475
FXUS66 KPDT 102249
AFDPDT
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PENDLETON OR
349 PM PDT SAT OCT 10 2026
KEY MESSAGES
- COLD AIR MASS EXPECTED TO MOVE THROUGH THE AREA THIS WEEKEND
AND NEXT WEEK
- BREEZY CONDITIONS THIS WEEKEND ALONG THE EASTERN OREGON
CASCADES, WASHINGTON CASCADES, LOWER COLUMBIA BASIN AND YAKIMA
VALLEY
- RETURN OF MOSTLY DRY CONDITIONS, LIGHT WINDS, AND ABOVE NORMAL
TEMPERATURES MIDDLE OF NEXT WEEK
DISCUSSION
SCATTERED TO BROKEN CLOUD LAYERS AROUND 6000 FT WERE COMMON
ACROSS THE FORECAST AREA THIS AFTERNOON WITH OF MORE SUN THROUGH
THE COLUMBIA RIVER GORGE AND SOUTHEAST WASHINGTON. A ZONAL FLOW
PATTERN WAS GIVING WAY TO A MID LEVEL TROUGHING OF COOLER AIR
ALOFT OVER THE PAC NW THAT WILL CONTINUE TO AMPLIFY THROUGH
MONDAY NIGHT INTO THE GREAT BASIN. CHALLENGING FORECAST IN TERMS
OF WHERE THE COLD AIR WILL HAVE IMPACTS. THERE IS A LARGE
DISCREPANCY IN THE SHORT TERM ENSEMBLE MODELS AND THE NBM'S
MORE WEIGHTED RAW INPUTS AND BIAS CORRECTED MEMBER DATA HAVING
VERY COLD AIR THE THE 20S ACROSS THE WALLOWA VALLEY OVERNIGHT.
HREF SHOWS A MORE MUTED TEMP TREND AS CLOUD COVER, WHICH KEPT
TEMPS IN THE THE MID 30 LAST NIGHT AGAIN SHOWS ITS HAND
OVERNIGHT NOT ONLY IN THE TOTAL CLOUD COVER BUT IN LOW LEVEL
HRRR FIELDS BETWEEN ABOUT MIDNIGHT AND 14Z (INCREASING TRENDS).
THE UNCERTAINTY LIES IN THE CLOUD COVER; IF ANY APPRECIABLE
CLEARING OCCURS OR THE CLOUDS FAIL TO REDEVELOP, COLDER SUB
FREEZING TEMPERATURES COULD WILL DEVELOP QUICKLY. AT THIS TIME,
FORECASTER CONFIDENCE DOESN'T REACH THE THRESHOLDS TO CONTINUE
FREEZE WARNINGS IN THE VERY NEAR TERM. WITH REDMOND AND BEND
REACHING 32 AND COLDER LAST NIGHT, THE CENTRAL OREGON FORECAST
ZONE IS NOW BEING CONSIDERED AS HAVING ITS SEASON-ENDING
FREEZE. SHOWERS ACROSS THE WALLOWAS ARE ALSO POSSIBLE SUNDAY
NIGHT AS THE NBM IS PUTTING IN FAIRLY HIGH POPS IN THE 50 TO
70% RANGE OVER THESE HIGH ELEVATIONS. MONDAY NIGHT AND TUESDAY
MORNING MAY PRESENT THE SAME ISSUES WITH CLOUD COVER ACROSS A
LARGER AREA WITH RESPECT TO FREEZE HEADLINES. THERE IS A
ENSEMBLE MEMBER TREND WHERE THE CLOUD COVER IS CLEARING OUT
BETTER ACROSS THE WESTERN ZONES, IF NOT MONDAY MORNING ACROSS
THE NORTHWEST, CERTAINLY BY TUESDAY MORNING, OVER THE ENTIRE
AREA. NORTH CENTRAL OREGON, SOME OF THE FOOTHILLS OF THE BLUES
AND NORTHWARD INTO THE KITTITAS AND YAKIMA VALLEY AREAS SHOULD
BE PRONE TO FREEZING BY TUESDAY MORNING. KITTITAS VALLEY ALREADY
HAS AN 80% CHANCE FROM NBM MEMBERS OF REACHING BELOW 32 DEGREES
FOR MONDAY MORNING, COINCIDENT WITH HIGH CONFIDENCE IN CLEARING
SKY AND A FREEZE WATCH IS BEING HOISTED FOR THAT ZONE.
ONCE THE UPPER LOW/TROUGH MOVES THROUGH THE REGION TUESDAY,
TEMPERATURES BEGIN A SHARP REBOUND AS AFTERNOON HIGHS RISE OUT
OF THE 60S AND BACK INTO THE 70S FOR THE COLUMBIA BASIN AND
RIVER GORGE, FOR THE LATTER HALF OF THE WEEK. CORRESPONDING "NOT
AS COLD LOWS" IN THE UPPER 30S AND LOWER TO MID 40S ARE THE
NBM'S FAVORED TEMPS FOR NON MOUNTAIN ZONES.
AVIATION /00Z TAFS THROUGH 00Z MONDAY/
VFR CONDITIONS ARE FORECAST AT ALL SITES THROUGH THIS EVENING,
ALBEIT WITH FEW-BKN CLOUDS ~4-7 KFT AGL. ASIDE FROM BREEZY
WESTERLY WINDS AT DLS, AND PERIODIC GUSTS ELSEWHERE, LIGHT WINDS
OF 10 KTS OR LESS ARE FORECAST INTO TONIGHT. NORTH TO NORTHEAST
WINDS WILL INCREASE IN MAGNITUDE AT FOR ALL SITES SUNDAY.
CHANCES OF MVFR CIGS/VSBYS INCREASE LATER TONIGHT INTO SUNDAY
MORNING, MAINLY AT BDN/RDM WHERE 12Z HREF PROBABILITIES ARE
50-90% FOR MVFR CIGS AND 10-40% FOR MVFR VSBYS, AND 12Z REFS
PROBABILITIES ARE 40-60% FOR MVFR CIGS AND <10% FOR MVFR VSBYS
SUNDAY MORNING. ELSEWHERE, CHANCES OF MVFR CONDITIONS ARE LOW
(20% OR LESS).
PRELIMINARY POINT TEMPS/POPS
PDT 38 54 31 57 / 0 10 10 10
ALW 40 55 35 57 / 0 10 10 10
PSC 44 60 35 62 / 0 10 0 0
YKM 42 59 34 63 / 20 10 0 0
HRI 41 58 34 61 / 0 10 0 0
ELN 38 55 29 60 / 40 10 0 0
RDM 32 48 22 55 / 0 10 0 0
LGD 35 50 31 55 / 0 10 20 10
GCD 29 50 29 55 / 0 0 10 10
DLS 45 63 38 67 / 0 0 0 0
PDT WATCHES/WARNINGS/ADVISORIES
WA...FREEZE WATCH FROM SUNDAY EVENING THROUGH MONDAY MORNING FOR
WAZ026.
OR...NONE.
DISCUSSION...71
AVIATION...86
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