705
FXUS66 KPDT 260604
AFDPDT
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PENDLETON OR
1004 PM PST THU DEC 25 2025
UPDATED FOR AVIATION
AVIATION
06Z TAFS...TAFS RANGE FROM VFR TO LIFR AT THIS TIME DUE TO STRATUS
AND FOG. PRECIPITATION WILL MOVE IN DURING THE OVERNIGHT AND EARLY
MORNING HOURS AS WELL. THEREFORE THE EXPECTATION IS THAT MOST, IF
NOT ALL SITES WILL SEE AT LEAST MVFR CONDITIONS, AND SOME MANY
COULD GET LOWER, THOUGH CONFIDENCE IS FLIGHT CATEGORIES (AND
TIMING) IS BELOW AVERAGE AT BEST. BY FRIDAY AFTERNOON, ALL SITES
SHOULD BE BACK TO VFR.
WINDS WILL GENERALLY BE LESS THAN 10 KTS THROUGH MUCH OF THE
PERIOD, BUT ARE EXPECTED TO INCREASE AND BECOME GUSTY DURING THE
AFTERNOON AND EVENING HOURS AT PDT, ALW AND PSC AND COULD GUST IN
THE 20 TO 25 KT RANGE.
PREV DISCUSSION
/ISSUED 311 PM PST THU DEC 25 2025/
DISCUSSION...
KEY MESSAGES:
1. WIDESPREAD LIGHT PRECIPITATION PERSISTS TODAY AND FRIDAY.
2. SIGNIFICANT MOUNTAIN SNOWFALL FRIDAY AND EARLY SATURDAY.
*WINTER ADVISORIES ISSUED*
3. DRIER AND COOLER CONDITIONS EARLY IN THE WEEK.
CURRENT RADAR AND VISIBLE SATELLITE IMAGERY SHOWS LIGHT, SPOTTY
RETURNS ACROSS THE AREA MOVING NORTH-NORTHEAST UNDER PARTLY TO
MOSTLY CLOUDY SKIES. THIS IS IN RESPONSE TO AN UPPER LEVEL
SHORTWAVE AND ATTENDANT COLD FRONT PASSING ACROSS THE REGION AS IT
SPINS OFF A PARENT LOW PRESSURE CURRENTLY LOCATED OFF THE NORTHERN
CALIFORNIA COAST. THESE SYNOPTIC FEATURES WILL KEEP LIGHT MOUNTAIN
SNOW SHOWERS POSSIBLE AS AROUND AN INCH OF ADDITIONAL SNOWFALL IS
EXPECTED ACROSS THE CASCADE AND BLUE MOUNTAINS THROUGH THE DAY.
LIGHT LOWER ELEVATION RAIN WILL CONTINUE TO TAPER OFF THIS
AFTERNOON AND EVENING AS THE COLD FRONT DISSIPATES. ADDITIONAL
RAIN AMOUNTS OF AROUND 0.05" ARE EXPECTED ACROSS LOWER ELEVATIONS
OF THE COLUMBIA BASIN AND BLUE MOUNTAIN FOOTHILLS, WITH CLOSER TO
0.10" ACROSS CENTRAL OREGON. THE PRESENCE OF LOW LEVEL MOISTURE
AND LOW WINDS WITH THE WEAK, DISSIPATING COLD FRONT, ALLOWED AREAS
OF FOG TO DEVELOP EARLY THIS MORNING ACROSS CENTRAL OREGON,
NORTH-CENTRAL OREGON, AND THE NORTHERN BLUE MOUNTAIN FOOTHILLS OF
WASHINGTON. AS MOST OF THESE AREAS HAVE SEEN FOG LIFT AND
VISIBILITIES IMPROVE, THE BLUE MOUNTAIN FOOTHILLS OF WASHINGTON
IS STILL EXPERIENCING LOW VISIBILITIES OF ONE QUARTER MILE OR
LESS - ESPECIALLY AROUND THE WALLA WALLA AREA. THIS HAS WARRANTED
THE EXTENSION OF THE DENSE FOG ADVISORY UNTIL 4 PM THIS
AFTERNOON.
THIS UPPER LEVEL LOW WILL OPEN AND JOIN WITH A DROPPING UPPER
LEVEL TROUGH FROM THE GULF OF ALASKA LATE TONIGHT INTO FRIDAY
MORNING TO BRING ANOTHER ROUND OF WIDESPREAD PRECIPITATION TO THE
AREA. BOTH OF THESE FEATURES WILL BRING ADDITIONAL MOISTURE AND
ADVECT COOLER AIR THROUGH THE REGION TO PROVIDE SIGNIFICANT
SNOWFALL ACROSS THE CASCADE AND BLUE MOUNTAINS. SNOW LEVELS WILL
BE DROPPING THROUGH THE DAY ON FRIDAY, FROM THE 3000-4000 FOOT
RANGE EARLY FRIDAY MORNING TO 500-1500 FEET EARLY SATURDAY
MORNING. PASS LEVEL SNOWFALL OF UP TO 12 INCHES OVER THE CASCADES
AND UP TO 10 INCHES ACROSS THE NORTHERN BLUES IS EXPECTED.
CONFIDENCE IN THESE SNOW AMOUNTS IS HIGH (80%) AS THE NBM
ADVERTISES A 60-80% CHANCE OF 10 INCHES OVER SNOQUALMIE AND
SANTIAM PASSES AND A 40-50% CHANCE OVER HIGHER TERRAIN OF THE
NORTHERN BLUE MOUNTAINS THAT INCLUDE SKI BLUEWOOD. THUS, WINTER
WEATHER ADVISORIES HAVE BEEN ISSUED FROM 4 AM FRIDAY THROUGH 7 AM
SATURDAY ACROSS THE OREGON/WASHINGTON CASCADES AND THE NORTHERN
BLUE MOUNTAINS. THERE IS ALSO A 30-50% CHANCE OF MEASURABLE
SNOWFALL ACROSS THE NORTHERN BLUE MOUNTAIN FOOTHILLS (WALLA WALLA
AND PENDLETON) LATE FRIDAY NIGHT THROUGH SATURDAY MORNING, WITH
HIGHER CHANCES (70-90%) FOR PILOT ROCK AND ATHENA.
THESE SYNOPTIC FEATURES LATE FRIDAY INTO SATURDAY WILL ALSO BRING
WITH IT THE POTENTIAL FOR BREEZY WINDS ACROSS THE COLUMBIA BASIN.
ENSEMBLES ARE SUGGESTING THAT A LIFTING OCCLUDED FRONT AND MID-
LEVEL JET ASSOCIATED WITH THE DROPPING SYSTEM WILL ENHANCE WINDS
BETWEEN 7 PM FRIDAY AND 7 AM SATURDAY. HIGHEST WINDS ARE EXPECTED
TO OCCUR ALONG THE EAST SLOPES OF THE WASHINGTON CASCADES, SIMCOE
HIGHLANDS, BLUE MOUNTAIN FOOTHILLS, AND THE LOWER COLUMBIA BASIN
WITH SUSTAINED WEST-SOUTHWEST WINDS OF 15-25 MPH WITH GUSTS OF
35-45 MPH. CONFIDENCE IN THESE WINDS IS MODERATE (40-60%) AS THE
HREF AND NBM ADVERTISE A 40-80% CHANCE OF 40 MPH GUSTS OR MORE.
ENSEMBLES ARE STILL STRUGGLING WITH THE STRENGTH OF THE INCOMING
TROUGH THAT WILL BE DROPPING ALONG THE BRITISH COLUMBIA COAST,
WHICH DIRECTLY RELATES TO THE LOCATION OF THE MID-LEVEL JET AND
ITS EFFICIENCY IN INCREASING WINDS. THE CURRENT SPREAD IN WIND
GUSTS ACROSS ENSEMBLE CLUSTERS ARE 10-15 MPH, WITH 54% OF
ENSEMBLES ALIGNING WITH THE EARLIER MENTIONED WIND VALUES.
CURRENTLY, IT IS UNLIKELY (40-50%) THAT A WIND ADVISORY WILL BE
NECESSARY ACROSS THE AFOREMENTIONED AREAS LATE FRIDAY EVENING
THROUGH SATURDAY MORNING.
ENSEMBLES ARE IN GOOD AGREEMENT WITH THE PATTERN EARLY IN THE WEEK
AS AN UPPER LEVEL RIDGE MOVES ONSHORE IN THE WAKE OF SATURDAY'S
SYSTEM. THIS RIDGE WILL BRING DRIER CONDITIONS AND COOLER
TEMPERATURES WITH HIGHS PEAKING IN THE MID-30S AND LOWS IN THE
LOW 20S ACROSS THE COLUMBIA BASIN THROUGH TUESDAY. WEDNESDAY IS
WHEN UNCERTAINTY RETURNS IN ENSEMBLE MEMBERS AS AN UPPER LEVEL
TROUGH DROPS ALONG THE BRITISH COLUMBIA COAST FROM THE GULF OF
ALASKA. THE PRIMARY ENSEMBLE INCONSISTENCIES RELATE TO STRENGTH,
WITH 66% OF ENSEMBLES HINTING AT A STRONGER TROUGH AND 4% MORE
ENSEMBLE MEMBERS SUGGESTING AN EARLIER ARRIVAL OF THE FEATURE.
THIS SCENARIO MAY BRING WIDESPREAD MOISTURE EARLIER WEDNESDAY
MORNING, BUT LOW CONFIDENCE RESIDES WITH THIS RESULT AS ENSEMBLE
MEMBERS ARE IN CONFLICT AS TO HOW THE ARRIVING TROUGH AND
DEPARTING RIDGE WILL INTERACT MID-WEEK. 75
AVIATION...00Z TAFS...MOST SITES (KDLS/KPDT/KRDM/KBDN/KYKM) WILL BE
VFR THROUGH EARLY THIS EVENING. THE FOG WILL REMAIN IN KALW DURING
EVENING HOURS WITH VSBY AS LOW AS 1/4SM. THE FOG MIGHT BRIEFLY LIFT
IF RAIN WERE TO DEVELOP OVERNIGHT THUS HELPING IMPROVE VSBY, BUT
CHANCES ARE SLIM DUE TO WEAK MOISTURE TRANSPORT (<20%). AS THE
OFFSHORE LOW CONTINUES, THERE IS STILL A SLIGHT CHANCE (<30%) OF
RAIN FOR MOST SITES AND OVERNIGHT LIGHT SNOW FOR KRDM/KBDN. THIS
COULD POTENTIALLY DROP VSBYS AND CIGS TO MVFR CONDITIONS OR LOWER.
SOUTHWESTERLY WINDS OF 12-15KTS WITH GUSTS UP TO 25KTS MAY RETURN
EARLY FRIDAY MORNING HOURS FOR KRDM/KBDN, WHICH COULD BRING CHANCES
OF LIGHT BLOWING SNOW IF FURTHER MATERIALIZES. KPSC WILL BE MVFR
THROUGH EARLY EVENING AND MAY HAPPEN AGAIN EARLY FRIDAY MORNING WITH
THE RAIN AND MIST, BUT WITH LOW CONFIDENCE (<30%). FEASTER/97
PRELIMINARY POINT TEMPS/POPS
PDT 34 47 30 40 / 60 70 70 40
ALW 36 46 32 38 / 70 80 80 50
PSC 34 48 30 42 / 60 70 40 10
YKM 30 43 25 41 / 30 50 20 0
HRI 34 48 31 43 / 60 60 50 20
ELN 27 37 23 35 / 20 60 40 0
RDM 30 43 24 38 / 60 50 30 10
LGD 36 44 29 34 / 60 70 90 70
GCD 34 43 27 34 / 60 70 70 50
DLS 37 47 35 44 / 60 80 80 20
PDT WATCHES/WARNINGS/ADVISORIES
OR...WINTER WEATHER ADVISORY FROM 4 AM FRIDAY TO 7 AM PST SATURDAY
FOR ORZ502-509.
WA...WINTER WEATHER ADVISORY FROM 4 AM FRIDAY TO 7 AM PST SATURDAY
FOR WAZ030-522.
FREEZING FOG ADVISORY UNTIL 10 AM PST FRIDAY FOR WAZ026.
DENSE FOG ADVISORY UNTIL 10 AM PST FRIDAY FOR WAZ029.
SHORT TERM...75
LONG TERM....75
AVIATION...77
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