245
FXUS66 KPDT 140538
AFDPDT
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PENDLETON OR
938 PM PST TUE JAN 13 2026
UPDATED FOR AVIATION
AVIATION
06Z TAFS....VFR CONDITIONS ARE EXPECTED THROUGH THE TAF PERIOD.
THERE IS A CHANCE (GENERALLY <30 PERCENT) IN MOST LOCATIONS THOUGH
30-50 PERCENT AT YKM OF MVFR OR LOWER CONDITIONS WEDNESDAY
MORNING.
WINDS WILL BE LIGHT THROUGH THE PERIOD.
PREV DISCUSSION
/ISSUED 254 PM PST TUE JAN 13 2026/
DISCUSSION...
KEY MESSAGES:
1. STAGNANT CONDITIONS THROUGH WEEK.
*AIR STAGNATION ADVISORY ACTIVE*
2. DRY CONDITIONS AND COOLING TREND THROUGH WEEKEND.
CURRENT RADAR AND VISIBLE SATELLITE IMAGERY SHOWS DRY CONDITIONS
AS HIGH LEVEL CLOUDS STREAM ACROSS THE REGION FROM THE NORTHWEST.
THIS IS IN RESPONSE TO THE UPPER LEVEL RIDGE AND SURFACE HIGH
PRESSURE OVER THE PACIFIC NORTHWEST, WHICH WILL KEEP CONDITIONS
DRY AND ANY INCOMING SYSTEMS WELL TO OUR NORTH. THE ABUNDANCE OF
HIGH PRESSURE WILL LEAD TO SINKING AIR AND INVERSION DEVELOPMENT
ACROSS THE LOWER COLUMBIA BASIN, COLUMBIA GORGE, NORTH-
CENTRAL/CENTRAL OREGON, AND THE KITTITAS/YAKIMA VALLEYS THROUGH
MUCH OF THE WEEK. INVERSIONS WILL LIMIT VERTICAL MIXING AS
EVIDENT IN GUIDANCE THAT SUGGESTS MIXING HEIGHTS OF 1500 FEET OR
LESS, COUPLED WITH LOW TRANSPORT WINDS. THESE CONDITIONS WILL
HELP TO DEGRADE AIR QUALITY THROUGH THE WEEK. CURRENT AIR QUALITY
INDEX (AQI) VALUES HOVER IN THE MODERATE CATEGORY OVER MUCH OF THE
AREA, AND LIKELY DEGRADING THROUGH THURSDAY. THUS, AN AIR
STAGNATION ADVISORY HAS BEEN ISSUED OVER THE AFOREMENTIONED AREAS
THROUGH 10 AM FRIDAY.
DUE TO REDUCED WINDS AND LOW LEVEL MIXING, THERE MAY ALSO BE
AREAS OF FOG DEVELOPING OVERNIGHT AND EXTENDING THROUGH THE
MORNING HOURS. DENSE FOG ADVISORIES HAVE BEEN NECESSARY ACROSS THE
KITTITAS VALLEY THE LAST TWO MORNINGS AND ARE EXPECTED TO AGAIN
DEVELOP TONIGHT AND OVERNIGHT INTO THURSDAY MORNING. IN FACT, NBM
GUIDANCE SUGGESTS THERE IS A 15-25% CHANCE OF VISIBILITIES OF ONE
MILE OR LESS EXTENDING ACROSS THE COLUMBIA BASIN, COLUMBIA GORGE,
AND NORTHERN BLUE MOUNTAIN FOOTHILLS OVERNIGHT INTO WEDNESDAY
MORNING, BUT BEST CHANCES OF 50-60% STILL RESIDE OVER KITTITAS
VALLEY. CHANCES LOOK TO DROP SLIGHTLY OVERNIGHT INTO THURSDAY
MORNING, WITH 20-25% ACROSS THE KITTITAS VALLEY AND LESS THAN 10%
ELSEWHERE.
THE UPPER LEVEL RIDGE SHIFTS OFFSHORE THURSDAY, BRINGING A COOLER
AIRMASS ACROSS THE REGION AS HIGH TEMPERATURES STRUGGLE TO BREAK
OUT OF THE MID-TO UPPER 30S ACROSS THE COLUMBIA BASIN AND BLUE
MOUNTAIN FOOTHILLS THROUGH THE WEEKEND AS THE RIDGE EXTENDS ALL
THE WAY UP THE PACIFIC COAST INTO ALASKA. TEMPERATURES ARE
CURRENTLY FORECAST TO BOTTOM-OUT SUNDAY, WITH MORNING LOWS
DIPPING INTO THE LOW TO MID-20S AND HIGHS IN THE MID-TO UPPER 30S
ACROSS THE COLUMBIA BASIN, COLUMBIA GORGE, BLUE MOUNTAIN
FOOTHILLS, AND THEY KITTITAS/YAKIMA VALLEYS.
THE UPPER LEVEL RIDGE BEGINS TO SLOWLY WEAKEN MONDAY AHEAD OF A
DESCENDING TROUGH, BRINGING THE BEST CHANCE FOR PRECIPITATION TO
RETURN TO THE AREA. HOWEVER, CONFIDENCE IS QUITE LOW AS ENSEMBLE
MEMBERS STRUGGLE WITH THE STRENGTH OF THE INCOMING UPPER LEVEL
TROUGH AND TIMING OF HOW QUICKLY THE UPPER LEVEL RIDGE WEAKENS.
48% OF ENSEMBLE MEMBERS ADVERTISE LIGHT RAIN BEGINNING OVER
MOUNTAINOUS TERRAIN LATE TUESDAY MORNING, WITH THE CONSENSUS OF
ALL MEMBERS BY EARLY WEDNESDAY MORNING. ONLY THE AFOREMENTIONED
48% OF MEMBERS SUGGEST PRECIPITATION REACHING LOWER ELEVATIONS OF
THE COLUMBIA BASIN AND BLUE MOUNTAIN FOOTHILLS. THESE
INCONSISTENCIES LEAD TO THE NBM ONLY HIGHLIGHTING A 45-55% CHANCE
OF ANY MEASURABLE PRECIPITATION (0.01" OR GREATER) OVER THE
CASCADES AND BLUE MOUNTAINS, AND A 5-15% CHANCE OVER LOWER
ELEVATIONS OF THE LOWER COLUMBIA BASIN, COLUMBIA GORGE, AND BLUE
MOUNTAIN FOOTHILLS. SNOW LEVELS DURING THIS TIMEFRAME ARE FORECAST
TO BE BETWEEN 3000-4000 FEET, SO ANY FALLING PRECIPITATION OVER
MOUNTAINOUS TERRAIN SHOULD BE SNOW. 75
AVIATION...00Z TAFS...THE HIGH PRESSURE IS THE MAIN WEATHER
DRIVER, LEADING TO LIGHT AND VARIABLE WINDS AT ALL SITES FOR THIS
PERIOD. MODEL HAVE SUBTLE HINTS AT VERY LOW (LESS THAN 20%)
CHANCE FOR 1000FT CIGS OR IFR VISIBILITY RESTRICTIONS AT YKM.
GIVEN THE LOW CHANCE, AND CALIBRATING THIS WITH THE OBS FROM LAST
NIGHT(CLEAR), WILL LEAVE IT OUT AT THIS TIME, HOWEVER THE RISK OF
IFR IMPACT DEVELOPMENT BETWEEN 9Z AND 15Z IS STILL A POSSIBILITY,
BUT LOW AT YKM. RUSSELL/71
PRELIMINARY POINT TEMPS/POPS
PDT 33 48 28 40 / 0 0 0 0
ALW 35 47 30 40 / 0 0 0 0
PSC 31 44 30 42 / 0 0 0 0
YKM 32 48 30 47 / 0 0 0 0
HRI 31 45 29 41 / 0 0 0 0
ELN 32 44 28 42 / 0 0 0 0
RDM 29 59 24 49 / 0 0 0 0
LGD 32 51 30 50 / 0 0 0 0
GCD 36 57 32 55 / 0 0 0 0
DLS 34 48 32 45 / 0 0 0 0
PDT WATCHES/WARNINGS/ADVISORIES
OR...AIR STAGNATION ADVISORY UNTIL 10 AM PST FRIDAY FOR ORZ041-044-
507-508-510-511.
WA...AIR STAGNATION ADVISORY UNTIL 10 AM PST FRIDAY FOR WAZ024-
026>029-521.
DENSE FOG ADVISORY UNTIL NOON PST WEDNESDAY FOR WAZ026.
SHORT TERM...75
LONG TERM....75
AVIATION...77
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