941
FXUS66 KPDT 012356
AFDPDT
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PENDLETON OR
455 PM PDT TUE SEP 1 2026
KEY MESSAGES
- ISOLATED SHOWERS AND THUNDERSTORMS IN THE EASTERN MOUNTAINS
TODAY, WITH GREATER & MORE WIDESPREAD CHANCES WEDNESDAY AND
THURSDAY.
- BREEZY WINDS ACROSS THE REGION DEVELOP WITH THE PASSING
SYSTEM.
- TEMPERATURES COOL TOMORROW TO FALL LIKE LEVELS AND LAST
THROUGH AT LEAST THIS WEEK.
DISCUSSION
RADAR AND SATELLITE DEPICTS PRECIP AND CLOUD COVER SECLUDED TO
THE EASTERN MOUNTAIN REGIONS WITH LOW TO MODERATE SHOWERS
APPROACHING AT/NEAR THE JOSEPH AND ENTERPRISE AREA. A SLIGHT
CHANCE (UP TO 15%) OF A THUNDERSTORM OR TWO WILL DEVELOP WITH
LOW CAPE VALUES (100-150 J/KG) AND WEAK WIND SHEAR VALUES. AS
THE SHORTWAVE CONTINUES TO MOVE THROUGH THE AREA, POP'S WILL
INCREASE AS WE HEAD INTO THE EARLY MORNING HOURS THROUGH
THURSDAY.
WEDNESDAY: THE SHORTWAVE CONTINUES TO MOVE TOWARDS ONSHORE WITH
INCREASING SOUTH/SOUTHWESTERN FLOW THAT WILL CONTINUE MOISTURE
TRANSPORTATION. NBM CONTINUES TO ADVERTISE A MAXIMA AREA OF CAPE
DEVELOPING NEAR CROOK AND GRANT COUNTIES IN THE EARLY MORNING
HOURS AROUND SUNRISE. HIGHEST VALUES DEVELOP UP TO 100-150 J/KG
WITH WEAK WIND SHEAR, SO ANY STORMS ARE EXPECTED TO PULSING AND
NOT LAST A LONG TIME. WEATHER PATTERN APPEARS TO BE MORE
STRATIFORM THAN CONVECTIVE IN NATURE DUE TO THE LACK OF DAYTIME
HEATING AND IT BEING THE TIME OF THE YEAR WITH CONVECTION
SEASON DYING DOWN. ISOLATED THUNDERSTORM DEVELOPMENT IS MOSTLY
SITUATED ACROSS PARTS OF THE BLUE AND EASTERN MOUNTAINS (UP TO
15% CHANCES). POP'S ACROSS THE ENTIRE AREA INCREASE UP TO 70-90%
BY THE AFTERNOON HOURS, WITH IT BEING MOSTLY STRATIFORM WITH AN
OCCASIONAL THUNDERSTORM POSSIBLE NEAR THE SLOPES AND FOOTHILLS
OF MOUNTAINS (UP TO A 10% CHANCE). BREEZY WINDS WITH GUSTS UP TO
20 TO 30 MPH IS EXPECTED THROUGHOUT THE COLUMBIA BASIN AND
KITTITAS VALLEY, ESPECIALLY NEAR THE CASCADE GAPS WITH THIS
SYSTEM.
THURSDAY: THE PATTERN ON THURSDAY IS SIMILAR TO WEDNESDAY WET,
BREEZY PATTERN WITH PRECIPITATION CHANCES CONTINUING IN THE
40-70% PERCENT RANGE WITH HIGHER VALUES IN SOME OF THE MOUNTAIN
REGIONS. THE ONCOMING SHORTWAVE CONTINUES TO PUSH AT/NEAR THE
COAST. CAPE VALUES CONTINUE TO BE UNIMPRESSIVE WITH GUIDANCE
DEVELOPING UP TO 100-150 J/KG WITH WEAK WIND SHEAR. THIS
SUGGESTS AGAIN THAT ANY STORM DEVELOPMENT WILL NOT BE LONG LIVED
AND PULSATE THROUGHOUT THE DAY (70-90% CHANCE). THE COLUMBIA
BASIN COULD SEE QPF AMOUNTS UP TO A QUARTER OF AN INCH WITH
AMOUNTS UP TO .75 TO 1.0 INCHES IN THE MOUNTAIN REGIONS (60-80%
CHANCE). PARTS OF THE CASCADE AND WALLOWA CRESTS CAN SEE LOCALLY
HIGHER AMOUNTS OF UP TO 1.5" (50-70% CHANCE).
FRIDAY AND BEYOND: THINGS BECOME UNCERTAIN GOING INTO FRIDAY AND
BEYOND, AS CLUSTERS AND GUIDANCE START TO DIVERGE ON STRENGTH
AND TIMING OF THE WEATHER SYSTEM. BY FRIDAY, ABOUT 60% OF
SOLUTIONS KEEPS THE LOW CLOSED AND CONTINUE ON THE WETTER
PATTERN, WHILE THE OTHER 40% OPENS UP THE WAVE AND BRING DRIER
CONDITIONS ACROSS THE AREA. MODELS ARE STILL ALMOST EVENLY SPLIT
GOING THROUGH THE REST OF THE WEEKEND WITH 57% (CLUSTERS 1 AND
3) STILL SHOWING THE WETTER SOLUTION, WITH SOME TIMING ISSUES
BETWEEN CLUSTERS 1 AND 3. REGARDLESS, NO SIGNIFICANT IMPACTS ARE
CURRENTLY EXPECTED THROUGH SUNDAY (70-90% CHANCE) AND WE WILL
CONTINUE TO MONITOR THIS EVOLVING SYSTEM.
AVIATION /00Z TAFS THROUGH 0Z WEDNESDAY/
VFR CONDITIONS CURRENTLY
AREA-WIDE WITH CONCERNS REVOLVING AROUND PRECIPITATION CHANCES AND
POSSIBLY EVEN LOCALLY SUB-VFR FLIGHT CATEGORIES TOMORROW. AN
UNSETTLED PATTERN IN PLACE THE NEXT 24-HRS A UPPER-LEVEL TROUGH
MOVING ONSHORE NOW INTO SOUTHERN OR AND ANOTHER STRONGER TROUGH
OFFSHORE THE BC COAST. GUSTY WINDS TONIGHT IN THE GORGE WITH
ELEVATED SUSTAINED WINDS AT THE SURFACE CONTINUING ACROSS CENTRAL OR
AND THE NORTHERN BLUES TERMINALS. AS THE LATTER UPPER-LEVEL TROUGH
EVOLVES, RAIN CHANCES INCREASE ROUGHLY-WEST TO EAST AFTER 18Z
TOMORROW AREA-WIDE. BEST CHANCES IN CENTRAL OR AND THE GORGE BEFORE
SPREADING INTO KPSC, KPDT, AND KALW BETWEEN GENERALLY 21Z-00Z
TOMORROW. THERE IS INCREASING POTENTIAL (30-60%) FOR MVFR CEILINGS
DEVELOPING IN CENTRAL OR WITH PRECIPITATION OVER TIME. THE BEST
CHANCES EXIST IN BEND AFTER 21Z TOMORROW. BEST CHANCES FOR THUNDER
ARE CONFINED TO THE EASTERN MOUNTAINS WITH THE HIGHEST CHANCES AT
KPDT AND KALW AROUND 10%.
PRELIMINARY POINT TEMPS/POPS
PDT 48 75 45 68 / 10 50 80 40
ALW 54 76 50 69 / 10 50 90 50
PSC 56 79 50 73 / 0 30 60 30
YKM 55 75 50 70 / 0 30 50 30
HRI 55 77 50 71 / 10 40 60 30
ELN 49 71 44 66 / 10 30 60 40
RDM 43 65 40 63 / 10 80 90 40
LGD 48 73 47 66 / 30 70 90 80
GCD 48 73 46 65 / 10 60 100 70
DLS 57 72 53 69 / 0 80 90 60
PDT WATCHES/WARNINGS/ADVISORIES
WA...AIR QUALITY ALERT UNTIL 10 AM PDT WEDNESDAY FOR WAZ026-522-523.
OR...AIR QUALITY ALERT UNTIL NOON PDT WEDNESDAY FOR ORZ041-505-506-
509>511.
DISCUSSION...95
AVIATION...95
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