298
FXUS66 KPDT 301103
AFDPDT
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PENDLETON OR
303 AM PST TUE DEC 30 2025
DISCUSSION
KEY MESSAGES:
1. QUIET WEATHER THROUGH THURSDAY, WITH AIR STAGNATION AND THE
POTENTIAL FOR FOG BEING THE ONLY CONCERNS.
2. PRECIPITATION RETURNS FROM THURSDAY THROUGH THE WEEKEND.
3. LOW (10-30%) FREEZING RAIN OR SLEET THURSDAY IN CENTRAL AND
NORTH-CENTRAL OREGON THURSDAY MORNING AND THURSDAY NIGHT INTO
FRIDAY MORNING FOR PORTIONS OF THE COLUMBIA BASIN, YAKIMA VALLEY
AND COLDER LOWER ELEVATION LOCATIONS.
A LARGE UPPER LEVEL RIDGE WAS LOCATED OVER THE WESTERN CONUS. THIS
RIDGE WILL REMAIN OVER THE REGION TODAY BEFORE MOVING EASTWARD
TONIGHT INTO WEDNESDAY. DUE TO THE RIDGE OVERHEAD, AND LIGHT
WINDS, AIR STAGNATION REMAINS A CONCERN AND ADVISORIES HAVE BEEN
ISSUED. OTHERWISE, DRY WEATHER WITH TEMPERATURES ABOUT 5 DEGREES
BELOW NORMAL WILL REMAIN IN PLACE THROUGH THURSDAY.
BY THURSDAY, A MORE SOUTH TO SOUTHWEST FLOW WILL BE IN PLACE AND
MOISTURE WILL BEGIN TO MOVE NORTHWARD FROM CALIFORNIA DURING THE
DAY ON THURSDAY, AND CONTINUE INTO THURSDAY NIGHT BEFORE WHAT
LOOKS TO BE A LULL ON FRIDAY. THE HIGHEST QPF AMOUNTS WILL BE OVER
THE MOUNTAINS, WHERE 0.25 TO 0.50 INCHES COULD FALL WHILE
GENERALLY LESS THAN 09.10 INCHES WILL OCCUR OVER THE LOWER
ELEVATIONS.
DEPENDING ON HOW MUCH PRECIPITATION MOVES IN AND HOW QUICKLY
THERE IS A LOW (10-30 PERCENT) POTENTIAL FOR FREEZING RAIN OR
SLEET IN IN CENTRAL AND NORTH-CENTRAL OREGON THURSDAY MORNING AND
THEN ACROSS PORTIONS OF THE COLUMBIA BASIN, YAKIMA AND KITTITAS
VALLEYS AND OTHER LOWER ELEVATION COLD SPOTS THURSDAY NIGHT INTO
FRIDAY MORNING DUE TO THE COLD AIR TRAPPED AT THE SURFACE. MODELS
DIFFER ON HOW MUCH QPF FALLS DURING THESE TIMES AND WE WILL SEE
HOW THE SITUATION EVOLVES OVER THE NEXT FEW DAYS. OVERALL QPF IS
EXPECTED TO BE LIGHT AND TEMPERATURES ARE EXPECTED TO GET ABOVE
FREEZING DURING THE DAY.
ON FRIDAY, LOW PRESSURE IS FORECAST TO MOVE NORTH OFF THE OREGON
AND WASHINGTON COASTS AND WILL BRING TROUGH ACROSS THE REGION BY
SATURDAY, WITH SOME ADDITIONAL PRECIPITATION, MAINLY OVER THE
MOUNTAINS, WITH MOSTLY DRY WEATHER FOR THE LOWER ELEVATIONS SUNDAY
AND MONDAY.
SNOW LEVELS WILL INITIALLY START OFF IN THE 2500-3000 FOOT RANGE
IN THE WASHINGTON CASCADES ON THURSDAY, 3500-4500 FOOT RANGE IN
THE BLUES AND WALLOWAS AND THE 5500-6500 FOOT RANGE IN THE OREGON
CASCADES. SNOW LEVELS WILL RISE TO 4500-5000 FEET IN THE
WASHINGTON CASCADES AND OVER 6500 FEET ELSEWHERE ON FRIDAY. ANY
PRECIPITATION THAT FALLS OVER THE MOUNTAINS WOULD NOT BE SNOW
DURING THIS TIME, EXCEPT AT THE HIGHER ELEVATIONS. SNOW LEVELS
WILL FALL AGAIN ON SATURDAY INTO SUNDAY AND WILL BE BETWEEN
2500-3000 FEET BY SUNDAY MORNING IN THE WASHINGTON CASCADES AND
3500-4000 FEET ELSEWHERE. SOME SNOW ACCUMULATION IS POSSIBLE
DURING THIS PERIOD, AND IT LOOKS LIKE GENERALLY 4 INCHES OR LESS
IN THE CASCADES, AT PASS LEVEL, AND PERHAPS 6 OR MORE ALONG THE
CRESTS WITH AN INCH OR TWO IN THE BLUES.
AVIATION
12Z TAFS...VFR CONDITIONS ARE EXPECTED THROUGH THE DAY TODAY, WITH
THE POSSIBLE EXCEPTION OF SOME LOWER CONDITION (IFR/LIFR) IN THE
BDN/RDM AREA. TONIGHT INTO WEDNESDAY MORNING, THERE IS A CHANCE
(30-40 PERCENT) AT PDT, YKM AND ALW. WINDS WILL BE LIGHT THROUGH
THE PERIOD.
PRELIMINARY POINT TEMPS/POPS
PDT 37 21 35 23 / 0 0 0 0
ALW 34 25 34 25 / 0 0 0 0
PSC 39 22 34 23 / 0 0 0 0
YKM 39 22 36 22 / 0 0 0 0
HRI 37 23 33 23 / 0 0 0 0
ELN 33 20 34 22 / 0 0 0 0
RDM 41 22 47 26 / 0 0 0 10
LGD 41 30 44 31 / 0 0 0 0
GCD 45 28 48 30 / 0 0 0 10
DLS 39 27 37 28 / 0 0 0 10
PDT WATCHES/WARNINGS/ADVISORIES
OR...AIR STAGNATION ADVISORY UNTIL NOON PST THURSDAY FOR ORZ044-507-
508-510-511.
WA...AIR STAGNATION ADVISORY UNTIL NOON PST THURSDAY FOR WAZ026>029.
SHORT TERM...77
LONG TERM....77
AVIATION...77
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