805
FXUS66 KPDT 251326
AFDPDT
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PENDLETON OR
526 AM PST THU DEC 25 2025
UPDATE
ADDED DENSE FOG ADVISORIES OVER CENTRAL AND NORTH CENTRAL OREGON
ZONES AS AREA ROADCAMS SHOW DENSE FOG IN ADDITION TO RDM AND BDN
HAVING VISIBILITY REDUCED TO 1/4SM AND M1/4SM OVER THE LAST HOUR
OR TWO. ADVISORIES IN EFFECT UNTIL 18Z LEVERAGING BEST LAV
GUIDANCE.
PREV DISCUSSION
/ISSUED 412 AM PST THU DEC 25 2025/
DISCUSSION...
AN OFFSHORE LOW IS PROVIDING SOUTHWESTERLY WINDS AND WEAK
MOISTURE TRANSPORT ACROSS THE REGION. THIS LOW IS FORECAST TO MOVE
ONSHORE TONIGHT WILE FILLING AND BECOMING ABSORBED BY A SHARP
UPPER TROUGH ALONG THE PAC NW COAST BY MIDDAY FRIDAY. SOME OF THE
MOST IMPACTFUL WEATHER WILL BE THE POTENTIAL FOR MOUNTAIN PASS
LEVEL SNOW, THAT WHILE IS ONGOING IN LIGHT AMOUNTS, WILL SEE
ACCUMULATIONS RAMPING UP BEGINNING AROUND FRIDAY MORNING AND
PERSISTING THROUGH AT LEAST SATURDAY. NBM/WPC SNOW ACCUMS SUGGEST
HIGH LEVEL ADVISORY CRITERIA FOR THAT DAY AND A HALF PERIOD AS
ACCUMS BEGIN TO PUSH PAST ONE INCH PER HOUR RATES FRIDAY MORNING
WITH RRFS SNOW ENSEMBLES PLUMES INDICATING OCCASIONAL HIGHER
POTENTIAL THAN ONE INCH PER HOUR RATES. STILL WITH THE NBM POPS
DRYING UP ON SATURDAY, WE HAVE LIMITED THE TIME FRAME FOR A NEW
WINTER WEATHER ADVISORY, STARTING AROUND 12Z FRIDAY THROUGH ABOUT
MID MORNING SATURDAY. WINTER STORM SEVERITY INDEX PEGS THESE
AREAS AS HIGH CONFIDENCE, (70-90%) FOR MINOR IMPACTS INCLUDING
WINTER DRIVING CONDITIONS. ONCE THIS SYSTEM SLIDES EAST OF THE
REGION THIS WEEKEND, A LARGE 588DM ANTICYCLONE DEVELOPS OVER THE
EASTERN PACIFIC WHICH BUILDS A RIDGE INTO WESTERN NORTH AMERICA
FOR ABOUT THE FIRST HALF OF NEST WEEK.
AVIATION...
AN OFFSHORE LOW IS PROVIDING SOUTHWESTERLY WINDS AND WEAK
MOISTURE TRANSPORT ACROSS THE REGION. ONE BAND OF SHOWERS IS NOW
LIFTING NORTH ACROSS NORTH CENTRAL OREGON AND DLS, WHILE ANOTHER
IS OFF SW OREGON FOR LATER TODAY AND TONIGHT. HREF IS SHOWING
DECENT PROBABILITIES (50 TO 60%) FOR IFR TO LIFR CATEGORY CEILINGS
OR VSBYS AT PSC THIS MORNING WHICH IS REFLECTED WITH 300 TO 700
FT CEILINGS THOUGH AROUND 17Z. ON AND OFF SHOWERS WILL BRING BRIEF
MVFR CEILINGS FOR THE DURATION OF THE TAF PERIOD.
PRELIMINARY POINT TEMPS/POPS
PDT 53 35 49 31 / 40 40 70 60
ALW 52 37 49 32 / 50 50 80 70
PSC 47 32 48 31 / 40 40 60 30
YKM 43 30 44 25 / 50 30 40 20
HRI 48 33 49 31 / 30 40 60 40
ELN 38 26 38 24 / 70 40 50 40
RDM 51 28 46 24 / 10 40 50 30
LGD 50 35 44 28 / 50 40 90 80
GCD 50 35 43 28 / 40 60 80 70
DLS 46 36 46 36 / 60 50 70 70
PDT WATCHES/WARNINGS/ADVISORIES
OR...WINTER WEATHER ADVISORY FROM 4 AM FRIDAY TO 7 AM PST SATURDAY
FOR ORZ502-509.
DENSE FOG ADVISORY UNTIL 10 AM PST THIS MORNING FOR ORZ510-511.
WA...WINTER WEATHER ADVISORY FROM 4 AM FRIDAY TO 7 AM PST SATURDAY
FOR WAZ030-522.
SHORT TERM...71
LONG TERM....71
AVIATION...71
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