852
FXUS66 KPDT 291210
AFDPDT
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PENDLETON OR
410 AM PST SAT NOV 29 2025
UPDATED AVIATION...12Z TAFS
MOST SITES ARE CURRENTLY VFR EXCEPT
KRDM AND KBDN BEING LIFR DUE TO LOW CIGS AND FOG/MIST, RESPECTIVELY.
KRDM AND KBDN WILL THEN BECOME VFR AROUND LATE THIS MORNING. BESIDES
LOW CLOUDS, KDLS, KPDT, AND KALW MAY SEE LIGHT SNOW AND/OR A WINTERY
MIX THAT COULD AFFECT THEIR VSBYS AND CIGS AROUND THIS EVENING
INTO OVERNIGHT (04Z-07Z) (30-40% CONFIDENCE). KRDM, KBDN, AND
KPSC MIGHT ALSO SEE LOW CLOUDS RETURNING DURING THE AFOREMENTIONED
TIMEFRAME AS THIS WEAK SYSTEM PASSES THROUGH. WINDS WILL BE LESS
THAN 12 KTS. FEASTER/97
PREV DISCUSSION
/ISSUED 329 AM PST SAT NOV 29 2025/
DISCUSSION
DRY CONDITIONS ARE PRESENT REGION-WIDE THIS MORNING
AS THE FORECAST AREA IS UNDER A DRY NORTHWESTERLY FLOW ALOFT. 00Z
AND 06Z SOUNDINGS FROM SLE, UIL, MFR, AND OTX ALL SHOW A BONE DRY
LAYER ALOFT, RANGING IN ALTITUDE FROM APPROXIMATELY AS LOW AS 800
HPA TO AS HIGH AS 500 HPA. THIS DRY LAYER HAS SHOWN UP ON HIGH-
ELEVATION, RIDGETOP SURFACE OBSERVATIONS (RAWS AND CWOP) TO THE
TUNE OF DEW POINTS IN THE -15 TO -30 DEGREES FAHRENHEIT RANGE.
IT'S A DIFFERENT STORY IN THE LOWER LEVELS WITH NIGHTTIME
MICROPHYSICS RGB IMAGERY SHOWING FAIRLY WIDESPREAD LOW STRATUS
PEAKING OUT BENEATH SCATTERED TO BROKEN CIRRUS. AT THE SURFACE,
SOME PATCHY DENSE FOG HAS PERSISTED IN PORTIONS OF CENTRAL OREGON,
MOST NOTABLY SOUTH AND EAST OF THE BEND METRO ALONG US 97 AND US
26.
LOOKING AHEAD, ENSEMBLE GUIDANCE SHOWS A PERSISTENT NORTHWESTERLY
FLOW ALOFT THROUGH THE MIDDLE OF THE WEEK, WITH A COUPLE EMBEDDED
SHORTWAVES PASSING OVERHEAD. THIS PATTERN FAVORS NEAR- TO BELOW-
NORMAL TEMPERATURES, AND SOME UPSLOPE SNOW WITH EACH PASSING
SHORTWAVE.
THE FIRST OF THE AFOREMENTIONED SHORTWAVES WILL ARRIVE LATER THIS
AFTERNOON, PASSING OVER THE PACIFIC NORTHWEST OVERNIGHT INTO EARLY
SUNDAY MORNING. THE COOL AIR MASS COUPLED WITH THE TIMING OF THE
SHORTWAVE FAVOR A LIGHT WINTRY MIX FOR THE FORECAST AREA, THOUGH
ENSEMBLE-MEAN PWATS IN HREF, REFS, AND GLOBAL ENSEMBLES ALL
SUGGEST A RELATIVELY MOISTURE-STARVED SYSTEM WHICH SHOULD HINDER
EFFICIENT PRECIPITATION PRODUCTION. RECALL THAT DRY LAYER ALOFT ON
OBSERVED SOUNDINGS? THERE IS STILL A DECENT BIT OF ENSEMBLE SPREAD
AMONG THE HREF AND REFS WITH REGARD TO HOW WELL THAT LAYER WILL
SATURATE THROUGH THE LATE AFTERNOON AND EVENING. MOREOVER,
ENSEMBLE-MEAN QPF HAS TRENDED DOWNWARD IN SUCCESSIVE RUNS THE PAST
24 HOURS, SO THINKING PRECIPITATION WITH THIS SYSTEM WILL BE
LIMITED. THAT SAID, SNOW LEVELS ARE FORECAST TO DIP DOWN TO
1000-1500 FT MSL SO A DUSTING TO AN INCH OF SNOW ACROSS THE BLUE
MOUNTAIN FOOTHILLS, CENTRAL AND NORTH-CENTRAL OREGON, AND THE
BASINS WITHIN THE BLUE MOUNTAINS IS STILL A DISTINCT POSSIBILITY.
NBM GUIDANCE GENERALLY PAINTS LOW (LESS THAN 20 PERCENT) CHANCES
OF MEASURABLE SNOW IN THE COLUMBIA BASIN/GORGE, LOW-MEDIUM (10-50
PERCENT) CHANCES FOR THE BLUE MOUNTAIN FOOTHILLS AND
CENTRAL/NORTH-CENTRAL OREGON, AND MEDIUM-HIGH (50-90 PERCENT)
CHANCES FOR THE GRANDE RONDE VALLEY AND BLUE MOUNTAINS REGION.
DRY CONDITIONS ARE EXPECTED TO RETURN BY LATE SUNDAY MORNING,
LASTING INTO OR THROUGH MONDAY. THE SECOND SHORTWAVE IS THEN
ADVERTISED FOR LATE MONDAY THROUGH TUESDAY AFTERNOON OR NIGHT,
WITH SOME NOTABLE ENSEMBLE SPREAD IN TIMING. SNOW CHANCES ARE
REDUCED ACROSS THE LOWER ELEVATIONS WITH THIS SYSTEM, BUT A
BETTER MOISTURE TAP SHOULD FACILITATE BETTER CHANCES OF ADVISORY-
LEVEL SNOW FOR THE BLUE MOUNTAINS.
BY THE END OF THE WEEK, ENSEMBLE SOLUTIONS BEGIN TO DIVERGE WITH
REGARD TO PATTERN DETAILS, BUT IN GENERAL A TRANSITION TO A MORE
ZONAL UPPER-LEVEL PATTERN IS PRESENT AMONG ALL ENSEMBLE CLUSTERS.
AS FAR AS TANGIBLE WEATHER, THIS WOULD RESULT IN WARMER, WETTER,
BREEZIER CONDITIONS.
PRELIMINARY POINT TEMPS/POPS
PDT 25 38 23 39 / 60 0 0 0
ALW 28 37 26 38 / 60 10 0 10
PSC 25 40 25 38 / 30 0 0 0
YKM 23 42 25 39 / 10 0 0 0
HRI 25 39 24 38 / 50 0 0 0
ELN 21 39 23 38 / 10 0 0 10
RDM 24 41 19 49 / 20 0 0 0
LGD 25 40 21 43 / 70 0 0 0
GCD 25 39 22 47 / 60 0 0 0
DLS 33 44 31 44 / 30 0 0 0
PDT WATCHES/WARNINGS/ADVISORIES
OR...NONE.
WA...NONE.
SHORT TERM...86
LONG TERM....86
AVIATION...97
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