438
FXUS66 KPDT 192237
AFDPDT
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PENDLETON OR
337 PM PDT SAT SEP 19 2026
KEY MESSAGES
- WARMING AND DRYING TREND THROUGH MONDAY.
- CHANCE FOR MOUNTAIN SHOWERS TOWARD END OF THE WEEK.
DISCUSSION
CURRENT RADAR AND VISIBLE SATELLITE IMAGERY SHOWS DRY CONDITIONS
UNDER MOSTLY CLEAR SKIES. THIS IS IN RESPONSE TO AN UPPER LEVEL
RIDGE AXIS CENTERED OVER THE PACIFIC NORTHWEST. THE RIDGE WILL
CONTINUE TO SLOWLY TRACK EAST, WHICH ENHANCES SOUTHWEST FLOW
ALOFT TO ALLOW FOR WARMER AIR TO ADVECT INTO THE REGION.
SLIGHTLY ABOVE NORMAL TEMPERATURES WILL RESULT THIS AFTERNOON AS
HIGHS WILL REACH INTO THE UPPER 70S TO LOW 80S ACROSS THE
COLUMBIA BASIN, BLUE MOUNTAIN FOOTHILLS, AND CENTRAL OREGON. THE
WARMING TREND PERSISTS ON SUNDAY WITH HIGHS IN THE MID-80S,
PEAKING ON MONDAY WITH AFTERNOON TEMPERATURES REACHING INTO THE
UPPER 80S ACROSS THE AFOREMENTIONED AREAS. MINIMUM HUMIDITIES
WILL ALSO BE ON THE DECLINE DURING THIS TIMEFRAME, DROPPING INTO
THE MID- TO UPPER TEENS ACROSS PORTIONS OF CENTRAL OREGON AND
THE JOHN DAY BASIN SUNDAY AND MONDAY. THE TREND SHIFTS ON
TUESDAY TO COOLER AND MORE MOIST, WHICH IS ASSOCIATED WITH AN
UPPER LEVEL SHORTWAVE MOVING ONSHORE OVER THE CENTRAL BRITISH
COLUMBIA COAST. THIS TREND WILL BE SLOW AND STEADY AS HIGH
TEMPERATURES TICK DOWN 2-4 DEGREES EACH DAY THROUGH THE
REMAINDER OF THE WEEK. THE IMPROVEMENT OF HUMIDITIES WILL LAG
SLIGHTLY AND TREND SLOWER, EVENTUALLY STAYING IN THE LOW TO
MID-20S ON FRIDAY IN RELATION TO A SECOND AND MORE ROBUST
APPROACHING SYSTEM.
THE FIRST SHORTWAVE ON TUESDAY WILL STRUGGLE TO DIG INTO THE
PACIFIC NORTHWEST DUE TO THE INCUMBENT AND SLOWLY DEPARTING
RIDGE OF HIGH PRESSURE. GUIDANCE STRONGLY SUGGESTS THE AREA
STAYING DRY AS THE SYSTEM PASSES, WITH ONLY 48% OF ENSEMBLE
MEMBERS HINTING AT RAIN CHANCES ONLY OVER THE JOHN DAY
HIGHLANDS. THE UPPER LEVEL RIDGE WILL REBUILD SLIGHTLY WEDNESDAY
AND EARLY THURSDAY AHEAD OF THE NEXT SYSTEM LATE THURSDAY INTO
FRIDAY. GUIDANCE DISAGREES WITH THE TIMING AND STRENGTH OF THIS
SYSTEM, WHICH IS EXPECTED TO WEAKEN QUICKLY ON ITS APPROACH
TO THE SOUTHERN BRITISH COLUMBIA AND NORTHERN WASHINGTON
COASTS. ENSEMBLES ADVERTISE LIGHT MOUNTAIN SHOWERS BEGINNING
THURSDAY AFTERNOON ACROSS THE CASCADES, WITH 56% OF MEMBERS
SUGGESTING WIDESPREAD LIGHT SHOWERS THURSDAY NIGHT INTO FRIDAY
MORNING DUE TO A STRONGER AND EARLIER ARRIVING SYSTEM. JUST 24
HOURS AGO, IT WAS THE CONSENSUS THAT THE SYSTEM WILL BE SLOWER
AND KEEP SHOWERS MORE CONFINED TO THE CASCADE AND BLUE
MOUNTAINS. THE NBM IS ALIGNING MORE WITH THE LATTER SCENARIO OF
PRIMARILY DRY LOWER ELEVATIONS AND 0.01-0.05" AT HIGHER
ELEVATIONS ACROSS OUR MOUNTAIN ZONES. DUE TO THE OVERALL LOW
CONFIDENCE, THE SHIFTING OF ENSEMBLE CONSENSUS FROM A SLIGHTLY
WETTER TO DRIER OUTCOME OVER SUBSEQUENT MODEL RUNS IS EXPECTED
OVER THE NEXT 24 TO 48 HOURS, WITH THE PRIMARY OUTCOME LIKELY TO
ALIGN WITH LIGHT SHOWERS AND MINIMAL WEATHER IMPACTS. 75
AVIATION /00Z TAFS THROUGH 00Z MONDAY/
VFR CONDITIONS TO
PREVAIL THROUGH THE PERIOD. WINDS WILL BE LIGHT, 12KTS OR LESS,
AND DIURNALLY DRIVEN THROUGH THE PERIOD. LAWHORN/82
PRELIMINARY POINT TEMPS/POPS
PDT 49 83 50 84 / 0 0 0 0
ALW 54 84 56 85 / 0 0 0 0
PSC 52 86 53 87 / 0 0 0 0
YKM 54 84 54 85 / 0 0 0 0
HRI 51 86 53 86 / 0 0 0 0
ELN 52 80 52 81 / 0 0 0 0
RDM 43 84 45 84 / 0 0 0 0
LGD 49 83 51 85 / 0 0 0 0
GCD 49 85 50 86 / 0 0 0 0
DLS 57 88 59 87 / 0 0 0 0
PDT WATCHES/WARNINGS/ADVISORIES
WA...NONE.
OR...NONE.
DISCUSSION...75
AVIATION...82
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