862
FXUS66 KPDT 202209
AFDPDT
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PENDLETON OR
209 PM PST MON JAN 20 2025
SHORT TERM...TODAY THROUGH WEDNESDAY
BOTTOM LINE UP FRONT
1. COLD!!!
2. BREEZY WINDS THROUGH THE GRANDE RONDE VALLEY
CURRENT SATELLITE SHOWS SCATTERED HIGH CLOUDS MOVING OVER PORTIONS
OF THE REGION WITH MOSTLY CLEAR SKIES ELSEWHERE. CURRENT GROUND
OBSERVATIONS SHOW THAT VERY FEW PLACES ARE ABOVE FREEZING AT THIS
TIME. A FEW LOCALIZED AREAS IN THE BASIN, GORGE AND CENTRAL OR BEING
THE EXCEPTION.
MODELS ARE IN FIRM AGREEMENT WITH THE LEADING EDGE OF THE UPPER
LEVEL HIGH PRESSURE SYSTEM PARKED OVER THE REGION. NORTHWEST FLOW
ALOFT IS WHAT IS BRINGING IN THE BELOW FREEZING TEMPERATURES AND
COUPLED WITH CLEAR SKIES WILL ALLOW OVERNIGHT TEMPERATURES TO DIP
BELOW FREEZING ACROSS THE VAST MAJORITY OF THE REGION. THIS WILL
ASSIST WITH KEEPING OVERNIGHT TEMPERATURES TONIGHT COLD. MODEL
GUIDANCE AS WELL AS ENSEMBLES INDICATE THE REGION WILL REMAIN
SUBFREEZING OVERNIGHT EACH NIGHT THROUGH WEDNESDAY NIGHT. OVER 80%
OF THE RAW ENSEMBLE GUIDANCE SHOWS THAT THE PENDLETON AREA WILL SEE
TEMPERATURES BETWEEN 20-25 DEGREES, 50-80% SHOWS THE BASIN SEEING 20-
30 DEGREES, CENTRAL AND NORTH CENTRAL OR SEEING 15-25 DEGREES, THE
GORGE SEEING 20-30 DEGREES AND THE YAKIMA/KITTITAS VALLEYS SEEING 20-
25 DEGREES. NBM SHOWS THE WALLOWA VALLEY, ESPECIALLY NEAR ENTERPRISE
SEEING TEMPERATURES IN THE NEGATIVES AS WELL AS AREAS NEAR SENECA.
CONFIDENCE IN THE OVERALL FORECAST FOR OVERNIGHT TEMPERATURES BEING
SUBFREEZING HIGH (90%). NOW LETS CHAT ABOUT HIGHS, HIGHS TODAY WILL
BARELY CREST ABOVE FREEZING FOR MANY AREAS WITH THE EXCEPTIONS BEING
SOME LOCALIZED AREAS OF THE BASIN, GORGE AND CENTRAL OR. AS WE MOVE
TO TOMORROW, MODELS AND ENSEMBLES DO SHOW THERE TO BE A SLIGHT
INCREASE IN DAYTIME TEMPERATURES FROM TODAY. HOWEVER, ONLY 56% OF
THE RAW ENSEMBLES SEEM TO AGREE TEMPERATURES WILL BE IN THE UPPER
30S THROUGH THE PENDLETON AREA, 44% AGREE TEMPERATURES WILL BE IN
THE LOW 30S. MOVING TO CENTRAL OR, 87% OF THE ENSEMBLES AGREE THE
REGION WILL SEE UPPER 30S TO LOW 40S. 61% FOR THE GORGE SEEING UPPER
30S TO LOW 40S AND 35% FOR 40 TO 45 DEGREES. 40% AGREE THE BASIN
BETWEEN 30-35 DEGREES, 40% AGREE 35-40 DEGREES WHILE THE REMAINING
ENSEMBLES HAVE TEMPERATURES BELOW 30 DEGREES. YAKIMA/KITTITAS
VALLEYS ROUGHLY 50% OF THE ENSEMBLES AGREE TEMPS WILL BE 35-40
DEGREES WITH THE OTHER 50% SHOWING TEMPERATURES BELOW 35 DEGREES.
CONFIDENCE WITH THE HIGH TEMPERATURES TO BE MODERATE (50-70%).
MODELS SHOW A BRIEF SHORTWAVE DISTURBANCE WILL RIPPLE ACROSS THE
LEADING EDGE OF THE HIGH ASSISTING IN FLATTENING THE RIDGE A BIT.
THIS WILL BRIEFLY SHIFT THE WINDS TO A WESTERLY PATTERN. LOOKING THE
SURFACE PRESSURE GRADIENTS, THERE IS A CLEAR TIGHTENING ALONG THE
GRANDE RONDE VALLEY. PRESSURE GRADIENT ARE NOT TIGHTENED ENOUGH TO
WARRANT AN ADVISORY, HOWEVER, 70-90% OF THE RAW ENSEMBLES DO SHOW
WIND GUSTS OF 30-40 MPH OCCURRING BEGINNING LATER THIS EVENING AND
PERSISTING THROUGH THE EARLY MORNING. OTHERWISE, MODELS SHOW THE
SHORTWAVE EXITING THE REGION EARLY TUESDAY MORNING AND THE LEADING
EDGE OF THE UPPER LEVEL RIDGE MOVING BACK IN OVERHEAD BRING
NORTHWEST FLOW ALOFT AND WINDS RETURNING TO NEAR 10 MPH THROUGH
WEDNESDAY. BENNESE/90
LONG TERM...THURSDAY THROUGH MONDAY
CONTINUED RIDGING ON THURSDAY
WILL PRODUCE DRY CONDITIONS THROUGH THURSDAY AFTERNOON, WITH
SLIGHTLY ABOVE NORMAL TEMPERATURES. THERE IS GOOD AGREEMENT IN
GUIDANCE THAT A WAVE OF LOW PRESSURE WILL SWEEP INTO THE PACNW
THURSDAY EVENING. THIS COLD FRONT WILL MOVE MOISTURE OVER THE
MOUNTAINOUS AREAS (CASCADES AND BLUE MOUNTAINS) PRODUCING MODERATE
CHANCES (40-60%) OF SNOWFALL ABOVE 1500-2500 FT. AS THE FRONT
PROGRESSES ON FRIDAY, MUCH OF THE FORECAST AREA WILL SEE CHANCES (20-
50%) FOR PRECIPITATION WITH SNOW LEVELS DECREASING TO BELOW 1000 FT.
THROUGH FRIDAY AFTERNOON, THE BLUE MOUNTAINS ARE ANTICIPATED TO
RECEIVE THE GREATEST SNOWFALL AMOUNTS WITH VALUES BETWEEN 2 AND 5
INCHES OF SNOWFALL (PROBABILITIES DEMONSTRATE A 40-60% CHANCE OF 2
INCHES, WITH A 20-30% CHANCE FOR UP TO 4 INCHES). THE WASHINGTON
CASCADES WILL SEE BETWEEN 1 AND 4 INCHES, WITH THE HIGHEST AMOUNTS
NOTED AROUND SNOQUALMIE PASS WHERE THERE WILL BE A LOW CHANCE (15-
35%) OF SNOWFALL OF 2 INCHES, DROPPING TO <10% CHANCE FOR UP TO 4
INCHES.
THE FRONT WILL MOVE SOUTH OF THE AREA BY LATE FRIDAY NIGHT, WITH
DRIER CONDITIONS NOTED BY SATURDAY LATE MORNING/EARLY AFTERNOON. AS
THIS SYSTEM DEPARTS, THERE WILL BE A RETURN OF RIDGING, WITH
GENERALLY DRY CONDITIONS. LIGHT ADDITIONAL SNOWFALL IS EXPECTED
THROUGH EARLY SATURDAY MORNING WITH LESS THAN AN INCH SEEN ACROSS
CENTRAL OREGON EXCEPT AROUND THE SOUTHERN OREGON CASCADES WHERE UP
TO 2 INCHES FAVORED (30-40% CHANCE). BRIEF PERIODS OF GUSTY WIND
COULD ACCOMPANY THE FRONTAL PASSAGE, WITH GUSTS 15 TO 20 MPH
FORECAST.
TEMPERATURES WILL CONTINUE TO COOL ON SATURDAY, WHICH IS EXPECTED TO
BE THE COLDEST DAY IN THE EXTENDED PERIOD. AS MENTIONED PREVIOUSLY,
THURSDAY WILL SEE TEMPERATURES ABOVE NORMAL ACROSS MUCH OF OREGON,
WITH COOLER THAN NORMAL TEMPERATURES NOTED ACROSS THE COLUMBIA BASIN
THROUGH WASHINGTON. AFTER THE FRONTAL PASSAGE ON FRIDAY,
TEMPERATURES WILL DIP TO 5 TO 10 DEGREES BELOW NORMAL FOR MUCH OF
THE FORECAST AREA, WITH VALUES ALMOST 15 DEGREES COOLER THAN NORMAL
OVER PORTIONS OF THE BLUE MOUNTAINS. WITH FURTHER COOLING ON
SATURDAY AS THE SYSTEM DIVES FURTHER SOUTH, TEMPERATURES WILL COOL
AN ADDITIONAL 5 TO 10 DEGREES DIPPING TO VALUES OF 10 TO 15 DEGREES
BELOW NORMAL. ON SATURDAY, THERE MUCH OF OREGON WILL SEE A HIGH
CHANCE (70-90%) FOR MAXIMUM TEMPERATURES TO BE 32 DEGREES OR LOWER,
WITH A 20-40% CHANCE OF HIGH TEMPERATURES REACHING ONLY UP TO 28
DEGREES. SUNDAY AND MONDAY WILL SEE A SLIGHTLY WARMER TEMPERATURES,
THOUGH THE MAJORITY OF THE AREA WILL REMAIN 5 TO 10 DEGREES BELOW
NORMAL THROUGH MONDAY.
OVERALL CLUSTER ANALYSIS IS IN FAIR AGREEMENT THROUGH THE EXTENDED
TIME FRAME WITH THE PROGRESSION OF THE INCOMING SYSTEM. SOME
VARIANCES IN TIMING AND INTENSITY ARE PRESENT, BUT THE OVERALL
PATTERN IS GENERALLY AGREED ON. BRANHAM/76
AVIATION...00Z TAFS
WIDESPREAD VFR. DRY CONDITIONS AND LIGHT
WIND ARE EXPECTED THROUGH THE PERIOD. A WEAK, DRY WAVE WILL MOVE
QUICKLY THROUGH THE AREA TUESDAY MORNING/AFTERNOON, WHICH MAY
PRODUCE A FEW CLOUDS OVER THE HIGHER TERRAIN. BRANHAM/76
PRELIMINARY POINT TEMPS/POPS
PDT 22 39 22 37 / 0 0 0 0
ALW 23 38 23 37 / 0 0 0 0
PSC 25 37 24 36 / 0 0 0 0
YKM 18 37 20 36 / 0 0 0 0
HRI 25 38 24 37 / 0 0 0 0
ELN 18 38 22 36 / 0 0 0 0
RDM 21 47 21 45 / 0 0 0 0
LGD 18 37 18 40 / 0 0 0 0
GCD 18 42 20 44 / 0 0 0 0
DLS 26 44 28 41 / 0 0 0 0
PDT WATCHES/WARNINGS/ADVISORIES
OR...NONE.
WA...NONE.
SHORT TERM...90
LONG TERM....76
AVIATION...76
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