534
FXUS66 KPDT 182209
AFDPDT
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PENDLETON OR
209 PM PST TUE NOV 18 2025
KEY POINTS
1. HIGH MOUNTAIN PRECIPITATION, LOW ELEVATION DRY
2. COLD OVERNIGHT TEMPERATURES WITH PATCHY FOG/FREEZING FOG
3. ACTIVE WEATHER WILL RETURN LATE IN THE WEEK
DISCUSSION
CURRENT SATELLITE SHOWS A LAYER OF MID LEVEL CLOUDS
HOVERING OVER THE EASTER PORTION OF THE CWA KEEPING THE OCHOCO-JOHN
DAY HIGHLANDS EASTWARDS OVERCAST. A LAYER OF HIGH LEVEL CLOUDS HAVE
MOVED OVER THE VAST MAJORITY OF THE CWA THIS AFTERNOON AS WELL.
MODELS ARE SHOWING A DRY AIR SLOT WILL PUSH IN BEHIND THESE CLOUDS
BRINGING DRY AND COLD CONDITIONS TO THE MAJORITY OF THE REGION
WITH SOME HIGH MOUNTAIN RAIN.
TODAY THROUGH THURSDAY AFTERNOON...THE REMAINDER OF THE DAY WILL
CONTINUE TO BE DRY WITH ONLY THE HIGH ELEVATIONS OF THE CASCADES
SEEING ANY FORM OF PRECIPITATION AS THE TROUGH CONTINUES TO MEANDER
OVER THE REGION. WITH THE DRY COLD AIR FILTERING INTO THE REGION
FROM THE NW, OVERNIGHT TEMPERATURES WILL DIP INTO AT OR BELOW
FREEZING RANGE WITH 60-80% OF THE RAW ENSEMBLES SHOWING MUCH OF
CENTRAL/NORTH CENTRAL OR, OCHOCO-JOHN DAY HIGHLANDS, THE GORGE,
FOOTHILLS OF THE BLUES, SIMCOE HIGHLANDS AND PORTIONS OF THE EASTERN
SLOPES OF THE CASCADES SEEING TEMPERATURES BELOW FREEZING. WITH THAT
SAID, A FREEZE WARNING HAS BEEN ISSUED FOR THE OR AND WA PORTIONS OF
THE GORGE FOR FREEZING TEMPERATURES STARTING TONIGHT AT 11 PM AND
CONTINUING THROUGH WEDNESDAY MORNING AT 10 AM. ALONG WITH THE COLD
TEMPERATURES, THERE IS ROUGHLY 30% PROBABILITIES THAT THERE WILL BE
PATCHY FOG ACROSS PORTIONS OF THE REGION THAT REMAIN ABOVE FREEZING
AND FREEZING FOG IN AREAS THAT DROP BELOW. A BRIEF TROUGH WEDNESDAY
AFTERNOON WILL CONTINUE TO KEEP THE LOWER ELEVATIONS DRY WITH
CONTINUED LIGHT HIGH MOUNTAIN PRECIPITATION AHEAD OF THE NEXT
INCOMING SYSTEM.
WEDNESDAY NIGHT MODELS SHOW THE LEADING EDGE OF THE NEXT TROUGH
BEGINNING TO PUSH ITS WAY ONSHORE. BY WEDNESDAY AFTERNOON, MOUNTAIN
SHOWERS WILL BEGIN AND WITH THE COOLER AIR FROM TODAY AHEAD OF THIS
NEXT SYSTEM, MODELS SHOW SNOW LEVELS WILL DROP TO BELOW 3500 FEET IN
THE FAR NORTHERN WA CASCADES AND 4500 FEET ACROSS THE REMAINING
CASCADES THROUGH TONIGHT AND CONTINUE THROUGH TOMORROW. THIS NEXT
SYSTEM WILL BRING IN SOME MOISTURE ALLOWING SOME LIGHT PRECIPITATION
TO FALL ALONG THE CASCADES BEFORE SPREADING ACROSS CENTRAL OR AND
THE EASTERN MOUNTAINS. HOWEVER, MODELS DO SHOW THIS SYSTEM TO BE
RELATIVELY DRY WITH ONLY 0.01(OVER THE EASTERN MOUNTAINS) UP TO
0.05 INCHES (OVER THE WA CASCADES) OF QPF AVAILABLE AND ONLY 60%
PROBABILITIES OF 0.10 INCHES OF SNOW FALLING ALONG THE SNOQUALMIE
CORRIDOR THROUGH THURSDAY MORNING AND VERY LIGHT SNOW OVER THE
EASTERN MOUNTAINS AS ANOTHER BRIEF RIDGE DRYS THE AREA OUT AHEAD
OF THE NEXT INCOMING TROUGH.
THURSDAY NIGHT ONWARDS...MODELS SHOW AN UPPER LEVEL ELONGATED LOW
OFF THE COAST OF CANADA SLITHERING ITS WAY SOUTHWARD BRINGING WITH
IT SW FLOW ALOFT AND A WEAK AR. HOWEVER, CLUSTERS ARE SHOWING THERE
TO BE SOME DIFFERENCE WITH THE TIMING OF THE SEPARATING LOW AND
TROUGH. THURSDAY EYEING, A FEW MODELS (GFS/CAN) SHOW THE LOW TO
SERRATE FROM THE TROUGH ANS SWING SOUTH TOWARDS CALIFORNIA AND AN
ELONGATED TROUGH MOVES OVER THE CASCADES WHILE THE REMAINING MODELS
HAVE THE SYSTEM STILL AS ONE (ECMWF/NAM). REGARDLESS, ENSEMBLES AND
MODELS ALIKE SHOW THIS WILL BRING BACK INCREASED PROBABILITIES OF
PRECIPITATION ACROSS THE WA CASCADES, BLUES AND THE WALLOWAS. CB/90
AVIATION...(PREVIOUS DISCUSSION)...18Z TAFS
LOW CIGS WILL LINGER
AROUND FOR KRDM (IFR) AND KBDN (MVFR) BEFORE CLOUD COVERAGE
DECREASES INTO THIS AFTERNOON. EVEN THOUGH KRDM/KBDN MAY RETURN TO
VFR FOR THE REST OF THE DAY, LOW CLOUDS COULD DEVELOP LATER THIS
EVENING (40-50% CONFIDENCE). OTHERWISE, VFR CONDITIONS ARE
ANTICIPATED FOR THE REMAINING SITES WITH LIGHT WINDS. FEASTER/97
PRELIMINARY POINT TEMPS/POPS
PDT 31 48 31 47 / 10 0 10 10
ALW 34 48 35 47 / 10 0 10 20
PSC 30 48 32 50 / 0 0 0 0
YKM 29 50 32 51 / 0 0 0 0
HRI 31 48 33 49 / 0 0 0 10
ELN 27 46 30 47 / 0 0 10 0
RDM 22 51 27 49 / 0 0 20 10
LGD 29 51 34 51 / 10 0 10 20
GCD 31 55 34 51 / 10 0 10 20
DLS 34 50 39 52 / 0 0 30 20
PDT WATCHES/WARNINGS/ADVISORIES
OR...FREEZE WARNING FROM 11 PM THIS EVENING TO 10 AM PST WEDNESDAY
FOR ORZ041.
WA...FREEZE WARNING FROM 11 PM THIS EVENING TO 10 AM PST WEDNESDAY
FOR WAZ024.
SHORT TERM...90
LONG TERM....90
AVIATION...97
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