131
FXUS66 KPDT 240622
AFDPDT
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PENDLETON OR
1022 PM PST TUE DEC 23 2025
UPDATE
*DENSE FOG ADVISORY* ISSUED ACROSS THE NORTHERN BLUE MOUNTAIN
FOOTHILLS OF WASHINGTON UNTIL 6 AM AS VISIBILITIES OF ONE QUARTER
TO ONE HALF MILE ARE BEING OBSERVED VIA OBSERVATIONS AND AREA
WEBCAMS. A TEMPERATURE INVERSION IS ALREADY SETTING UP BEHIND THE
LIFTING WARM FRONT, WHICH CONTINUES TO BRING VERY LIGHT SHOWERS
AND LOW LEVEL MOISTURE TO THE AREA. THESE CONDITIONS ARE EXPECTED
TO PERSIST THROUGH THE EARLY MORNING HOURS.
*HIGH WIND WARNINGS* HAVE ALSO BEEN ISSUED BETWEEN 7 AM AND 2 PM
WEDNESDAY ALONG THE GRANDE RONDE VALLEY, WALLOWA COUNTY, AND THE
BLUE MOUNTAIN FOOTHILLS OF WASHINGTON AND OREGON. SOUTH-SOUTHEAST
WINDS OF 30-40 MPH WITH GUSTS UP TO 65 MPH WILL BE POSSIBLE, AS
DOWNSLOPING WINDS RESULTING FROM AN INCOMING COLD FRONT FROM THE
WEST WILL ENHANCE THE PRESSURE GRADIENT ALONG THE EASTERN
MOUNTAINS. THIS GRADIENT, COUPLED WITH MORNING TEMPERATURE
INVERSIONS NEAR THE HEIGHT OF TERRAIN, ARE EXPECTED TO DUCT
DOWNSLOPING WINDS TO CREATE SUPER CRITICAL FLOW AND HIGH WINDS AS
THE AIR RUSHES DOWN BLUE MOUNTAIN FOOTHILLS. THE PASSING COLD
FRONT MID-AFTERNOON WILL ALLEVIATE THE PRESSURE GRADIENT,
HALTING QUICK DOWNSLOPING WINDS. 75
AVIATION...06Z TAFS
VARIABLE CONDITIONS CURRENTLY ACROSS SITES,
WITH VFR AT KPSC/KYKM/KRDM/KDLS, MVFR AT KPDT/KBDN, AND LIFR AT KALW
DUE TO REDUCED VISIBILITIES OF 1/4 TO 1/2SM ASSOCIATED WITH A
LIFTING WARM FRONT BRINGING LOW LEVEL MOISTURE AND SURFACE HIGH
PRESSURE. THESE CONDITIONS ARE EXPECTED TO PERSIST THROUGH THE EARLY
MORNING HOURS. KBDN/KRDM ARE ALSO EXPECTED TO DROP TO LIFR
CONDITIONS OVERNIGHT AS A RESULT OF REDUCED CEILINGS OF 400FT. IFR
CONDITIONS ARE LIKELY AT KPDT OVERNIGHT AS WELL, ASSOCIATED WITH
CEILINGS AROUND 500FT. MVFR CONDITIONS OVER KYKM AND KDLS ALSO
OVERNIGHT DUE TO REDUCED CEILINGS OF 1.5KFT. THESE CEILINGS WILL
LIFT SLIGHTLY THROUGH MID-MORNING AS WINDS PICK UP FOR
KPDT/KALW/KRDM/KBDN AHEAD OF A MODERATE COLD FRONT PASSING THE AREA
DURING THE LATE MORNING THROUGH EARLY AFTERNOON TIMEFRAME.
CONDITIONS LOOK TO IMPROVE TOWARD THE END OF THE PERIOD IN THE WAKE
OF THE DEPARTING SYSTEM. 75
PREV DISCUSSION
/ISSUED 218 PM PST TUE DEC 23 2025/
KEY POINTS...
1. WIDESPREAD LOW ELEVATION RAIN TODAY THROUGH AFTERNOON
THROUGH WEDNESDAY MORNING
2. MOUNTAIN PASS SNOW THROUGH CHRISTMAS EVE
*SPS IN AFFECT*
3. BREEZY WINDS CHRISTMAS EVE
*SPS IN AFFECT 1 AM THROUGH 4 PM WEDNESDAY*
DISCUSSION...CURRENT SATELLITE SHOWS MOSTLY SKIES ACROSS
THE CWA. RADAR SHOWS A FEW RETURNS MOVING ACROSS THE COUNTIES
THROUGH THE CENTER OF THE CWA WITH GROUND OBSERVATIONS SHOWING 0.01-
0.04 INCHES OF RAIN ALONG THE LOWER ELEVATIONS AND NEAR 0.20 INCHES
ALONG SOME OF THE HIGHER ELEVATIONS THROUGH THE BLUES. RAIN IS
EXPECTED TO CONTINUE TO LINGER THROUGH TOMORROW AFTERNOON.
MODELS SHOW AN ACTIVE WEATHER PATTERN WITH AN ASSOCIATED ATMOSPHERIC
RIVER (AR) IS EXPECTED TO IMPACT THE CASCADES, MOST NOTABLY OVER THE
WASHINGTON CASCADES. MODERATE RAIN FAVORED, WITH AMOUNTS BETWEEN 0.5-
1 INCH (60-80% CONFIDENCE) AT THE CASCADE CREST WITH LESSER AMOUNTS
FOUND AT THE LOWER ELEVATIONS. LOWER ELEVATIONS WILL SEE UP TO 0.05
INCHES OF RAIN OVERNIGHT AND AGAIN INTO WEDNESDAY WITH 80-90%
CONFIDENCE. MODELS SHOW THE UPPER LEVEL LOW WITH THE AR TO MOVE JUST
ENOUGH TO PUSH THE BAND OF PRECIPITATION ACROSS THE OR PORTIONS OF
THE CWA MOVING FORM THE SOUTHEAST TO THE NORTHWEST BEFORE BECOMING
MOSTLY FOCUSED OVER THE CASCADES BY TONIGHT.
SNOW LEVELS WILL INCREASE TO NEAR 4500-5000 FEET TODAY AS THE MODELS
SHOW THE ATMOSPHERIC RIVER TO BE A BIT WARMER THAN ORIGINALLY
ANTICIPATED. SHORT TERM MODELS DO SHOW A SWATH OF SNOW ACCUMULATIONS
ACROSS THE WA CASCADES THROUGH THE EVENING WITH 60-80% PROBABILITIES
OF UP TO AN INCH OF SNOWFALL. HOWEVER, A SHOT OF COOLER AIR WILL
COME INTO THE AREAS WEDNESDAY NIGHT BRINGING THE SNOW LEVELS BACK
DOWN TO NEAR 3000-3500 WITH ANOTHER ACCUMULATION OF NEAR 1 INCH (30-
50%). HIGHEST AMOUNTS HAVE SINCE SHIFTED TO CHRISTMAS NIGHT INTO
FRIDAY MORNING WITH 70-90% PROBABILITIES OF 2-3 INCHES OF SNOWFALL.
MODELS CONTINUE TO SHOW A SURFACE LEVEL LOW TIGHTENING THE PRESSURE
GRADIENTS ACROSS THE REGION, ESPECIALLY THROUGH CENTRAL OR EASTWARD.
PRESSURE GRADIENT MODELS SHOW A TIGHTENING OF THE GRADIENTS OF NEAR
15 MB FROM CENTRAL OR ALONG THE JOHN-DAY OCHOCO HIGHLANDS AND
THROUGH THE EASTERN MOUNTAINS. THIS WILL LEAD TO BREEZY CONDITIONS
ACROSS THE AFOREMENTIONED AREAS. THIS SURFACE LOW WILL BRING SOUTH
WINDS OF 15 TO 25 MPH WITH GUSTS UP TO 30-40 MPH EXPECTED WITH
HIGHER WINDS NEARING 45 MPH ALONG THE HIGHER TERRAIN (70-90%
CONFIDENCE). THE SOUTH WINDS WILL CREATE A CROSS WIND ALONG THE I-84
CORRIDOR SO HIGH PROFILE TRUCKS SHOULD HEED CAUTION WHEN DRIVING THE
PASS.
SATURDAY ONWARDS, MODELS ARE IN DECENT AGREEMENT SHOWING A
PERSISTENT RIDGE MOVING IN OVER THE REGION. DRY CONDITIONS WILL
RETURN BEGINNING WITH SEASONAL TEMPERATURES. BY THE END OF THE
PERIOD, TEMPERATURES COULD BEGIN TO CREST TO NEARLY 10 DEGREES
ABOVE SEASONAL AVERAGE ALONG THE HIGHER TERRAIN AND THROUGH CENTRAL
OR AND THE JOHN-DAY BASIN (60-70% CONFIDENCE). WITH THAT SAID,
PATTERN RECOGNITION FOR THIS TIME OF YEAR SUGGESTS THAT WITH THE
UPPER LEVEL RIDGE LINGERING FOR A FEW DAY, WINTER TIME FOG WILL
SETTLE OVER THE REGION LATER IN THE PERIOD. 90
PRELIMINARY POINT TEMPS/POPS
PDT 34 55 35 49 / 40 30 20 30
ALW 37 54 39 49 / 50 40 30 50
PSC 35 52 32 46 / 60 30 10 40
YKM 33 46 29 43 / 90 70 10 40
HRI 33 53 33 46 / 60 30 20 30
ELN 30 42 27 39 / 80 80 10 60
RDM 30 51 29 50 / 40 40 10 10
LGD 38 51 38 49 / 20 40 40 50
GCD 39 52 36 50 / 10 50 40 60
DLS 38 51 36 45 / 80 70 30 50
PDT WATCHES/WARNINGS/ADVISORIES
OR...HIGH WIND WARNING FROM 7 AM TO 2 PM PST WEDNESDAY FOR ORZ049-050-
507-508.
WA...HIGH WIND WARNING FROM 7 AM TO 2 PM PST WEDNESDAY FOR WAZ029.
DENSE FOG ADVISORY UNTIL 6 AM PST WEDNESDAY FOR WAZ029.
UPDATE...75
DISCUSSION...90
AVIATION...75
CLICK HERE TO GO TO PREVIOUS BULLETINS.
Main Text Page