182
FXUS66 KPDT 221724
AFDPDT
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PENDLETON OR
1024 AM PDT WED OCT 22 2025
UPDATED AVIATION DISCUSSION
AVIATION...18Z TAFS
VFR CONDITIONS EXPECTED. LIGHT, TERRAIN-
DRIVEN WINDS LESS THAN 10 KTS WILL PREVAIL ACROSS ALL SITES, WITH
FEW-SCT MID-LEVEL CIGS ROLLING THROUGH THE REGION AS WELL. SOME
CLEARING WILL TAKE PLACE THIS EVENING, BEFORE MID-LEVEL CIGS
RETURN OVERNIGHT HEADING INTO THURSDAY. 74
PREV DISCUSSION... /ISSUED 331 AM PDT WED OCT 22 2025/
DISCUSSION...TODAY THROUGH THURSDAY: UPPER LEVEL RIDGING WILL
PERSIST OVER THE REGION THROUGH THURSDAY, BUT WILL WEAKEN LATER
THIS AFTERNOON AND OVERNIGHT AS A SHORTWAVE TROUGH AND WEAK COLD
FRONT LIFT ACROSS THE WESTERN HALF OF WA. BREEZY SOUTHERLY WINDS
IN THE GRANDE RONDE VALLEY AND DOWNSLOPING/SOUTHEAST WINDS ALONG
THE NORTHERN BLUE MOUNTAIN RIDGES AND WEST SLOPES WILL CONTINUE
LATE THIS MORNING, BUT WILL DIMINISH AS THE INCOMING COLD FRONT
WEAKENS THE PRESSURE GRADIENT ACROSS THE BLUES. OTHERWISE, THE
TROUGH.FRONT PASSAGE WILL BRING LIGHT RAIN TO THE WA CASCADE CREST
LATE THIS EVENING AND OVERNIGHT.
FRIDAY THROUGH SUNDAY: DETERMINISTIC AND ENSEMBLE GUIDANCE IN
GREAT AGREEMENT OF A DEEP TROUGH DROPPING OUT OF THE GULF OF
ALASKA AND SETTING UP JUST OFFSHORE THE PACNW BY FRIDAY. THE
TROUGH WILL THEN PUSH INLAND FRIDAY NIGHT AND OVER THE WEEKEND
BEHIND A LEADING COLD FRONT PASSAGE AND A SERIES OF SHORTWAVE
TROUGHS AND SURFACE LOWS ROTATING AROUND THE BOTTOM OF THE PARENT
TROUGH. THERE IS MOD-HIGH CONFIDENCE (65-80%) THAT A STRONG
SOUTHWEST TO NORTHEAST ORIENTED JET MAX (35-60KTS) DEVELOPING
BETWEEN 700-850MB AND TIGHT SURFACE PRESSURE GRADIENTS DEVELOPING
EAST OF THE CASCADE CREST WILL FACILITATE AT LEAST BREEZY TO
WINDY SOUTH TO SOUTHWEST WINDS (GUSTS 35-55MPH) DEVELOPING OVER
EXPOSED RIDGES AND THE LOWER ELEVATIONS ACROSS THE FORECAST AREA
FRIDAY EVENING THROUGH SATURDAY. BREEZY WINDS PERSIST THROUGH
SUNDAY, BUT LACK OF JET SUPPORT ALOFT WILL RESULT IN WEAKER WINDS
THAN AT LEAST SATURDAY.
OTHERWISE, THIS SERIES OF SYSTEMS WILL BRING PERSISTENT
PRECIPITATION CHANCES TO THE MOUNTAINS (65-95%) AND LOWER
ELEVATIONS (45-80%) STARTING FRIDAY NIGHT THROUGH SUNDAY
AFTERNOON. THE HEAVIEST PRECIPITATION WILL COINCIDE WITH A WEAK TO
MODERATE ATMOSPHERIC RIVER (70-90% CHANCE OF IVT > 250 KG/M/S)
THAT WILL ARRIVE WITH THE COLD FRONT PASSAGE FRIDAY NIGHT, AND
WILL PUSH OFF TO THE SOUTH OF THE FORECAST AND WEAKEN BY LATE
SATURDAY AFTERNOON (CONFIDENCE 65-80%). WHILE LOWER ELEVATION
LOCATIONS WILL SEE MOSTLY RAIN THROUGHOUT THE WEEKEND, SNOW LEVELS
WILL GRADUALLY DROP TO PASS LEVEL SATURDAY AND PERSIST THROUGH
MONDAY AS THE TROUGH PERSISTS OVERHEAD. THIS WILL RESULT IN
MODERATE TO LOCALLY HEAVY SNOWFALL IN THE MOUNTAINS, WITH
GENERALLY A 75-90% CHANCE OF 6 INCHES OR GREATER OF SNOW ACROSS
SANTIAM AND WHITE PASSES, BUT ONLY A 30-50% CHANCE AT PASS LEVEL
IN SNOQUALMIE PASS(CHANCES 60-80% ALONG RIDGES IN THE PASS). OF
NOTE, THERE IS ALSO A 60-85% CHANCE OF 10 INCHES OR GREATER OF
SNOWFALL IN THE SANTIAM AND WHITE PASSES OVER THE WEEKEND. THERE
IS ALSO A 50-80% CHANCE OF 6 INCHES OR GREATER FROM THE AREAS
AROUND AND BETWEEN SKI BLUEWOOD AND TOLLGATE. OTHERWISE, AREAS ON
THE OUTSKIRTS OF BEND AND ALONG THE US97 CORRIDOR DOWN TO LA PINE
MAY SEE THEIR FIRST SNOWFALL OF THE YEAR, THOUGH CHANCES OF
ANYTHING GREATER THAN AN INCH OF SNOW IS AROUND 20-50%. AS OF NOW,
CONFIDENCE IS GROWING (60-70%) IN THE NEED FOR AT LEAST WINTER
WEATHER ADVISORIES FOR SOME MOUNTAIN ZONES OVER THE WEEKEND.
MONDAY AND TUESDAY: MODERATE CONFIDENCE (60-70%) THAT ZONAL FLOW
WILL DEVELOP OVER THE PACNW INTO EARLY NEXT WEEK, THOUGH A
SHORTWAVE PASSING OVERHEAD WILL CONTINUE TO BRING LIGHT MOUNTAIN
SNOW ALONG THE CASCADE CREST AND INTERIOR NORTHERN BLUES, WITH LIGHT
RAIN ALONG THE LOWER SLOPES OF THESE MOUNTAIN AREAS (CONFIDENCE
50-70%). WEAK RIDGING WILL THEN DEVELOP MONDAY NIGHT THROUGH
TUESDAY, WITH A BRIEF PERIOD OF DRY CONDITIONS EARLY TUESDAY,
THEN LIGHT MOUNTAIN PRECIPITATION DEVELOPING AS THE RIDGE AXIS
PUSHES INTO THE NORTHERN ROCKIES TUESDAY AFTERNOON. LAWHORN/82
PRELIMINARY POINT TEMPS/POPS
PDT 62 40 65 44 / 0 0 0 0
ALW 63 45 64 47 / 0 0 0 0
PSC 62 39 65 42 / 0 0 0 0
YKM 63 39 63 42 / 0 0 0 0
HRI 63 40 65 42 / 0 0 0 0
ELN 60 37 60 37 / 0 10 0 10
RDM 70 32 67 39 / 0 0 0 0
LGD 68 36 65 41 / 0 0 0 0
GCD 71 35 67 42 / 0 0 0 0
DLS 67 47 67 47 / 0 10 0 0
PDT WATCHES/WARNINGS/ADVISORIES
OR...NONE.
WA...NONE.
SHORT TERM...82
LONG TERM....82
AVIATION...74
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