645
FXUS66 KPDT 241200
AFDPDT
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PENDLETON OR
500 AM PDT THU SEP 24 2026
KEY MESSAGES
- NEAR TO ABOVE NORMAL TEMPERATURES WITH DRY CONDITIONS THROUGH
TODAY
- WIDESPREAD SHOWERS AND BREEZY TO WINDY CONDITIONS DEVELOP
LATER TONIGHT THROUGH FRIDAY, THEN A RETURN TO DRY AND QUIET
CONDITIONS WITH BELOW NORMAL TEMPERATURES THIS WEEKEND
- LIGHT SHOWERS FOR MONDAY AFTERNOON INTO TUESDAY WITH
MODERATE CONFIDENCE IN TIMING AND EXTENT(40%) BUT LOW
CONFIDENCE IN AMOUNT(10%).
DISCUSSION
NIGHTTIME SATELLITE IMAGERY TONIGHT SHOWS
SCATTERED DECKS OF CIRRUS MOVING ACROSS THE FORECAST AREA, WHILE
SURFACE OBSERVATIONS SHOW QUIET CONDITIONS.
TODAY THROUGH SUNDAY: MOSTLY QUIET CONDITIONS WITH NEAR TO
ABOVE NORMAL TEMPERATURES WILL PREVAIL AGAIN TODAY AS THE PACNW
SITS UNDERNEATH A SOUTHWEST FLOW ALOFT. AS AN UPPER TROUGH
APPROACHES COASTAL PACNW LATER THIS MORNING, A MODEST SOUTHERLY
LOW LEVEL JET (25-35KTS) WILL DEVELOP OVER NORTHEAST OR. THESE
JET WINDS WILL MIX DOWN TO THE SURFACE, RESULTING IN SOUTHERLY
WINDS (15-25 MPH WITH GUSTS UP TO 35 MPH) THROUGH THE GRAND
RONDE VALLEY AND NORTH/SOUTH VALLEYS IN WALLOWA COUNTY THROUGH
THIS AFTERNOON.
LATER TONIGHT, SHOWER ACTIVITY WILL INCREASE ACROSS THE CASCADE
CREST AS THE UPPER TROUGH AND AN ATTENDANT SURFACE LOW CONTINUE
TO APPROACH THE PACNW. RAIN SHOWERS WILL THEN SPREAD EASTWARD
ACROSS THE REMAINDER OF THE FORECAST AREA EARLY FRIDAY MORNING
INTO THE AFTERNOON AS THE TROUGH AND REMNANTS OF THE LOW
CONTINUE EAST. THERE WILL BE A 60-90% CHANCE OF AT LEAST
MEASURABLE RAIN ACROSS MUCH OF THE FORECAST AREA FRIDAY, WITH
ONLY A 30-45% CHANCE OF 0.25 INCHES IN THE NORTHERN BLUES AND A
65-95% CHANCE OF 0.5 INCHES ALONG THE CASCADE CREST AND EAST
SLOPES. IN ADDITION TO PRECIPITATION, THE UPPER TROUGH AND
SURFACE LOW PASSAGE WILL BRING INCREASING WEST TO SOUTHWEST
WINDS ACROSS THE FORECAST AREA. WINDS WILL BE 20-30 MPH WITH
GUSTS 35-50 MPH THROUGH THE CASCADE GAPS AND INTO THE COLUMBIA
BASIN AND ADJACENT FOOTHILLS/VALLEYS, WITH WINDS 15-25 MPH AND
GUSTS UP TO 35 MPH ELSEWHERE. SURFACE WINDS WILL BE SUPPORTED BY
A 40-50KT LOW LEVEL JET THAT WILL MIX DOWN ACROSS PORTIONS OF
THE COLUMBIA BASIN FRIDAY AFTERNOON, WITH MOD-HIGH CONFIDENCE
(75-90%) THAT GUSTS 45MPH OR HIGHER WILL BE OBSERVED IN
WIND PRONE AREAS.
SHOWER ACTIVITY AND WINDY CONDITIONS WILL DIMINISH FRIDAY NIGHT
INTO SATURDAY AS THE UPPER TROUGH AND SURFACE LOW EXIT TO THE
NORTHEAST. WEAK BROAD TROUGHING WILL THEN DEVELOP OFFSHORE THE
PACNW SATURDAY, THEN SLIDE ACROSS THE REGION THROUGH SUNDAY.
LACK OF MOISTURE AND STRONG FLOW ALOFT WITH THIS FEATURE WILL
RESULT IN DRY CONDITIONS WITH MOSTLY LIGHT WINDS, AND
TEMPERATURES BELOW NORMAL OVER THE WEEKEND. LAWHORN/82
MONDAY THROUGH WEDNESDAY: MONDAY HAS SPLIT FLOW CONDITIONS
STILL PRESENT FOR THE REGION, WITH TROUGHING TO THE SOUTH AND
RIDGING TO THE NORTH, BRINGING LOW IMPACTS OF DRY CONDITIONS AND
LIGHT WINDS(40% CONFIDENCE). ENSEMBLE MEMBERS ARE IN AGREEMENT
WITH TIMING, STRENGTH, AND POSITION OF THE SPLIT FLOW
CONDITIONS AND THE TROUGH TO THE SOUTH(93% OF MEMBERS). MONDAY
AFTERNOON INTO TUESDAY, ENSEMBLE MEMBERS ARE SPLIT 50%/50% ON
THE PRESENCE OF EITHER A SHORTWAVE TROUGH OR A RIDGE BUILDING
OVER THE BASIN. BOTH SITUATIONS BRINGING LIGHT SHOWERS(40%
CONFIDENCE) WITH LOW CONFIDENCE(10% CONFIDENCE) IN RAINFALL
AMOUNTS FOR THE CASCADE CREST AND EAST SLOPES. 35% OF THE
ENSEMBLE CLUSTER MEMBERS SHOW LIGHT SHOWERS FOR THE CWA AROUND
MIDDAY TUESDAY. TUESDAY INTO WEDNESDAY HAS SIMILAR CONDITIONS
PRESENT WITH THE SPLIT CHANGING TO FAVOR THE RIDGE PATTERN
BUILDING OVER THE REGION AT 52%/48%. LOW CONFIDENCE (10%) IN
LIGHT SHOWERS FOR TUESDAY AFTERNOON INTO WEDNESDAY. TEMPERATURES
FOR THE REGION WILL BE NEAR/ SLIGHTLY BELOW NORMAL.
AVIATION /12Z TAFS THROUGH 12Z FRIDAY/
DLS/PDT/RDM/BDN: VFR PRESENT FOR THE TAF PERIOD, WITH RAIN
PRESENT FROM 08Z ONWARD FOR KDLS,KRDM AND KBDN. CLOUD CEILINGS
OF 7000FT(KDLS) AND 8000FT KBDN AND KRDM) WILL BE PRESENT
ALONGSIDE THE RAIN. BREEZY CONDITIONS WITH GUSTS UP TO 20KT FOR
KRDM AND KBDN.
YKM/ALW/PSC: VFR CONDITIONS TO PREVAIL THROUGH THE PERIOD. LOW
PRESSURE SYSTEM APPROACHING THE AREA THIS EVENING WILL PRODUCE
RAIN IMPACTS AT SITE YKM STARTING AROUND 9Z. WINDS WILL BE
LIGHT, 12KTS OR LESS, THROUGH THE PERIOD. LAWHORN/82
PRELIMINARY POINT TEMPS/POPS
PDT 79 50 71 43 / 0 0 70 0
ALW 80 55 71 47 / 0 0 70 10
PSC 79 52 73 43 / 0 10 70 0
YKM 74 53 65 41 / 0 60 50 0
HRI 79 52 73 43 / 0 10 70 0
ELN 70 48 60 36 / 0 60 70 10
RDM 84 44 60 31 / 0 60 30 0
LGD 85 51 69 40 / 0 0 30 0
GCD 88 52 69 38 / 0 0 30 0
DLS 78 55 67 45 / 0 70 60 10
PDT WATCHES/WARNINGS/ADVISORIES
WA...NONE.
OR...NONE.
DISCUSSION...07/82
AVIATION...07/82
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