398
FXUS66 KPDT 282230
AFDPDT
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PENDLETON OR
230 PM PST SUN DEC 28 2025
KEY MESSAGES
- FOG AND AIR STAGNATION CONCERNS AS A HIGH PRESSURE RIDGE PERSISTS
THROUGH WEDNESDAY.
- PRECIPITATION CHANCES WITH LIGHT MOUNTAIN SNOW RETURN THURSDAY
ONWARD.
DISCUSSION
CURRENT RADAR AND SATELLITE IMAGERY SHOW CLEAR SKIES
ACROSS THE FORECAST AREA WITH HIGH CLOUDS MOVING SOUTHWARD TOWARDS
THE UPPER SLOPES OF WA CASCADES. PATCHY FOG MAY DEVELOP TONIGHT BUT
WILL BE LOCALIZED FOR PORTION OF MOUNTAIN AREAS.
A HIGH PRESSURE SYSTEM WILL CONTINUE THROUGH WEDNESDAY WITH FOG
REMAINING AS A CONCERN FOR THESE DAYS DURING MORNING AND OVERNIGHT
HOURS. THANKS TO THE NORTHWEST FLOW ALOFT, COOLER AIR WILL BRING
NIGHTTIME TEMPERATURES TO BELOW FREEZING (MOSTLY IN THE 20S) ACROSS
THE REGION ALONG WITH DEWPOINTS. THAT SAID, CONFIDENCE IS MODERATE
(>50%) FOR FREEZING FOG TO DEVELOP. VISIBILITIES COULD ALSO BE
AFFECTED, BUT CANNOT RULE OUT ON THE TIMING NOR HOW DENSE THE FOG
MAY ACTUALLY GET. NBM STILL FAVORS LESS THAN 15% PROBABILITY OF 3
STATUE MILES OR LESS FOR VISIBILITIES. AIR STAGNATION COULD
POTENTIALLY DEVELOP FOR MONDAY THROUGH WEDNESDAY. WITH THE MIXING
HEIGHTS REACHING TO 1.5 KFT OR LOWER DURING MORNING AND AFTERNOON
HOURS AND TRANSPORT WINDS LESS THAN 10KTS, THIS CONCERN COULD BE
BORDERLINE ADVISORY-LEVEL, BUT WE DECIDED TO HOLD OFF FOR NOW AND
CONTINUE MONITORING IN THE MEANTIME. WINDS WILL BE LIGHT ACROSS THE
FORECAST AREA WITH SOME BREEZES OVER THE MOUNTAINS.
MODELS ARE IN BETTER AGREEMENT WITH THE FRONTAL SYSTEM APPROACHING
THE PACNW THURSDAY ONWARD AS THE RIDGE GRADUALLY BREAKS DOWN WITH
THE UPPER TROUGH MOVING IN. ADDITIONALLY, THIS SYSTEM WILL BRING
WARM AIRMASS, WHICH WILL INCREASE HIGH TEMPS BY FEW DEGREES ABOVE
AVERAGE. LIGHT SHOWERS WILL DEVELOP ACROSS THE WA/OR CASCADES
BEFORE BECOMING MORE WIDESPREAD OVERNIGHT WITH LIGHT RAIN FOR THE
LOWER ELEVATIONS AND MOUNTAIN RAIN/SNOW MIX. QPF AMOUNTS MAY
EXCEED TO 0.10 INCH OR HIGHER ALONG THE CASCADES AND OTHER
MOUNTAIN AREAS BUT LESS FOR THE LOW ELEVATIONS. SNOWFALL AMOUNTS
MAY EXCEED TO AN INCH OR LOWER OVER THE CREST OF WA/OR CASCADES
AND OTHER MOUNTAIN AREAS. HOWEVER, THE RAW ENSEMBLES HAS A 10-20%
PROB FOR SNOWFALL AMOUNTS NO MORE THAN 0.5 INCHES. FEASTER/97
AVIATION...00Z TAFS.
LIGHT WINDS WILL PERSIST OVERNIGHT AS THE
AREA AS HIGH PRESSURE CONTINUES TO DOMINATE THE REGION. THE RETURN
OF STRATUS IS OF LOW PROBABILITY (RANGING BETWEEN ABOUT 10 UP TO TO
20 PERCENT CONFIDENCE) ALONG TERMINALS IN THE SHADOW OFF CASCADES,
(DLS/RDM/BDN) AND TO A LESSER DEGREE YKM BASED ON HREF PROBABILITIES
FOR MVFR AND IFR CIGS. WINDS WILL BE LARGELY LOCALLY TERRAIN DRIVEN
AND 5 KNOTS OR LESS.
PRELIMINARY POINT TEMPS/POPS
PDT 23 37 21 35 / 0 0 0 0
ALW 25 34 25 34 / 0 0 0 0
PSC 22 35 22 34 / 0 0 0 0
YKM 22 35 21 37 / 0 0 0 0
HRI 24 35 22 33 / 0 0 0 0
ELN 20 32 20 34 / 0 0 0 0
RDM 20 44 20 45 / 0 0 0 0
LGD 22 38 25 41 / 0 0 0 0
GCD 23 43 25 47 / 0 0 0 0
DLS 28 38 26 38 / 10 0 0 0
PDT WATCHES/WARNINGS/ADVISORIES
OR...NONE.
WA...NONE.
DISCUSSION...97
AVIATION...71
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