697
FXUS66 KPDT 041740
AFDPDT
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PENDLETON OR
940 AM PST WED MAR 4 2026
KEY MESSAGES
- WIDESPREAD PRECIPITATION TODAY WITH LIGHT TO MODERATE MOUNTAIN
SNOW AND BREEZY TO WINDY WINDS. *WINTER WEATHER ADVISORY IN EFFECT*
-PERSISTENT PRECIP THURSDAY INTO NEXT WEEK WITH BREEZY TO GUSTY
WINDS.
DISCUSSION
CURRENT CONDITIONS: WATER VAPOR AND RADAR IMAGERY
SHOWS THE TRANSIENT RIDGE BREAKING DOWN AS THE UPPER TROUGH OFFSHORE
PUSHES LIGHT RAIN SHOWERS ACROSS THE BLUE MOUNTAINS, PORTIONS OF THE
COLUMBIA BASIN OF WA/OR AND NORTH CENTRAL OR. SURFACE OBSERVATIONS
REVEAL PRECIP AMOUNTS UP TO 0.10 INCH WITHIN THOSE AREAS FROM THE
PAST HOUR.
TODAY THROUGH TONIGHT: THE UPPER TROUGH PASSAGE WILL MAKE ITS WAY
ACROSS THE PACNW WITH THE SOUTHERLY FLOW THROUGH LATER THIS MORNING.
BY AFTERNOON INTO LATE EVENING, THE TROUGH AXIS AND FRONTAL SYSTEM
WILL THEN PUSH FURTHER EAST INTO OUR REGION BEFORE MOVING OUT
OF OUR AREA TONIGHT THROUGH THURSDAY MORNING. PRECIP CHANCES
WILL CONTINUE TO INCREASE, RESULTING IN WIDESPREAD RAIN SHOWERS
AND LIGHT TO MODERATE MOUNTAIN SNOW OR RAIN/SNOW MIX. WA/OR
CASCADES CREST AND BLUE MOUNTAINS WILL SEE PRECIP TOTALS
EXCEEDING 0.50 INCH (60-90% PROB FROM NBM 24-HR PRECIP) THROUGH
THIS AFTERNOON. HOWEVER, THERE IS A 20-40% PROB OF 1 INCH OF
GREATER FOR THE CASCADES CREST AND 40-50% PROB FOR THE BLUES.
THIS IS DUE TO THE MOISTURE SUPPORT WEAKENING OVER THE CASCADES
CREST WHILE INCREASING FOR THE BLUES AND EASTERN OR MOUNTAINS
WITH THE TROUGH AXIS MOVING EASTWARD TONIGHT THROUGH THURSDAY
MORNING. THE LOWLANDS MAY SEE ABOUT 0.10 INCH OR LESS (50-80%
PROB). IN ADDITION TO THE FRONTAL SYSTEM, STEEPER LAPSE RATES
ARE EXPECTED ACROSS PORTIONS OF OUR FORECAST AREA AND ALONG THE
NORTHERN BLUE MOUNTAINS AND ADJACENT FOOTHILLS, RESULTING IN A
GENERAL RISK FOR THUNDERSTORMS IN THESE AREAS THIS AFTERNOON
INTO THE EARLY EVENING (10-20% CHANCE).
LIGHT TO MODERATE MOUNTAIN SNOW WILL DEVELOP ACROSS THE CASCADES,
BLUE MOUNTAINS AND PORTIONS OF EASTERN OR. AS THE UPPER TROUGH MAKES
ITS WAY TO THE PACNW THIS MORNING, SNOW LEVELS WILL START OFF ABOVE
5KFT AT PASS LEVELS FOR WET SNOW TO ACCUMULATE BETWEEN 2 AND 5
INCHES OVER THE PORTIONS OF EASTERN OR MOUNTAINS, AND THE CREST OF
WA CASCADES (30-50% CONFIDENCE). BY THE AFTERNOON THROUGH THURSDAY
MORNING, THE UPPER TROUGH WILL THEN PUSH FURTHER EAST ACROSS THE
PACNW ALONG WITH THE FRONTAL SYSTEM. THIS WILL BRING WIDESPREAD SNOW
OVER THE MOUNTAIN AREAS WITH SNOW LEVELS OF 3-4KFT DURING THAT TIME.
THE BLUE MOUNTAINS AND WALLOWA MOUNTAINS MAY SEE SNOW TOTALS
EXCEEDING 5 INCHES THIS AFTERNOON THROUGH THURSDAY MORNING AS THE
TROUGH AXIS PASSES (50-90% CONFIDENCE). CONFIDENCE IS 75-95% FOR
SANTIAM PASS TO GET SNOW ACCUMULATIONS MORE THAN 6 INCHES, RESULTING
IN KEEPING THE WINTER WEATHER ADVISORY IN EFFECT FOR THE EAST SLOPES
OF OR CASCADES FOR WEDNESDAY FROM 4AM-10PM PST. SNOQUALMIE PASS MAY
HAVE SNOW ACCUMULATIONS OF 1 INCH OR LESS WITH HIGHER SNOW LEVELS
(ABOVE 2.5KFT). MODEL GUIDANCE (RAP AND NAMNAST) ARE IN GOOD
AGREEMENT WITH THESE SNOW AMOUNTS FOR THOSE MOUNTAIN AREAS. THE
MODELS CONTINUE TO SHOW TIGHT SURFACE PRESSURE GRADIENTS FORECAST
OVER KITTITAS VALLEY TO THE COLUMBIA BASIN. BREEZY WINDS (GUSTS 35-
50 MPH) ARE EXPECTED WITH THE FRONTAL PASSAGE TODAY AS WELL (70-90%
CONFIDENCE). THE STRONGEST WINDS WILL MAINLY DEVELOP OVER THE
CASCADE PEAKS/RIDGES AND RIDGES IN THE COLUMBIA BASIN.
THURSDAY INTO NEXT WEEK: MODELS AND ENSEMBLES WILL REMAIN IN GREAT
AGREEMENT WITH THAT NORTHWEST FLOW ALOFT THURSDAY BEFORE BECOMING
MORE NORTHERLY THURSDAY NIGHT INTO FRIDAY. PERSISTENT LIGHT SNOW AND
RAIN/SNOW MIX ARE FORECAST ALONG THE MOUNTAIN AREAS (WA/OR CASCADE
CRESTS, BLUE MOUNTAINS, AND EASTERN OR MOUNTAINS) THROUGH FRIDAY.
PRECIP CHANCES WILL GRADUALLY DECREASE TO 20-40% FOR THE BLUES AND
EASTERN OR FRIDAY AFTERNOON THROUGH LATE SATURDAY NIGHT. LOWLANDS
WILL ENTER A DRY PERIOD STARTING LATER FRIDAY AFTERNOON INTO LATE
SATURDAY NIGHT, THANKS TO THAT BROAD HIGH PRESSURE OFFSHORE.
SUNDAY ONWARD, WE WILL ENTER INTO A TROUGHING PATTERN WHERE
MULTIPLE OF FRONTAL SYSTEMS MAY RETURN. THERE IS TIMING AND
STRENGTH DISCREPANCIES AMONGST THE CLUSTER MEMBERS WITH THE
UPPER TROUGH NEXT WEEK, BUT SEEMED TO BE FAVORABLE OF THE
ASSOCIATED PRECIP.
THANKS TO THESE SYSTEMS, GUSTY WINDS (35-50 MPH) WILL BE EXPECTED
OVER THE RIDGES AT THE WA CASCADES AND KITTITAS VALLEY (60-80%
CONFIDENCE). THE TIMING FOR THOSE STRONG WINDS WOULD BE THURSDAY,
SUNDAY, AND MONDAY DURING AFTERNOON AND EVENING HOURS. THE REMAINING
LOCATIONS WILL HAVE BREEZY WINDS (20-30 MPH) (60% CONFIDENCE).
FEASTER/97
AVIATION /18Z TAFS THROUGH 18Z THURSDAY/
SHOWERS AND MODERATE RAIN CONTINUE THROUGH THE REGION AND WILL
PERSIST THROUGH THE MORNING THROUGH LATE AFTERNOON HOURS. PDT IS
CURRENTLY SEEING MVFR CONDITIONS WITH LOW VISIBILITIES AND CIGS.
WE'LL SEE SLIGHT CHANCES (5-15% CHANCE) FOR THE REST OF SITES
SEEING MVFR CONDITIONS WITH HEAVIER RAIN BANDS PASSING THROUGH
SITES. PRECIPITATION WILL DRY OUT FOR MOST OF THE SITES BY THE
MID TO LATE AFTERNOON HOURS, WHERE VFR CONDITIONS WILL PREVAIL.
BREEZY WINDS WILL BE EXPECTED AT MOST SITES AS THE SYSTEM PUSHES
THROUGH, WITH THE STRONGEST WINDS EXPECTED THROUGH 02Z, WITH
PSC/PDT/DLS SEEING BREEZY 15-25 MPH GUSTS THROUGH THE REST OF
THE TAF PERIOD.
PRELIMINARY POINT TEMPS/POPS
PDT 52 37 51 35 / 90 60 30 30
ALW 53 38 52 37 / 100 70 50 40
PSC 58 37 58 36 / 80 30 0 20
YKM 56 34 53 33 / 70 10 0 20
HRI 56 38 56 36 / 90 40 10 20
ELN 50 35 48 33 / 80 20 10 20
RDM 47 29 44 28 / 90 30 0 10
LGD 49 35 44 31 / 100 90 70 60
GCD 46 32 41 30 / 100 80 60 40
DLS 54 41 53 41 / 100 50 30 30
PDT WATCHES/WARNINGS/ADVISORIES
WA...NONE.
OR...WINTER WEATHER ADVISORY UNTIL 10 PM PST THIS EVENING FOR
ORZ509.
DISCUSSION...97
AVIATION...95
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