298
FXUS66 KPDT 171217
AFDPDT
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PENDLETON OR
517 AM PDT MON AUG 17 2026
KEY MESSAGES
- SHOWER AND ISOLATED THUNDERSTORM CHANCES MAINLY ACROSS FAR
EASTERN OREGON THIS AFTERNOON AND EVENING.
- BREEZY WESTERLY WINDS AND LOW RELATIVE HUMIDITY TUESDAY
AFTERNOON AND EVENING, ESPECIALLY ACROSS THE COLUMBIA BASIN OF
OREGON.
- ANOTHER CHANCE OF SHOWERS AND THUNDERSTORMS TOWARD THE
WEEKEND.
DISCUSSION
LIGHT WEST TO NORTHWEST WINDS WERE SEEN ON MOST STATIONS
OVERNIGHT WITH SCATTERED TO BROKEN HIGH LEVEL CLOUDS SPREADING
OVER THE NRN HALF OF OR AND SE HALF OF WA. THE NBM IS
FORECASTING TEMPERATURES ABOUT A DEGREE OR TWO WARMER TODAY AND
SIMILAR TEMPERATURES INTO WEDNESDAY AFTERNOON. MU-CAPES OF
AROUND 500-750 J/KG SHOULD BE SUFFICIENT FOR ISOLATED
THUNDERSTORM DEVELOPMENT (15% CONFIDENCE OR LESS) ACROSS THE
BLUE MOUNTAINS OF EASTERN OREGON THIS AFTERNOON. EVERY MEMBER OF
THE HREFS CONVECTIVE ALLOWING MODELS SHOWS SOME PATTERN OF
ISOLATED TO WIDELY SCATTERED DEVELOPMENT AFTER ABOUT 12Z
LINGERING THROUGH THE EVENING. SPC CONVECTIVE OUTLOOK COVERS THE
OREGON BLUE MOUNTAIN IN A GENERAL THUNDER OUTLOOK TODAY AND
THIS EVENING.
AS A RESULT OF LOWER PRESSURE DEVELOPING OVER THE COLUMBIA
BASIN AND HIGHER PRESSURE MARINE AIR WEST OF THE CASCADES,
BREEZY TO WINDY CONDITIONS ARE SET TO DEVELOP THROUGH THE
EASTERN COLUMBIA GORGE KITTITAS VALLEY TONIGHT AND MONDAY. IMPACT
ON FIRE WEATHER IS EXPECTED AS THE WARMER TEMPERATURES PROMOTE
LOWER RELATIVE HUMIDITY IN THE AFTERNOON TUESDAY COUPLED WITH
THE BREEZY TO WINDY CONDITIONS.
WEAK SPLIT UPPER LEVEL FLOW PATTERN REMAINS IN PLACE THROUGH
ABOUT WEDNESDAY BEFORE MODELS START SHOWING A TIGHTENING
GRADIENT UPPER HEIGHT FIELD AND MORE SOUTHERLY FLOW ALOFT ACROSS
THE PAC NW AND INTERIOR. THIS WILL BRING A RETURN TO THE
SOUTHWEST EARLY FLOW ALOFT AND A TILT THE ODDS A LITTLE MORE
(15-30%) TOWARD SHOWERS FOR THE MOUNTAINS OVER THE WEEKEND.
AVIATION /12Z TAFS THROUGH 12Z TUESDAY/
SCATTERED HIGH CLOUDS WERE PRESENT ON SATELLITE IMAGERY WITH
METARS INDICATING ALL TERMINAL HAD VISIBILITY GREATER THAN 6SM.
HAVE INCLUDED THE CHANCE FOR SMOKE TO RETURN TODAY WHILE
REMAINING IN THE VFR CATEGORY. ALL LOCATIONS WILL SEE LIGHT
WINDS WITH THE EXCEPTION OF DLS WHERE GUSTY WEST WINDS SHOULD
DEVELOP BY LATE TODAY AND PERSIST THROUGH THE EVENING.
FIRE WEATHER
ISOLATED SHOWERS AND THUNDERSTORMS (<20% MONDAY) ARE POSSIBLE
MAINLY ACROSS WALLOWA COUNTY IN SOUTHWEST FLOW.
AS THE FLOW BECOMES MORE WESTERLY MONDAY NIGHT INTO TUESDAY,
WINDS WILL INCREASE AND BECOME GUSTY, WITH GUSTS AS HIGH AS 20
TO 30 MPH AND POSSIBLY AS HIGH AS 35 MPH ACROSS THE KITTITAS
VALLEY, SIMCOE HIGHLANDS, BLUE MOUNTAIN FOOTHILLS AND THE
COLUMBIA BASIN AND GORGE. THESE WINDS AND LOW RELATIVE
HUMIDITIES WILL YIELD ELEVATED FIRE WEATHER CONDITIONS TUESDAY
AND COULD BRING CRITICAL CONDITIONS ONCE AGAIN.
BEYOND THAT, THERE IS THE POTENTIAL FOR MORE THUNDERSTORMS GOING
INTO NEXT WEEKEND.
PRELIMINARY POINT TEMPS/POPS
PDT 89 58 90 56 / 0 0 0 0
ALW 91 64 90 63 / 0 0 0 0
PSC 94 60 94 56 / 0 0 0 0
YKM 94 61 93 59 / 0 0 0 0
HRI 92 63 93 58 / 0 0 0 0
ELN 90 60 86 57 / 0 0 0 0
RDM 88 49 90 47 / 0 0 0 0
LGD 92 57 91 54 / 20 20 0 0
GCD 92 56 92 54 / 10 10 0 0
DLS 93 62 89 60 / 0 0 0 0
PDT WATCHES/WARNINGS/ADVISORIES
WA...AIR QUALITY ALERT UNTIL NOON PDT TODAY FOR WAZ026-522-523.
OR...AIR QUALITY ALERT UNTIL NOON PDT TODAY FOR ORZ041-503-505-506-
508>511.
FIRE WEATHER WATCH FROM TUESDAY AFTERNOON THROUGH TUESDAY
EVENING FOR ORZ691.
DISCUSSION...71
AVIATION...71
FIRE WEATHER...77
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