726
FXUS66 KPDT 251138
AFDPDT
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PENDLETON OR
338 AM PST TUE NOV 25 2025
DISCUSSION
A SURFACE TROUGH AND WARM FRONTAL SYSTEM MOVES ONSHORE THIS
MORNING SPREADING MOISTURE OVER A SLOWLY RETREATING HIGH PRESSURE
OVER THE INTERIOR NORTHWEST. HIGH CONFIDENCE EXISTS IN SURFACE
TEMPERATURES REMAINING AT OR BELOW ZERO THROUGH THE DURATION OF
THE AFTERNOON ACROSS THE WASHINGTON SLOPES AND SOME OF THE LOWER
ELEVATIONS IN THE KITTITAS (60-100% CHANCE EVEN AT PEAK HEATING).
NBM MEAN BRINGS THE VALLEY INTO THE MID 30S BRIEFLY THIS
AFTERNOON. LIGHT ICING THIS EVENING IN THE KITTITAS VALLEY IS
POSSIBLE, GENERALLY LESS THAN 0.05” BASED ON NBM. FRAM FREEZING
RAIN ACCUMS MODEL LOOKS A BIT MORE UNIFORM IN FREEZING RAIN
AMOUNTS OF MUCH LESS THAN 0.05”. THESE ARE IN THE CONTEXT OF
PROBABILITY OF FREEZING RAIN BEING ABOUT 25% AS THEY ARE BALANCED
WITH THE SNOW LEVELS AND RESULTANT SNOW PROBABILITIES. ROAD
TEMPERATURE FORECASTS ALSO SUPPORT ICING TUESDAY EVENING THROUGH
THE OVERNIGHT. A START TIME FOR ADVISORY MESSAGING STILL LOOKS
REASONABLE AS THE HREF LPMM HOURLY SNOWFALL ACCUMS KICK IN AROUND
9-10 AM. THE SNOW RATES ACROSS THE LOWER SLOPES LOOK TO BE AROUND
A ONE HALF INCH PER HOUR ACCUMULATION, AND BY MIDNIGHT SNOW COULD
RANGE AS MUCH AS A FOOT ON THE CREST TO ABOUT HALF THAT AT CLE
ELUM, EXPECT SOME SIMILAR SNOWS ON THE BLUES AND THE EASTERN
MOUNTAINS. RAIN SHADOWING ACROSS THE CENTRAL OREGON IS EXPECTED,
HOWEVER WETTING RAIN ARE LIKELY (80 PERCENT CONFIDENCE) IN THE
COLUMBIA BASIN AND FOOTHILLS OF THE BLUES WHILE SNOW FALLS ACROSS
THE HIGHER ELEVATIONS OF THE EASTERN MOUNTAINS. WARM ADVECTION
SEEMS TO WIN OUT AFTER MIDNIGHT AND PRECIPITATION TYPES FLIP BACK
TO RAIN. RUSSELL/71
AVIATION
12Z TAFS...VFR CONDITIONS WILL START THE PERIOD ACROSS
ALL SITES. UNSETTLED WEATHER IS EXPECTED TO ROLL THROUGH THE AREA
LATE IN THE MORNING THROUGH THE EARLY AFTERNOON HOURS, BRINGING SUB-
VFR CEILINGS AND VISIBILITIES THROUGH ALL TAF SITES (WITH THE
EXCEPTION OF BDN AND RDM THAT WILL ESCAPE THE WORST OF THE
CONDITIONS, REMAINING IN VFR FOR THE ENTIRE PERIOD). WINDS ARE NOT
EXPECTED TO BE STRONG IN THIS SYSTEM, BUT IT WILL HELP ENABLE
WIDESPREAD CEILINGS LESS THAN 3000 FEET AND LOWER VISIBILITIES
THROUGH SOME OF THE RAIN SHOWERS. YKM IS THE ONLY SITE AS OF NOW
WITH A CHANCE OF RAIN SNOW MIX AT 22Z, BUT GFSLAMP GUIDANCE HINTED
AT SOME POSSIBILITY OF FREEZING RAIN AROUND 06Z TO 08Z, BUT
CONFIDENCE ISN'T HIGH ENOUGH TO WARRANT IT IN THE TAF, BUT THE
CHANCE REMAINS SMALL (5 TO 15 PERCENT CHANCE).
PRELIMINARY POINT TEMPS/POPS
PDT 45 37 47 35 / 50 90 60 60
ALW 44 39 46 38 / 50 90 70 70
PSC 43 34 44 37 / 50 90 40 60
YKM 41 31 44 35 / 70 90 40 70
HRI 43 36 45 37 / 50 90 40 60
ELN 38 29 41 32 / 80 90 40 80
RDM 48 34 53 29 / 20 40 20 10
LGD 45 34 46 34 / 40 90 70 50
GCD 47 36 51 34 / 30 70 30 20
DLS 44 39 48 41 / 70 90 60 70
PDT WATCHES/WARNINGS/ADVISORIES
OR...NONE.
WA...WINTER WEATHER ADVISORY FROM 10 AM THIS MORNING TO 4 AM PST
WEDNESDAY FOR WAZ026-522-523.
DISCUSSION...71
AVIATION...95
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