064
FXUS66 KPDT 190646
AFDPDT
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PENDLETON OR
1046 PM PST THU DEC 18 2025
AVIATION
RAIN AND WINDY CONDITIONS WILL IMPACT THE TERMINALS ACROSS THE
AREA FOR A FEW MORE HOURS. IFR VISIBILITY CAN BE EXPECTED TO
CONTINUE AT KDLS AS MODERATE RAIN CONTINUES TO SPILL OVER THE
CASCADES WITH MVFR CIGS. THIS AXIS OF PRECIPITATION WILL SHIFT
SOUTH OVERNIGHT WITHIN 4 TO 5 HOURS. ANY KIND OF LOW IFR
VISIBILITY ARE NOT THAT LIKELY (LESS THAN 10% FOR VISIBILITY LESS
THAN 2 MILES) , HOWEVER MOMENTUM TRANSFER CAN DRIVE WIND GUSTS TO
40-50 WITH PROBABILITIES OF 40-50% AT RDM AND BDN OVERNIGHT. THE
COLD FRONT THAT IS DRIVING SOUTH ACROSS THE AREA SHOULD BE THROUGH
BY 18Z.
PREV DISCUSSION
/ISSUED 325 PM PST THU DEC 18 2025/
DISCUSSION...
KEY POINTS...
1. BREEZY THROUGH FRIDAY MORNING
2. MOUNTAIN PASS SNOW FRIDAY TO SATURDAY
3. ACTIVE WEATHER PATTERN OVER THE WEEKEND
TODAY THROUGH SATURDAY...CURRENT SATELLITE SHOWS THE CLOUD DECK TO
BE COVERING THE ENTIRE REGION. WINDS HAVE BEGUN TO SLIGHTLY PICK UP
AS AN UPPER LEVEL SHORTWAVE AND ASSOCIATED COLD FRONT MAKES ITS WAY
ACROSS THE CASCADES. CURRENT GROUND OBSERVATIONS SHOW THERE HAS BEEN
SOME RAIN ACCUMULATIONS ACROSS THE REGION WITH AREAS SEEING BETWEEN
0.02 TO 0.06 INCHES OF RAIN WITH MOUNTAIN ACCUMULATIONS NEARING 0.30
INCHES. WEBCAMS SHOW SNOWFALL STILL OCCURRING OVER THE WA AND BLUE
MOUNTAIN PASSES. A WINTER WEATHER ADVISORY FOR THE WA CASCADES
REMAINS IN EFFECT THROUGH 4 PM THIS AFTERNOON. GROUND OBSERVATIONS
ALREADY ARE SHOWING AREAS IN CENTRAL OR AND ALONG THE FOOTHILLS OF
THE BLUES WITH GUSTS REACHING 38-44 MPH. A WIND ADVISORY IS ALSO IN
EFFECT THROUGH 4 AM TOMORROW.
THE UPPER LEVEL SHORTWAVE WITH THE ASSOCIATED COLD FRONT WILL BRING
INCREASED WINDS ACROSS THE REGION. MODELS SHOW THE COLD FRONT TO BE
SET UP ALONG THE CASCADES AND WILL CONTINUE TO MAKE ITS WAY OVER THE
REGION. WINDS ARE ALREADY BEGINNING TO PICK UP THROUGH CENTRAL OR
AND ARE EXPECTED TO REMAIN ELEVATED THERE THROUGH THE OCHOCO-JOHN
DAY HIGHLANDS AND THROUGH THE FOOTHILLS OF THE SOUTHERN AND NORTHERN
BLUES THROUGH 4AM WITH HIGH CONFIDENCE (80-90%) IN WINDS REACHING 35-
45 MPH. ONCE THE COLD FRONT PASSES, WINDS WILL RETURN TO A MORE
SOUTH-WESTERLY DIURNAL FLOW WITH SUSTAINED WINDS UNDER 15 MPH.
NOT ONLY DO MODELS SHOW AND UPPER LEVEL SHORTWAVE AND COLD FRONT,
BUT ANOTHER ATMOSPHERIC RIVER IS BEGINS USHERED IN BEHIND. ANOTHER
ROUND OF PRECIPITATION IS EXPECTED FRIDAY INTO SATURDAY WITH THE
MOUNTAIN PASSES SEEING UPWARDS OF 10-15 INCHES ALONG SNOQUALMIE PASS
(80-90% CONFIDENCE). GUIDANCE AND ENSEMBLES SHOW THE OR CASCADES
WILL SEE A 60-80% PROBABILITY OF 6-8 INCHES. LASTLY, THE BLUE
MOUNTAINS WILL SEE A 40-60% CHANCE OF 3-5 INCHES THROUGH SATURDAY. A
WINTER STORM WARNING HAS BEEN ISSUED FOR THE WA CASCADES FROM 4AM
FRIDAY THROUGH 4 PM SATURDAY, A WINTER WEATHER ADVISORY HAS BEEN
ISSUED FOR THE OR CASCADES FROM 4 AM FRIDAY THROUGH 4 AM SATURDAY.
PLEASE PLAN AHEAD FOR WEEKEND TRAVEL AND VISIT
WWW.WEATHER.GOV/SAFETY/WINTER FOR TIPS AND TRICKS FOR THE SNOW.
SUNDAY ONWARD...MODELS SHOW A BRIEF BREAK IN BETWEEN SYSTEMS ON
SUNDAY AHEAD OF ANOTHER UPPER LEVEL SHORTWAVE AND COLD FRONT. MODELS
SHOW ANOTHER ATMOSPHERIC RIVER BEING TIED UP WITH THE SHORTWAVE.
HOWEVER, NOT NEARLY AS ROBUST AS THE LAST. RAIN ALONG THE LOWER
ELEVATIONS AND HIGH ELEVATION SNOW WILL PEAK SUNDAY THROUGH MONDAY
ACCORDING TO THE MODELS (60-80% CONFIDENCE). 90
AVIATION...00Z TAFS...NO CHANGE FROM PREVIOUS DISCUSSION. MVFR OR
LOWER CONDITIONS EXPECTED THROUGH THE PERIOD AT MOST SITES. A
FRONTAL SYSTEM MOVING ACROSS THE REGION WILL CONTINUE TO BRING
PRECIP IMPACTS TO ALL SITES THROUGH THE TONIGHT. THIS FRONTAL SYSTEM
IS ALSO PRODUCING CIGS THAT ARE AT IFR CONDITIONS FOR SITES DLS/YKM
WITH MVFR VSBY AT SITES DLS/BDN AT THIS TIME. LOW CIGS WILL PERSIST
INTO THIS EVENING AT SITE DLS WHILE SITE YKM WILL CONTINUE TO REMAIN
AT MVFR OR LOWER THROUGH TOMORROW MORNING. SITES RDM/BDN WILL ALSO
SEE MVFR CIGS (1.5KFT TO 2.5KFT) DEVELOP OVERNIGHT AS WINDS
DECREASE. WINDS WILL BE INCREASING TO 12-17KTS WITH GUSTS 25KTS AT
SITES DLS/PDT/RDM/BDN/ALW/PSC INTO THIS AFTERNOON, WITH WINDS
INCREASE TO 20-30KTS AND GUSTS 30-40KTS LATER THIS EVENING AND
OVERNIGHT AT SITES PDT/RDM/BDN/ALW/PSC. LOW LEVEL WIND SHEAR 40-
60KTS FROM THE SOUTHWEST AND WITHIN 2KFT GROUND LEVEL WILL ALSO
IMPACT ALL SITES, EXCEPT YKM, THROUGH AROUND 09Z TONIGHT. LAWHORN/82
PRELIMINARY POINT TEMPS/POPS
PDT 56 38 47 31 / 100 90 60 10
ALW 54 39 47 35 / 100 100 70 20
PSC 54 38 50 34 / 100 80 10 10
YKM 46 28 45 26 / 100 90 20 20
HRI 55 39 49 32 / 100 90 30 10
ELN 41 26 38 23 / 100 90 30 30
RDM 56 34 45 23 / 100 100 90 10
LGD 46 35 44 25 / 100 100 100 20
GCD 50 39 47 23 / 100 90 90 10
DLS 48 38 46 34 / 100 100 60 60
PDT WATCHES/WARNINGS/ADVISORIES
OR...WIND ADVISORY UNTIL 4 AM PST FRIDAY FOR ORZ041-507-508-510-511.
FLOOD WATCH THROUGH LATE FRIDAY NIGHT FOR ORZ509>511.
WA...WIND ADVISORY UNTIL 4 AM PST FRIDAY FOR WAZ024-028-029-521.
FLOOD WATCH THROUGH FRIDAY AFTERNOON FOR WAZ522-523.
SHORT TERM...99
LONG TERM....99
AVIATION...71
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