469
FXUS66 KPDT 312306
AFDPDT
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PENDLETON OR
304 PM PST WED DEC 31 2025
DISCUSSION
A WIND ADVISORY IN EFFECT ACROSS THE GRANDE RONDE VALLEY WILL BE
ALLOWED TO EXPIRE ON TIME (3 PM) AS THE WINDS HAVE SHOWED A
DOWNTREND EARLY THIS AFTERNOON, AND THIS IS THE TREND WE SEE IN
THE PRESSURE GRADIENT VALUES BETWEEN BAKER CITY AND MEACHAM. THE
FORECAST TREND LOOKS TO PICK UP AGAIN AFTER MIDNIGHT WITH MORE
WINDY CONDITIONS ON NEW YEARS DAY.
AIR STAGNATION EPISODE WILL CONTINUE TONIGHT INTO NEW YEARS DAY,
AND FINALLY BE RELIEVED BY THE ONSET OF THE THE NEXT WARM FRONTAL
OVERRUNNING PATTERN THAT BEGINS EARLY THURSDAY, SPREADING RAIN AND
FREEZING RAIN ACROSS THE LOWLANDS, AND INCREASING OVERALL WIND
FLOW WITH TIME.
WINTER WEATHER ADVISORIES WERE HOISTED FOR THE THREAT OF FREEZING
RAIN, AS WELL AS THE POTENTIAL FOR A MIX OR SNOW IN THE HIGHEST
ELEVATION, AND LATER IN THE EVENT AS WELL AS SNOW LEVELS GET A BIT
LOWER. INITIALLY THE LOW SNOW LEVELS ACROSS SOUTH CENTRAL WA AND
THE SLOPES WILL BE LIFTED AWAY BY A NORTHWARD LIFTING WARM FRONTAL
BOUNDARY TONIGHT AND NEWS YEARS DAY, AND POPS WILL INCREASE
RAPIDLY BETWEEN 4 AND AND 10 AM NEW YEARS DAY.
UNCERTAINTY IS HIGH WITH RESPECT TO 2 THINGS, 1) SURFACE
TEMPERATURES, AND 2) ACTUAL RAIN AMOUNTS. WITH THE VERY LIGHT
WINDS, AND MARGINALLY COLD AIR, THE TOTAL CONVERSION TO FREEZING
RAIN ON THE GROUND CAN BE LESS EFFICIENT THAN IS THERE WERE A
LITTLE ,MORE WINDS AND OBVIOUSLY COLDER AIR IN THE THE UPPER 20S.
THIS GOES INTO THE THE OVERALL UNCERTAINTY OF THE OVERALL IMPACTS,
HOWEVER THE MORE SHELTERED VALLEY MAY DAM THE COLD AIR LONGER
ADDING TO THE OVERALL POTENTIALLY HIGHER ICE TO LIQUID RATIOS. ON
THE SAME IDEA, RELATIVELY LOW RAIN RATS CAN BE ADDITIVE TO THE
ILRS WHERE THE STRONGER WINDS AND VERY COLD AIR IS LACKING. ICE
ACCUMULATIONS BASED ON THE NAM COBB OUTPUT SUPPORTS ON THE ORDER
OF 0.10-0.15” ACROSS THE EASTERN COLUMBIA GORGE. RUSSELL/71
AVIATION…..
00Z TAFS...VFR CONDITIONS AT MOST SITES, BUT LIFR
CONDITIONS ARE CURRENTLY BEING OBSERVED AT KPSC DUE TO REDUCED
CEILINGS OF 200 FEET AND VISIBILITY THROUGH THE END OF THE
PERIOD AS FREEZING RAIN IS LIKELY EARLY THURSDAY AFTERNOON. LIFR
CONDITIONS ARE ALSO EXPECTED AT KALW TONIGHT AS CEILINGS DROP TO
300-400 FEET AND FOG DEVELOPS TO DROP VISIBILITIES TO 1/4SM EARLY
THURSDAY MORNING. LOW CEILINGS ARE ALSO LIKELY AT KPDT DURING THE
MORNING HOURS, BRIEFLY DROPPING CONDITIONS TO LIFR EARLY. FREEZING
RAIN AND RAIN WILL MOVE INTO KRDM/KBDN DURING THE EARLY MORNING
HOURS, REACHING KDLS BY MID-MORNING, AND KPSC/KPDT/KALW BY EARLY
AFTERNOON. ICE ACCUMULATIONS OF 0.05-0.15" WILL BE POSSIBLE FOR
KDLS/KPDT/KALW/KPSC THROUGH FRIDAY MORNING. 75
PRELIMINARY POINT TEMPS/POPS
PDT 22 34 29 47 / 0 60 80 40
ALW 25 34 31 45 / 0 50 80 60
PSC 23 33 29 42 / 0 40 70 30
YKM 23 36 28 42 / 0 30 50 20
HRI 24 33 29 43 / 0 50 80 30
ELN 21 33 28 39 / 0 30 50 20
RDM 27 44 34 54 / 20 70 50 10
LGD 30 41 36 47 / 0 70 80 60
GCD 31 44 39 52 / 10 90 90 30
DLS 28 36 34 44 / 10 60 90 50
PDT WATCHES/WARNINGS/ADVISORIES
OR...WINTER WEATHER ADVISORY FROM 10 AM THURSDAY TO 1 AM PST FRIDAY
FOR ORZ041-044-507-508-510-511.
AIR STAGNATION ADVISORY UNTIL NOON PST THURSDAY FOR ORZ044-507-
508-510-511.
WA...WINTER WEATHER ADVISORY FROM 10 AM THURSDAY TO 1 AM PST FRIDAY
FOR WAZ024-521.
AIR STAGNATION ADVISORY UNTIL NOON PST THURSDAY FOR WAZ026>029.
WINTER WEATHER ADVISORY FROM 4 AM THURSDAY TO 5 AM PST FRIDAY
FOR WAZ026>029-522-523.
SHORT TERM...75
AVIATION...75
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