176
FXUS66 KPDT 230544
AFDPDT
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PENDLETON OR
1044 PM PDT THU OCT 22 2026
.UPDATED AVIATION DISCUSSION.
KEY MESSAGES
- RAIN AND SLIGHT CHANCE (10-15%) OF THUNDERSTORMS TODAY, WITH
THE BEST CHANCES OF WETTING RAIN (0.10" OR GREATER) OVER THE
BLUE MOUNTAINS (90-99% CHANCE) THROUGH EARLY FRIDAY.
- BREEZY TO WINDY WESTERLY TO NORTHWESTERLY WINDS LATE THIS
AFTERNOON INTO FRIDAY, STRONGEST THROUGH THE CASCADE GAPS
WHERE WIND ADVISORIES IN EFFECT.
- WIDESPREAD NEAR- TO SUB-FREEZING LOW TEMPERATURES IN THE
COLUMBIA BASIN AND SURROUNDING LOWLANDS SATURDAY MORNING
(50-95% CHANCE). FREEZE WATCHES ISSUED.
DISCUSSION
WATER VAPOR IMAGERY SHOWS A LARGE CLOSED LOW OVER
CENTRAL CALIFORNIA, AND A WEAK MID-LEVEL CIRCULATION WRAPPING
NORTH- NORTHWEST AROUND THE PARENT LOW IS EVIDENT OVER SOUTHEAST
OREGON. MEANWHILE, A SHORTWAVE TROUGH IS APPROACHING THE
PACIFIC NORTHWEST FROM THE NORTHEAST PACIFIC OCEAN, AND IS
FORECAST TO MOVE ONSHORE LATE THIS AFTERNOON.
WIDESPREAD SHOWERS HAVE DEVELOPED ACROSS CENTRAL TO EASTERN
OREGON AND SOUTH-CENTRAL TO SOUTHEAST WASHINGTON, AND ISOLATED
EMBEDDED LIGHTNING HAS BEEN OBSERVED OVER THE BLUE MOUNTAINS AND
THEIR ADJACENT FOOTHILLS. MODEST INSTABILITY IS PRESENT (100
J/KG OR LESS MUCAPE PER SPC'S RAP-BASED MESOANALYSIS), AND 12Z
HREF MEAN FORECAST VALUES REMAIN BELOW 500 J/KG THROUGH THE DAY
(HIGHEST FOR THE NORTHEAST BLUE MOUNTAINS). ASIDE FROM THE
ISOLATED LIGHTNING WITHIN THE ONGOING BAND OF SHOWERS, THE BEST
CHANCE FOR NOTABLE CONVECTION WILL BE THIS AFTERNOON AND
EVENING ACROSS THE BLUE MOUNTAINS REGION OF GRANT, UNION, AND
WALLOWA COUNTIES; CONVECTION DEVELOPING ACROSS SOUTHEAST OREGON
AND SOUTHWEST IDAHO WILL TRACK NORTH TO NORTHEAST AND THE
PORTION IN OREGON MAY (50% CONFIDENCE) CLIP THE AFOREMENTIONED
COUNTIES. MAIN HAZARDS ASSOCIATED WITH THIS ACTIVITY WILL BE
LIGHTNING AND GUSTY OUTFLOW WINDS.
LOOKING AHEAD TO LATE THIS AFTERNOON INTO THE EVENING HOURS,
BREEZY TO WINDY WESTERLY TO NORTHWESTERLY WINDS ARE FORECAST TO
RAMP THROUGH THE CASCADE GAPS AND ACROSS WIND-PRONE PORTIONS OF
NORTH-CENTRAL OREGON AS PRESSURE GRADIENTS INCREASE IN STRENGTH
(8-11 MB DIFFERENCE BETWEEN PDX AND GEG IN LATEST NWP GUIDANCE)
AND A MODEST LOW-LEVEL JET (25-40 KTS) DEVELOPS. CONFIDENCE IS
MEDIUM-HIGH (60-90%) IN REACHING ADVISORY-LEVEL WIND GUSTS (45
MPH OR GREATER) THROUGH THE KITTITAS VALLEY, EASTERN COLUMBIA
RIVER GORGE, AND WIND-PRONE PORTIONS OF NORTH-CENTRAL OREGON;
WIND ADVISORIES ARE IN EFFECT FROM 7 PM THIS EVENING UNTIL 11 AM
FRIDAY MORNING.
PRECIPITATION IS FORECAST TO TAPER OFF THROUGH FRIDAY MORNING
FROM WEST TO EAST AS THE SHORTWAVE TROUGH MOVES OVERHEAD, AND A
VERY DRY AIR MASS (PWAT OF 0.15-0.40") REPLACES THE MOIST AIR
MASS CURRENTLY IN PLACE. THIS WILL SET THE STAGE FOR NEAR- TO
SUB-FREEZING TEMPERATURES FRIDAY NIGHT INTO SATURDAY MORNING.
WHILE MOST PUBLIC FORECAST ZONES HAVE OBSERVED A SEASON-ENDING
FREEZE, A WIDESPREAD FREEZE HAS NOT YET OCCURRED IN THE LOWEST
ELEVATIONS OF OUR FORECAST AREA. GIVEN THE ANTICIPATED DRY AIR
MASS, PREDOMINANTLY LIGHT WINDS, AND MOSTLY CLEAR SKIES,
CONFIDENCE IS MEDIUM-HIGH (50-95%) THAT A SEASON-ENDING FREEZE
WILL BE OBSERVED IN THE LOWER COLUMBIA BASIN, EASTERN COLUMBIA
RIVER GORGE, YAKIMA VALLEY, AND THE FOOTHILLS OF THE NORTHERN
BLUE MOUNTAINS, SO HAVE ISSUED FREEZE WATCHES.
UNCERTAINTY IN THE 500-HPA HEIGHT FIELD BURGEONS SUNDAY THROUGH
EARLY NEXT WEEK DUE TO CONTINUED ENSEMBLE SPREAD IN SOLUTIONS
REGARDING THE DEVELOPMENT AND EVOLUTION OF A CLOSED LOW IN THE
GULF OF ALASKA REGION. ROUGHLY 50-60% OF ENSEMBLE MEMBERS
DEPICT A COMPACT CLOSED LOW MOVING INLAND MONDAY THROUGH MID-
WEEK, WHILE ANOTHER 20-30% OF MEMBERS SHOW A WEAKER LOW, AND
THE REMAINING MEMBERS ADVERTISE AN UPPER-LEVEL RIDGE OVER THE
PACIFIC NORTHWEST. THE SCENARIO THAT SHOWS A STRONGER CLOSED LOW
WOULD RESULT IN SHOWER CHANCES AND COOLER TEMPERATURES, WHILE
THE WEAKER LOW WOULD WARMER AND DRIER, AND THE UPPER-LEVEL RIDGE
WOULD BE WARM AND COMPLETELY DRY.
AVIATION /06Z TAFS THROUGH 06Z SATURDAY/
VARIED CONDITIONS ACROSS ALL SITES THIS EVENING, WITH VFR AT
KDLS/KRDM/KBDN/KYKM AND MVFR AT KPDT/KALW/KPSC DUE TO LIGHT RAIN
REDUCING VISIBILITIES OF 4 TO 5 SM. RAIN WILL CONTINUE TO DEPART
EAST OVERNIGHT, IMPROVING VISIBILITIES TO ABOVE VFR CRITERIA.
BREEZY CONDITIONS WITH GUSTS OF 20-25KTS EXPECTED FOR MOST
SITES THROUGH THE MORNING, WITH LOWER WINDS OF AROUND 10KTS
OVER KPDT/KALW. CLOUDS CLEAR THROUGH THE AFTERNOON. 75
PRELIMINARY POINT TEMPS/POPS
PDT 41 57 26 58 / 90 0 0 0
ALW 43 57 32 59 / 100 10 0 0
PSC 42 63 28 58 / 60 0 0 0
YKM 40 65 30 57 / 0 0 0 0
HRI 43 60 28 57 / 80 0 0 0
ELN 40 57 24 55 / 0 0 0 0
RDM 28 53 19 60 / 10 0 0 0
LGD 40 51 25 59 / 100 10 0 0
GCD 37 52 26 62 / 100 10 0 0
DLS 44 63 33 62 / 0 0 0 0
PDT WATCHES/WARNINGS/ADVISORIES
WA...WIND ADVISORY UNTIL 11 AM PDT FRIDAY FOR WAZ024-026.
FREEZE WATCH FROM FRIDAY EVENING THROUGH SATURDAY MORNING FOR
WAZ024-027>029.
OR...WIND ADVISORY UNTIL 11 AM PDT FRIDAY FOR ORZ041-510.
FREEZE WATCH FROM FRIDAY EVENING THROUGH SATURDAY MORNING FOR
ORZ041-044-507.
DISCUSSION...86
AVIATION...75
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