AFDPDT AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE PENDLETON OR 218 AM PDT MON SEP 26 2022 .SHORT TERM...TODAY THROUGH WEDNESDAY NIGHT... UNSEASONABLY WARM CONDITIONS REMAIN THE FOCUS THROUGH TUESDAY BEFORE AN UPPER-LEVEL TROUGH ARRIVES WEDNESDAY USHERING IN A BRIEF PERIOD OF SHOWERS AND BREEZY WINDS FOR THE MID-WEEK. AN ROBUST RIDGE OF HIGH PRESSURE CENTERED OVER THE INTER-MOUNTAIN WEST CONTINUES TO PERSIST TODAY FACILITATING CALM AND DRY WEATHER, ALBEIT RATHER WARM FOR THIS TIME OF YEAR. TEMPERATURES ARE EXPECTED TO INCREASE ANOTHER DEGREE OR TWO ON TUESDAY AS WELL DUE TO A THERMAL TROUGH PREVIOUSLY WEST OF THE CASCADES SHIFTING EASTWARD IN RESPONSE TO AN APPROACHING SYSTEM OFF THE COAST AMPLIFYING THE PATTERN AND BUMPING THE AXIS OF THE UPPER-LEVEL RIDGE FURTHER INTO THE ROCKIES. BOTH TODAY AND TUESDAY HIGH TEMPERATURES LIKELY RISE INTO THE MID 80S TO LOW 90S FOR THE COLUMBIA BASIN, CENTRAL OREGON, AND MANY OF THE LOWER VALLEY AREAS LIKE THE JOHN-DAY BASIN AND THE GRANDE RONDE VALLEY. WHILE IN THE CONTEXT OF THIS PAST SUMMER THESE MAY NOT SEEM SIGNIFICANT, BY LATE SEPTEMBER STANDARDS THEY’LL BE WITHIN 1-5 DEGREES OF DAILY RECORD VALUES FOR MANY OF THE AFOREMENTIONED AREAS, ESPECIALLY ON TUESDAY. FORTUNATELY A COOLING TREND BEGINS WEDNESDAY AS THE PATTERN BECOMES MORE ACTIVE. BOTH DETERMINISTIC AND ENSEMBLE GUIDANCE ARE IN EXCELLENT AGREEMENT REGARDING OF THE ARRIVAL AND PROGRESSION OF A DEEP LONG- WAVE TROUGH AND ACCOMPANYING COLD-FRONTAL BOUNDARY WEDNESDAY. SHOWER ACTIVITY IS EXPECTED TO ARRIVE NEAR THE CASCADE CRESTS LATER IN THE MORNING/MIDDAY BEFORE SHOWERS BECOME POSSIBLE NEAR THE EASTERN MOUNTAINS LATER IN THE AFTERNOON INTO EVENING. OVERALL QPF VALUES DON’T LOOK PARTICULARLY IMPRESSIVE OUTSIDE OF 0.20-0.40IN RIGHT ALONG THE CRESTS OF THE WASHINGTON CASCADES. AS THE AXIS OF THE TROUGH AND COLD-FRONTAL BOUNDARY MOVES THROUGH THE CWA WEDNESDAY EVENING AND OVERNIGHT IT’S POSSIBLE A SHOWER OR TWO MAY BLEED INTO THE COLUMBIA BASIN BUT OVERALL THE TREND IS TO KEEP CONDITIONS MOSTLY DRY OUTSIDE OF THE MOUNTAIN AREAS. BREEZY WINDS ALSO LIKELY ACCOMPANY THIS DISTURBANCE LATER WEDNESDAY INTO WEDNESDAY EVENING AROUND THE CASCADE GAPS AND EAST SLOPE AREAS INTO THE COLUMBIA BASIN. ANTICIPATE GUSTS UP TO 30-35MPH FOR SPOTS LIKE THE SIMCOE HIGHLANDS; NOTHING OUT OF THE ORDINARY FOR A FALL-LIKE WEATHER SYSTEM OF THIS NATURE. SCHULDT/99 .LONG TERM...THURSDAY THROUGH MONDAY...A DEEP UPPER LEVEL TROUGH WILL BRING LIGHT SHOWERS TO THE MOUNTAINS AND ADJACENT VALLEYS ON THURSDAY AND WILL EXIT THE REGION THURSDAY NIGHT. IT WILL BE BREEZY TO WINDY ON THURSDAY AS WELL. HIGH PRESSURE ALOFT WILL FOLLOW FOR DRIER AND WARMER CONDITIONS THAT ARE FORECAST FOR THE REMAINDER OF THE LONG TERM PERIOD. DETERMINISTIC AND ENSEMBLES ARE ALL IN AGREEMENT WITH THE POSITION OF THE UPPER LEVEL TROUGH ON THURSDAY, ALTHOUGH THE RUN-TO-RUN CONTINUITY WITH THE POSITION OF THE TROUGH HAS NOT BEEN GOOD. LOOKING AT THE PROBABILITY OF 0.1 INCH OR MORE QPF ON BOTH THE GEFS AND ECMWF ENS MEANS, THE WA AND NORTHERN OR CASCADES WILL LIKELY RECEIVE WETTING RAIN AND THE NORTHERN BLUES AND WALLOWAS WILL HAVE A CHANCE. HOWEVER, THE PROBABILITY OF 0.5 INCH OVER THE MOUNTAIN ZONES IS LESS THAN 20 PERCENT. HIGH PRESSURE ALOFT WILL REBUILD FOR DRIER CONDITIONS FRIDAY THROUGH SATURDAY, AND SATURDAY`S TEMPERATURES WILL BE AROUND 10 DEGREES ABOVE SEASONAL AVERAGE WITH HIGHS IN THE 70S TO MID 80S. THERE ARE SOME DIFFERENCES IN THE ENSEMBLES ON THE PLACEMENT OF THE RIDGE AXIS AS WELL AS THE AMPLITUDE AND TIMING OF A DEVELOPING OFFSHORE TROUGH. THESE DIFFERENCES BECOME MORE PRONOUNCED SUNDAY THROUGH MONDAY. THERE WILL LIKELY BE A DRY SOUTHWEST FLOW ALOFT AHEAD OF THE TROUGH ON SUNDAY BASED ON THE MAJORITY OF THE ENSEMBLE RUNS. ON MONDAY, THERE IS MORE SPREAD IN THE ENSEMBLES BUT MOST KEEP THE TROUGH OFFSHORE WITH A CONTINUED DRY SOUTHWEST FLOW ALOFT OVER THE REGION. WISTER/85 && .AVIATION...06Z TAFS (PREVIOUS DISCUSSION)...VFR CONDITIONS CONTINUE OVER THE NEXT 24 HOURS. WINDS REMAIN DIURNAL, WITH SPEEDS BETWEEN 5 TO 10 KTS, THOUGH BDN AND RDM MAY SEE GUSTS TO AROUND 15 KTS TOMORROW AFTERNOON. GOATLEY/87 && .PRELIMINARY POINT TEMPS/POPS... PDT 85 51 87 53 / 0 0 0 0 ALW 87 54 89 55 / 0 0 0 0 PSC 86 55 87 58 / 0 0 0 0 YKM 86 53 87 54 / 0 0 0 0 HRI 86 53 88 57 / 0 0 0 0 ELN 86 52 88 54 / 0 0 0 0 RDM 87 47 87 47 / 0 0 0 0 LGD 87 50 89 51 / 0 0 0 0 GCD 90 53 91 51 / 0 0 0 0 DLS 89 57 90 57 / 0 0 0 0 && .PDT WATCHES/WARNINGS/ADVISORIES... OR...NONE. WA...NONE. &&