDAY. 90
AVIATION /18Z TAFS THROUGH 18Z WEDNESDAY/
VFR CONDITIONS ACROSS MOST SITES HOWEVER A SLOW MOVING BAND OF RAIN
SHOWERS AND MOISTURE STRETCHING W-E ACROSS NRN OREGON HAS CEILINGS
IFR AND MVFR KBDN/KRDM RESPECTIVELY. THE FORECAST IS FOR THESE
CEILINGS TO LIFT AT LEAST ONE CATEGORY THROUGH THE AFTERNOON BEFORE
RETURNING TO MVFR LEVELS INTO THE EVENING. MVFR CEILINGS MAY ALSO
IMPACT KDLS LATE TUESDAY EVENING AS LIGHT RAIN BEGINS. RAIN SPREADS
OVER THE REGION THROUGH WEDNESDAY MORNING. ELSEWHERE, CEILINGS WILL
HOVER BETWEEN 5-7KFT BUT CEILINGS WILL BE REDUCED GOING BY WEDNESDAY
MORNING WITH THE NEXT STORM. WINDS WILL STAY LIGHT AND BELOW 10KTS
AT ALL TERMINALS THROUGH THE PERIOD.
AVIATION /00Z TAFS THROUGH 00Z THURSDAY/
SCATTERED SHOWERS WILL LIFT OFF THE WASHINGTON CASCADES AND
NORTHERN BLUE MOUNTAINS AROUND 7 – 9Z, FOR ALL TERMINALS,
PRECIPITATION WILL BE RAIN. CONDITIONS DETERIORATE SLOWLY
THROUGH THE OVERNIGHT AND WEDNESDAY AFTERNOON. FOR KPSC, CHANCES
FOR CEILINGS BELOW 1000FT RAMP UP TO ONLY 20% THROUGH 18Z
WEDNESDAY MORNING, HOWEVER GO TO AROUND 80% FOR THE MVFR
CATEGORY RANGE.
PRELIMINARY POINT TEMPS/POPS
PDT 38 57 34 52 / 40 90 90 50
ALW 40 57 38 52 / 30 90 100 70
PSC 38 59 39 60 / 20 90 80 20
YKM 35 52 31 58 / 20 90 50 10
HRI 38 58 36 57 / 30 90 80 30
ELN 32 47 32 50 / 20 90 70 20
RDM 36 55 27 48 / 40 90 70 40
LGD 38 55 33 46 / 80 90 100 80
GCD 38 53 30 44 / 80 100 100 90
DLS 41 55 37 57 / 60 100 70 30
PDT WATCHES/WARNINGS/ADVISORIES
WA...WINTER WEATHER ADVISORY FROM 11 AM WEDNESDAY TO 11 PM PDT
THURSDAY FOR WAZ522.
OR...WINTER STORM WARNING FROM 5 AM WEDNESDAY TO 5 PM PDT THURSDAY
FOR ORZ509.
DISCUSSION...90
AVIATION...71
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