473
FXUS66 KPDT 261145
AFDPDT
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PENDLETON OR
445 AM PDT MON OCT 26 2026
KEY MESSAGES
- PERSISTENT CHANCES OF MOUNTAIN RAIN AND HIGH ELEVATION SNOW
THROUGH THURSDAY
- BREEZY WINDS TUESDAY AND WEDNESDAY IN THE LOWER ELEVATIONS
- NEAR TO BELOW NORMAL TEMPERATURES THROUGH THE WEEK
DISCUSSION
NIGHTTIME AND WATER VAPOR SATELLITE IMAGERY
TONIGHT SHOWS AN UPPER CLOSED LOW SPINNING OFF THE COAST OF THE
PACNW. A BAND OF MID TO HIGH LEVEL CLOUD COVER IS CURRENTLY
PUSHING ACROSS EASTERN WA/OR, WHILE MID LAYER CLOUD COVER WITH
EMBEDDED LIGHT RAIN SHOWERS HAVE DEVELOPED ALONG THE CASCADE
EAST SLOPES, WITH MORE SHOWERS WEST OF THE CREST.
TODAY THROUGH FRIDAY: A PROLONGED BROAD TROUGHING/LOW PRESSURE
PATTERN IS IN STORE FOR THE PACNW THROUGH THIS WORK WEEK
(CONFIDENCE 80-90%). THIS WILL START WITH THE UPPER LOW
CURRENTLY OFFSHORE THE PACNW SWINGING INLAND LATER TODAY,
PRODUCING LIGHT RAIN SHOWERS WITH HIGH MOUNTAIN SNOW SHOWERS
(ABOVE 5-6KFT). WHILE THE UPPER LOW TRANSITIONS INTO AN OPEN
WAVE TROUGH THIS EVENING, A REINFORCING SHORTWAVE TROUGH WILL
DIVE ALONG THE PACNW COAST THEN SWING INLAND TUESDAY MORNING AND
AFTERNOON. WHILE PERSISTENT MOUNTAIN RAIN/SNOW SHOWERS CONTINUE
IN THE NORTHERN BLUES AND CASCADES, THE SHORTWAVE PASSAGE WILL
RESULT IN INCREASED SHOWER CHANCES ACROSS THE EASTERN MOUNTAINS
THROUGH EARLY TUESDAY.
TUESDAY EVENING, A SECOND UPPER CLOSED LOW WILL DEVELOP ALONG
COASTAL BC, THEN REMAIN PARKED JUST OFFSHORE WA WEDNESDAY
THROUGH FRIDAY. LIGHT TO MODERATE MOUNTAIN RAIN SHOWERS WITH
SNOW SHOWERS MAINLY ABOVE 4KFT WILL RESULT IN THE HEAVIEST
ACCUMULATIONS OF AROUND 1-3 INCHES WITH HIGHER AMOUNTS ABOVE
5KFT TUESDAY NIGHT INTO WEDNESDAY MORNING (CONFIDENCE 60-80%).
SNOW LEVELS ACROSS THE FORECAST AREA WILL LOWER GRADUALLY
THROUGH THE LATTER HALF OF THE WORK WEEK, HOWEVER RAIN/SNOW
SHOWERS WILL BECOME LIGHT THROUGH FRIDAY AS THE LOW REMAINS
OFFSHORE. SNOW LEVELS WILL LOWER ENOUGH FOR A LIGHT DUSTING TO
ATTEMPT TO ACCUMULATE AT PASS LEVEL (SNOQUALMIE, WHITE, SANTIAM)
WITH LIGHT SNOW OR RAIN/SNOW MIX ABOVE 4.5KFT IN THE NORTHERN
BLUES. THERE'S MODERATE CONFIDENCE (55-65%) IN ADDITIONAL
MOUNTAIN SNOW ACCUMULATIONS TOTALING AROUND 2 INCHES THROUGH
FRIDAY.
OTHERWISE, THE PARADE OF UPPER LOW PRESSURE SYSTEMS THROUGH THE
REGION WILL RESULT IN AFTERNOON TEMPERATURES LOWERING INTO THE
50S MONDAY THROUGH WEDNESDAY, THEN LOWER FURTHER INTO THE MID
40S TO LOW 50S THURSDAY/FRIDAY (CONFIDENCE 60-85%). BREEZY
WINDS (15-25MPH WITH GUSTS TO AROUND 35MPH) WILL DEVELOP THROUGH
THE CASCADE GAPS AND LOWER ELEVATIONS TUESDAY WITH THE
SHORTWAVE PASSAGE, THEN MAINLY ACROSS CENTRAL OR TO THE COLUMBIA
BASIN WEDNESDAY WITH THE APPROACH OF THE SECOND CLOSED LOW
(CONFIDENCE 55-70%).
SATURDAY AND SUNDAY: ENSEMBLE GUIDANCE IS IN AGREEMENT OF THE
UPPER CLOSED SLIDING INLAND STARTING FRIDAY NIGHT INTO SATURDAY,
WITH CONTINUED CHANCES OF LIGHT RAIN/SNOW IN THE MOUNTAINS.
HOWEVER, GUIDANCE SPLITS ON WHETHER THE UPPER CLOSED LOW BECOMES
AN OPEN WAVE TROUGH AND DIGS SOUTH OR REMAINS A BROAD CLOSED LOW
THAT CONTINUES TO MOVE ACROSS THE PACNW. THE UPPER TROUGH
SOLUTION WOULD RESULT IN MOUNTAIN SHOWERS DISSIPATING ACROSS THE
FORECAST AREA BY SATURDAY AFTERNOON, THEN DRY CONDITIONS
PERSISTING THROUGH SUNDAY. THE UPPER LOW SOLUTIONS RESULT IN
CONTINUED LIGHT MOUNTAIN RAIN/SNOW CHANCES THROUGH THE REMAINDER
OF THE WEEKEND. WITH A CLOSE TO 40/60 SPLIT AMONGST ENSEMBLE
MEMBERS, CONFIDENCE IN THE PRECIPITATION FORECAST OVER THE
WEEKEND IS LOW (15-20%). OTHERWISE, BOTH SOLUTIONS WILL RESULT
IN COOLER CONDITIONS PREVAILING THROUGH THE WEEKEND, WITH
AFTERNOON HIGH TEMPS IN THE MID 40S TO LOW 50S (CONFIDENCE
45-55%). LAWHORN/82
AVIATION /12Z TAFS THROUGH 12Z TUESDAY/
VFR CONDITIONS
EXPECTED TO PREVAIL THROUGH THE PERIOD. A LOW PRESSURE SYSTEM
IMPACTING THE REGION TODAY WILL CONTINUE TO BRING RAIN IMPACTS,
OR CHANCES OF RAIN IMPACTS, TO ALL SITES THROUGH AROUND 00Z,
EXCEPT THROUGH 05Z AT SITE DLS. CIGS WILL MAINLY BE ABOVE 4KFT
AGL THROUGH THE PERIOD, HOWEVER BKN-OVC CIGS WILL LOWER TO
AROUND 3.5KFT AT SITE DLS AFTER 05Z. WINDS WILL BE AROUND 12KTS
OR LESS THROUGH THE PERIOD. LAWHORN/82
PRELIMINARY POINT TEMPS/POPS
PDT 53 37 54 33 / 40 40 40 20
ALW 54 42 54 39 / 50 50 50 50
PSC 57 39 59 37 / 10 10 10 10
YKM 56 35 57 33 / 20 10 0 30
HRI 56 40 57 37 / 30 20 20 0
ELN 53 31 53 28 / 40 10 0 60
RDM 47 32 48 28 / 50 20 30 0
LGD 54 36 52 31 / 90 70 70 50
GCD 50 34 49 29 / 70 40 50 0
DLS 58 42 59 39 / 70 50 20 60
PDT WATCHES/WARNINGS/ADVISORIES
WA...NONE.
OR...NONE.
DISCUSSION...82
AVIATION...82
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