807
FXUS66 KPDT 291129
AFDPDT
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PENDLETON OR
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.
AVIATION...06Z TAFS...(PREVIOUS DISCUSSION)
VFR CONDITIONS
CURRENTLY ACROSS ALL SITES, WITH THE EXCEPTIONS BEING MVFR AT
KBDN/KRDM DUE TO REDUCED CEILINGS OF 1KFT. THESE CONDITIONS ARE
EXPECTED TO DEGRADE TO IFR OVERNIGHT AS CEILINGS DROP TO AROUND
500 FEET. KALW IS ALSO ANTICIPATED TO DROP TO IFR CONDITIONS WITH
CEILINGS ALSO AROUND 500 FEET EARLY SATURDAY MORNING. MVFR
CONDITIONS ARE ALSO EXPECTED AT KPDT DUE TO CEILINGS OF 1.5KFT
OVERNIGHT INTO EARLY SATURDAY MORNING. IMPROVEMENT IS EXPECTED
ACROSS ALL SITES, WITH THE EXCEPTION OF CONTINUING IFR/MVFR
CONDITIONS AT KALW/KPDT DUE TO REDUCED CEILINGS OF 500 FEET AND
1.5KFT RESPECTIVELY. WINDS WILL STAY LIGHT AND BELOW 10 KTS
THROUGH THE PERIOD. 75
PRELIMINARY POINT TEMPS/POPS
PDT 40 25 38 23 / 10 60 0 0
ALW 38 28 37 26 / 10 60 10 0
PSC 41 25 40 25 / 10 30 0 0
YKM 42 23 42 25 / 10 10 0 0
HRI 40 25 39 24 / 10 50 0 0
ELN 38 21 39 23 / 10 10 0 0
RDM 45 24 41 19 / 0 20 0 0
LGD 42 25 40 21 / 10 70 0 0
GCD 47 25 39 22 / 0 60 0 0
DLS 45 33 44 31 / 10 30 0 0
PDT WATCHES/WARNINGS/ADVISORIES
OR...NONE.
WA...NONE.
DISCUSSION...86
AVIATION...75
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