312
FXUS66 KPDT 010616
AFDPDT
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PENDLETON OR
1016 PM PST WED DEC 31 2025
UPDATED AVIATION DISCUSSION...
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 IF 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 RATES 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...06Z TAFS
LOW STRATUS AND FOG IS EXPANDING IN
COVERAGE OVER THE COLUMBIA BASIN AND ALONG THE FOOTHILLS OF THE
BLUE MOUNTAINS, CURRENTLY AFFECTING VSBYS AND/OR CIGS AT
PDT/ALW/PSC. VSBYS AS LOW AS 1/4SM ARE FORECAST OVERNIGHT INTO
THURSDAY MORNING AT THE AFOREMENTIONED SITES. ELSEWHERE,
CONFIDENCE IN FOG AND STRATUS IS LOW (30 PERCENT OR LESS) UNTIL
PRECIPITATION SPREADS FROM SOUTH TO NORTH BEGINNING 10-12Z
THURSDAY MORNING. WARM AIR ALOFT IN TANDEM WITH ENTRENCHED SUB-
FREEZING AIR AT THE SURFACE IN THE COLUMBIA BASIN AND
SURROUNDING LOWLANDS RAISES CONCERNS FOR PERIODS OF -FZRA AT ALL
SITES. PRECIPITATION IS EXPECTED (80 PERCENT CONFIDENCE) TO TURN
OVER TO -RA AT BDN/RDM BY 15-17Z WHILE OTHER SITES HAVE A BETTER
CHANCE (40-70 PERCENT) OF REMAINING -FZRA. CIGS WILL ALSO DECREASE
THURSDAY MORNING AND AFTERNOON, WITH MVFR OR LOWER FORECAST AT
ALL SITES. OTHERWISE, MOSTLY LIGHT WINDS OF 10 KTS OR LESS.
PRELIMINARY POINT TEMPS/POPS
PDT 22 34 29 47 / 0 70 80 40
ALW 25 34 31 45 / 0 60 90 70
PSC 23 33 28 43 / 0 50 70 30
YKM 23 35 29 42 / 0 40 60 20
HRI 24 33 28 43 / 0 60 80 30
ELN 21 33 28 39 / 0 40 60 40
RDM 27 43 34 53 / 30 70 60 0
LGD 30 41 35 46 / 0 80 90 70
GCD 31 43 38 51 / 10 90 90 40
DLS 28 36 33 45 / 10 70 90 50
PDT WATCHES/WARNINGS/ADVISORIES
OR...WINTER WEATHER ADVISORY FROM 4 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 4 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.
DISCUSSION...71
AVIATION...86
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