573
FXUS66 KPDT 280010
AFDPDT
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PENDLETON OR
510 PM PDT MON OCT 27 2025
UPDATED FOR AVIATION
AVIATION
00Z TAFS...VFR CONDITIONS ARE EXPECTED THROUGH THE TAF PERIOD.
WINDS WILL BE IN THE 10 TO 15 KT RANGE AT A FEW SITES THIS EVENING
THEN ALL SITES WILL BE 10 KTS OR LESS THROUGH THE PERIOD.
PREV DISCUSSION
/ISSUED 245 PM PDT MON OCT 27 2025/
DISCUSSION...KEY MESSAGES:
1. DISSIPATING MOUNTAIN SNOW, RETURNING TUESDAY.
2. COLD TEMPERATURES INTO TUESDAY MORNING.
*FREEZE WARNING ISSUED*
3. WIDESPREAD SHOWERS AND BREEZY WINDS LATE FRIDAY THROUGH SATURDAY.
CURRENT RADAR AND VISIBLE SATELLITE IMAGERY SHOWS SCATTERED LIGHT
SHOWERS ALONG THE CASCADE CREST AND NORTHERN BLUE MOUNTAINS UNDER
PARTLY CLOUDY TO MOSTLY SUNNY SKIES OVER DECREASING ELEVATIONS.
THIS IS IN RESPONSE TO SURFACE HIGH PRESSURE DEVELOPING ACROSS THE
COLUMBIA BASIN IN THE WAKE OF THE DEPARTING UPPER LEVEL SYSTEM TO
OUR EAST. AN UPPER LEVEL RIDGE WILL CONTINUE TO BUILD ALONG THE
COAST AND SHIFT OVER OUR AREA TUESDAY MORNING, ALLOWING LOW
TEMPERATURES TO DROP INTO THE UPPER 20S TO LOW 30S ACROSS THE
COLUMBIA BASIN, CENTRAL OREGON, BLUE MOUNTAIN FOOTHILLS, AND THE
YAKIMA/KITTITAS VALLEYS. MOST AREAS HAVE RECEIVED A SEASON ENDED
FREEZE, WITH EXCEPTION OF THE EASTERN GORGE AND THE LOWER COLUMBIA
BASIN OF OREGON, BUT THE LATTER IS EXPECTED TO EXPERIENCE FREEZING
TEMPERATURES TONIGHT INTO TUESDAY MORNING. THUS, A FREEZE WARNING
HAS BEEN ISSUED FOR THE LOWER COLUMBIA BASIN OF OREGON FROM
MIDNIGHT TO 9 AM TUESDAY.
A WEAK IMPULSE MAY BRING A LIGHT DUSTING OF SNOW OVER THE
WASHINGTON CASCADES TUESDAY MORNING AHEAD OF THE NEXT SYSTEM THAT
WILL RETURN MORE SUBSTANTIAL SHOWERS TUESDAY EVENING INTO
WEDNESDAY. SNOW LEVELS WILL BE INCREASING TUESDAY FROM 3500-4500
FEET IN THE MORNING TO 8500-9000 FEET BY THE EVENING. AS A RESULT,
ONLY HIGHER ELEVATIONS ARE EXPECTED TO GET ANY MEASURABLE AMOUNTS
OF SNOW, WITH MOST AREAS PICKING UP 0.25-0.50" OF RAINFALL
TUESDAY EVENING THROUGH WEDNESDAY MORNING. PRECIPITATION SHOULD
CEASE BY 11 AM AS DRIER CONDITIONS ENSUE WITH AN UPPER LEVEL RIDGE
BUILDING OVER THE AREA THROUGH EARLY FRIDAY.
A PRESSURE GRADIENT WILL DEVELOP ALONG THE BLUE MOUNTAINS LATE
TUESDAY ASSOCIATED WITH THE PASSING SYSTEM, WHICH WILL ELEVATE WINDS
ACROSS THE GRANDE RONDE VALLEY, NORTHERN BLUE MOUNTAINS, AND WALLOWA
COUNTY TUESDAY EVENING THROUGH WEDNESDAY MORNING. THE NAM AND SREF
BOTH HIGHLIGHT A PRESSURE GRADIENT OF 6.5-7 MB BETWEEN MEACHAM
(KMEH) AND BAKER CITY (KBKE). THIS WOULD CORRELATE TO SUSTAINED
SOUTH WINDS OF 20-30 MPH WITH GUSTS UP TO 40 MPH, WHICH IS BELOW
ADVISORY CRITERIA. CONFIDENCE IN THESE WIND VALUES IS HIGH
(75-85%) AS THE HREF SUGGESTS A 90-95% OF WIND GUSTS REACHING 35
MPH OR GREATER.
THE UPPER LEVEL RIDGE SHIFTS EAST AND FLATTENS ON FRIDAY IN
RESPONSE TO AN INCOMING UPPER LEVEL TROUGH, BRINGING A RETURN TO
WIDESPREAD MOISTURE IN THE EVENING. GUIDANCE HAS BEEN LEANING MORE
ON A DELAYED TIMEFRAME IN RAIN INITIATION, MEANING THERE IS A GOOD
BIT OF SPREAD IN RELATION TO WHEN THE RAIN IS EXPECTED TO ARRIVE.
THE CURRENT FORECAST HAS INCREASING CHANCES THROUGH THE DAY,
PEAKING AFTER 5 PM FRIDAY. HOWEVER, THE SPREAD OF 12-HOUR RAINFALL
AMOUNTS BETWEEN 11 AM AND 11 PM ARE QUITE SUBSTANTIAL. FOR
INSTANCE, THE 25TH PERCENTILE FOR 12 HOUR RAINFALL IN THE TRI-
CITIES IS 0" BUT THE 75TH IS 0.08" WITH THE MEAN OF 0.06". THIS
HIGHLIGHTS THE UNCERTAINTY IN TIMING, BUT IT IS EXPECTED THAT THE
MEAN SHOULD ALIGN MORE WITH THE 25TH PERCENTILE IN SUBSEQUENT
MODEL RUNS AS THE RECENT TREND IN GUIDANCE HAS THE RIDGE SLOWER IN
ITS FLATTENING/DEPARTING. THIS WILL HAVE TO FURTHER ANALYZED AS
THE EVENT NEARS, BUT IT MAY BE WORTH KEEPING THE RAIN GEAR HANDY
IF PARTICIPATING IN ANY OUTDOOR ACTIVITIES FRIDAY
AFTERNOON/EVENING. IN ADDITION TO THE WIDESPREAD SHOWERS, BREEZY
WINDS ARE EXPECTED SATURDAY ACROSS THE COLUMBIA BASIN AND SIMCOE
HIGHLANDS. SUSTAINED WEST-SOUTHWEST WINDS OF 20-25 MPH WITH GUSTS
UP TO 35 MPH WILL BE POSSIBLE, PEAKING DURING THE AFTERNOON HOURS.
75
AVIATION...18Z TAFS...VFR CONDITIONS WILL PERSIST THROUGHOUT THE
TAF PERIOD. AS THE NORTHWESTERLY FLOW GRADUALLY TAKES OVER, WE MAY
SEE AN UPTICK FOR SUSTAINED WINDS (UP TO 12KTS) THIS LATE MORNING
FOR KBDN/KALW/KPSC THROUGH THE DAY TODAY WITH KPDT JOINING IN
THIS AFTERNOON. THESE WINDS WILL BE SLIGHTLY BREEZY, AT BEST BUT
SHOULD START DECREASING AROUND THIS EVENING. OTHERWISE, THE
REMAINING SITES WILL HAVE WINDS BELOW 12KTS. FEASTER/97
PRELIMINARY POINT TEMPS/POPS
PDT 31 58 38 58 / 0 0 10 20
ALW 36 57 41 57 / 0 10 20 40
PSC 30 53 36 61 / 0 0 20 20
YKM 30 50 34 58 / 0 10 50 10
HRI 31 53 36 60 / 0 0 10 10
ELN 26 47 31 54 / 0 10 70 10
RDM 26 63 34 58 / 0 0 20 0
LGD 27 53 37 56 / 0 0 10 20
GCD 28 58 33 58 / 0 0 0 0
DLS 35 54 41 61 / 0 10 60 10
PDT WATCHES/WARNINGS/ADVISORIES
OR...FREEZE WARNING FROM MIDNIGHT TONIGHT TO 9 AM PDT TUESDAY FOR
ORZ044.
WA...NONE.
SHORT TERM...75
LONG TERM....75
AVIATION...77
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