132
FXUS66 KPDT 091002
AFDPDT
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PENDLETON OR
302 AM PDT FRI OCT 9 2026
KEY MESSAGES
- BREEZY WESTERLY WINDS AND LIGHT MOUNTAIN PRECIPITATION TODAY,
WITH BREEZY NORTHERLY WINDS SUNDAY
- BELOW FREEZING MORNING TEMPERATURES IN PORTIONS OF CENTRAL
OR, GRANDE RONDE VALLEY, AND WALLOWA VALLEY THIS WEEKEND INTO
EARLY NEXT WEEK
- CHANCE FOR LIGHT PRECIPITATION EARLY NEXT WEEK WITH COLDER
THAN NORMAL TEMPERATURES BEGINNING NEXT WEEK
DISCUSSION
NIGHTTIME SATELLITE IMAGERY TONIGHT SHOWS CIRRUS
SPREADING EAST ACROSS THE FORECAST AREA AHEAD OF AN APPROACHING
COLD FRONT AND UPPER LEVEL TROUGH.
TODAY THROUGH SUNDAY: UNSETTLED WEATHER CONDITIONS WILL RETURN
TO THE PACNW TODAY AS A COLD FRONT AND UPPER TROUGH DROP INTO
THE REGION FROM THE NORTH/NORTHWEST. THE COLD FRONT BOUNDARY IS
EXPECTED TO BRING LIGHT SHOWERS TO THE CENTRAL WA CASCADE CREST
LATER THIS MORNING, WITH SHOWER ACTIVITY SLIDING SOUTH ALONG
THE CASCADE CREST THROUGHOUT THE DAY. SHOWERS WILL ALSO REACH
THE NORTHERN BLUES, FAR NORTHEAST OR, AND FAR SOUTHEAST WA BY
THIS AFTERNOON AND EVENING, BUT OTHERWISE DRY CONDITIONS WILL
PERSIST ELSEWHERE. PRECIPITATION IN THE MOUNTAINS WILL BE FAIRLY
LIGHT, WITH CHANCES OF 0.1 INCHES IN 24-HRS ONLY BETWEEN 25-45%
IN THE NORTHERN BLUES, OR CASCADE CREST/EAST SLOPES, AND
SOUTHERN PORTIONS OF THE WA CASCADE EAST SLOPES; CHANCES OF
0.25 INCHES OF LIQUID PRECIP IN THE CENTRAL WA CASCADES WILL BE
CLOSER TO 70-90%. SNOW LEVELS WILL BE ON THE DECLINE TO AROUND
4-5KFT LATER TONIGHT, RESULTING IN A 60-65% CHANCE OF 0.5 INCHES
OF SNOW ACCUMULATIONS ALONG THE HIGHER ELEVATIONS OF THE
CENTRAL WA CASCADE CREST. WEST TO NORTHWEST BREEZY WINDS
(15-25MPH WITH GUSTS 30-40MPH) WILL DEVELOP ACROSS MUCH OF THE
LOWER ELEVATIONS WITH THE COLD FRONT PASSAGE TODAY, WITH
STRONGEST GUSTS UP TO 45 MPH EXPECTED IN PORTIONS OF THE
KITTITAS VALLEY, SIMCOE HIGHLANDS, AND THE EASTERN GORGE.
SATURDAY INTO SUNDAY MORNING, THE UPPER TROUGH WILL TRANSITION
INTO AN UPPER CLOSED LOW AS IT DESCENDS INTO THE PACNW FROM BC.
AS THE UPPER LOW TRACKS SOUTH, LIGHT SNOW/RAIN SHOWERS WILL
DEVELOP ALONG THE CASCADE CREST AND PORTIONS OF THE EASTERN
MOUNTAINS. ACCUMULATIONS OF ANY SNOW WILL BE LIMITED TO ABOVE
5KFT, BUT EVEN THEN CHANCES OF 0.1 INCHES OF ACCUMULATIONS ARE
30-50% BELOW 6KFT ALONG THE CASCADE CREST AND THE EAGLE CAPS.
SUNDAY, THE UPPER LOW WILL CONTINUE TO DIG SOUTH AND EXIT THE
PACNW INTO NORTHERN CA, HOWEVER UPPER TROUGHING WILL REMAIN OVER
THE REGION. WHILE THE PRECIPITATION CHANCE WILL COME TO AN END
ACROSS THE CASCADE CREST, A WEAK MOISTURE PLUME RIDING UP THE
BACK OF THE TROUGH WILL CLIP THE HIGHER TERRAIN OF THE EASTERN
MOUNTAINS, RESULTING IN A CHANCE (40-55%) OF MEASURABLE
PRECIPITATION (0.01 INCHES). SATURDAY NIGHT INTO SUNDAY, BREEZY
NORTH WINDS (15-20 MPH WITH GUSTS TO AROUND 35 MPH) WILL DEVELOP
FROM THE COLUMBIA BASIN INTO CENTRAL OR WITH A PUSH OF COLD AIR
ADVECTION INTO THE INTERMOUNTAIN PACNW.
THE COLD FRONT/UPPER LOW PASSAGE WILL PROMOTE MUCH COOLER
CONDITIONS ACROSS THE FORECAST AREA STARTING FRIDAY NIGHT AND
CONTINUING INTO EARLY NEXT WEEK. CURRENTLY, A FREEZE WATCH IS
IN EFFECT FOR THE WALLOWA VALLEY, GRANDE RONDE VALLEY, AND
CENTRAL OR FOR FRIDAY NIGHT AS THERE IS MODERATE CONFIDENCE
(60-75%) IN FREEZING OVERNIGHT TEMPERATURES DEVELOPING. IF NOT
BY SATURDAY MORNING, CHANCES FOR FREEZING TEMPERATURES WILL
INCREASE IN THESE AREAS AND IN THE KITTITAS VALLEY AND BLUE
MOUNTAIN FOOTHILLS SATURDAY NIGHT AS COLD AIR ADVECTION
CONTINUES INTO THE REGION. CONFIDENCE IS MOD-HIGH (65-85%) THAT
FREEZE WARNINGS WILL BE NEEDED FOR THE AFOREMENTIONED AREAS
SATURDAY NIGHT. LAWHORN/82
MONDAY THROUGH THURSDAY: CLUSTER ANALYSIS OF ENSEMBLE MEMBERS
DEPICTS AN UPPER-LEVEL TROUGH WITH AN ASSOCIATED CLOSED LOW
DEVELOPING OFFSHORE THE PACNW ON MONDAY AND PROPAGATING OVER
THE REGION IN THE NEXT COUPLE OF DAYS. CURRENTLY, THERE IS
TEMPORAL UNCERTAINTY WITH THIS TROUGH OF HOW FAST IT IS MOVING
AND ALSO UNCERTAINTY IN THE OVERALL STRENGTH AND PLACEMENT OF
THIS UPPER- LEVEL TROUGH AND ASSOCIATED LOW. ALONG WITH THIS
SYSTEM, PER MODEL GUIDANCE OF THE NBM, THERE IS THE PRESENCE OF
A SMALL SHORTWAVE ON THE BACKSIDE OF THE TROUGH THAT COULD BRING
A CHANCE (20-30%) FOR LIGHT RAIN ON MONDAY, BUT THE GREATER
CHANCE FOR PRECIPITATION LOOKS TO BE ON WEDNESDAY (50%),
PRIMARILY ALONG THE OREGON CASCADES AND THE BLUES. AS THIS
SYSTEM PUSHES THROUGH, WE DO HAVE THE CHANCE (55-65%) FOR
FREEZING MORNING TEMPERATURES MONDAY,TUESDAY,AND WEDNESDAY
MORNING FOR CENTRAL OREGON AND THE WALLOWA VALLEY, WITH
TEMPERATURES IN THE LOW 30S BUT GREATEST CHANCE SEEMS TO BE ON
MONDAY (65-70%).
AFTER WEDNESDAY, PER CLUSTER ANALYSIS, WE SEE THE DEVELOPMENT OF A
RIDGE PATTERN BEGINNING THURSDAY INTO FRIDAY AND MODELS ARE IN GOOD
AGREEMENT WITH THIS PATTERN SETUP (65%), ALTHOUGH THERE IS SOME
TEMPORAL UNCERTAINTY WITH THIS RIDGE PATTERN AND UNCERTAINTY IN THE
OVERALL STRENGTH OF IT AS WELL. THERE IS A LOW CHANCE (25-30%) FOR
FREEZING MORNING TEMPERATURES THURSDAY, BUT TEMPERATURES SHOULD
BEGIN TO WARM UP TO THE MID 60S-LOW 70S ON THURSDAY.
AVIATION /06Z TAFS THROUGH 06Z SATURDAY/
VFR CONDITIONS WILL
PERSIST THROUGHOUT THE PERIOD. HOWEVER, CEILINGS WILL FALL FOR
SEVERAL HOURS. DLS,PDT,RDM,ALW, AND PSC SHOULD SEE CEILINGS
AROUND 6-7 KFT, YKM AROUND 10 KFT, AND BDN AROUND 4 KFT DURING
THAT TIME. TIMING FOR THE ONSET OF LOW CEILINGS SHOULD BE AROUND
17-18Z FOR DLS AND YKM. OTHER AIRPORTS (PDT,RDM,BDN,ALW,PSC)
WILL SEE THE ONSET BETWEEN 21-23Z(90% CONFIDENCE). VISIBILITIES
WILL REMAIN ABOVE 6SM. WINDS ARE EXPECTED TO REMAIN TERRAIN
DRIVEN AND GENERALLY BELOW 12KTS DURING THE EARLY MORNING HOURS.
HOWEVER, BREEZY CONDITIONS WILL DEVELOP THROUGHOUT THE DAY WITH
WINDS IN THE TEENS AND GUSTS IN THE TWENTIES. GARTY/26
PRELIMINARY POINT TEMPS/POPS
PDT 71 35 58 35 / 10 20 0 0
ALW 72 40 59 39 / 20 20 0 10
PSC 75 38 63 37 / 0 0 0 0
YKM 70 36 61 40 / 10 0 0 40
HRI 72 39 61 36 / 0 0 0 0
ELN 63 32 55 32 / 10 0 10 50
RDM 71 28 54 25 / 0 10 0 10
LGD 74 32 55 33 / 0 30 0 10
GCD 78 34 55 30 / 0 20 0 10
DLS 70 42 63 40 / 10 0 0 10
PDT WATCHES/WARNINGS/ADVISORIES
WA...NONE.
OR...FREEZE WATCH FROM LATE TONIGHT THROUGH SATURDAY MORNING FOR
ORZ049-050-511.
DISCUSSION...01/82
AVIATION...26
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