149
FXUS66 KPDT 271851 AAA
AFDPDT
AREA FORECAST DISCUSSION...UPDATED AVIATION.
NATIONAL WEATHER SERVICE PENDLETON OR
1051 AM PST SAT DEC 27 2025
KEY POINTS
1. MOUNTAIN SNOW WILL CONTINUE THROUGH THE EARLY MORNING
*ADVISORY IN EFFECT THROUGH 7 AM*
2. A HIGH PRESSURE RIDGE WILL DOMINATE THROUGH MID-WEEK
3. LIKELY RETURN OF PRECIPITATION LATE NEXT WEEK
DISCUSSION
CURRENT RADAR SHOWS SOME RETURNS OVER THE CASCADES
PRIMARILY FOCUSED ALONG THE WA. CASCADES. SOME LINGERING RETURNS OVER
THE NORTHERN BLUES AS WELL. GROUND OBSERVATIONS SHOW LIGHT
PRECIPITATION AMOUNTS HAVE FALLEN OVER THE LAST THREE HOURS OF 0.01.
WEBCAMS DO SHOW WET ROADS ALONG SNOQUALMIE PASS AND THE 84 CORRIDOR,
BUT CANNOT DISTINGUISH AND PRECIPITATION FALLING IN THE CAMERA
FOOTAGE ALONG THE 90. HOWEVER, CAMERAS IN THE TOLLGATE AND SPOT
SPRINGS AREA SHOW PRECIPITATION STILL FALLING. MODELS SHOW THAT THE
MOUNTAIN SNOW WILL CONTINUE THROUGH THE EARLY MORNING WITH RAW
ENSEMBLES SHOWING A 40-60% PROBABILITY OF UP TO ANOTHER 3 INCHES
FALLING BY 7 AM THROUGH THE WA CASCADES AND THE NORTHERN BLUES BELOW
4500 FT. WINDS WILL ALSO REMAIN A BIT ON THE BREEZIER SIDE THROUGH
THE EARLY HOURS AS WELL WITH SOME AREAS SEEING SUSTAINED WINDS
BETWEEN 10-15 MPH WITH GUSTS OF 25-30 MPH.
ONCE THE REMNANTS OF THE SYSTEM MOVE TO THE EAST, MODELS SHOW THE
LEADING EDGE OF AN UPPER LEVEL RIDGE MOVING INTO THE REGION. MODELS
SHOW SOME LINGERING MOUNTAIN SHOWERS WILL PERSIST SATURDAY WITH THE
MAJORITY OF THE PRECIPITATION OVER THE OR CASCADES, EASTERN
MOUNTAINS AND THE BLUES WITH 80-90% OF THE RAW ENSEMBLES IN AGREEMENT
THAT SNOW ACCUMULATIONS OF 1-1.5 INCHES OF SNOW WILL ACCUMULATE
SATURDAY. BY SATURDAY NIGHT AND INTO SUNDAY, MODELS SHOW THE RIDGE
TO BE PUSHING IN WITH THE AXIS JUST OFF THE COAST A MODELS SHOW IT
TO CONTINUE TO REMAIN OVERHEAD THROUGH THURSDAY NIGHT. WITH THE COLD
AIR THAT CAME INTO THE REGION THE LAST FEW DAYS COUPLED WITH THE
INCOMING HIGH PRESSURE, PATTERN RECOGNITION OF THE AREA LETS US KNOW
THAT THE BIGGEST WEATHER CONCERN WHILE UNDER THE HIGH PRESSURE WILL
BE FOG. LOOKING AT RAW ENSEMBLE VISIBILITIES, THEY ALREADY SHOW THE
EFFECTS OF THE SYSTEM WITH LOWER VISIBILITIES COULD PLAGUE THE REGION
AS SOON AS SUNDAY (20-30% CONFIDENCE). DENSE FOG AND FREEZING FOG
WILL BE THE PRIMARY CONCERN THROUGH MID-WEEK (50-60% CONFIDENCE).
THURSDAY MODELS SHOW THE RIDGE TO BEGIN TO BREAK DOWN AS AN UPPER
LEVEL BEGINS TO DIG IN FROM THE NORTHWEST. CLUSTERS SHOW THAT THERE
IS A DIFFERENCE IN THE MODEL SOLUTIONS MAINLY WITH THE TIMING AND
AMOUNT OF PRECIPITATION THIS NEXT EVENT WILL BRING. REGARDLESS OF
THOSE SOLUTIONS, MODELS ARE IN AGREEMENT THAT THERE WILL BE A CHANGE
IN THE WEATHER PATTERN AS THE WEEKEND APPROACHES. 90
AVIATION...18Z TAFS
THE MAIN AVIATION CONCERNS REVOLVE AROUND
RISK FOR FOG AND LOW OVERNIGHT-EARLY TOMORROW. LATEST SATELLITE AND
OBS SHOWS PASSING HIGH CLOUDS AND STRATOCU WITH SOME CLEARING ACROSS
THE COLUMBIA BASIN. LIGHT MOUNTAIN SNOW IS APPARENT FROM CAMS AND
OBS OVER THE EASTERN MOUNTAINS THAT SHOULD TAPER OFF THE NEXT 2-4
HOURS. LOOKING AHEAD, STRONG 500 MB HEIGHT RISES ARE ANTICIPATED
OVER THE NEXT 12-HRS AS AN UPPER RIDGE BUILDS INTO THE REGION AND
SURFACE HIGH PRESSURE. THIS WILL DOMINATE THE WEATHER INTO EARLY
NEXT WEEK.
FOG/STRATUS IS THE MAIN THREAT AFTER 00Z. LIGHT WINDS AND LIMITED
MIXING ARE FORECAST TONIGHT-EARLY TOMORROW. MEANTIME, MODEST LOW-
LEVEL MOISTURE IN PLACE STEMMING FROM RECENT RAINFALL OVER THE LAST
36 HOURS ACROSS THE LOW ELEVATIONS AND TERMINALS. COMPLICATING THE
FORECAST THOUGH IS INCREASING MID AND HIGH CLOUDS STARTING LATE
TODAY AND A WARM GROUND SEEN BY SOIL TEMPERATURES. THIS SETUP MAY
DELAY OR LIMIT FOG DEVELOPMENT, AND FAVORING MORE MVFR-IFR STRATUS
AND LOCALIZED/PATCHY FOG AT THIS TIME. THIS IN TANDEM WITH PRESENT
DEW POINTS/SPREAD INCREASE THE UNCERTAINTY IN TERMS OF EFFECTIVE
RADIATIVE COOLING OVERNIGHT. PRESENTLY SUB-2 KFT CEILINGS ARE
FORECAST 6SM BR AT KPDT, KALW, AND KDLS. LOWER CONFIDENCE IN KYKM
AND KPSC SEEING LOW STRATUS OR FOG THUS NO MENTION AT THIS TIME.
WILL NEED TO MONITOR DEW POINT TREND THIS AFTERNOON/DAYTIME MIXING
AND THE SKY COVER AS MORE MOISTURE PRESENT WOULD INCREASE THE FOG
RISK TONIGHT.
PRELIMINARY POINT TEMPS/POPS
PDT 40 25 38 23 / 30 10 0 0
ALW 38 26 37 25 / 50 10 0 0
PSC 43 22 37 22 / 0 0 0 0
YKM 40 21 36 21 / 0 10 0 0
HRI 43 24 38 23 / 10 0 0 0
ELN 35 19 32 21 / 0 10 0 0
RDM 39 19 39 20 / 0 10 0 0
LGD 33 23 35 22 / 60 0 0 0
GCD 34 22 38 22 / 30 0 0 0
DLS 45 30 40 28 / 10 10 0 0
PDT WATCHES/WARNINGS/ADVISORIES
OR...NONE.
WA...NONE.
SHORT TERM...90
LONG TERM....90
AVIATION...80
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